LINAC2026 - 33rd Linear Accelerator Conference

16 Aug 2026, 08:00 → 21 Aug 2026, 18:05 Asia/Seoul

Daejeon Convention Center

Hyung Jin Kim (Institute for Basic Science)

We are delighted to announce and invite you to participate in the 33rd Linear Accelerator Conference (LINAC 2026), which will take place from 16–21 August 2026 at the Daejeon Convention Center in Daejeon, Korea. The conference will be hosted by the Institute for Basic Science (IBS).

The LINAC conference series is the premier biennial gathering for the worldwide community of linear accelerator experts. It provides a unique opportunity to learn about the most recent advances in research, development, and applications of linear accelerators for both hadron and lepton beams.

In keeping with its long and successful tradition, LINAC2026 will feature a comprehensive scientific program with invited and contributed talks, poster sessions, and an industrial exhibition. A rich program of social events will complement the scientific sessions, fostering informal knowledge exchange and providing participants with the opportunity to experience Korean culture. Conference attendees will also be invited to visit the RAON heavy-ion accelerator facility, currently under operation in Daejeon.

Active participation of students and early-career researchers is strongly encouraged. A number of scholarships will be made available to support student attendance.

Industry partners and sponsors are warmly invited to contribute to the success of LINAC2026. The industrial exhibition and a variety of sponsorship opportunities will provide excellent visibility to companies and organizations involved in the design, construction, and operation of accelerators and related technologies.

We look forward to welcoming you to Daejeon in August 2026 for what promises to be a stimulating and memorable conference.

LINAC2026 - Exhibition_Participation Guideline_v5.pdf

LINAC2026 - Exhibition & Sponsor Manual_Jun 25_v8.pdf

[LINAC 2026] Poster.jpg

Sunday 16 August

Registration

SUPO - Student Poster Session: SUPO

1 Maximum Entropy Tomography for Nonlinear Beam Transport: 4D Transverse Phase Space Reconstruction at CAFE2

This work extends the Maximum Entropy Tomography (MENT) framework from linear to nonlinear beam transport. This nonlinear MENT method enables high-accuracy phase space reconstruction where nonlinear effects are significant, such as for the intrinsically nonlinear longitudinal dynamics in RF hadron linacs and in front ends where elements exhibit large, overlapping fringe fields.
Following numerical verification, the method was successfully applied to reconstruct the full 4D transverse phase space in the MEBT of the CAFE2 accelerator at IMP. Coupling information was acquired via quadrupole scans​ with the perpendicular-scan technique, and the reconstruction explicitly incorporated nonlinear transport effects. The results show significantly improved agreement with measured data compared to a linear model, thereby validating nonlinear MENT as a general framework and demonstrating its value as a practical tool for high-fidelity diagnostics. This capability is crucial for precise beam prediction and control, with direct applications in modern hadron linacs and potential utility in other accelerator domains.

Speaker: Liwen Liu (Institute of Modern Physics, Chinese Academy of Sciences)

2 A physics-motivated surrogate framework for beam transport optimization in linear accelerators

Optimization of beam transport systems in linear accelerators is a nonlinear and computationally intensive task due to the complex interdependencies between beam properties and machine parameters. In this work, a physics-motivated surrogate modeling approach is developed to optimize the processes of the best accelerator parameters exploration. The proposed framework approximates particle-tracking simulations using a neural surrogate architecture designed to reflect the desired skeleton of the beam transport system. The model predicts beam evolution at several longitudinal locations corresponding to key regions of the beamline, allowing the surrogate to capture the sequential snapshots of beam dynamics cases. The trained model is then used within a constrained optimization procedure to minimize normalized transverse emittance while maintaining acceptable beam size along the beamline. The AREAL linear accelerator (at CANDLE SRI) is used as a validation case to demonstrate the effectiveness of the method.

Speaker: Hayk Sargsyan (Center for the Advancement of Natural Discoveries using Light Emission)

3 Analytical Optimization of Longitudinal Phase Space and Wakefields Compensation for the Main Linac of STCF

In the Super Tau-Charm Facility (STCF) Main Linac, intense short-range longitudinal wakefields from high-charge bunches cause severe energy spread degradation and nonlinear longitudinal phase space (LPS) distortions. We present an analytical model describing LPS evolution under RF acceleration, wakefields, and longitudinal space charge. By utilizing an equivalent truncated-Gaussian distribution, we derived closed-form analytical expressions for the high-order moments of the LPS. Based on this, an analytical optimization method is proposed to determine the optimal RF phase that minimizes the root-mean-square (RMS) energy spread. Theoretical predictions show excellent agreement with Elegant macro-particle tracking simulations, particularly in the core bunch region. With this optimized configuration, wakefield-induced degradation is effectively compensated, successfully fulfilling the stringent beam requirements of the STCF.

Speaker: Hao Hu (Huazhong University of Science and Technology)

4 Beam dynamics simulation and lattice optimization for the Siam Photon Source injector

The Siam Photon Source (SPS) injector, comprising a pre-injector linac and a low-energy beam transport line (LBT), delivers a 40 MeV electron beam to a booster synchrotron for acceleration to 1.2 GeV. While this system has operated in its original configuration since commissioning, prior machine studies (in 2006 and 2016) revealed that overall beam transmission efficiency had degraded to below 30%. To address these losses without disrupting ongoing user beam services, start-to-end beam dynamics simulations were developed to serve as an optimization model. The model integrates space-charge tracking in the pre-injector (using ASTRA) with beam optics matching and multi-particle tracking through the LBT lattice (using ELEGANT). By benchmarking the simulated beam parameters against both the original conceptual design and recent measurements, several discrepancies were identified. This paper details the simulation methodology and proposes machine corrections—including the optimization of RF power and phase in the bunching components, and quadrupole tuning and polarity adjustments—to control the beam envelope and increase the transmission efficiency.

Speaker: Dr Thakonwat Chanwattana (Synchrotron Light Research Institute)

5 Charge carrier dynamics and emission from copper and cesium telluride cathodes in RF photoguns

Pico- and subpicosecond electron bunches with low transverse emittance and charges up to hundreds of picocoulombs, routinely generated in high-gradient RF photoguns, are essential for high-brightness light sources. Photoemission governs the initial bunch properties and is central to forming high-brightness beams. Classical photoemission models (Spicer and Fowler–DuBridge) do not always adequately describe emission under high-gradient, high-brightness conditions.

In this work, we further develop a transport-equation formalism to describe self-consistent charge-carrier dynamics in photocathodes [1,2]. This approach accounts for non-equilibrium charge-carrier dynamics under laser pulse excitation and RF fields, and predicts the temporal structure of emitted electron bunches. As a case study, photoelectron emission from copper and cesium telluride cathodes is investigated. Self-consistent dynamics are simulated using the numerical code PhDyn. Calculated quantum efficiencies and emission curves agree with experimental data, demonstrating predictive capability for high-brightness electron source design.

Speaker: Mikhail Vladimirov (National Research Nuclear University MEPhI)

6 Deep Learning-Based Surrogate Model for 4D Phase-Space Reconstruction in the RAON LEBT

Precise measurement of the 4D phase-space distribution (x, x', y, y') is essential for optimizing accelerator performance and ensuring stable operation. However, the prolonged measurement time of traditional scanning-based diagnostics limits their application in real-time tuning. In this study, we propose a deep learning-based surrogate model for the rapid reconstruction of heavy-ion beam distributions in the Low Energy Beam Transport (LEBT) section at RAON.
Deep learning integrated with physics simulations was adopted in this study to achieve physically reasonable prediction. This method enables the reconstruction of the 4D phase-space distribution at the exit of the ion source, providing a robust framework for real-time diagnostics and autonomous tuning for accelerator systems. The model is trained and validated using high-fidelity particle tracking simulations to ensure numerical stability and minimize statistical bias. This approach significantly reduces the computational overhead compared to conventional tracking codes, allowing for instantaneous beam characterization required for dynamic machine protection and optimization.

Speaker: Woohyeong Kim (Gangneung–Wonju National University)

7 Development of a High-Power Traveling Wave Resonant Ring for SRF Linac Applications

The reliable operation of high-power RF components, including superconducting cavity input couplers and RF windows, is critical for superconducting radio-frequency (SRF) accelerator facilities. Prior to installation into accelerator systems, these components typically require high-power conditioning to verify their RF performance and thermal stability. However, establishing megawatt-level RF test facilities is challenging due to the complexity and limited availability of high-power RF sources.To address this challenge, the Institute of High Energy Physics (IHEP) has developed a 650 MHz traveling-wave resonant ring (TWRR) system,which enables megawatt-level circulating power by accumulating RF energy in a closed-loop structure with a relatively low-power RF source.The system was tested under high-power CW operation. A circulating power of approximately 1.2 MW was achieved with an injected RF power of only 42.7 kW.Stable continuous-wave operation was maintained for 8 h without interruption.These results demonstrate the feasibility of MW-level CW RF conditioning using a compact TWRR and provide an effective test platform for future CEPC RF components.

Speaker: fanyu wang (Institute of High Energy Physics, Chinese Academy of Sciences)

8 EEX-based methods towards nanometer-scale modulation and brightness enhancement

Emittance exchange (EEX) is an attractive approach for generating high-frequency bunch trains from transverse modulations. Ongoing efforts aim to explore the limits of longitudinal modulations achievable with EEX beamlines and methods for enhancing radiation brightness for a given beam. One project investigates the generation of nanometer-scale longitudinal modulation using a transmission electron microscope (TEM) grid combined with a quadrupole demagnifier that controls the period of the transverse density modulation. Another project explores the feasibility of generating a sawtooth correlation—known to maximize radiation brightness from a single bunch--using transverse wigglers. We present the goals and status of these projects. This includes the design of an EEX beamline compatible with nanometer-scale modulation and a transverse wiggler system for producing sawtooth correlations.

Speaker: Buse Naz Temizel Ozdemir (Northern Illinois University)

9 Experimental Validation of an X-Band LLRF Prototype for High-Gradient Linear Accelerators

Low-Level RF (LLRF) systems are essential for maintaining amplitude and phase stability in modern linear accelerators, directly affecting beam quality and operational reliability. The increasing use of X-band technology in compact, high-gradient linacs enables ultra-short RF pulses and higher accelerating fields, while also increasing sensitivity to phase noise, timing jitter, and thermal effects. To address these challenges, a dedicated X-band LLRF prototype has been developed within the framework of the EuPRAXIA Doctoral Network for application in next-generation X-band linear accelerators. The system combines a high-speed RF front-end with FPGA based digital back-end optimized for fast pulsed operation, low-latency processing, and precise amplitude and phase control. After extensive laboratory testing, the prototype has been validated on a real accelerator test bench. This paper presents the system's concept and experimental results, including pulse-to-pulse stability and phase noise performance. The results confirm the feasibility of the proposed X-band LLRF approach for future high-gradient linac applications.

Speaker: Mr Phani Deep Meruga (Instrumentation Technologies (Slovenia), Sapienza University of Rome)

10 Features of long particle bunch self-modulated in plasma

Plasma wakefield acceleration is a promising method of accelerating charged particles based on the excitation of strong electric fields in plasma. These fields arise when a driver, such as a particle beam or a laser pulse, propagates through the plasma and displaces electrons, forming a wave with accelerating gradients far exceeding those of conventional accelerators. In this work we study the case of a particle beam driver much longer than the plasma wavelength. Under these conditions the self-modulation instability develops, causing the beam to split into a sequence of microbunches. Using numerical simulations with the two-dimensional quasi-static code LCODE*, we investigate the properties of the formed microbunch train and its contribution to the excited wakefield. Based on these results, an analytical model describing the radial density profile of the microbunches is developed. The model predictions are in very good agreement with the simulation results. The analysis shows that the beam evolves into microbunches with a sharply peaked radial density distribution, differing from the initial Gaussian profile, which significantly increases the efficiency of wakefield excitation.

Speaker: Vlada Yarygova (Budker Institute of Nuclear Physics)

11 FPGA-Based Frequency Shift Correction for Linear Accelerators

The muon high-precision (g-2)/EDM experiment, which is planned at the J-PARC, utilizes the world’s first dedicated muon linear accelerator (linac), requiring stringent Radio-Frequency (RF) field stability. The Radio Frequency Quadrupole (RFQ), the linac's initial stage, experiences frequency shifts that cause operation outside the RFQ bandwidth. Due to budget constraints, conventional tuning methods are impractical. This study presents a real-time digital feedback system developed within a Low-Level RF (LLRF) framework to maintain frequency-shifted operation and to correct IQ time variations caused by the frequency shifts, which was implemented on a Field-Programmable Gate Array (FPGA), proving a cost-effective and compact solution. This approach eliminates the need for additional external hardware such as dedicated tuners. Following the successful validation using a simulation test cavity, the system was integrated with the actual RFQ. This system met the stability requirements for achieving muon beam acceleration tests. This LLRF-based approach ensures beam integrity and represents a significant milestone towards achieving the precision goals of the J-PARC experiment.

Speaker: Osman Emre Delialioglu (The Graduate University for Advanced Studies, SOKENDAI)

12 Intrabeam Scattering studies in Free Electron Lasers with RF-Track

Intrabeam Scattering (IBS) has recently been recognized as a limiting factor for free electron laser (FEL) performance, making it a critical concern for the linear accelerator community. There is a growing need for accurate numerical tools to compute IBS and integrate it with other collective effects, as most previous studies assumed Gaussian beams, which are not representative of FEL conditions. In response, the tracking code RF-Track has been enhanced with a novel kinetic-hybrid Monte Carlo algorithm for IBS calculations. This contribution reports on IBS studies for several FELs, including SwissFEL at PSI and FERMI at Elettra. For SwissFEL, simulation results are benchmarked against experimental measurements. Benchmarks of emittance growth are compared with other tracking codes, and predictions for IBS impact on future facilities are discussed.

Speaker: Paula Desire Valdor (European Organization for Nuclear Research)

13 Investigation of the Operational Aspects of Ferroelectric Fast Reactive Tuners (FE-FRTs)

Integrating ferroelectric fast reactive tuners (FE-FRTs) into SRF cavities offers a promising route to mitigate microphonics. This work reports the design and characterisation of an FE-FRT coupled to a 1.3 GHz two-cell cavity, supported by a lumped element equivalent circuit model and 3D CST simulations. From this framework, external Q-factors, FPC specifications, and generator power requirements are derived, including power loss estimates to identify optimal working points. The tuner’s non-linear response to RF current is characterised, accounting for higher-order modes (HOMs) in both the cavity and the tuner resonator. By appropriate resonant frequency choice, monopole HOMs in the tuner can be kept away from harmonics of the fundamental mode; however, the permittivity variation in the FE wafers during operation could shift a HOM close to the third harmonic at 3.9 GHz, potentially coercing the stable operating range. In our example design, the two monopole HOMs below the fourth harmonic exhibit fields mainly on the sapphire window rather than on the FE wafers, thereby strongly reducing direct excitation by the fundamental field and mitigating associated risks for LINAC operation.

Speaker: Maleesh Shehan Rathnasiri Dissanayake Mudiyanselage (Lancaster University)

14 Pole Shape Optimization of a Tunable Permanent Magnet Quadrupole for Future Accelerator Beamlines

Next-generation storage rings require low emittance and high brilliance, and their quadrupole magnets must provide both high magnetic gradients and stringent multipole field quality. Conventional electromagnetic quadrupoles consume substantial electrical power and require cooling systems because of Joule heating. In this study, a permanent magnet quadrupole (PMQ) that generates its magnetic field without an excitation power supply and allows the gradient to be varied mechanically was designed.
Starting from a two-dimensional pole shape and an end-edge chamfer angle determined in previous work, the geometry was extended to a three-dimensional model that accounted for a 2 mm longitudinal pole extension at each end, introduced during fabrication to clamp the poles to the aluminum yoke. This extension altered the fringe-field distribution and degraded the integrated multipole content. A parametric sweep of the chamfer angle was therefore performed over the machinable range, and the angle minimizing the integrated harmonic content was selected.
The resulting geometry satisfies the field quality criteria for next-generation storage rings, with allowed multipole components below $5\times 10^{-5}$, forbidden components at the $10^{-5}$ level, and a field uniformity of 0.1% at $r_{ref} = 3 mm$. These results demonstrate the feasibility of a high-quality PMQ that provides a variable magnetic gradient without steady-state power consumption or cooling.

Speaker: Junwon Choi (Kangwon National University)

15 Progress of S-band high efficiency periodic permanent magnet klystron

High-efficiency klystrons can significantly reduce the operational costs of particle accelerators. However, for the of low-duty-factor klystrons commonly used in linear accelerators, the power consumption of electromagnetic focusing coils remains non-negligible. This paper presents the progress of an S-band 50 MW high-efficiency klystron employing periodic permanent magnet (PPM) focusing aiming to achieve high conversion efficiency while minimizing auxiliary power consumption. Due to the relatively large dimensions of S-band tubes, the focusing structure is constrained and the beam rigidity is limited. These factors impose stringent requirements on beam dynamics design and require coordinated optimization of the magnetic field configuration and electron bunching process.. Simulation results validate the feasibility of applying PPM focusing to a high-efficiency S-band klystron, with an overall tube efficiency of 54%.The proposed S-band PPM klystron provides a promising approach for improving the efficiency and reducing the operational cost of high-power RF sources in accelerator application.

Speaker: Han Xiao (Institute of High Energy Physics)

16 Reconstruction of beam transverse parameters in the Fermilab side-coupled linac using a normalized coordinate framework

Quadrupole scans are a commonly used tool for beam second moment reconstruction. Limitations in the strength of the magnets and layout of the beamline elements frequently preclude simple quadrupole-drift-detector scans from collecting sufficient data for reconstruction. Using a normalized coordinate framework, we characterize the prerequisites for a robust simple quadrupole scan and expand these prerequisites to reconstruction from more complex optics. The beam second moments are investigated at two locations in the Fermilab Side-Coupled Linac under simple and complex optics, using this framework to maximize information gained from wire scanner profile measurements.

Speaker: Erin Chen (Fermi National Accelerator Laboratory)

17 Status of the SAFEST Project the SAPIENZA Linac Prototype for VHEE Flash Radioterapy

FLASH radiotherapy is emerging as a transformative cancer-treatment modality, achieving tumor control while reducing normal-tissue toxicity and improving the therapeutic index. To exploit this effect, especially for deep-seated tumors, Very High-Energy Electrons (VHEE) in the 50–150 MeV range are required. Within the SAFEST project, aimed at a 100 MeV machine, Sapienza University of Rome, with INFN, is developing a compact C-band linear accelerator prototype. The system is designed to deliver 24 MeV loaded electrons, providing 2 Gy per pulse over a 10 × 10 cm² field at 100 Hz. Accelerator optimization included electromagnetic, vacuum and beam-dynamics studies to ensure beam parameters suitable for FLASH dose delivery. To reach high gradients and enable future VHEE operation in a compact footprint, the work focuses on the in-house design and construction of a C-band travelling-wave structure. The final technical design report is complete, and installation is underway at Sapienza University. Two irradiation configurations, pencil beam and wide beam, are planned for in vitro studies. This compact electron source is a milestone toward next-generation VHEE facilities for FLASH therapy.

Speaker: Riccardo Boldrini (Sapienza University of Rome)

18 Study of RF Beam Separation and Scanning Uniformization Techniques for High Power Particle Accelerators

High-power particle accelerator beams have important applications in many fields. Multi-terminal beam delivery can improve beam utilization, while the extremely high peak current density on the target surface limits the safe and stable operation of target stations. To meet the demand for simultaneous multi-terminal beam delivery, RF beam separation was studied. A scheme based on a RF deflecting cavity and septum magnets was used to distribute the beam among different target stations. Beam dynamics simulations show that this scheme can achieve loss-free transport. After separation, the beam emittance increases significantly, mainly due to RF-field nonlinearity. To address the peak current density limitation on a single target, beam scanning uniformization was studied. A technical scheme based on point scanning and circular scanning was adopted to achieve beam uniformization on the target surface. Numerical simulations show that the peak current density is reduced to 8.62 μA/cm². Beam dynamics simulations show that point scanning can inject the beam spot into the target center, and circular scanning enables the beam spot to form a circular distribution on the target.

Speaker: Jie Zeng (Institute of Modern Physics, Chinese Academy of Sciences)

Welcome Reception

Monday 17 August

Registration

Welcome Address

MO1A - Plenary Talks

19 Present status and future plans for linear accelerators in Korea

This talk presents the status of major linear accelerators in Korea: the RAON (heavy ion accelerator), the KOMAC (100 MeV proton accelerator), and the Pohang XFEL linear accelerator. Also future plans for each facility is to be presented including the energy upgrade of the RAON to 200 MeV/u (uranium) and the energy upgrade of the KOMAC to 200 MeV to study the radiation effects of semiconductor chips.

Speaker: Yeonsei Chung (Institute for Basic Science)

20 Updates on the Worldwide efforts for transmutation of spent nuclear fuel with accelerator driven systems

To address the challenge of nuclear waste storage, the international community is pursuing accelerator-driven subcritical systems (ADS) to reduce both the volume and radiotoxicity of spent nuclear fuel. ADS utilizes high-intensity linacs, which must operate with high reliability to prevent thermal stress on reactor structures. This presentation provides an overview of global transmutation activities, considering both government-funded research and industry-sponsored projects.

Speaker: Bruce Yee-Rendon (Japan Atomic Energy Agency)

10:20 Group Photo

10:30 Coffee Break

MO2A - Plenary Talk

21 High-dimensional beam tomography with PolariX: Experimental results from DESY and PSI

PolariX transverse deflection structures (TDS) are installed at different accelerators at DESY and PSI to enable advanced characterization of the particle beams for applications like free-electron lasers, beam-driven plasma acceleration, or advanced acceleration R&D projects. The variable streaking angle of PolariX – a differentiating capability of this TDS – allows us to apply a variety of tomographic methods for beam characterization. These methods provide insight into the behavior of particle beams by reconstructing their phase space in high dimensions, revealing information that is typically inaccessible. In this contribution, we present on overview of the experimentally acquired high-dimensional beam reconstructions from DESY and PSI. Furthermore, we show our latest developments of the applied tomographic methods including a significant improvement in measurement speed – an important step towards regular usability.

Speaker: Sonja Jaster-Merz (Deutsches Elektronen-Synchrotron DESY)

MO2A - Invited Talks

22 Beam commissioning of the ESS accelerator: Results and Challenges

In 2025, the beam produced by the European Spallation Source (ESS) accelerator, a 600 m-long superconducting proton machine, first reached the beam dump. This presentation will give an overview over the results achieved during the commissioning rounds in 2025 and 2026, and the challenges remaining for high power and user operation.

Speaker: Sofia Johannesson (European Spallation Source)

23 Status of the LCLS-II-HE Upgrade

SLAC is engaged in an upgrade for the LCLS-II SC linac, the LCLS-II-HE project. The presentation should give an update of progress including summary of CM production and testing and schedule for installation and commissioning.

Speaker: Daniel Gonnella (SLAC National Accelerator Laboratory)

24 Coupled dynamics and transverse matching of intense heavy ion beams

Ion beams are extracted from the Electron Cyclotron Resonance source with an initial angular momentum. The focusing in the FRIB diver linac is provided by electric and magnetic solenoids and quadrupoles. Understanding the coupled dynamics and proper matching of the beams along the superconducting linac is critical to maintaining high-power, low-loss operation. The errors in the measured 4D rms emittances of various heavy-ion beams are highly sensitive to the quadrupole scan procedure.

Speaker: Alec Gonzalez (Facility for Rare Isotope Beams)

12:30 Lunch

MO1P - Invited Talks

25 Four-dimensional phase space tomography from one-dimensional measurements of a hadron beam

One-dimensional measurements are used to infer the four-dimensional phase space density of an accumulated proton beam in the Spallation Neutron Source (SNS) accelerator. The reconstruction was performed by maximizing the distribution’s entropy subject to the measurement constraints and thus represents the most conservative inference from the data. The reconstructed distribution reproduces the measured profiles down to the noise level, and simulations indicate that the problem is reasonably well constrained. Similar measurements could serve as benchmarks for beam dynamics simulations in the SNS or hadron accelerators.

Speaker: Austin Hoover (Oak Ridge National Laboratory)

26 Simple and Stable 3-GeV Linear Accelerator in High Brilliance Synchrotron Light Source NanoTerasu

NanoTerasu is a highly brilliant synchrotron light source mainly focusing on soft to tender X-ray region. The NanoTerasu compact accelerator system with high performance consists of a storage ring with a circumference of 349 m and a 3-GeV linear accelerator with length of 110 m. The linear accelerator is designed not only for full energy injection to the storage ring, but also for future extension to soft-X ray free electron laser. The prominent feature of the injector system is a low-emittance compact rf electron gun employing transparent-grid scheme in a gridded thermionic cathode. The low-emittance beam from the electron gun is bunch compressed to 5 ps with a sub-harmonic buncher and accelerated up to 3-GeV with an S-band accelerating structure and 40 of 2 m long C-band accelerator structures. Since the commissioning of the linear accelerator started on April 2023, a 3 GeV electron beam with bunch charge of 0.3 nC and a normalized emittance of 10 micro-mrad has been supplied to the storage ring. This system, which is compact and simple configuration, yet produces a highly brilliant and stable electron beam, will be a good example for future electron accelerators.

Speaker: Takao Asaka (National Institutes for Quantum Science and Technology)

27 Systematic Mitigation of Intra-Beam Stripping and Distributed Beam Loss in High-Intensity H⁻ Linacs: Experimental and Operational Experience at J-PARC

Charge-exchange injection using H⁻ beam enables high-intensity proton accumulation in rapid cycling synchrotrons and storage rings. As a result, high-power H⁻ linacs are indispensable for modern pulsed neutron sources and high-energy physics facilities.
Compared with proton linacs, H⁻ linacs are intrinsically susceptible to loss induced by electron stripping. Intra-beam stripping (IBSt) is a fundamental, intensity-dependent mechanism that can dominate residual activation and is governed by phase-space distribution and focusing lattice. In addition, H$^0$ generated by stripping produce broad loss patterns sensitive to aperture constraints.
At the J-PARC linac, these mechanisms were investigated through experiments, simulations, and long-term operation. Their dependencies on lattice and apertures were quantitatively characterized, with good agreement between simulations, monitors, and radiation measurements.
Based on this understanding, a systematic mitigation strategy was established. Radiation hot spots were eliminated, and total activation was reduced by more than a factor of two, enabling stable high-power operation and providing guidance for future high-intensity H⁻ linacs.

Speaker: Yong Liu (High Energy Accelerator Research Organization)

MOOP - Oral Posters

28 Evolution of f-Divergence Between High-Dimensional Phase Space Distributions During Beam Transport

F-divergence can be used to precisely quantify the differences between beam distributions in high-dimensional phase space, as it comprehensively captures the total contribution of discrepancies from all points in phase space. Current applications of f-divergence are primarily confined to the static comparison of distributions. This paper aims to investigate its evolution during beam transport. We mathematically prove that f-divergence remains invariant in both linear and nonlinear transport processes, and validate this conclusion through beam transport simulations. Further research indicates that space charge forces can break this conservation. We show how this property of f-divergence can be used as a tool to help us understand, predict, or control beam degradation caused by space charge effects.

Speaker: Yu Du (Institute of Modern Physics, Chinese Academy of Sciences)

29 Concept of emittance exchange using two bending magnets and two transverse deflectors at CLEAR (CERN Linear Accelerator for Research)

Second beam line has recently been installed and commissioned at CLEAR (CERN Linear Accelerator for Research). The line begins with a switchyard consisting of two dipole bending magnets that offset the beam from its original path, along with quadrupoles and sextupoles placed between the bends to close the first- and second-order dispersion, respectively. In this work, based on analytical methods and numerical simulations, we present a concept for an emittance exchange scheme realized using the switchyard. We show that transverse-to-longitudinal phase space exchange can be achieved by activating a transverse deflector located upstream, together with an additional deflector downstream (the only missing element). Furthermore, we demonstrate that such a scheme enables advanced beam phase-space tailoring and expands the CLEAR beam parameters beyond its nominal operational range.

Speaker: Alexander Malyzhenkov (European Organization for Nuclear Research)

30 Wakefield mitigation studies and beamline upgrades for stable nanometer beam operation at KEK-ATF

The KEK-ATF is an R&D facility for the final focus system to develop nanometer beam technology for the International Linear Collider. The vertical beam size growth as a function of bunch intensity has been observed at the focal point (IP), mainly caused by wakefield effects. ATF provides an excellent environment for studying wakefield impacts on nanometer-scale beams. Mitigation and understanding of wakefield effects are important for achieving stable nanometer beams. To reduce wakefield effects, several upgrades have been implemented in the ATF final focus beamline. Vacuum components that significantly affect the beam, such as flanges and bellows, have been improved by introducing step-free structures and RF shielding. In addition, the collimator, one of the dominant wakefield sources, has been upgraded to allow position adjustment, enabling minimization of wakefield effects caused by orbit distrtions and misalignments. In this paper, we report the current status of these mitigation studies, their experimental results, and future prospects toward stable nanometer beam operation.

Speaker: Dr Yuki Abe (High Energy Accelerator Research Organization)

31 High-Power Testing of an X-Band Dielectric Assist Accelerating Structure under Short-Pulse RF Excitation

The dielectric assist accelerating (DAA) structure is a power-efficient RF accelerating cavity. A room-temperature C-band DAA structure has demonstrated a high shunt impedance of approximately 600 MΩ/m. Nevertheless, the attainable accelerating field in DAA structures has so far been limited to approximately 10–12 MV/m, mainly because of RF breakdown-related phenomena, including multipacting.
To increase the achievable accelerating field, we have investigated short-pulse RF excitation in DAA structures. This approach is motivated by recent studies of dielectric disk accelerating structures, in which an accelerating gradient exceeding 100 MV/m was achieved under short-pulse operation.
We have developed a two-cell X-band standing-wave DAA structure employing sapphire cells coated with hydrogenated amorphous carbon. High-power RF tests have been carried out at Nextef2 in KEK. We tested different RF pulse conditions, including single RF pulses shorter than the cavity filling time and step-pulse inputs, and achieved an accelerating field of up to 16 MV/m.
In this presentation, we will describe recent efforts toward higher-gradient operation.

Speaker: DAISUKE SATOH (National Institute of Advanced Industrial Science and Technology)

32 The High-Power Gallium-Indium Liquid Target at SARAF: Design, Validation, and Multi-Disciplinary Applications

The Soreq Applied Research Accelerator Facility (SARAF) is advancing to Phase II to deliver continuous wave proton and deuteron beams (5-40 MeV, ~5 mA). Handling the resulting ~200 kW beam power requires a robust dump capable of dissipating high power densities. To meet this challenge, a windowless liquid Gallium-Indium (Ga-In) jet target, GaLiT, was designed. It generates a stable ~5 m/s jet with a verified thickness of 5.6±0.3 mm, sufficient to stop the incident beam. Ga-In offers superior heat transfer and reduced chemical hazards compared to liquid lithium.
Beyond serving as a beam dump, this system functions as a high-intensity neutron source, designated MARZEPAN, yielding >10^15 n/s with energies up to ~45 MeV. This facility supports a broad spectrum of physics applications:
Fusion Material Research: Simulating reactor environments and radiation damage studies.
Astrophysics: Enabling research into stellar nucleosynthesis via tunable neutron spectra.
Fundamental Nuclear Physics: Producing short-lived isotopes via systems like SARONA for weak interactions and cross-section measurements.
This contribution presents the design, prototypes, and scientific applications of GaLiT.

Speaker: Dr Sergey Vaintraub (Soreq Nuclear Research Center)

33 L4-RFQ2 RF conditioning and breakdown localization studies

CERN's Linear Accelerator 4 (Linac4) is an H⁻ accelerator that has been in operation since 2020. After acceleration, the ions are converted to protons via electron stripping and sent downstream to various experiments on the CERN site. Its first accelerating structure is a 3 m long Radio-Frequency Quadrupole (RFQ), operating at 78 kV inter-vane voltage and a peak surface field of 34 MV/m. In 2025, a dedicated campaign was conducted to condition and test the recently constructed spare RFQ, providing the opportunity to study vacuum breakdown behavior in this complex structure.
This work presents high-power RF conditioning results to improve the understanding of breakdown limitations in the new RFQ. It also focuses on localizing breakdown events using signals from 16 pick-ups distributed along the cavity. These measurements are compared with RF simulations to correlate signal patterns with breakdown locations and provide insight into the underlying physical mechanisms.

Speaker: Pablo Martinez Reviriego (European Organization for Nuclear Research)

34 Fault Tree Modeling and Reliability Analysis of the CAFE2 Accelerator

The CAFE2 accelerator, upgraded from CAFe at IMP, supports superheavy element research. Based on the RAMI framework, this paper decomposes CAFE2 using PBS and applies fault tree analysis at system, subsystem, and equipment levels to identify beam trip events. Historical data show that the superconducting section and control system are the main causes of beam losses. Although CAFE2 has high beam availability, systematic reliability modeling is needed. A preliminary fault tree model is established, and future work will refine it with collected fault data to improve operational stability.

Speaker: Xin Ma (Chinese Academy of Sciences)

35 Status update of permanent magnet radiation resiliency studies at CEBAF

The proposed energy upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) incorporates Fixed-Field Alternating-gradient (FFA) arcs utilizing permanent magnet technology. Given the radiation environment within the CEBAF tunnel enclosure, validating the long-term magnetic stability of these materials is a critical step for the project's technical feasibility. This contribution presents an overview of the ongoing permanent magnet radiation resiliency program at Jefferson Lab, which has expanded into one of the largest and most comprehensive in-situ studies of its type ever performed in an accelerator environment. We briefly review the experimental methodology used to monitor demagnetization and summarize the operational experience from the initial data-taking campaign. Furthermore, we discuss the upgrades implemented for the second exposure campaign, currently underway, which aims to refine dose correlation and reduce systematic uncertainties. We report on the latest results from the program and the roadmap for certifying permanent magnet optics for the proposed upgrade energies.

Speaker: Ryan Bodenstein (Thomas Jefferson National Accelerator Facility)

36 Machine Learning Applications for Beam Diagnostics and Automated Tuning at CLEAR

Machine learning (ML) is increasingly recognized as a fundamental tool in modern accelerator physics, offering new capabilities to complement and extend traditional analytical approaches. A structured programme of ML studies has been initiated at CLEAR (CERN Linear Electron Accelerator for Research), covering three principal directions: beam diagnostics, charge forecasting, and automated tuning via reinforcement learning. Deep learning models were explored to reconstruct transverse beam profiles from indirect measurements, offering a pathway toward radiation-resistant non-invasive diagnostics. Classical and deep learning approaches were benchmarked for charge prediction, demonstrating the potential for accurate real-time beam characterization. A reinforcement learning framework was interfaced with the CERN control infrastructure, enabling proof-of-principle autonomous beam steering through iterative magnet corrections. These results demonstrate the feasibility of integrating ML into routine CLEAR operations and position the facility as an attractive testbed for the development and validation of machine learning techniques for particle accelerators.

Speaker: Antonio Gilardi (European Organization for Nuclear Research)

37 Generative Phase-Space Reconstruction for Low-Intensity Beam Characterization in the J-PARC Muon Linac MEBT Line

The J-PARC Muon Linac is being developed for precision measurements of the muon anomalous magnetic moment and the search for the muon electric dipole moment using a reaccelerated thermal muon beam. The Medium Energy Beam Transport (MEBT) line, planned for commissioning in 2027, will transport and match the muon beam to the Inter-digital H-mode drift tube linac (IH-DTL). Because the expected muon intensity is extremely low, conventional destructive and scan-based phase-space diagnostics are challenging. In this study, phase-space characterization methods for the J-PARC Muon Linac MEBT are investigated using MCP-based beam profile monitors composed of a microchannel plate, phosphor screen, and camera. Low-intensity muon beam projections are used for quadrupole-scan analysis and machine-learning-based prediction. A differentiable simulation code is combined with a generative neural-network beam model to reconstruct transverse phase-space distribution from downstream profile images at different quadrupole settings. The results indicate that MCP profile measurements with generative reconstruction provide a promising approach for MEBT beam characterization and commissioning.

Speaker: Emre Cosgun (High Energy Accelerator Research Organization)

MOPO - Poster Session

38 A design study for a portable muon source

Because muons possess high material penetration capabilities, they are an extremely effective tool for non-destructive testing of large-scale structures. While cosmic-ray muons have traditionally been used for imaging infrastructure such as bridges and tunnels, as well as the interiors of buildings, challenges have included long measurement times and limitations on installation locations. In this study we propose the design of a portable muon source and accelerator utilizing a superconducting microtron that can be mounted on a standard　highway truck. In this presentation, we will detail the muon generation process, potential applications, key technologies required for implementation, and the technical challenges encountered during development. Through these discussions, we will present a novel concept for a compact accelerator with a view toward societal implementation.

Speaker: Zachary Liptak (Hiroshima University)

39 A new 4-Rod RFQ for the ion therapy injector at HIT Heidelberg

An improved version of the 4-rod RFQ was developed to gain higher mechanical precision on the rod - alignment, and to reach a higher quality factor. Design elements as developed during a prototyping project within the Hessian funding initiative LOEWE3 were implemented in this project for the first time. This resulted in substantially reinforced rod-supports with complete dipole suppression.
The RFQ was manufactured during 2025 and was installed at the test stand of the Heidelberg Therapy Center HIT in April 2026. First results from detailed beam measurements will be reported.

Speaker: Ulrich Ratzinger (Bevatech GmbH)

40 A new method to characterize single-cavity RF pulse compressors based on reflection measurements

Pulsed high-power Radio Frequency (RF) systems frequently employ pulse compressors to augment peak output power, thereby reducing the required number of RF sources and enhancing cost-efficiency. A prominent class of these devices utilizes single resonant cavities supporting two degenerate modes to achieve high performance within a compact footprint. However, the inherent coupling of these modes complicates experimental characterization, a challenge exacerbated by the fact that these units are typically non-dismountable.
This work proposes a novel analytical method to disentangle the complex electromagnetic data encoded within these systems. By separately extracting the parameters of the individual degenerate modes and the characteristics of the associated waveguide network, the method provides a granular view of device performance. This approach enables a more comprehensive interpretation of measurement data, offering a pathway for the precise tuning and optimization of monolithic RF pulse compression systems.

Speaker: Pablo Martinez Reviriego (European Organization for Nuclear Research)

41 A physics-motivated surrogate framework for beam transport optimization in linear accelerators

Optimization of beam transport systems in linear accelerators is a nonlinear and computationally intensive task due to the complex interdependencies between beam properties and machine parameters. In this work, a physics-motivated surrogate modeling approach is developed to optimize the processes of the best accelerator parameters exploration. The proposed framework approximates particle-tracking simulations using a neural surrogate architecture designed to reflect the desired skeleton of the beam transport system. The model predicts beam evolution at several longitudinal locations corresponding to key regions of the beamline, allowing the surrogate to capture the sequential snapshots of beam dynamics cases. The trained model is then used within a constrained optimization procedure to minimize normalized transverse emittance while maintaining acceptable beam size along the beamline. The AREAL linear accelerator (at CANDLE SRI) is used as a validation case to demonstrate the effectiveness of the method.

Speaker: Hayk Sargsyan (Center for the Advancement of Natural Discoveries using Light Emission)

42 A proposed high energy XFEL scheme based on CEPC linac

Coherent X-ray beams with energy above 50 keV have been found to have important applications in many research fields.
The linac injector of the proposed Circular Electron-Positron Collider (CEPC), with electron energy up to 30 GeV, is a strong candidate for driving such high-energy X-ray free-electron lasers (XFELs).
In this work, we propose a SASE FEL scheme based on the CEPC linac.
By optimizing key parameters of the CEPC linac beam, such as electron beam energy and normalized emittance as well as energy spread, this design can drive the SASE process efficiently and produce X-rays with photon energies ranging from 50 to 100 keV.
Simulation results indicate that, with an electron beam energy of 25 GeV and a normalized emittance of 0.35 μm·rad, the proposed facility can achieve high-brilliance spectral output at photon energies of 50 keV and above.
This paper presents the detailed setup and simulation results of the proposed FEL scheme.

Speaker: Xueyi Xu (Institute of High Energy Physics)

43 advanced linear accelerator technology for non-destructive testing

Non-destructive testing is one of critical areas of industrial application for radiation technology, widely used in pressure vessel inspection, and cargo inspection. Electron linear accelerators play a pivotal role in these applications by generating X-rays through hitting the target by electron beam. To meet the evolving demands of non-destructive testing, research has been conducted on self-focusing technology. By combining multiple self-focusing methods, the focal size of compact X-ray sources based on electron linear accelerators has been reduced to below 1mm. Among them, the focal size of S-band accelerators has been reduced to 1mm, and the focal size of C-band accelerators has been reduced to 0.5mm, effectively improving detection accuracy. At the same time, compared with S-band accelerator X-ray sources, C-band accelerators reduce equipment size and weight to one-third, which is conducive to complex component detection and mobile detection.

Speaker: Jinghe Yang (China Institute of Atomic Energy)

44 AI-ML Deployment in the ATLAS Control Room: Online Interface & Virtual Accelerator Model

Significant progress has been made in the development of AI-ML tools at the ATLAS heavy-ion linac at Argonne. Although all tools were successfully tested online, they were not accessible to the operators in the control room. To facilitate this, we have developed a dedicated AI-ML interface that allows the user to select the beamline to tune, the task to perform, hit the execute button and watch the results. In addition to presenting the main features and capabilities of the interface and its integration into the ATLAS control system, we will report on the operational experience and feedback from the operators. Another important update is the development of a virtual model for the ATLAS linac. A model that allows offline testing before online deployment, uses the same interface with the same online experience, and most importantly, mimics all aspects of the machine. After presenting a general procedure on how to develop an effective virtual accelerator model, we highlight a few example applications. Finally, moving a step closer towards a digital twin, we plan to add real-time online exchange between the virtual accelerator and the real machine, albeit in one direction at this time.

Speaker: Brahim Mustapha (Argonne National Laboratory)

45 Beam dynamics and RF design of a split-coaxial radio frequency quadrupole for axial injection

A 36.526 MHz coaxial-split RFQ(Radio Frequency Quadrupole) accelerator has been developed for cyclotron injection. The main advantage of this cavity is that it can overcome the problem of an excessively large transverse size of conventional RFQs at low frequency, which is beneficial for the axial injection of the cyclotron and reduces the influence on the cyclotron yoke magnet. This coaxial-split RFQ is designed to accelerate a 3.5 mA H₂⁺ beam from 20 keV to 70 keV in continuous wave operation. Electromagnetic simulations have shown that the average power loss of this 1.618 m long RF accelerator is about 12 kW in CW mode. Due to the special structure of the coaxial-split RFQ, the dynamics and RF structural design of the cavity are mainly presented in this paper.

Speaker: Junzhao You (Peking University)

46 Beam Dynamics Design of a 15 GHz Compact X-band Standing Wave Accelerating Structure Based on Genetic Algorithm

A fully automated beam dynamics design method based on genetic algorithm is proposed for a 15 GHz X-band three-cell standing wave accelerating structure to meet the miniaturization requirements of X-ray based intraoperative radiotherapy devices. The genetic algorithm simultaneously optimizes the field distribution and phase relationships of the three cavities, achieving both electron beam bunching and acceleration within a single framework without manual intervention. The design results demonstrate that the accelerating structure can achieve the required energy within an extremely compact length, satisfying the stringent volume constraints of IORT equipment.

Speaker: Zihe Gao (Shanghai Synchrotron Radiation Facility)

47 Beam dynamics design of an RFQ injector and injection line for an H2+ high-current separated-sector cyclotron

The China Institute of Atomic Energy proposes an H2+ high-current separated-sector cyclotron facility as a continuous neutron source, targeting a 150 MeV, 10 mA proton beam after stripping extraction. The RFQ front end is designed for pre-acceleration and injection matching into the second-stage cyclotron. The matching requirements include low-loss transport through the RFQ and transfer line, envelope and phase-space matching at the cyclotron entrance, control of bunch length, phase width and energy spread, and mitigation of space-charge effects. A 50.85 MHz four-rod RFQ is optimized with RFQGen to accelerate and bunch a 30 keV, 8 mA H2+ beam to 2.03 MeV with 97.07% transmission. For the RFQ-exit beam above 7.5 mA, an injection line with quadrupole magnets, bending magnets and a double-gap buncher is designed for focusing, deflection, compression and six-dimensional phase-space matching. TRANSPORT, OPAL and CST simulations show that the 14 m line keeps beam loss below 10%, and for beam currents above 5 mA the phase width remains within 60 degrees. These results provide a beam-dynamics basis for subsequent optimization.

Speaker: jing fang (China Institute of Atomic Energy)

48 Beam Loss Measurements with Neutron and Ionization Chamber Monitors during ESS Beam Commissioning to the Tuning Beam Dump

The European Spallation Source (ESS) employs 266 ionization chamber beam loss monitors (icBLMs) and 82 neutron beam loss monitors (nBLMs). These detectors provide detailed information on beam loss distribution along the ~600 m ESS linac and play a critical role in machine protection. During the second round of beam commissioning to the Tuning Beam Dump in spring 2026, systematic tests were performed with both BLM systems to evaluate their performance, including operational challenges and limitations. The stability of the systems and the readout signals was checked in low- and high-loss scenarios and under different environmental conditions. This paper provides a brief overview of the BLM system design and machine protection functions, followed by recent beam loss measurement results obtained with beam.

Speaker: Hooman Hassanzadegan (European Spallation Source)

49 BeamNetUS: Accelerating Beam-Based Research

BeamNetUS is a collaborative user network of twelve beam test facilities spanning six U.S. Department of Energy national laboratories, dedicated to advancing particle accelerator research, technology development, and applications. Through an annual open call for proposals, BeamNetUS invites exploratory research aimed at seeding new collaborations and fostering innovation across the accelerator community and beyond.
Users gain access to state-of-the-art experimental capabilities, specialized expertise, and a diverse suite of distributed resources. The pilot run in 2025 supported a broad range of experimental awards encompassing materials science, photon source and accelerator component R&D, plasma physics, and beam diagnostics and control, including studies leveraging artificial intelligence and machine learning.
In 2026, three additional facilities joined BeamNetUS, further expanding the network’s reach and enhancing its already broad portfolio of research and development opportunities. This contribution provides an overview of the BeamNetUS program and highlights its recent progress, achievements, and future outlook.

Speaker: Aodhan McIlvenny (Lawrence Berkeley National Laboratory)

50 Comprehensive Study of the Refurbishment and Breakdown Mitigation of an SF6-Insulated Acrylic Jacket in a 750 keV Cockcroft-Walton Injector System

The reliability of high-voltage Cockcroft-Walton injector systems is strongly dependent on the performance of insulating structures operating in SF₆ environments. This work presents a comprehensive study of the refurbishment and breakdown mitigation of an SF₆-insulated acrylic jacket in a 750 keV Cockcroft-Walton injector system that exhibited persistent arc-down events due to surface tracking, material degradation, and contamination from SF₆ decomposition byproducts. A full disassembly and inspection identified surface roughening, carbon tracking, and localized defects in high-field regions as primary contributors to electrical instability. Refurbishment efforts included precision mechanical polishing of the acrylic jacket to restore surface uniformity, electro-polishing of electrodes to minimize field enhancement, and bead blasting and cleaning of the ceramic column to eliminate conductive paths across insulating gaps. Damaged components were repaired or replaced, including mitigation of a severely crazed region of the acrylic jacket through the implementation of Vespel hardware and a PEEK insulating washer to redistribute the local electric field.

Speaker: Isaac Wiens (Los Alamos National Laboratory)

51 Concept of emittance exchange using two bending magnets and two transverse deflectors at CLEAR (CERN Linear Accelerator for Research)

Second beam line has recently been installed and commissioned at CLEAR (CERN Linear Accelerator for Research). The line begins with a switchyard consisting of two dipole bending magnets that offset the beam from its original path, along with quadrupoles and sextupoles placed between the bends to close the first- and second-order dispersion, respectively. In this work, based on analytical methods and numerical simulations, we present a concept for an emittance exchange scheme realized using the switchyard. We show that transverse-to-longitudinal phase space exchange can be achieved by activating a transverse deflector located upstream, together with an additional deflector downstream (the only missing element). Furthermore, we demonstrate that such a scheme enables advanced beam phase-space tailoring and expands the CLEAR beam parameters beyond its nominal operational range.

Speaker: Alexander Malyzhenkov (European Organization for Nuclear Research)

52 Consideration on Assembly Process of a Prototype ILC Cryomodule Using 3D CAD

Under MEXT Advanced Accelerator element Technology Development (ATD) program, a prototype ILC cryomodule (CM) is being designed and manufactured at KEK. The CM consists of eight 9-cell superconducting cavities, magnetic shields, power couplers, frequency tuners, a thermal shield, cooling pipes, and a superconducting magnet for beam focusing.
Due to the large number of components and strict spatial constraints, the assembly process is complex and requires careful planning.
The entire assembly process is divided into several steps, including cavity string assembly, coupler installation, and integration into the vacuum vessel. To optimize the assembly workflow and minimize risks, assembly processes for each step are being studied using detailed 3D CAD simulations. These simulations are used to evaluate component interference, tooling accessibility, and assembly sequence efficiency. This paper reports on the results of the 3D CAD-based assembly study and discusses their implication for reliable assembly of the cryomodule.

Speaker: Takafumi Hara (High Energy Accelerator Research Organization)

53 Dark current simulation in a cryogenic photocathode gun

High-gradient photocathode electron guns, serving as electron sources for advanced linear light sources, have been fully validated to enhance the overall performance of the system. As cryogenic electron guns emerge as the future trend for ultra-compact electron sources, the extremely high electric fields within the cavity induce significantly stronger dark currents. This paper simulates this effect and proposes preliminary methods for suppressing such dark currents.

Speaker: Cheng Wang (Shanghai Synchrotron Radiation Facility)

54 Design and Development Status of the SSR2 Cavity and Cryomodule

The pre-production development of the single-spoke resonator 2 (SSR2) cavity and its associated cryomodule is underway for the superconducting linear accelerator (SCL2) at RAON. This research presents the main design parameters of the SSR2 cavity, along with analyses of the electric and magnetic field distributions. The designs of the frequency tuner and fundamental power coupler are also described. The total heat load of the cryomodule is evaluated, and the overall layout and key design features of the cryomodule are discussed.

Speaker: Heetae Kim (Institute for Basic Science)

55 DESIGN OF A MINIATURIZED P-BAND KLYSTRON RF STRUCTURE USING CAPACITIVELY LOADED COAXIAL CAVITIES

To satisfy the beam power upgrade from 100 kW to 500 kW for the China Spallation Neutron Source Phase II (CSNS-Ⅱ), 30 sets of high-efficiency and miniaturized P-band (324 MHz/648 MHz) klystrons will be deployed for the linear superconducting accelerator, with the development of fully domestic klystrons initiated. Traditional P-band single-beam klystrons adopt double-reentrant cylindrical resonant cavities, which suffer from large structural size, long tube length and high construction and maintenance costs due to the dimensional resonance effect. For klystron miniaturization, a P-band klystron RF structure based on capacitively loaded coaxial cavities is proposed as an alternative technical scheme. The structure comprises five resonant cavities, with coaxial waveguide coupling at the input and WR2300 rectangular waveguide coupling at the output, and a second harmonic cavity introduced via the CSM method. 3D particle-in-cell simulation results show that under 100 kV beam voltage, 65 A beam current and 500 W input power, the structure achieves 1.5 MW peak output power and 8.5 MHz bandwidth, with its longitudinal length reduced by ~24% compared with commercial counterparts.

Speaker: Meifei Liu (Institute of High Energy Physics)

56 Design of a Plate-type RFQ Accelerator for Ion Therapy

A new radiofrequency quadrupole (RFQ) accelerator has been designed for ion therapy at the Institute of Modern Physics, Chinese Academy of Sciences. This RFQ, operating at 162.5 MHz, accelerates carbon ions to 0.8 MeV/u. To achieve a compact RFQ with high beam transmission efficiency, an adiabatic capture design and an equal-separatrix-area technique were employed in beam dynamic design. To realize an RFQ with high quality factor, high shunt impedance, and convenient maintenance, a novel plate-type radiofrequency (RF) structure was proposed and employed in RF design. In this paper, the results of the RFQ design and simulations are reported in detail.

Speaker: Zhongshan Li (Institute of Modern Physics)

57 Design of a precision clock unit for the injection kicker pulsed power supply in the BEPCII-U storage ring

The upgrade of Beijing Electron–Positron Collider (BEPCII) is a double-ring machine used for both high-energy physics experiments and synchrotron radiation research.In order to further improve the performance of the machine, BEPCII has upgraded the brightness in the high-energy zone (BEPCII-U). As a key system in BEPCII-U, the fast Kicker pulse power supply system for storage ring injection is crucial. Its performance directly affects the injection efficiency of the machine. In the fast pulse power supply system, the precision clock unit plays an important role in triggering and pulse blocking protection of the fast pulse power supply. The fast pulse power supply requires low output time jitter, which places high demands on the precision clock unit. The designed precision clock unit uses FPGA as the main controller. The system includes a precision clock adjustment section, an output clock distribution section, and a display section. A prototype of a precision clock unit is built. Offline testing and joint debugging between systems were conducted on the prototype, and its performance meets the design specifications.

Speaker: Peng Liu (Chinese Academy of Sciences)

58 Design of Beam Transport Lines for the 200 MeV Energy Upgrade at KOMAC

The Korea Multi-purpose Accelerator Complex (KOMAC) in Gyeongju, currently operates a 100 MeV high-current proton linear accelerator. This facility actively supports a wide range of applications, including semiconductor radiation testing and fundamental scientific research. Recently, a upgrade plan has been initiated to upgrade the maximum beam energy to 200 MeV to meet increasing user demands.

Following the energy upgrade, the implementation of new target rooms and dedicated beam transport lines is essential. The current expansion plan includes two distinct target rooms: one optimized for terrestrial radiation test and the other specialized for space radiation test. This study presents the beam optics of the transport lines required to deliver the 200 MeV proton beams while satisfying the specific beam parameters requested by each target room.

Speaker: Seok Ho Moon (Korea Multi-purpose Accelerator Complex)

59 Design of H-mode DTL with PMQ for Rapid-Cycling Facility

A high-intensity rapid-cycling accelerator facility to produce the medical isotope products is proposed in China. To meet the injection requirements of the rapid-cycling synchrotron, an H-mode DTL structure with transverse focusing is adopted to compensate the space-charge effect and maintain high beam quality. In this paper, the physical design of the drift tube linac (DTL) is presented. A novel design method for DTL accelerators, which enable rapid global optimization of all cavities and efficient evaluation of multiple cavity parameters, is introduced first time. Beam dynamics simulation results show that the designed beam transmission 100% was obtained with the low emittance growth.

Speaker: Guoxin Chen (Institute of Modern Physics, Chinese Academy of Sciences)

60 Design of the Positron Linac for the FCC-ee Injector Complex

The FCC-ee injector complex is mainly composed of an electron source, a positron source, a damping ring, and a high-energy linac. The positron linac, which is part of the positron source, accelerates the positron beams from about 200MeV to 2.86 GeV before their injection to the damping ring. It is designed, simulated and optimized for the best positron beam performance at the end of the linac with a maximized positron yield for positrons accepted by the damping ring. The required bunch charge at the end of the Positron Linac is 13.5 nC, assuming a 50% loss in the damping ring and an additional loss of 20% positrons from the target exit to the damping ring entrance. A chicane collimator is used to dump electrons and photons from the upstream Capture Linac. The Positron Linac is composed of two sections, where NC solenoids surrounding the accelerating structures with 0.5 T magnetic field and FODO cells with quadrupoles placed between the structures are used for beam focusing. A 3 m long RF accelerating structure working at 2 GHz is used. RF gradients and phases are optimized for a maximum positron yield. Imperfections are studied and the impact is found to be negligible.

Speaker: Yongke Zhao (Zhangjiang Laboratory)

61 Design Study of a Large-Aperture Capacitive Pick-up Type Bunch Shape Monitor for Nonrelativistic Ion Beams

The longitudinal bunch shape is important for beam dynamics and accelerator optimization. In our previous study, a capacitive pick-up type bunch shape monitor (CPU-BSM) was developed for nondestructive measurement of nonrelativistic ion-beam bunch shapes. However, beamline applications may require a larger aperture due to beam size, alignment tolerances, and installation constraints. In this study, a large-aperture CPU-BSM was designed using CST Studio Suite, and the effects of enlarged aperture on the input beam–signal response correlation were evaluated. As the distance between the beam and the pick-up electrode increased, the resulting changes in signal amplitude and frequency response were analyzed. In addition, impedance matching was optimized to minimize signal distortion. Subsequently, a reconstruction algorithm for the large-aperture pick-up geometry was newly developed and applied. This study evaluates the feasibility of a large-aperture CPU-BSM and provides a basis for applying CPU-BSMs to various beamline conditions. Finally, we discuss the electronics and control system for the large-aperture CPU-BSM and its application to longitudinal phase-space tomography at RAON.

Speaker: Changsun Na (Pohang University of Science and Technology)

62 Development of a 500 MHz RFQ Linac for the Transportable Compact Neutron Source System RANS-III

The accelerator-driven compact neutron source systems RANS and RANS-II have been operated at RIKEN for many years. To enable on-site applications, the development of a transportable neutron source system, RANS-III, has been initiated, requiring significant reductions in size and weight for automobile transportation. To meet this requirement, a compact four-vane RFQ linac operating at 500 MHz was developed. The 500 MHz RFQ was designed to accelerate protons to the same output energy as the RANS-II RFQ to achieve a similar neutron energy spectrum. The design reduces the cavity diameter to approximately half that of RANS-II and the total weight to about one third. The total required RF power is 300 kW, supplied by four independent 75 kW amplifier subsystems to reduce RF voltage at each coupler port. The RFQ linac was fabricated, integrated with the ion source, and beam commissioning demonstrated proton acceleration. The accelerator system was installed on a trailer, transported to an indoor test facility, and neutron production was achieved by bombarding a lithium target. This paper reports the design concept, RF system, and commissioning results of the 500 MHz RFQ linac for RANS-III.

Speaker: Dr Shouta Ikeda (Institute of Science Tokyo)

63 Development of a Digital LLRF Control System for KAHIF RFQ

The Heavy-ion Irradiation Facility (KAHIF) RFQ is transitioning its Low-Level RF (LLRF) infrastructure from a legacy analog system to a modern digital architecture to enhance the stability of its 25.96 MHz pulsed operation. The existing analog system faces limitations in precise phase regulation and compensation for the nonlinear pulse droop inherent in its vacuum tube amplifier chain.

This paper presents the design and verification of a digital LLRF controller featuring a purely electronic Auto Frequency Control (AFC) loop and a hybrid Feedforward-PID amplitude control logic. A key contribution of this work is the development of a high-fidelity RLC equivalent circuit model that serves as the physical plant in an integrated closed-loop simulation environment. Simulation results demonstrate that the digital architecture robustly tracks resonance deviations and mitigates amplifier-induced instabilities, ensuring superior field stability. This study provides the essential technical foundation for the subsequent FPGA-based hardware implementation.

Speaker: Sangbeen Lee (Korea Atomic Energy Research Institute)

64 Development of a High-Power Traveling Wave Resonant Ring for SRF Linac Applications

The reliable operation of high-power RF components, including superconducting cavity input couplers and RF windows, is critical for superconducting radio-frequency (SRF) accelerator facilities. Prior to installation into accelerator systems, these components typically require high-power conditioning to verify their RF performance and thermal stability. However, establishing megawatt-level RF test facilities is challenging due to the complexity and limited availability of high-power RF sources.To address this challenge, the Institute of High Energy Physics (IHEP) has developed a 650 MHz traveling-wave resonant ring (TWRR) system,which enables megawatt-level circulating power by accumulating RF energy in a closed-loop structure with a relatively low-power RF source.The system was tested under high-power CW operation. A circulating power of approximately 1.2 MW was achieved with an injected RF power of only 42.7 kW.Stable continuous-wave operation was maintained for 8 h without interruption.These results demonstrate the feasibility of MW-level CW RF conditioning using a compact TWRR and provide an effective test platform for future CEPC RF components.

Speaker: fanyu wang (Institute of High Energy Physics, Chinese Academy of Sciences)

65 Development of a Prototype RF Absorbing Load for High‑Power Accelerator Applications

A prototype RF absorbing load has been designed at the Pohang Accelerator Laboratory to stably absorb multi‑megawatt peak power and several kilowatts of average power. Conventionally, silicon carbide (SiC) loads have been widely employed for residual RF power absorption. In this study, however, a different approach was adopted by coating an absorbing material onto an aluminum structure, thereby enabling effective RF absorption along with enhanced thermal conduction. The proposed dry load was designed with target specifications of 2.856 GHz operating frequency, 1 μs pulse width, 30 MW peak power, input VSWR of less than 1.1, and a repetition rate of 120 Hz. The total length of the load is 1.1 m, and the structure consists of six wedge sections and two taper sections to ensure efficient impedance matching and power attenuation. Following fabrication, cold tests were conducted, confirming that the measured RF characteristics satisfy the design requirements. Subsequently, high‑power tests were performed at a repetition rate of 60 Hz with a peak power of 32 MW. In the following sections, the experimental results obtained to date are presented and discussed in detail.

Speaker: Kwanghoon Kim (Pohang Accelerator Laboratory)

66 Development of a Resonance Laser Ionization System at RAON

The resonance ionization laser ion source (RILIS) has become the most-used ion source type in the ISOL (Iso tope Separator for On-Line) facilities worldwide due to its element selectivity and high ionization efficiency. The hot-cavity type RILIS developed at RAON is based on resonant excitation of atomic transitions by the frequency tuned laser beams which are overlapped temporally and spatially and transported to the 3 mm aperture of the hot-cavity. The RILIS laser system consists of 4 Ti:Sapphire lasers pumped by a 100 W Nd:YAG laser at 10 kHz repetition rate. An additional Nd:YAG laser of 10 W with 10 kHz is also fitted up for off-resonance ionization scheme. For the laser ionization scheme study, the RAON RILIS has been already tested with stable Sn isotopes in the off-line test facility, demonstrating the improved ionization efficiency.
This presentation reports on ongoing Mg and Al ion beam studies for the development of a resonance ionization laser ion source at the IRIS ISOL facility.

Speaker: Ha-Na Kim (Institute for Basic Science)

67 Development of a robotics system for SRF cavity assembly in a cleanroom at KEK

Contamination by particulate matter, such as dust and debris, during the assembly of SRF cavities and their associated components can significantly degrade cavity performance due to thermal losses and field emission. Therefore, it is essential to suppress both the generation and intrusion of particulates in addition to maintaining a clean environment. Human activity is a dominant source of particulate contamination in cleanrooms. To reduce contamination arising from human intervention, robotic systems have been introduced for SRF cavity assembly in a cleanroom environment. Simple assembly motions relevant to cavity assembly have been demonstrated using a direct teaching method. Based on these results, we have developed a simulation-based control framework and generated robot motions within the simulation environment. The simulated motions were transferred to the real system and validated experimentally. Using this framework, we are advancing its application to actual SRF cavity assembly tasks. This paper presents the current status of the study and future prospects for the development of robotic assembly systems at KEK.

Speaker: Dr Yuki Abe (High Energy Accelerator Research Organization)

68 Development of new metal ion beams from high current VARIS source at GSI

The heavy ion accelerator facility GSI (Darmstadt, Germany) is internationally recognized as a unique center for research, offering over 100 different ion species derived from 34 chemical elements, ranging from hydrogen to uranium. Scientific experiments utilizing high-energy ion beams provided by the heavy ion synchrotron SIS-18 are typically served by pulsed high-current ion sources. Currently, 28 elements (8 gaseous and 20 metallic) are available for operation using high-current ion sources. Metallic ion beams are generated with vacuum arc-driven ion sources (VARIS).
The improvement and development of VARIS is continuously pursued in parallel with routine accelerator operation. In recent years, VARIS development has focused on the production of new elements and ion species as requested by experimental programs. This paper presents the results of high-current beam development for the following ion species: 45Sc²⁺, 94Mo³⁺, 100Mo²⁺/³⁺, 112Sn²⁺, 141Pr³⁺, 160Gd³⁺, 170Er³⁺, 186W³⁺/⁴⁺, and 198Pt⁴⁺. In addition, an outlook on future development plans is provided.

Speaker: Dr Aleksey Adonin (GSI Helmholtz Centre for Heavy Ion Research)

69 Development of Third Harmonic Cavity Cryomodule for HALF

The Institute of High Energy Physics (IHEP) developed the 1.5 GHz third harmonic cavity system for the Hefei Advanced Light Facility (HALF) project. This paper primarily introduces development and test results of the 1.5 GHz cavity and cryomodule. The structure of the harmonic cavity has been simplified, and an integral welding method for the cavity with helium vessel has been adopted to enhance operational reliability.

Speaker: ZHENGHUI Mi (Chinese Academy of Sciences)

70 Direct Measurement of Piezo Stroke at Cryogenic Temperature Using a Laser Displacement Sensor

Piezoelectric actuators are widely used in SRF accelerators to compensate for Lorentz force detuning. Since the stroke (displacement) of piezo actuators decreases at cryogenic temperature, accurate evaluation under operating conditions is important. Existing approaches either use the SRF cavity response as an indirect indicator or estimate the stroke from capacitance measurements during cool-down. These methods do not measure the actuator stroke directly and involve trade-offs in precision, complexity, cost, and measurement time.
To address this, we developed a setup* for direct measurement of piezo actuator displacement at cryogenic temperature using a laser displacement sensor inside a cryocooler-cooled cryostat. The system was used to characterize two piezo actuators for the MEXT-ATD cryomodule. In this contribution we present the details of the direct stroke measurement setup and its comparison with the capacitance measurement approach.

Speakers: Dr Rishabh Bajpai (High Energy Accelerator Research Organization), Mathieu Omet (High Energy Accelerator Research Organization)

71 Emittance investigations at the ESS LINAC

The European Spallation Source (ESS) is in the final stages of commissioning its linear accelerator (linac), which aims to deliver a high-power proton beam for neutron production. Understanding the dynamics in the machine and comparing measurements with the model can provide a deeper insight into the machine’s performance and help avoid possible issues when we start ramping up the power. Several techniques are available for measuring both transverse and longitudinal emittance, making comparison and benchmarking important. At ESS, existing transverse emittance measurements show some variation between methods and differ from the design values. This work investigates possible sources of these discrepancies. In addition, the feasibility of deriving the longitudinal emittance using available beam diagnostic tools at the ESS linac is explored.

Speaker: Sofia Johannesson (European Spallation Source)

72 Estimation of BSM resolution in the Fermilab Linac

The Fermilab Linac delivers 400 MeV H- beam to the Booster rapid cycling synchrotron. Longitudinal dynamics in the Linac affects the beam losses in the Linac itself as welll as at the Booster. To understand better the longitudinal beam properties, two bunch shape monitors (BSM) in the Linac transition section where RF frequency changes from 201 MHz to 805 MHz, were recently brought back to operation.. A technique was developed to estimate the resolution of the BSMs directly from measurements by scanning the focusing/deflecting DC voltage of the deflecting plates and RF deflector phase. The estimations made for the Linac’s BSMs are correlated with known mechanical BSM details. The effect of finite resolution on the bunch length measurements is discussed.

Speaker: Ralitsa Sharankova (Fermi National Accelerator Laboratory)

73 Evolution of f-Divergence Between High-Dimensional Phase Space Distributions During Beam Transport

F-divergence can be used to precisely quantify the differences between beam distributions in high-dimensional phase space, as it comprehensively captures the total contribution of discrepancies from all points in phase space. Current applications of f-divergence are primarily confined to the static comparison of distributions. This paper aims to investigate its evolution during beam transport. We mathematically prove that f-divergence remains invariant in both linear and nonlinear transport processes, and validate this conclusion through beam transport simulations. Further research indicates that space charge forces can break this conservation. We show how this property of f-divergence can be used as a tool to help us understand, predict, or control beam degradation caused by space charge effects.

Speaker: Yu Du (Institute of Modern Physics, Chinese Academy of Sciences)

74 Fault Tree Modeling and Reliability Analysis of the CAFE2 Accelerator

The CAFE2 accelerator, upgraded from CAFe at IMP, supports superheavy element research. Based on the RAMI framework, this paper decomposes CAFE2 using PBS and applies fault tree analysis at system, subsystem, and equipment levels to identify beam trip events. Historical data show that the superconducting section and control system are the main causes of beam losses. Although CAFE2 has high beam availability, systematic reliability modeling is needed. A preliminary fault tree model is established, and future work will refine it with collected fault data to improve operational stability.

Speaker: Xin Ma (Chinese Academy of Sciences)

75 Feasibility study of a laser-plasma injector for PLS-II storage ring

The linear accelerator of the PLS-II in Pohang has been in operation for approximately 30 years, leading to performance degradation and stability issues. To address these challenges, this study proposes a storage ring injector based on a laser-plasma accelerator (LPA), capable of generating GeV-class electron beams with high accelerating gradients, and analyzes its feasibility. Assuming an electron beam is generated by an LPA, its longitudinal properties are controlled by passing it through an injector composed of quadrupoles, a magnetic chicane, and an RF cavity. In particular, an energy chirp is introduced via the magnetic chicane and subsequently compensated by the RF cavity, thereby reducing the energy spread and minimizing energy jitter. In addition, key parameters such as the strength of the chicane, the spacing between dipoles, and the RF power and phase are varied to determine the optimal conditions for injector operation. Through this approach, the feasibility of injection into the 3 GeV PLS-II storage ring is quantitatively analyzed, and the potential to significantly reduce the spatial footprint compared to conventional linear accelerators is evaluated.

Speaker: Soyeon Kim (Ulsan National Institute of Science and Technology)

76 Features of long particle bunch self-modulated in plasma

Plasma wakefield acceleration is a promising method of accelerating charged particles based on the excitation of strong electric fields in plasma. These fields arise when a driver, such as a particle beam or a laser pulse, propagates through the plasma and displaces electrons, forming a wave with accelerating gradients far exceeding those of conventional accelerators. In this work we study the case of a particle beam driver much longer than the plasma wavelength. Under these conditions the self-modulation instability develops, causing the beam to split into a sequence of microbunches. Using numerical simulations with the two-dimensional quasi-static code LCODE*, we investigate the properties of the formed microbunch train and its contribution to the excited wakefield. Based on these results, an analytical model describing the radial density profile of the microbunches is developed. The model predictions are in very good agreement with the simulation results. The analysis shows that the beam evolves into microbunches with a sharply peaked radial density distribution, differing from the initial Gaussian profile, which significantly increases the efficiency of wakefield excitation.

Speaker: Vlada Yarygova (Budker Institute of Nuclear Physics)

77 FPGA Machine Learning for ESS Beam Diagnostics using Vitis AI DPU and hls4ml on Xilinx Versal Board

In collaboration with the European Spallation Source (ESS) and Riga Technical University, we wanted to explore real-time ML model inference on FPGAs for beam waveform classification. To identify a viable solution, we evaluated two ML toolchains on the Xilinx Versal VCK190 adaptive SoC. The first uses the Vitis AI toolchain to integrate the DPUCVDX8G deep learning processing unit and 64-tile AI Engine in the Versal programmable logic. A custom ResNet50 retrained for seven beam waveform classes from the beam position monitor is compiled with Vitis AI framework and deployed at runtime. The second uses the hls4ml framework to convert a CNN-GRU Keras classifier trained on the same seven-class dataset to HLS C++ IP blocks. The model is partitioned into four AXI-Stream blocks to fit synthesis memory, with fixed-point quantization validated against the Keras reference. The Vitis AI toolchain achieved full hardware deployment with measured inference of 2-4 ms. The hls4ml IP blocks fit on the Versal FPGA with synthesis-estimated inference in the tens of microseconds, theoretically outperforming the DPU approach in latency, though demanding greater FPGA resource utilization.

Speaker: Ziga Kroflic (Cosylab)

78 Generative Phase-Space Reconstruction for Low-Intensity Beam Characterization in the J-PARC Muon Linac MEBT Line

The J-PARC Muon Linac is being developed for precision measurements of the muon anomalous magnetic moment and the search for the muon electric dipole moment using a reaccelerated thermal muon beam. The Medium Energy Beam Transport (MEBT) line, planned for commissioning in 2027, will transport and match the muon beam to the Inter-digital H-mode drift tube linac (IH-DTL). Because the expected muon intensity is extremely low, conventional destructive and scan-based phase-space diagnostics are challenging. In this study, phase-space characterization methods for the J-PARC Muon Linac MEBT are investigated using MCP-based beam profile monitors composed of a microchannel plate, phosphor screen, and camera. Low-intensity muon beam projections are used for quadrupole-scan analysis and machine-learning-based prediction. A differentiable simulation code is combined with a generative neural-network beam model to reconstruct transverse phase-space distribution from downstream profile images at different quadrupole settings. The results indicate that MCP profile measurements with generative reconstruction provide a promising approach for MEBT beam characterization and commissioning.

Speaker: Emre Cosgun (High Energy Accelerator Research Organization)

79 GeV scale electron beam generation by a downramp injection with a waveguide structure for laser wakefield accelerations

Laser wakefield acceleration (LWFA) enables compact accelerator with accelerating gradient of GV/cm scale in the wakefield in the plasma excited by ponderomotive force of intense laser. We used the waveguide to increase interaction length and downramp injection method to control the injection which results in electron beams with GeV scale energy and low energy spread. However, to combine the downramp into the plasma waveguide, it is difficult to optimize a matched spot size during the propagation due to its nonlinear characteristics that strongly affect the electron beam quality. We used the dynamic matched spot size profile in the first and second plasma region rather than fixed value on the particle-in-cell (PIC) simulation. We found that optimum plasma density profile with the dynamically matched spot size for the waveguide. Simulation results shows the electron beam with 2.5 GeV and energy spread of less than 1.0 % (rms) with matched spot size as compared with a misaligned case.

Speaker: Hyeon Myeong Jeong (Ulsan National Institute of Science and Technology)

80 High-Power Testing of an X-Band Dielectric Assist Accelerating Structure under Short-Pulse RF Excitation

The dielectric assist accelerating (DAA) structure is a power-efficient RF accelerating cavity. A room-temperature C-band DAA structure has demonstrated a high shunt impedance of approximately 600 MΩ/m. Nevertheless, the attainable accelerating field in DAA structures has so far been limited to approximately 10–12 MV/m, mainly because of RF breakdown-related phenomena, including multipacting.
To increase the achievable accelerating field, we have investigated short-pulse RF excitation in DAA structures. This approach is motivated by recent studies of dielectric disk accelerating structures, in which an accelerating gradient exceeding 100 MV/m was achieved under short-pulse operation.
We have developed a two-cell X-band standing-wave DAA structure employing sapphire cells coated with hydrogenated amorphous carbon. High-power RF tests have been carried out at Nextef2 in KEK. We tested different RF pulse conditions, including single RF pulses shorter than the cavity filling time and step-pulse inputs, and achieved an accelerating field of up to 16 MV/m.
In this presentation, we will describe recent efforts toward higher-gradient operation.

Speaker: DAISUKE SATOH (National Institute of Advanced Industrial Science and Technology)

81 Introduction to a Three-Dimensional Multi-Particle Simulation Code for Linear Accelerators

With the rapid advancement of high-intensity linear accelerators, achieving efficient and accurate design has become a critical challenge in modern accelerator physics. As beam intensity increases, the space charge effect — arising from the mutual repulsion among charged particles within the beam — becomes increasingly significant and must be incorporated into realistic simulations. In this paper, we develop a comprehensive multi-particle simulation program specifically tailored for linear accelerators. The program employs a novel three-dimensional space charge solver based on the tensor decomposition method, which offers both high computational efficiency and numerical accuracy. To validate the proposed program, we apply it to simulate the linear section of the China Spallation Neutron Source (CSNS). The simulation results are systematically compared with those obtained from Tracewin, a well-established beam dynamics code. Good agreement between the two sets of results demonstrates the effectiveness and reliability of our developed simulation program.

Speaker: Jiayin Du (Institute of High Energy Physics)

82 L-band gun development and operation at DESY

Gun5, the new generation of normal-conducting 1.3 GHz RF guns for high-gradient and long-pulse operation at DESY’s linac driven free-electron lasers is in operation at PITZ and European XFEL. The improved gun design allows for RF pulse durations of up to 1 ms at 10 Hz repetition rate, at gradients of ~60 MV/m at the cathode. Special features are two RF pickups for RF regulation and a symmetric power coupler to reduce RF asymmetries.
Four cavities of the Gun5 type have already been produced, and three of them have been tested at PITZ. Two guns are currently in operation at PITZ and the European XFEL. This article will give an overview on the operation experiences with these gun cavities.

Speaker: Dr Anne Oppelt (Deutsches Elektronen-Synchrotron DESY)

83 L4-RFQ2 RF conditioning and breakdown localization studies

CERN's Linear Accelerator 4 (Linac4) is an H⁻ accelerator that has been in operation since 2020. After acceleration, the ions are converted to protons via electron stripping and sent downstream to various experiments on the CERN site. Its first accelerating structure is a 3 m long Radio-Frequency Quadrupole (RFQ), operating at 78 kV inter-vane voltage and a peak surface field of 34 MV/m. In 2025, a dedicated campaign was conducted to condition and test the recently constructed spare RFQ, providing the opportunity to study vacuum breakdown behavior in this complex structure.
This work presents high-power RF conditioning results to improve the understanding of breakdown limitations in the new RFQ. It also focuses on localizing breakdown events using signals from 16 pick-ups distributed along the cavity. These measurements are compared with RF simulations to correlate signal patterns with breakdown locations and provide insight into the underlying physical mechanisms.

Speaker: Pablo Martinez Reviriego (European Organization for Nuclear Research)

84 Leveraging AI Tools in RF and SRF Operations at FRIB

RF and SRF operations require rapid decisions under tight time constraints while navigating machine data, logs, procedures and institutional knowledge. In many troubleshooting scenarios, the bottleneck is not diagnostic signal availability, but the time required to gather context, reconstruct event timelines, communicate status and transfer knowledge across shifts. This talk presents how AI can streamline RF/SRF operations while preserving engineering judgment. It focuses on document-grounded querying, multimodal interpretation of plots, screenshots and workflow acceleration for shift summaries, issue tracking and status reporting. Three use cases: faster trip triage, raw data processing and visualization and documentation, showing how AI can help convert scattered data into structured timelines, checklists and quick-reference guides. Responsible deployment is emphasized, with AI outputs treated as drafts and decision-support artifacts verified by personnel, measurements and procedures. Future work will describe a four-level LLM wiki framework for an RF/SRF “brain”: events/raw data acquisition, data cleaning/analysis/visualization, documentation and knowledge generation.

Speaker: Shriraj Kunjir (Facility for Rare Isotope Beams)

85 Machine Learning Applications for Beam Diagnostics and Automated Tuning at CLEAR

Machine learning (ML) is increasingly recognized as a fundamental tool in modern accelerator physics, offering new capabilities to complement and extend traditional analytical approaches. A structured programme of ML studies has been initiated at CLEAR (CERN Linear Electron Accelerator for Research), covering three principal directions: beam diagnostics, charge forecasting, and automated tuning via reinforcement learning. Deep learning models were explored to reconstruct transverse beam profiles from indirect measurements, offering a pathway toward radiation-resistant non-invasive diagnostics. Classical and deep learning approaches were benchmarked for charge prediction, demonstrating the potential for accurate real-time beam characterization. A reinforcement learning framework was interfaced with the CERN control infrastructure, enabling proof-of-principle autonomous beam steering through iterative magnet corrections. These results demonstrate the feasibility of integrating ML into routine CLEAR operations and position the facility as an attractive testbed for the development and validation of machine learning techniques for particle accelerators.

Speaker: Antonio Gilardi (European Organization for Nuclear Research)

86 Maximum Entropy Tomography for Nonlinear Beam Transport: 4D Transverse Phase Space Reconstruction at CAFE2

This work extends the Maximum Entropy Tomography (MENT) framework from linear to nonlinear beam transport. This nonlinear MENT method enables high-accuracy phase space reconstruction where nonlinear effects are significant, such as for the intrinsically nonlinear longitudinal dynamics in RF hadron linacs and in front ends where elements exhibit large, overlapping fringe fields.
Following numerical verification, the method was successfully applied to reconstruct the full 4D transverse phase space in the MEBT of the CAFE2 accelerator at IMP. Coupling information was acquired via quadrupole scans​ with the perpendicular-scan technique, and the reconstruction explicitly incorporated nonlinear transport effects. The results show significantly improved agreement with measured data compared to a linear model, thereby validating nonlinear MENT as a general framework and demonstrating its value as a practical tool for high-fidelity diagnostics. This capability is crucial for precise beam prediction and control, with direct applications in modern hadron linacs and potential utility in other accelerator domains.

Speaker: Liwen Liu (Institute of Modern Physics, Chinese Academy of Sciences)

87 Mixed or dual carbon and helium ion beams for heavy ion radiotherapy and radiography – recent advances and ideas

A mixed C/He ion beam with varying helium fraction has been investigated at GSI to study a new mode of image guidance for carbon ion beam therapy. “Mixed” refers to a beam with C and He ions extracted simultaneously from a single ion source (CAPRICE ECR) provided for the subsequent UNILAC-SIS18 accelerator complex during two previous beam times (¹²C³⁺/⁴He⁺ beam). Both ion species were simultaneously accelerated and extracted from SIS18 and characterised in the biophysics cave. Further combinations (¹²C³⁺/⁴He⁺ and ¹²C⁴⁺/³He⁺ from CH4 or CO2) were investigated at the ECR test bench with respect to beam currents, stability, and the C-to-He fraction, as determined by optical emission spectroscopy and mass spectrometry. All configurations met the requirements, but some with a residual oxygen contamination. The sequential injection of two different, i.e. “dual” ion beams, and the simultaneous acceleration and extraction, were successfully demonstrated at the UNILAC-SIS18. This opens the way for new modes of dual C/He oxygen-free beam operation. Some concepts are discussed for providing C/He ion beams for future beam times; either from two separate ion sources or a single ion source.

Speaker: Michael Galonska (GSI Helmholtz Centre for Heavy Ion Research)

88 Optics model of the 805 MHz section of the Fermilab Linac

The Side-Coupled Linac (SCL) section of the FNAL Linac accelerates the 20-25 mA H- beam from 116 MeV to 402 MeV in 7 modules. All major components of this section are re-calibrated using beam-based measurements. Module gradients and phases are determined from the phase scans. Longitudinal bunch parameters at the entrance of the section are reconstructed using a Bunch Shape Monitor. Calibrations of quadrupoles and correctors are improved using differential trajectories. Initial beam conditions are deduced from quadrupole scans. Using the model, the beam envelope along the SCL section is predicted using the TraceWin code and compared with measurements by wire scanners.

Speaker: Alexander Shemyakin (Fermi National Accelerator Laboratory)

89 Optimization of a cooling system for the IPHI RFQ upgrade

The IPHI RFQ, designed at CEA in the early 2000s and commissioned in 2016, was the first RFQ developed at CEA. It accelerates a 100 mA beam up to 3 MeV at high duty cycle. Subsequent RFQ projects (SPIRAL2, LINAC4, ESS) enabled improvements in RFQ design and modeling.
Based on this experience, an upgrade of the IPHI accelerator has been investigated to increase beam energy and improve efficiency. The proposed design is a 6 m long, four-vane RFQ, divided into six 1 m sections, constrained to operate with the existing RF amplifiers (352.21 MHz, 1.8 MW peak power, 70% duty cycle).
Under these conditions, RF power losses in the cavity walls reach about 1 MW and must be removed by a cooling system. The spatial distribution of the cooling channels impacts thermal expansion, leading to local deformations and associated cavity detuning. These effects must be controlled to ensure the electric field distribution remains consistent with beam dynamics requirements.
This paper presents the method used to optimize the cooling channel layout and its impact on RF performance. The final design achieves a detuning below 20 kHz and an intervane voltage error below 0.1%.

Speaker: Pierrick Hamel (Commissariat à l'Energie Atomique)

90 Optimization of low-energy-contributing power source positions during the BEPCII Linac energy upgrade

BEPCII Linac operated with 20 power sources before the energy upgrade in summer 2024. To support sustained 2.35 GeV electron-positron collisions and maintain at least one redundant power source for operational reliability, the Linac required an energy increase. Among these, Power sources No. 6 (K6) and No. 12 (K12) exhibited relative lower energy contribution. Phase-matching misalignment between adjacent accelerating structures was identified as the most probable cause after checking the peak power gain of pulse compressors, the input power reflection of accelerating structures, and the total transmission loss. During the energy upgrade, the microwave phase at the input of K6’s accelerating structure was directly measured and adjusted—increasing K6’s net energy gain significantly. However, no corresponding work was carried out on K12 due to the recovery issues after vacuum destruction. As an engineering solution, one additional pulse compressor was installed at K4, and both K6 and K12 were upgraded from single-klystron to dual-klystron configurations. This strategy ensured stable, high-luminosity operation—directly enabling BEPCII to achieve its target luminosity in April 2026.

Speaker: Xiang He (Institute of High Energy Physics, Chinese Academy of Sciences)

91 Performance Comparison of TeX Preprocessing Methods and Embedding Models for RAG on RAON Control System Technical Notes

RAON uses EPICS to integrate local control systems into central control. Technical notes for system installation and management are documented in TeX format and managed with relevant code and files in a Git-based configuration management environment on an internal network. This study examines the applicability of Retrieval-Augmented Generation (RAG) to control system technical documents for the introduction of AI technologies in control infrastructure.

TeX documents were converted into formats such as Markdown under multiple preprocessing scenarios with different metadata augmentation and chunk segmentation conditions. Different embedding models were applied to construct vector databases. Relevant queries were designed, and performance was compared in terms of retrieval accuracy and contextual relevance. This study aims to evaluate the feasibility of applying RAG to EPICS technical documents and to suggest directions for building a retrieval framework for TeX-based documentation.

Speaker: Won Hee Min (Chungnam National University, Institute for Basic Science)

92 Preliminary Design of an RF-focused Interdigital Drift Tube Linac

The development of compact and efficient low-energy linear accelerators is crucial for advanced scientific and medical applications. While H-mode Drift Tube Linacs (DTL) offer superior shunt impedance compared to conventional Alvarez structures, they traditionally suffer from transverse defocusing and longitudinal instability when operating at a 0$^\circ$ synchronous phase. This paper presents the comprehensive design and beam dynamics study of a Radio-Frequency Focused Interdigital (RFI) H-mode DTL. By modifying the drift tubes to include internal pole tips, transverse quadrupole focusing is achieved directly via the RF fields, eliminating the need for internal magnetic lenses. We evaluate three transverse focusing lattices (FDFD, FFDD, and FFFDDD) using TraceWin, determining the optimal balance between beam transmission and required focusing voltage. Furthermore, to address the inaccuracies of standard simulation tools in handling time-varying RF fringe fields, a customized 3D-field-based longitudinal optimization program was developed.

Speaker: Qi Yu Kong (Dongguan Neutron Science Center)

93 Preparation of subsystems for beam extraction from 28 GHz ECR Ion Source

Preparation of the major subsystems is underway for the beam extraction test of the 28 GHz ECR ion source under 18 GHz operating conditions. For the superconducting magnet, ramp-up tests are being conducted to ensure stable operation under the target operating conditions. For plasma generation, the gas injection system and the RF injection system using an 18 GHz klystron are being prepared. Beamline components, such as ESQs and solenoids, are being checked for transport of the extracted beam. An EPICS-based control environment and user interface are being developed for integrated operation of the entire system. This poster summarizes the preparation status of the superconducting magnet, RF system, gas injection system, beamline components, and control system.

Speaker: Dr Eunhun Im (Institute for Basic Science)

94 Present status of Kyoto University Free Electron Laser facility

Kyoto University Free Electron Laser (KU-FEL) facility has been developed for energy-related research by the Institute of Advanced Energy, Kyoto University. There are two accelerator-driven infrared coherent light sources in the facility. One is the oscillator-type FEL whose wavelength range is 3.4 to 26 micro-m. The other one is the THz-Coherent Undulator Radiation (THz-CUR) source whose frequency range is 0.1 to 0.4 THz*. In addition to the accelerator-driven light sources, several solid-state laser sources can be used together. The facility is open to domestic and international users. In fiscal year 2026, 21 external user groups will use the facility for their research. The current status and results of recent upgrade projects for improving the performance of the light sources will be presented.

Speaker: Heishun Zen (Kyoto University)

95 Progress of the intense uranium beam DTL project Alvarez 2.0 at GSI

The Alvarez-type post-stripper DTL at GSI accelerates intense ion beams with A/q≤8.5 from 1.4 to 11.4 MeV/u. After more than 45 years of operation, it suffers from aging and its design does not meet the requirements of the upcoming FAIR project. Series production of the new DTL Alvarez 2.0 is ongoing. In 2025, the last out of 25 cavity sections, forming five cavities, underwent the site acceptance test. Eight of them have been copper plated at GSI’s in house galvanic work shop with a rate of about 2.5 month per section. All 188 drift tubes have been ordered. Production of about 70 tubes is completed as well as copper plating of about 60 of them at CERN’s galvanic work shop. Forty drift tubes have been installed inside of the cavity sections. This year shall see the assembly of at least one cavity from five single sections. Production of many small parts is completed to a large extend. This contribution summarizes the actual project status and its perspectives.

Speaker: Lars Groening (GSI Helmholtz Centre for Heavy Ion Research)

96 Prototype drift tube development for separated drift tube linac

As a possible option for 200 MeV energy upgrade in Korea Multi-purpose Accelerator Complex (KOMAC), separated drift tube linac (SDTL) type is considered. In this study, a prototype drift tube for the SDTL is developed and tested. Based on the optimum cell parameters, detailed design of drift tube is derived. Especially, cooling channels of the drift tube consist of central and side channels to deal with RF heat load due to its long length. To verify the feasibility of the drift tube, prototype model is manufactured and its functional validity is confirmed by conducting coolant flow test in cooling channel and leak test for vacuum. In addition, multi-physics analysis on the drift tube including electromagnetic, thermal, and mechanical analysis are conducted. Characteristics of the drift tube in SDTL tank are assessed in the view of temperature rise, displacement, and frequency detuning.

Speaker: Sungbin Park (Korea Multi-purpose Accelerator Complex)

97 Reinforcement Learning-Based Orbit Correction in the RAON LEBT and MEBT Beamlines

Precise orbit control in low- and medium-energy beam transport sections is essential for efficient beam delivery in heavy-ion linacs. In the RAON accelerator, the LEBT and MEBT sections are strongly affected by space charge effects, nonlinear beam dynamics, and variations in beam conditions, limiting the performance of conventional correction methods. In this work, we develop a reinforcement learning (RL)-based orbit correction framework supported by a machine learning surrogate model trained on large-scale beam dynamics simulations. The surrogate provides fast predictions of beam centroid responses under varying magnet settings, enabling efficient RL training. We investigate multiple continuous-control algorithms to learn optimal correction strategies in a high-dimensional action space. The trained policies are validated using high-fidelity simulations and demonstrate robust convergence and effective orbit centering across diverse conditions. The framework is applied to both LEBT and MEBT, confirming scalability to more complex beamline configurations. These results highlight the potential of RL-based methods for automated and adaptive orbit correction in heavy ion linac systems.

Speaker: Chong Shik Park (Korea University Sejong Campus)

98 Research and Analysis on a C-Band Travelling Wave Cavity

Enhancing the accelerating gradient of electron linacs reduces facility size and cost. For the 100-km CEPC Higgs-factory ring, injector linac gradient is a critical parameter because, once final beam energy is fixed, accelerating gradient determines linac length and strongly influences overall system design. C-band accelerating structures are considered for the CEPC high-energy injector section to accelerate the beam to 30 GeV. A robust high-gradient design requires optimization of a constant-gradient traveling-wave structure with suitable phase advance and iris thickness from 3.5 mm to 6.0 mm to balance wakefield suppression, RF efficiency, and RF breakdown stability. This work systematically analyzes four operating modes and optimizes key RF and geometric parameters. The results reveal important trade-offs among accelerating efficiency, wakefield control, and breakdown mitigation, providing a practical design baseline for elliptical-iris C-band high-gradient linacs for future CEPC applications.

Speaker: GHAZAL RAO (Institute of High Energy Physics)

99 Research on High-Intensity Proton IH-DTL Accelerating Structure Based on APF

High-intensity proton linacs are crucial in spallation neutron sources（SNS）, compact accelerator-driven neutron source (CANS), proton therapy, together with other facilities that require higher beam intensity as the development of application systems. To meet the research and engineering demands of high-intensity pulsed proton linacs, a structure consisting of modular APF IH-DTLs and external magnetic triplets has been proposed. This structure can accelerate an 80 mA pulsed proton beam from 2.5 MeV to 13 MeV in mean energy. Alternating phase sequences, tapered aperture matching and variable-diameter cavity shaping are employed to optimize the transport of high-intensity proton beams. This structure can yield a viable scheme for the core accelerating part of 13 MeV, 80 mA high-intensity proton linac and lay a technical basis for APF IH-DTLs applied to intense beams.

Speakers: Jinghe Yang (China Institute of Atomic Energy), Shilin Li (China Institute of Atomic Energy)

100 RF Design of the compact RF power coupler for FCCee injector linacs

The high-energy linac of the Future Circular Collider electron–positron (FCC-ee) injector requires high-performance RF accelerating structures to efficiently reach 20 GeV with stable operation. A tapered travelling-wave structure operating at 3 GHz has been designed to optimize accelerating performance and suppress wakefields.
This work focuses on the development of a full 3D model of the accelerating structure, including the RF power couplers, to ensure efficient power transfer and reliable high-power operation. Several coupling strategies were investigated to achieve a compact design while minimizing higher-order multipole components in regions lacking axial symmetry.

Speaker: Pablo Martinez Reviriego (European Organization for Nuclear Research)

101 Simulation of DC bias-based multipacting supression in FCC-ee fundamental power couplers

In fundamental power couplers for RF accelerators, secondary electron emission can give rise to multipacting (MP), leading to RF losses, heating, and performance degradation. A mitigation technique consists of superimposing an electrostatic DC field onto the RF field by applying a bias voltage between the inner and outer conductors of the coaxial power coupler. This approach alters electron trajectories and disrupts the resonant conditions required for MP. This work investigates the effectiveness of DC bias in suppressing MP in FPCs designed for the Future Circular Collider (FCC-ee) accelerating cavities operating at 400.79 MHz and 801.58 MHz. Two baseline coaxial FPC designs are analyzed, with nominal maximum power levels of 382 kW and 195 kW, respectively, extended to 500 kW and 250 kW to account for operational margins. Using the Spark3D MP simulation tool, the required DC bias voltage for MP suppression is systematically evaluated across the full power range. The study also examines the influence of different secondary electron yield (SEY) models for copper surfaces in the coaxial structure and ceramic materials in the RF window on the required DC bias voltage.

Speaker: Ana Durdevic (European Organization for Nuclear Research)

102 Status of a C-band test platform for proof-of-principle ultra-short bunch generation

A C-band test platform has been built at IHEP-Dongguan for studies of high-gradient RF structures and advanced beam manipulation techniques toward future light source projects. Prototypes of 3.6-cell C-band RF photocathode gun achieved high-power operation close to 150 MV/m and beam extraction at about 137 MV/m cathode gradient, representing the first reported beam extraction from a C-band RF photo gun. Following the initial beam experiment, the original beamline has been reconfigured for proof-of-principle studies of angular dispersion modulation (ADM), a compression scheme widely adopt but not experimentally verified for ultra-short bunch generation in future light source applications. Preliminary simulation studies have been performed to evaluate bunch compression performance and beam transport properties. This contribution presents the present status and details of the upgraded C-band test platform, along with key simulation results for the coming ADM proof-of-principle experiment.

Speaker: Xingguang Liu (Chinese Academy of Sciences)

103 Status of the SAFEST Project the SAPIENZA Linac Prototype for VHEE Flash Radioterapy

FLASH radiotherapy is emerging as a transformative cancer-treatment modality, achieving tumor control while reducing normal-tissue toxicity and improving the therapeutic index. To exploit this effect, especially for deep-seated tumors, Very High-Energy Electrons (VHEE) in the 50–150 MeV range are required. Within the SAFEST project, aimed at a 100 MeV machine, Sapienza University of Rome, with INFN, is developing a compact C-band linear accelerator prototype. The system is designed to deliver 24 MeV loaded electrons, providing 2 Gy per pulse over a 10 × 10 cm² field at 100 Hz. Accelerator optimization included electromagnetic, vacuum and beam-dynamics studies to ensure beam parameters suitable for FLASH dose delivery. To reach high gradients and enable future VHEE operation in a compact footprint, the work focuses on the in-house design and construction of a C-band travelling-wave structure. The final technical design report is complete, and installation is underway at Sapienza University. Two irradiation configurations, pencil beam and wide beam, are planned for in vitro studies. This compact electron source is a milestone toward next-generation VHEE facilities for FLASH therapy.

Speaker: Riccardo Boldrini (Sapienza University of Rome)

104 Status update of permanent magnet radiation resiliency studies at CEBAF

The proposed energy upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) incorporates Fixed-Field Alternating-gradient (FFA) arcs utilizing permanent magnet technology. Given the radiation environment within the CEBAF tunnel enclosure, validating the long-term magnetic stability of these materials is a critical step for the project's technical feasibility. This contribution presents an overview of the ongoing permanent magnet radiation resiliency program at Jefferson Lab, which has expanded into one of the largest and most comprehensive in-situ studies of its type ever performed in an accelerator environment. We briefly review the experimental methodology used to monitor demagnetization and summarize the operational experience from the initial data-taking campaign. Furthermore, we discuss the upgrades implemented for the second exposure campaign, currently underway, which aims to refine dose correlation and reduce systematic uncertainties. We report on the latest results from the program and the roadmap for certifying permanent magnet optics for the proposed upgrade energies.

Speaker: Ryan Bodenstein (Thomas Jefferson National Accelerator Facility)

105 Study of transient beam effects in the SARAF injector

Soreq Applied Research Accelerator Facility (SARAF) aims to deliver up to 5 mA proton/deuteron beams at energies up to 40 MeV. SARAF is primarily a continuous wave (CW) machine, and thus, machine studies so far focused mainly on the steady state beam properties. However, the beam commissioning of the superconducting linac (scheduled to start in Q2 2026) will naturally commence with a low-duty-cycle pulsed beam in order to limit the risk of thermal damage and enable the measurements using destructive diagnostics. Furthermore, short interrupts in the beam current will always be required during operation to enable monitoring of the beam transmission using AC current transformers. Transient processes such as buildup of space charge neutralization in the LEBT and beam loading in the RFQ and cavities will influence the beam properties during the pulse formation. Understanding these processes is therefore critical for the machine commissioning and operation. In this talk, we will describe our study (supported by simulations and measurements) to identify the relevant processes, estimate their effects on the beam dynamics in the linac, and apply mitigations to minimize those effects.

Speaker: Dr Amichay Perry (Soreq Nuclear Research Center)

106 Study of Two Dimensional Beam Splitting by Transverse Field RF Cavities for Multi-Beam ADS

ADS is considered as an effective way for the transmutation of nuclear waste. With multi-beam injecting into multi-target in the reactor, neutron distribution will become uniform, which is beneficial to the the safety and economy of the reactor. With transverse field RF cavities, the adjacent micro bunches in CW beam could be deflectied to different directions and 2D beam splitting could be relized, resulting in multi-beam injection. The frequency of the RF Cavities should be different from the beam frequency, forming fixed phase shift. 5/12*f0 is chosen as the frequency of RF cavities and 12 symmetrically distributed beam is formed. High order magnets are adopted for cavity deflection compensation for high energy proton beam. Furthermore, circular scan for each beam line is conducted for PCD (Peak Current Density) reduction. Comparing with 35 μA/cm^2 for 5 mA beam in Φ250 single target, PCD is limited within 20 μA/cm^2 for 18 mA beam in Φ250 multi-target.

Speaker: Yuanshuai Qin (Institute of Modern Physics, Chinese Academy of Sciences)

107 Study on Transient Effects and Cascading Impacts in the STCF Injector Main Linac

The Main Linac of the Super Tau-Charm Facility (STCF) injector comprises 36 series-connected constant-gradient traveling-wave accelerating structures. Variations in injection timing induce complex coupling between the independent RF transient filling and transient beam loading effects, systematically altering the beam energy spread. As a bunch traverses successive structures, these localized coupled perturbations propagate, accumulate, and superimpose. This cascading impact severely restricts the overall energy stability and beam quality. This paper systematically investigates the dual-transient coupling mechanism in a single structure, perturbation differences under varying injection timings, and the cumulative amplification characteristics across the multi-stage configuration. The findings provide a vital theoretical foundation for RF timing co-regulation and transient perturbation suppression, effectively enhancing beam quality stability for the STCF.

Speaker: Hao Hu (Huazhong University of Science and Technology)

108 Superconducting Cavity Fault Compensation by Multi-objective Genetic Algorithm

This paper presents a compensation algorithm based on a Multi-Objective Genetic Algorithm (MOGA) for recovering beam parameters in high-intensity superconducting proton linacs when one or more radio-frequency cavities degrade or fail. The algorithm directly adjusts the amplitude and phase of adjacent or all cavities to restore the beam energy and energy spread at the linac exit. Compared with lookup-table methods, the MOGA-based approach offers greater flexibility in handling complex failure scenarios, including partial gradient loss and multi-cavity faults. Although computationally more intensive, the method has been successfully tested in beam dynamic study for the CSNS-II superconducting linac and experimentally verified on the C-ADS Injector I, demonstrating its capability to meet strict beam stability requirements for downstream injection. This work provides a robust and adaptive strategy for fault-tolerant operation in high-power proton accelerator facilities.

Speaker: Xinyuan Feng (Institute of High Energy Physics)

109 The design and benefits of higher energy proton radiography

Proton radiography (pRad) has operated with 800 MeV protons from the Los Alamos Neutron Science Center’s LINAC since 1997. Having demonstrated its exceptional ability to see through high areal densities and high Z material, discussions are ongoing on best way to bring this facility into the future. Higher energy protons decrease multiple blur terms in the final radiographic image, and are able to image larger test objects. This talk aims to discuss the many benefits of higher energy pRad, and at what point these benefits are no longer worth the cost. Using data collected from Los Alamos and GSI, as well as simulations, the design of lenses at higher energy and the tradeoffs of LINACS versus synchrotrons for radiography will be discussed.

Speaker: John Schmidt (Los Alamos National Laboratory)

110 The High-Power Gallium-Indium Liquid Target at SARAF: Design, Validation, and Multi-Disciplinary Applications

The Soreq Applied Research Accelerator Facility (SARAF) is advancing to Phase II to deliver continuous wave proton and deuteron beams (5-40 MeV, ~5 mA). Handling the resulting ~200 kW beam power requires a robust dump capable of dissipating high power densities. To meet this challenge, a windowless liquid Gallium-Indium (Ga-In) jet target, GaLiT, was designed. It generates a stable ~5 m/s jet with a verified thickness of 5.6±0.3 mm, sufficient to stop the incident beam. Ga-In offers superior heat transfer and reduced chemical hazards compared to liquid lithium.
Beyond serving as a beam dump, this system functions as a high-intensity neutron source, designated MARZEPAN, yielding >10^15 n/s with energies up to ~45 MeV. This facility supports a broad spectrum of physics applications:
Fusion Material Research: Simulating reactor environments and radiation damage studies.
Astrophysics: Enabling research into stellar nucleosynthesis via tunable neutron spectra.
Fundamental Nuclear Physics: Producing short-lived isotopes via systems like SARONA for weak interactions and cross-section measurements.
This contribution presents the design, prototypes, and scientific applications of GaLiT.

Speaker: Dr Sergey Vaintraub (Soreq Nuclear Research Center)

111 The plasma processing development in CSNS-II

The 80–300 MeV accelerating section of the CSNS-II linac is a superconducting accelerator, consisting of 10 double spoke modules and 8 elliptical cavity modules.For a user facility, the downtime associated with removing the module from the linac and returning it to the cleanroom for rinsing and reconditioning is unacceptable. Therefore, it is necessary to develop on-line performance recovery techniques for superconducting cavities to eliminate field emission and restore the operating gradient within a short time. On-line plasma cleaning has been proven to be a safe and effective technique for mitigating field emission in superconducting cavities. This report presents the development of plasma cleaning technology at CSNS-II, including the construction of the plasma cleaning platform, the implementation of plasma cleaning experiments, low-temperature CH₄ adsorption tests on a 2-cell elliptical cavity, and a comparison of vertical test results before and after plasma cleaning.

Speaker: Cong Zhang (Institute of High Energy Physics)

112 The Proton Beam Irradiation Facility (PBIF) Beamline design at the J-PARC linac

In recent years, the Japan Proton Accelerator Research Complex (J-PARC) has completed the design report for a Proton Beam Irradiation Facility (PBIF). This facility will be used for material irradiation, the manufacturing of medical radioactive isotopes, testing semiconductor soft errors, and providing proton beams for space applications, utilizing the H- beam generated by the J-PARC linac. The PBIF beamline will be in an existing tunnel within the J-PARC linac. It will extract the H- beam from the J-PARC's linac using a pulse bending magnet and septum arrangement and transport the beam through achromatic lattices. One of the main challenges for the PBIF beam line is to efficiently transport the beam from the main line of the J-PARC linac to the testing area, while ensuring that the design fits within the existing tunnel and does not interfere with the components already installed in the J-PARC linac. This work provides a report and discussion on the optical design of the PBIF beamline.

Speaker: Bruce Yee-Rendon (Japan Atomic Energy Agency)

113 Theoretical and Experimental Study of Resonant Frequency Shifting for Various Spark Gap Distance in Active Microwave Pulse Compressors

Microwave pulse compressors(MPCs) are used in linear accelerator RF systems to enhance peak power, as well as in other high power RF application such as IEMI testing. This paper presents a theoretical and experimental study on a low-power active MPC employing a spark gap switch. In particular, the change of resonant frequency as a function of spark gap length in an active MPC structure employing a self-breakdown type is investigated. During the charging time, the input impedance of the side arm of H-plane T-junction varies with spark gap distance, leading to a shift in the resonant frequency of MPC. In this work, this effect is modeled using an equivalent variable-length cylindrical post, and the resulting change in resonance condition with respect to gap length is analytically formulated. The proposed model explains the resonant frequency shift based on the variation of effective reactance in the side arm tee. To validate the model, an experimental setup based on a WR650 waveguide was constructed, and S-parameter was measured for various gap lengths. The results show a frequency shift with respect to gap length, which is good agreement with the equivalent circuit model.

Speaker: Taekheon Kim (National Security Research Institute)

114 Transverse phase space tomography and comparison with Allison scanner data in the RAON heavy ion accelerator

This work compares results from transverse tomography based on profile measurements with results from Allison scanners. It considers perturbing effects from non-linear (dipole) fields and space charge.

Speaker: Dong-O Jeon (Institute for Basic Science)

115 Travelling-Wave RF Photogun: From Back-of-the-Envelope Concept to High-Power Operation

Approximately 35 years after it was first conceptualised, a one-of-a-kind travelling-wave RF photogun has been designed, realised, and tested, achieving cathode peak fields of up to 180 MV/m. Installed at the C-band test stand at PSI, the system demonstrates robust and reliable high-power operation. We present an overview of the RF design, the unique tuning-free realisation, and the results of high-power testing, highlighting how travelling-wave gun technology opens new opportunities for electron sources. In addition, we describe the integration of field-emission tips to realise a travelling-wave field-emission gun capable of generating GHz bunch trains. This technology is expected to have broad impact across a range of applications, from high-average-current requirements such as medical therapy to ultra-high-brightness beams for MeV electron microscopy.

Speaker: Thomas Lucas (Paul Scherrer Institute)

116 Update on conditioning the new injector LINAC at the Canadian Light Source

In 2024 the Canadian Light Source (CLS) retired its ∼60 year old 2856 MHz, 250 MeV injector electron LINAC, and replaced it with a 3000 MHz LINAC designed and built by RI Research Instruments GmbH. The design includes a SLAC Energy Doubler (SLED) system to power two of the three main accelerating structures and is intended to produce a beam of the same energy. Many setbacks were encountered during the initial conditioning and commissioning phases, which required reconditioning the structures and seeking guidance from the community. Their input and lessons learned from past conditioning attempts shaped the latest RF conditioning campaign. While not without its own setbacks, this conditioning campaign succeeded and allowed the beam commissioning phase to proceed at a lower energy. This paper is a report on this most recent RF conditioning campaign and CLS’s current state of operations.

Speaker: Tylor Sové (Canadian Light Source (Canada))

117 Upgrade of the Cavity Phase Monitor System for Multi-Cavity Measurements at J-PARC LINAC

At J-PARC LINAC, cavity phase monitors (CPMs) monitor RF phase variation between neighboring cavities; existing system remains reliable but requires dedicated hardware per station and supports only two RF inputs per monitor. As LLRF DFB system has been upgraded from cPCI to MicroTCA.4, RF pickup signals are aggregated in a common rack, requiring CPM upgrade to multi-channel monitoring; as an initial step, we developed a MicroTCA.4-based CPM at MEBT1 with vector-sum capability. System acquires eight RF inputs from RFQ, Buncher 1/2 and Chopper 1/2; 324-MHz pickup signals are down-converted to 12 MHz on μRTM, digitized at 240 MHz, and converted to I/Q yielding amplitude/phase. Vector sums are formed for RFQ, Buncher 1/2, while Chopper 1/2 are single-channel; all phases referenced to RFQ. Existing LLRF firmware and EPICS IOC framework were adapted with modifications; new sequencer logic and GUI were developed. System is installed in the LLRF MicroTCA.4 environment, synchronized via shared ADC/FPGA clocks under temperature- and humidity-controlled conditions. Initial results demonstrate simultaneous multi-cavity monitoring with improved integration over the conventional distributed CPM.

Speaker: Ersin Cicek (High Energy Accelerator Research Organization)

118 Upgrade of the LLRF System for the X-Band Linearizer in SXFEL

The X-band linearizer at the Shanghai Soft X-ray Free-Electron Laser (SXFEL) is used to compensate the nonlinear energy chirp of the electron beam and requires a highly stable low-level radio-frequency (LLRF) system. To improve the performance of the X-band RF system, the LLRF chain was upgraded in three aspects: the clock and local-oscillator electronics, the X-band solid-state power amplifier, and the klystron output optimization based on digital feedforward and disturbance modeling. In the upgraded scheme, the X-band signal is down-converted to the S-band frequency range for processing on an MTCA-based S-band LLRF platform, and then up-converted back to X-band after vector modulation. Experimental results show that the phase stability at the X-band klystron output reached 0.09° RMS, and the beam stability downstream of the X-band linearizer was improved by nearly a factor of two. The upgraded system provides a practical solution for stable operation of the X-band linearizer at SXFEL.

Speaker: Chengcheng Xiao (Shanghai Advanced Research Institute, Chinese Academy of Sciences)

119 Wakefield mitigation studies and beamline upgrades for stable nanometer beam operation at KEK-ATF

The KEK-ATF is an R&D facility for the final focus system to develop nanometer beam technology for the International Linear Collider. The vertical beam size growth as a function of bunch intensity has been observed at the focal point (IP), mainly caused by wakefield effects. ATF provides an excellent environment for studying wakefield impacts on nanometer-scale beams. Mitigation and understanding of wakefield effects are important for achieving stable nanometer beams. To reduce wakefield effects, several upgrades have been implemented in the ATF final focus beamline. Vacuum components that significantly affect the beam, such as flanges and bellows, have been improved by introducing step-free structures and RF shielding. In addition, the collimator, one of the dominant wakefield sources, has been upgraded to allow position adjustment, enabling minimization of wakefield effects caused by orbit distrtions and misalignments. In this paper, we report the current status of these mitigation studies, their experimental results, and future prospects toward stable nanometer beam operation.

Speaker: Dr Yuki Abe (High Energy Accelerator Research Organization)

Tuesday 18 August

TU1A - Invited Talks

120 Operational Status of the KOMAC 100 MeV Proton Linac and Pilot R&D for the 200 MeV Upgrade

The 100 MeV proton linac at KOMAC has operated since 2013, providing irradiation services for materials, biomedical, semiconductor, and nuclear/basic science through four user beamlines. The accelerator comprises a 50 keV injector, 3 MeV RFQ, and DTL to 100 MeV. Major beamlines support multidisciplinary research, semiconductor radiation assessment, and isotope production, while a white-spectrum neutron service is in pilot operation with official user service planned for 2026. A Beam Test Stand supports accelerator R&D, including machine-learning-based tuning, emittance control, and advanced phase-space diagnostics. A 200 MeV upgrade based on a normal-conducting SDTL is in preparation. The LINAC’26 conference provides an opportunity to present the operational status, beamline utilization, and progress toward the 200 MeV upgrade.

Speaker: Han-Sung Kim (Korea Atomic Energy Research Institute)

121 PIP-II PROJECT PROGRESS AND CHALLENGES

The PIP-II Project is under construction to provide the Fermilab Accelerator Complex with a new H- SRF linac and beam transfer line delivering 800 MeV protons at Booster injection at double energy and double intensity (6.7x1012 proton per 20 Hz pulse) in comparison with the present Linac.
The design goals of PIP-II Linac will be described, including delivering 1.2 kW beam power on LBNF/DUNE target, CW operation compatibility and future upgrades.
The progress of the Linac construction and the development of the Commissioning Plan will be presented.
Finally, the challenges of operating the SRF Linac to drive the Fermilab Booster will be addressed.

Speaker: Dr Olivier Napoly (Fermi National Accelerator Laboratory)

122 High intensity, high polarization electron gun for Electron–Ion Collider

Polarized electron sources are essential for accelerator facilities such as the Electron–Ion Collider and polarized positron sources, which require guns with higher voltage and bunch charge than existing polarized gun. At Brookhaven National Laboratory, we developed an inverted High-Voltage DC (HVDC) polarized photoemission gun with a Distributed Bragg Reflector superlattice GaAs photocathode and a cathode cooling system suited for future high-current operation. The gun was conditioned to 350 kV with no measurable field emission and delivered polarized electron bunch charges up to 11.6 nC, reaching the current density of 14.5 A/cm² at the source. To our knowledge, this is a record operating voltage for a polarized DC gun and a record current density for a polarized electron source. We mitigated the surface charge limit through optimized surface doping and heat-cleaning procedures and by leveraging the high accelerating gradient at the cathode. We also studied the effects of the DBR layer and laser parameters on photocathode lifetime and identified an operating regime that provides long lifetime while maintaining high polarization at 30 µA.

Speaker: Erdong Wang (Brookhaven National Laboratory)

123 Photocathode-driven injector linac design for Korea-4GSR

As part of the ongoing Korea-4GSR (Fourth-Generation Synchrotron Radiation) project, a 200 MeV electron linac is being developed based on an S-band photocathode, rather than the conventional thermionic gun approach. The gun provides high electron energy (4 MeV) and low emittance, which simplifies the design of the initial accelerating RF system, magnets, and beam transport to the booster. The basic concept of the linac builds upon the successful PAL-XFEL design and has been further optimized to support 64-multibunch generation, precise energy feedback, injection timing control, and higher charge operation. Plans for gun testing and commissioning will also be presented.

Speaker: Chang-Ki Min (Pohang Accelerator Laboratory)

124 First robotic assisted string assembly of PIP-II SSR2 cavities at Fermilab

Achieving robotic-assisted string assembly has been a longstanding objective in superconducting cavity production to improve precision, repeatability, and throughput while reducing operator-dependent variability. At Fermilab, robotic systems have been successfully deployed for the installation of individual components on SSR2 cavities inside a cleanroom environment. The single-cavity installations validated the feasibility of robotic techniques and provided confidence to extend automation to the assembly of a full prototype cavity string. Leveraging lessons learned from earlier operations, the robotic system was adapted for the string assembly. This work describes the robotic-assisted assembly process in detail, including alignment strategies for coupler flanges, torque control for bellows connections, and mitigation of particulate generation in cleanroom conditions. Performance metrics of the cryomodule are presented, together with an analysis of improvements needed for robotic assembly. The effort also represents a broader R&D initiative at Fermilab to the long-term goal of scalable SRF cryomodule production.

Speaker: Mattia Parise (Fermi National Accelerator Laboratory)

125 Automated Commissioning and Intelligent Operational Strategies for the HIAF-iLinac SRF System

High-intensity superconducting linear accelerators present significant challenges regarding efficiency and reliability during both commissioning and operation. This paper summarizes the engineering practices in full-process automated operation and maintenance implemented for the HIAF-iLinac SRF system. To address the requirements of large-scale cavity commissioning, an automated conditioning framework integrating AI-driven waveform recognition was developed, enabling 24/7 unattended operation for 96 SRF cavities. Utilizing online parallel measurement tools, over 600 critical cavity parameters were precisely calibrated, providing an essential foundation for beam commissioning. To facilitate the design and optimization of high-performance real-time control algorithms, an FPGA-based high-fidelity digital twin platform was constructed, allowing for closed-loop verification and parameter pre-tuning of advanced control strategies before engineering deployment. Regarding facility operation, a "one-key" rapid loading technology supporting both pulsed and continuous-wave modes was implemented, reducing the closed-loop recovery time after faults to within 2 minutes.

Speaker: Feng Qiu (Institute of Modern Physics, Chinese Academy of Sciences)

10:30 Coffee Break

TU2A - Plenary Talk

126 Charge Selector Challenges in High Power Heavy Ion Linacs

Heavy ion linacs use charge stripping to increase accelerating efficiency. At FRIB, the charge selector intercepts unwanted charge states from their broad distribution after stripping at the energies of 17-20 MeV/u. Design of a movable collimator for high-power heavy ion beams becomes very challenging due to high volumetric power deposition, radiation damage, radioactivation, and mechanical constraints. Uranium beam, for instance, produces the average power density on the charge selector that is orders of magnitude higher than proton beams, and the radiation damage rates that heavy ions produce reach several dpa/minute. This talk will present the design challenges and our experience in the development of the FRIB charge selector.

Speaker: Alexander Plastun (Facility for Rare Isotope Beams)

Lightning Talks by Participating Industries

12:30 Lunch

TU1P - Invited Talks

127 Development and First Beam Generation of A Conduction-Cooled SRF Photogun

We report the first beam produced by the world’s first conduction-cooled superconducting radio-frequency (SRF) photogun. Over the past seven years, Euclid, in collaboration with Fermilab and Argonne National Laboratory, has developed a 1.5-cell, conduction-cooled Nb3Sn SRF photogun operating at 1.3 GHz. The primary objective of this effort is to demonstrate ultra-stable electron beams for ultrafast electron microscopy and diffraction (UEM/UED) applications. Although SRF systems were historically too costly for industrial deployment, two recent advancements: Nb₃Sn coatings and conduction cooling, have dramatically reduced system complexity and operating costs. This SRF photogun can deliver true CW operation while dissipating only ~2 W of RF power, eliminating the need for a high-power RF system and significantly reducing facility footprint. It is also featured with a raised Nb3Sn backwall serving as the photocathode, removing the need for an external cathode insert. In this talk, we present the development process of the cavity and cryostat, along with its cooldown performance, Q-slope behavior, synchronization characteristics, and the first beam generation.

Speaker: Chunguang Jing (Euclid Techlabs (United States))

128 RF System Design of a Polarized, High-Charge Electron Linac for the EIC Pre-Injector

The Electron–Ion Collider (EIC) requires a 750 MeV pre-injector operating at 30 Hz and delivering polarized electron bunch charges of 1 up to 2 nC. The electron source provides longitudinal polarization, whereas the spin must be vertical prior to injection into the ring. To achieve this, we implement a spin rotator at gun energy. The primary challenge is to preserve polarization and maintain a vertical spin orientation while transporting and accelerating high–space-charge bunches through the entire injector chain. A key constraint is that solenoid focusing fields cannot be superimposed with the accelerating fields, although this configuration is commonly used in S-band linac injectors for high-bunch-charge beams. We propose an EIC pre-injector design consisting of a bunching section, an L-band capture section, and an S-band linac to accelerate nC bunch charge, vertically polarized bunches to 750 MeV. We will present the overall injector concept, the pre-injector design, and the performance goals.

Speaker: Freddy Severino (Brookhaven National Laboratory)

129 FCC-ee Injector complex: status, highlights and outlook

The FCC-ee demands an injector complex capable of delivering high-current, high-brightness electron and positron beams with exceptional efficiency. Within the CHART/FCC-ee Injector Study collaboration, a revised injector layout has been developed to optimize performance, cost, and power consumption. A central pillar of this effort is the tuning-free, high-gradient normal-conducting RF structure technology pioneered at PSI for SwissFEL and since extended across S-, C-, and X-band systems. This scalable approach underpins future developments in the FCC-ee linacs, enabling reliable acceleration. In parallel, the P³ program at PSI is advancing the positron source, with commissioning foreseen in 2026, while upcoming work will enhance the electron source and refine RF requirements for the positron linac. This contribution presents the current injector complex status, key design highlights, and the outlook toward the FCC-ee injector technical design report.

Speaker: Paolo Craievich (Paul Scherrer Institute)

TUOP - Oral Posters

130 Beam commissioning of the linear accelerator of the SKIF Synchrotron Radiation Facility

Linear accelerator of the SKIF Synchrotron Radation Facility (SRF SKIF) was sucessfully commissioned in 2025. It provides the electron beams with the energy of 200 MeV for the subsequent injection to the booster synchrotron. Being an initial part of the SRF SKIF, the linear accelerator includes not only the key components, such as the electron gun, accelerating structures and magnet elements, but also a large variety of auxiliary systems. We give an overview of the linac commissioning details together with the operation features.

Speaker: Mariya Arsentyeva (Synchrotron Radiation Facility — Siberian Circular Photon Source «SKIF» Boreskov Institute of Catalysis)

131 Introduction of co-deposition method for improvement of quantum efficiency and lifetime of Cs-Te photocathodes in KU-FEL

Cs-Te photocathodes are widely used in photoinjectors for free electron lasers owing to their high quantum efficiency (QE). At KU-FEL, an infrared oscillator-type FEL in Kyoto University, a 1.6-cell RF gun with CsBr-coated Cs-Te photocathode has been developed for high-bunch-charge (~1 nC) multi-bunch operation. However, the QE and lifetime of the cathode in our RF gun are insufficient for practical use. In 2024, CERN group reported that the QE of Cs-Te photocathode made by co-deposition has significantly higher than that made by sequential deposition*. Therefore, we are planning to introduce the co-deposition method to our system to increase the QE and lifetime of the cathode. Right now, a co-deposition source compatible with our UHV chamber was designed and fabricated. Co-deposition experiments are planned in May 2026. Results with co-deposition and sequential deposition of Cs-Te photocathodes in our system will be reported in the conference.

Speaker: Mr Yutaro Kubo (Kyoto University)

132 Bayesian Optimization for Constrained Beam Transport Line Design in the RAON Injector

The design of low-energy beam transport (LEBT) lines involves high-dimensional optimization under multiple physical constraints, including beam size, transmission efficiency, and limited beamline geometry. In the RAON injector system, the integration of a new 14.5 GHz ECR ion source requires re-optimization of the beam transport line while maintaining compatibility with the existing injector configuration. In this study, Bayesian optimization (BO) is applied to the constrained design of a new ECR beam transport line for the RAON injector. Experimentally measured initial beam parameters from the Allison scanner are incorporated into beam dynamics simulations to reflect realistic operating conditions. A two-stage optimization strategy is employed to efficiently identify feasible solutions and improve beam matching performance within the constrained parameter space. The optimized beamline configuration satisfies the operational constraints of the RAON LEBT system while achieving improved beam matching performance. The results demonstrate that BO provides an effective approach for constrained beam transport line design problems.

Speaker: Chanmi Kim (Institute for Basic Science)

133 JINR DLNP Linear Accelerator: Commissioning Results and Preparations for the Official Startup

Last preparations for operation for users are ongoing at the new basic facility of the Laboratory of Nuclear Problems of the Joint Institute for Nuclear Research — the LINAC (formerly LINAC-200) accelerator. The facility can provide electron beam with a wide range of energies (5 to 200 MeV), pulse durations (0.25 to 3 us) and charges (240 nC to single electrons per pulse). The maximum pulse repetition rate is 25 Hz. The facility can also provide beams of gamma rays (by installing tungsten converter in the beamline) and neutrons (beryllium converter). Commissioning results and last facility upgrades are presented.

Speaker: Mikhail Nozdrin (Joint Institute for Nuclear Research)

134 Intrabeam Scattering studies in Free Electron Lasers with RF-Track

Intrabeam Scattering (IBS) has recently been recognized as a limiting factor for free electron laser (FEL) performance, making it a critical concern for the linear accelerator community. There is a growing need for accurate numerical tools to compute IBS and integrate it with other collective effects, as most previous studies assumed Gaussian beams, which are not representative of FEL conditions. In response, the tracking code RF-Track has been enhanced with a novel kinetic-hybrid Monte Carlo algorithm for IBS calculations. This contribution reports on IBS studies for several FELs, including SwissFEL at PSI and FERMI at Elettra. For SwissFEL, simulation results are benchmarked against experimental measurements. Benchmarks of emittance growth are compared with other tracking codes, and predictions for IBS impact on future facilities are discussed.

Speaker: Paula Desire Valdor (European Organization for Nuclear Research)

135 Progress Update on the ATLAS Multi-User Upgrade at Argonne

The ongoing multi-user upgrade of the superconducting ion linac, ATLAS at Argonne, will enable simultaneous acceleration and delivery of two different ion beams to different experimental areas. One nearly continuous stable beam from the ECR ion source and one pulsed radioactive beam from the EBIS charge breeder of nuCARIBU will be interleaved in time via an electrostatic deflector at injection and accelerated through the first two sections of the linac. At that point, one of the beams is deflected via kicker magnet to a lower energy experimental area while the other is sent for further acceleration in the third section of the linac and delivered to a higher energy experimental area. In addition to enhancing the nuclear physics program at ATLAS, this upgrade will also increase the availability of beam time for some applications. While the construction and installation of the new pulsed injection beamline is now complete, the design of the extraction beamline has changed. The original chicane designed to bypass the existing 40-deg bend has been replaced by simple kicker-septum magnet system. Details of the final design and progress made on the kicker and septum will be presented.

Speaker: Brahim Mustapha (Argonne National Laboratory)

136 The High Brilliance Neutron Source (HBS-I)

Neutrons are an essential tool for studying the structure and dynamics of matter. The High Brilliance Neutron Source (HBS) project aims to develop a scalable Compact Accelerator-driven Neutron Source that will enable neutron fluxes at the corresponding instruments comparable to existing fission-based or spallation neutron sources. After positive project evaluation in 2025, the German Science Council recommends strongly the construction of the first project stage (HBS-I). HBS-I uses pulsed 100 mA high-current proton beams to generate neutrons through a low-energy nuclear reaction at 20 MeV. The HBS-I Linac consists of a proton source, a 4-solenoid LEBT with chopper, two 4-Rod RFQ accelerators and a chain of 20 room temperature CH-cavities operated at 176 MHz. The maximum RF duty factor is 25%, resulting in a thermal load of up to 30 kW/m. The technology of this Linac is derived from the cw operated MYRRHA injector. The paper describes the status of the HBS-I proton Linac.

Speaker: Prof. Holger Podlech (Goethe University Frankfurt, HFHF - Helmholtz Research Academy Hesse for FAIR, Campus Frankfurt)

137 Generation and Application of Stripped Proton Beams at the CSNS Linac

The CSNS linac delivers a primary H⁻ beam to the RCS while also providing stripped proton beams generated through two mechanisms: foil stripping and intra-beam stripping. Carbon foil collimators selectively strip halo particles from the beam periphery, reducing the transverse emittance of the H⁻ beam, which allows a larger painting range during RCS injection and reduces beam loss. Intra-beam stripping is an unavoidable byproduct of high-intensity H⁻ transport whose effects will become more prominent at the higher beam power of the CSNS-II upgrade, and this work presents initial studies of its mechanisms. The intra-beam stripping generated proton beam has been used for detector calibration, while the higher-intensity foil-stripped proton beam can be used for isotope production. This work demonstrates a dual-beam operation design at the CSNS linac, turning stripped proton beams from a source of beam loss into new applications.

Speaker: Zhiping Li (Institute of High Energy Physics)

138 Recent progress in additive manufacturing of linear accelerator components

Compared with subtractive manufacturing methods such as CNC machining, additive manufacturing (AM) enables the fabrication of highly complex monolithic geometries. As a result, AM can improve functionality and reduce manufacturing costs. For linear accelerator (linac) components, this potential has been demonstrated in a growing number of studies and prototype developments. At the same time, recent advances in AM, particularly in metal powder-based processes, have significantly reduced earlier limitations related to linac-specific requirements such as vacuum outgassing and RF electrical conductivity. AM has therefore become a promising approach for the fabrication of linac components. It enables designs that are difficult or impossible to produce by conventional methods, including highly complex cooling structures and multimaterial components. Despite these advantages, conventional fabrication methods are still often preferred. This short review summarizes recent progress in the additive manufacturing of linac components. It discusses several successfully manufactured prototypes and shows which linac-specific requirements can already be fulfilled by AM today.

Speaker: Michael Mayerhofer (Universität der Bundeswehr München)

139 RF design of a spherical-cavity-type pulse compressor for muon linac

The development of a muon-dedicated traveling-wave disk-loaded structure (DLS) is in progress at the Japan Proton Accelerator Research Complex (J-PARC). Accelerating ultraslow muons to relativistic energies preserves low beam emittance and improves penetration capability, enabling new opportunities in precision particle physics experiments and muon imaging. However, unlike electrons, muons undergo substantial velocity changes during acceleration, even at high energies, requiring precise phase synchronization between the beam and RF fields. This requirement becomes more critical when using pulse-compressed RF power with temporal variation.
In this work, we present the RF design of a spherical-cavity-type pulse compressor (SCPC) for a DLS. Two degenerate $\mathrm{TE_{112}}$ modes with a 90-degree phase difference are utilized at 2592 MHz. RF performance was optimized using 3D electromagnetic simulations to achieve the target frequency characteristics and controlled mode degeneracy. Based on the RF loss distribution, thermal analysis evaluated temperature rise and cooling requirements, while structural simulations assessed deformation to estimate frequency detuning.

Speaker: Yuga Nakazawa (High Energy Accelerator Research Organization)

140 Comparative Study of Virtual Pepper-Pot and Differential Virtual Pepper-Pot Methods for 4D Transverse Phase Space Reconstruction of Small Beams

Precise 4-dimensional (4D) transverse phase space characterization is essential for fully understanding and controlling coupled beam dynamics and beam quality. The Virtual Pepper-Pot (VPP) method has been proposed to reconstruct the 4D transverse phase space, including transverse coupling information, from slit-based measurements. However, the finite slit width imposes intrinsic limitations on reconstruction accuracy by introducing geometric angular spread and limiting the ability to resolve small beam sizes. To overcome these limitations, a differential slit method named the Differential Virtual Pepper-Pot (DVPP) has been proposed. In this study, we investigate the performance of the DVPP method in comparison with the conventional VPP under the identical small electron beam conditions expected in the PAL eLABs facility. Their ability to recover transverse coupling information is evaluated for cases ranging from weak to strong coupling.

Speaker: Jiyoung Choi (Pohang University of Science and Technology)

TUPO - Poster Session

141 650 MHz CW MODE RF-GRIDED GUN DESIGN FOR SRF LINAC APPLICATIONS

To address the growing demand for high-power commercial electron irradiation, the Institute of Modern Physics (IMP) has developed a 100 mA, 4.6 MeV superconducting linac prototype. This compact facility features a conduction-cooled Nb3Sn SRF cavity (650 MHz, 5-cell, βopt=0.82) to drive high-intensity beams. However, the existing conventional DC gridded thermionic gun cannot provide the requisite temporal structure or injection velocity to match the SRF cavity acceptance. This severe longitudinal mismatch induces excessive beam loss and low transmission efficiency, inherently preventing continuous-wave (CW) operation. To overcome this critical bottleneck, IMP is developing a novel RF-modulated gridded thermionic gun designed to generate 650 MHz CW bunches. By superimposing an RF electric field directly onto the cathode surface, the emitted DC beam is effectively pre-modulated and bunched, enabling seamless, lossless transmission through the downstream cavity. This paper details the systematic electromagnetic design and comprehensive beam dynamics simulations of this RF-gridded gun, concluding with an outlook on its upcoming fabrication and integration.

Speaker: Mr Zehua Liang (Institute of Modern Physics, Chinese Academy of Sciences)

142 A Beam Dynamics Design Framework for a Compact RF-Focused Interdigital Linac (RFI)

The RF-Focused Interdigital linac (RFI) integrates the high shunt impedance of an IH-DTL with strong RF quadrupole focusing for compact low-energy ion acceleration. Current design codes, limited by idealized hard-edge approximations, neglecting soft-edge fringe fields and time-dependent focusing effects, which leads to beam envelope mismatch. To address these limitations, we present a novel dynamics design framework featuring an automated closed-loop interface between beam dynamics algorithms and CST 3D electromagnetic simulations. Longitudinally, it utilizes slice-based transit-time factor integration and dynamic phase-locking to adaptively optimize drift tubes geometry using real field data. Transversely, an iterative co-simulation scheme is introduced to determine the effective RF focusing parameters by coupling CST three-dimensional field with TraceWin particle tracking under an optimization loop. This framework enables accurate mapping from ideal lattices to 3D RF cavities, providing a novel and precise design methodology for magnet-free compact linacs.

Speaker: Yuxuan Yang (China Spallation Neutron Source)

143 A C-Band Parallel Coupled High Gradient Accelerating Structure

A C-band parallel-coupled accelerating structure overcomes the RF breakdown limit by reducing filling time. Unlike conventional traveling-wave designs, this architecture feeds each cavity cell simultaneously through a parallel network of coupling irises, distribution waveguides, and a power divider, eliminating inter-cell power transit delays. The cavity geometry is optimized to maximize shunt impedance (5.67 MΩ, Q₀=13024) while maintaining π‑mode synchronization for a relativistic beam. The accelerating structure is designed for strong overcoupling (β=17), enabling rapid energy transfer such that a 50 ns input pulse is fully exploited before reflection occurs. A symmetric dual-waveguide feed network with periodic corrugations ensures equal amplitude and precise phase advance across all ten cells, verified by time-domain simulations showing less than 5% cell-to-cell field variation. With a 150 MW input pulse, the on-axis electric field distribution yields an accelerating gradient of 80 MVm⁻¹, far exceeding typical C‑band performance. This work proves that parallel-coupled structures break the traditional trade-off between gradient and pulse length for compact high-gradient linacs.

Speaker: Dr Jibran Latif (Spallation Neutron Source Science Center)

144 A Complexity-Native Framework for Intelligent Particle Accelerators

Next-generation particle accelerators are strongly coupled, multiscale, and nonlinear systems in which local optimization alone cannot guarantee global stability. This paper proposes a complexity-native framework that treats the accelerator as a complex adaptive system rather than a set of independently optimized subsystems. This framework integrates three coupled layers—physical complexity, information-flow network, and system cognition—to interpret three core operational challenges: hidden coupling, delayed feedback, and anomaly propagation, while enabling stability-first intelligent operation. A concise superconducting accelerator case illustrates how helium-pressure fluctuation may propagate through cavity detuning, tuner lag, RF compensation, power-module imbalance, and protection shutdown, supporting integrated diagnosis and early warning.

Speaker: Xiaoyu Huang (Advanced Energy Science and Technology Guangdong Laboratory)

145 A high efficiency 650 MHz/800 kW CW Klystron for CEPC

The next-generation large colliders, such as FCC and CEPC, propose unprecedented demands on the energy efficiency of radio-frequency (RF) power sources. For CEPC, whose RF system alone will require over 100 MW of wall-plug power, the 650 MHz / 800 kW continuous‑wave (CW) klystron is a mission-critical component. To meet this challenge, IHEP has launched a dedicated high-efficiency klystron program with the ambitious target of exceeding 80% efficiency. Here, we report a landmark breakthrough achieved with the second prototype.Dduring high‑power testing, the tube delivered 803 kW of CW output power with an efficiency of 78.5%. The test results of this klystron have been reviewed and accepted by the expert panel.This transformative improvement in efficiency will slash the energy demand and operating cost of future large-scale accelerators.This paper will present the detailed progress of this prototype, highlighting the key advances that have enabled this major step forward in high-efficiency klystron technology for CEPC.

Speaker: Ouzheng Xiao (Institute of High Energy Physics, National Synchrotron Radiation Laboratory)

146 A one-dimensional code for waveguided superradiant THz FEL

In THz regime,superradiance with zero-slippage by introducing a waveguide can greatly enhance the energy conversion efficiency of electron beam. In this paper, a one-dimensional numerical code for waveguided superradiant THz FEL is developed. The code solves the beam–radiation interaction equations based on a frequency-domain method without employing the slowly varying envelope approximation (SVEA) or undulator-period averaging. By incorporating waveguide dispersion, the model is capable of simulating the synchronism between the radiation group velocity and the electron beam. For the free space case, the developed code was benchmarked against PUFFIN 1D, showing a deviation of less than 1.5%. Upon incorporating waveguide effects, a comparative study was conducted between a single bunch and a bunch train under the zero-slippage condition. The results demonstrate that the bunch train not only enhances the average energy conversion efficiency but also effectively suppresses the FEL spectral broadening induced by the waveguide.

Speaker: Ruiying Luo (Huazhong University of Science and Technology)

147 Analytical Optimization of Longitudinal Phase Space and Wakefields Compensation for the Main Linac of STCF

In the Super Tau-Charm Facility (STCF) Main Linac, intense short-range longitudinal wakefields from high-charge bunches cause severe energy spread degradation and nonlinear longitudinal phase space (LPS) distortions. We present an analytical model describing LPS evolution under RF acceleration, wakefields, and longitudinal space charge. By utilizing an equivalent truncated-Gaussian distribution, we derived closed-form analytical expressions for the high-order moments of the LPS. Based on this, an analytical optimization method is proposed to determine the optimal RF phase that minimizes the root-mean-square (RMS) energy spread. Theoretical predictions show excellent agreement with Elegant macro-particle tracking simulations, particularly in the core bunch region. With this optimized configuration, wakefield-induced degradation is effectively compensated, successfully fulfilling the stringent beam requirements of the STCF.

Speaker: Hao Hu (Huazhong University of Science and Technology)

148 Attosecond-Resolution Ultrafast Electron Diffraction Enabled by THz Streaking

Ultrafast electron diffraction (UED) provides atomic-scale access to transient structural dynamics, yet its temporal resolution is fundamentally constrained by finite electron bunch durations and pump–probe timing jitter. We introduce a THz-streaking approach that overcomes these limitations by using a high-gradient (~1 GV m⁻¹) THz deflecting field synchronized with the diffraction process. The transient THz field angularly streaks the femtosecond diffraction pattern, mapping temporal information onto a spatial coordinate on the detector. This time-to-space encoding enables single-shot retrieval of attosecond dynamics without requiring sub-femtosecond electron pulses or stringent synchronization. Particle-tracking simulations demonstrate that the temporal resolution can be effectively decoupled from both electron bunch duration and timing jitter. This approach extends UED into the attosecond regime and enables direct access to coupled electronic and lattice dynamics in ultrafast processes.

Speaker: Jiapeng Li (Huazhong University of Science and Technology)

149 Automated Conditioning Utilizing Machine Learning: Network Optimization and Reinforcement Learning

RF-conditioning is an essential pre-processing step of all normal conducting cavities. This time-intensive work can pose great risks to equipment and cavity if conditioning-effects such as multipacting, discharges or degassing aren’t taken seriously.
To reduce the workload for human personnel, it was proposed to develop a deep-learning based algorithm to conduct conditionings on its own. This algorithm is trained on experimental data recorded from various conditionings performed by several experimenters. During initial training, the algorithm is tasked to predict the experimenters’ action based on the power, pressure and frequencies recorded over the last seconds. So far within this project developed networks have been able to perform this task with very small deviations.
To teach the network to not only reproduce human behaviors, but identify the optimal course during conditioning, pre-trained networks were combined with reinforcement learning to enable continued learning during experiments. The results of those experiments shall be discussed in this paper.

Speaker: Stephan Wagner-Rossel (Goethe University Frankfurt)

150 Bayesian Optimization for Constrained Beam Transport Line Design in the RAON Injector

The design of low-energy beam transport (LEBT) lines involves high-dimensional optimization under multiple physical constraints, including beam size, transmission efficiency, and limited beamline geometry. In the RAON injector system, the integration of a new 14.5 GHz ECR ion source requires re-optimization of the beam transport line while maintaining compatibility with the existing injector configuration. In this study, Bayesian optimization (BO) is applied to the constrained design of a new ECR beam transport line for the RAON injector. Experimentally measured initial beam parameters from the Allison scanner are incorporated into beam dynamics simulations to reflect realistic operating conditions. A two-stage optimization strategy is employed to efficiently identify feasible solutions and improve beam matching performance within the constrained parameter space. The optimized beamline configuration satisfies the operational constraints of the RAON LEBT system while achieving improved beam matching performance. The results demonstrate that BO provides an effective approach for constrained beam transport line design problems.

Speaker: Chanmi Kim (Institute for Basic Science)

151 Beam commissioning of the linear accelerator of the SKIF Synchrotron Radiation Facility

Linear accelerator of the SKIF Synchrotron Radation Facility (SRF SKIF) was sucessfully commissioned in 2025. It provides the electron beams with the energy of 200 MeV for the subsequent injection to the booster synchrotron. Being an initial part of the SRF SKIF, the linear accelerator includes not only the key components, such as the electron gun, accelerating structures and magnet elements, but also a large variety of auxiliary systems. We give an overview of the linac commissioning details together with the operation features.

Speaker: Mariya Arsentyeva (Synchrotron Radiation Facility — Siberian Circular Photon Source «SKIF» Boreskov Institute of Catalysis)

152 Beam dynamics and optics matching for the 270-MeV injector linac and transport line of SPS-II

The Siam Photon Source II (SPS-II) project is developing a 270-MeV injector linac based on the proven technology of the NanoTerasu facility. This paper presents the beam dynamics simulations and optics matching for the injector linac and the subsequent Low-Energy Beam Transport line (LBT). Particle tracking through the thermionic electron gun, sub-harmonic cavities, and S-band accelerating structures was modeled using PARMELA. Following the linac, the LBT optics were optimized using MAD-X to transport the beam and match the Twiss parameters required at the booster synchrotron injection point. The combined simulation results confirm that the injector linac and LBT provide a well-matched electron beam for injection into the SPS-II booster synchrotron.

Speakers: Dr Prach Boonpornprasert (Synchrotron Light Research Institute), Dr Thakonwat Chanwattana (Synchrotron Light Research Institute)

153 Comparative Study of Virtual Pepper-Pot and Differential Virtual Pepper-Pot Methods for 4D Transverse Phase Space Reconstruction of Small Beams

Precise 4-dimensional (4D) transverse phase space characterization is essential for fully understanding and controlling coupled beam dynamics and beam quality. The Virtual Pepper-Pot (VPP) method has been proposed to reconstruct the 4D transverse phase space, including transverse coupling information, from slit-based measurements. However, the finite slit width imposes intrinsic limitations on reconstruction accuracy by introducing geometric angular spread and limiting the ability to resolve small beam sizes. To overcome these limitations, a differential slit method named the Differential Virtual Pepper-Pot (DVPP) has been proposed. In this study, we investigate the performance of the DVPP method in comparison with the conventional VPP under the identical small electron beam conditions expected in the PAL eLABs facility. Their ability to recover transverse coupling information is evaluated for cases ranging from weak to strong coupling.

Speaker: Jiyoung Choi (Pohang University of Science and Technology)

154 Controlled plasma density down-ramp generation in a segmented capillary for laser–plasma accelerators

Control of the longitudinal plasma density profile is critical for optimizing laser–plasma accelerator performance, especially for injection in confined plasma channels. To address this, we propose a segmented capillary discharge plasma source and its underlying flow-control framework for generating controlled plasma density down-ramps, and demonstrate its validation theoretically and experimentally. The orifice generates localized pressure discontinuities via the Venturi effect, producing longitudinal density transitions inside the channel. CFD simulations and analytical modeling were performed to investigate pressure-gradient formation and flow choking. The resulting density down-ramps were experimentally verified using optical emission spectroscopy under discharge conditions. This approach provides a flexible platform for engineering plasma density profiles for advanced laser–wakefield acceleration experiments.
We further tested the proposed source in LWFA experiments at GIST/IBS, where density-tailored injection produced reduced low-energy tails and concentrated high-energy peaks, demonstrating its applicability to beam-quality optimization in plasma accelerators.

Speaker: Junyeong Jeong (Ulsan National Institute of Science and Technology)

155 Correlating Longitudinal Electron Beam Structures with XFEL Pulse Duration and Peak Power using an X-band Transverse Deflector System

We have been developing an X-band transverse deflector system (X-TDS) with 1 fs time resolution at a deflecting voltage of 80 MV for 8 GeV electron at SACLA, to investigate longitudinal electron beam structures for both SASE and sub-femtosecond XFEL operations, with ongoing efforts toward machine learning–based diagnostics. Longitudinal electron beam structures critically determine XFEL pulse properties. To further enhance XFEL performance and ensure robust operation under the extreme conditions, reliable diagnostics of longitudinal beam structures are essential. The X-TDS system, including RF source, pulse compression, a deflecting cavity, and low-level RF control, is scheduled for installation after the undulator section at SACLA this summer, with first beam operation in autumn. We develop a machine learning–based method to reconstruct phase space from energy–time measurements and relate it to XFEL pulse properties. In this presentation, we introduce the X-TDS system including the high-power test results and propose a data-driven analysis framework for reconstructing longitudinal phase space structures, along with example applications for XFEL performance optimization.

Speaker: Kenji Yasutome (RIKEN SPring-8 Center)

156 Cryogenic Testing of 650 MHz, 704 MHz, and 1.3 GHz SRF Cavities at the UKRI-STFC Daresbury Laboratory’s Vertical Test Facility

UKRI-STFC Daresbury Laboratory operates a flexible vertical test facility (VTF) for testing superconducting radio-frequency (SRF) cavities. Thanks to a series of expansion and upgrade activities, including a new cavity test insert, improved magnetic hygiene, and increased cooldown rate (principally to facilitate residual magnetic flux expulsion), the facility is now capable of testing a single high-beta 650 MHz PIP-II cavity (with fast cooldown), up to three high-beta 704 MHz ESS cavities, or a single 1.3 GHz cavity (either bulk Nb or thin film) per test cycle. The team are able to switch between 650 MHz, 704 MHz, and 1.3 GHz cavity testing configurations with minimal downtime between test runs. This contribution details the expanded capabilities resulting from the various upgrades, different modes of operation, and operational practices that enable cryogenic cavity testing at Daresbury.

Speaker: Ayomikun Emmanuel Temiloluwa Akintola (Science and Technology Facilities Council, ASTeC, STFC Daresbury Laboratory)

157 Design and simulation of a compact microtron for THz free-electron laser applications

A compact microtron accelerator has been developed as an electron source for a THz free-electron laser (FEL). The microtron scheme is adopted to realize a highly compact THz FEL system compared with conventional FEL facilities. The accelerator employs a 2.8 GHz magnetron with a peak power of 2.5 MW. In this work, the design and beam dynamics of the microtron are presented with emphasis on the pillbox-type cavity and electron beam transport characteristics. The cavity was designed to operate at the fundamental TM010 mode with optimized geometry for efficient RF coupling and stable beam acceleration. EM simulations were performed to evaluate the resonant frequency, quality factor, field distribution, and shunt impedance of the cavity. In addition, beam dynamics simulations were carried out to investigate electron bunch acceleration, phase stability, and transverse beam behavior within the microtron magnetic field configuration. The simulation results demonstrate stable electron acceleration and recirculation suitable for THz FEL applications. The designed microtron is expected to provide an efficient and compact accelerator platform for future THz radiation generation studies.

Speaker: geonwook park (Korea University of Science and Technology)

158 Design for a Femtosecond-Synchronized Nanosecond Laser Pulse Train System for the Korea-4GSR Photocathode RF Gun

The Korea-4GSR injector requires a highly stable and precisely synchronized laser pulse train system for multi-bunch operation of the photocathode RF gun. To support this requirement, a laser system capable of generating nanosecond-interval pulse trains with femtosecond-level timing synchronization is being designed.
The proposed system employs a beam-split, delay, and recombination scheme to generate a 64-pulse train with 2 ns spacing synchronized to a 500 MHz RF reference. In addition, a 500 MHz femtosecond oscillator is being considered for integration into the system to enable precise timing diagnostics and long-term synchronization stability.
The synchronized laser system is expected to provide improved timing stability and reliable operation for both single-bunch and multi-bunch injector modes of Korea-4GSR. This paper presents the overall design concept of the laser pulse train generation system and the planned synchronization and diagnostic configuration.

Speaker: Namseok Go (Pohang Accelerator Laboratory)

159 Design, fabrication, and testing of a plate electrode CH-mode cavity

The normal temperature drift tube linac, serving as an injector for medical synchrotrons, is typically based on APF and KONUS beam dynamics within IH-mode cavities to achieve cost-effectiveness and operational stability. While the APF structure combines acceleration and focusing through phase adjustment, its relatively low accelerating gradient results in a lengthy cavity. Conversely, the KONUS scheme offers a high accelerating gradient and compact design by operating near a zero-degree synchronous phase. However, it requires internal quadrupole triplets for transverse focusing, increasing both cost and mechanical complexity. To address these limitations, this paper proposes a novel acceleration structure that employs flat plate electrodes instead of conventional cylindrical drift tubes. Integrated into a CH-mode cavity with vanes to optimize the electric field and RF performance, this design is combined with KONUS dynamics to enable transverse focusing during near-zero-degree acceleration, leading to a more compact and efficient system. This paper presents the design, fabrication, and preliminary test results of this innovative structure.

Speaker: Fu Ma (Institute of Modern Physics, Chinese Academy of Sciences)

160 Development and Testing of Tools for ORM Measurements and Quadrupole Centering

In preparation for commissioning of Linac2 (PIP-II) at Fermilab, software tools automating Orbit Response Matrix measurement and beam-based localization of quadrupole magnetic centers are being developed. The intention is to realize the procedures in a low-loss mode compatible with otherwise regular operation. The ORM is measured using simultaneous low-amplitude excitation of multiple dipole correctors at distinct frequencies, followed by Discrete Fourier Transform analysis of the recorded BPM signals to extract per-element transfer functions with quantified noise. One of the applications of the measured ORM is prediction of coefficients for creating local perturbations with the dipole correctors (bumps). For centering the trajectory in a quadrupole, such a bump is created around the quadrupole. The current of the quadrupole is oscillated, and responses of downstream BPMs are recorded and analyzed. The procedure is repeated at several beam positions inside the quadrupole, changed by the bump. The dependence of the BPM signal on this beam position provides information about the quadrupole center. The tools are tested at the Fermilab 400 MeV Linac during regular productions runs.

Speaker: Abhishek Pathak (Fermi National Accelerator Laboratory)

161 Development of a C-band High-gradient Traveling Wave Accelerating Tube for the Southern Advanced Photon Source (SAPS)

The Southern Advanced Photon Source (SAPS) constitutes a 3.5 GeV fourth-generation storage ring. A full-energy linac injector based on a low-emittance C-band RF gun and C-band high-gradient accelerating structures (HGAS) has been proposed. To meet the engineering requirements for compactness and reliability, a compact C-band traveling wave accelerating tube has been designed and fabricated. The structure geometry is optimized to suppress the ratio of peak E-field and average E-field to reduce RF breakdown probability and increase shunt impedance. Specifically, the cavity shape and inter-coupling coefficients are refined to achieve a more uniform surface electric field. Cavity design and water cooling simulations have been conducted utilizing Superfish and CST, while RF parameters have been tuned using the resonant perturbation method, to obtain the S11 parameter being less than −50 dB . The prototype has successfully passed high-power testing, operating stably under rated conditions with an acceptable breakdown rate. This work demonstrates the feasibility of using such a compact, high-gradient C-band structure for the SAPS injector.

Speaker: Ahong Li (Institute of High Energy Physics, Spallation Neutron Source Science Center)

162 Development of a Novel Adaptive Beam Loading Compensation System for a High Current Pulsed Proton Linac

In high current pulsed beam accelerators such as the J-PARC linac, beam loading compensation is essential for maintaining uniform accelerating fields in the presence of beam loading and reducing momentum variation within a pulse. In practice, fluctuations in high power RF components and beam conditions cause the optimal compensation parameters to vary continuously. To address this issue, we developed an adaptive beam loading compensation system that models the RF system using transfer functions derived from measured time domain responses and calculates optimal parameters in the frequency domain. The accelerating field converges to its optimal value within about two to three iterations without error accumulation or divergence. This enables stable field control under typical operating conditions. Furthermore, the system has been further improved and is operated to maintain field stability even under thinned intermediate-pulse operation. These results demonstrate the applicability of the transfer function measured in the RF system of accelerators.

Speaker: Kenta Futatsukawa (High Energy Accelerator Research Organization)

163 Development of a resonator for the measurement of the beam quadrupole moment in a high-intensity heavy-ion linac

Non-invasive measurements of the beam quadrupole moment provide information for the evaluation of the beam emittance and Courant-Snyder parameters for transverse matching. Such a procedure is required for each charge state of heavy ion beams at multiple locations along the FRIB linac. We are developing a quadrupole mode resonator, enabling us to extract the information about the beam quadrupole moment with much greater accuracy than non-resonant devices such as Beam Position Monitors. We have built a full-scale prototype resonator in which the quadrupole mode is excited by the 33rd harmonic of the beam frequency of 40.25 MHz. The results of RF measurements and quadrupole signal acquisition with monopole and dipole mode suppression will be reported. These studies are a necessary step towards the design and construction of the vacuum-tight resonator and its use for beam measurements.

Speaker: Alexander Plastun (Facility for Rare Isotope Beams)

164 Development of an Automated Lorentz Force Detuning Compensation System for the ITN Cryomodule at KEK

At KEK, an International Linear Collider prototype cryomodule with eight TESLA-type cavities is under development. The cryomodule will operate in pulsed mode at 5 Hz. During RF operation, electromagnetic forces mechanically deform the cavity structure, shifting the resonance frequency through Lorentz Force Detuning (LFD).
A common method for LFD compensation is feedforward control using a piezo actuator driven by a half-sine waveform to restore resonance during the flat-top. Effective compensation requires optimization of waveform amplitude, frequency, DC offset, and phase relative to the RF pulse. Manual tuning is feasible for a small number of cavities but is time-consuming and difficult to scale.
To address this, an automated LFD compensation algorithm is being developed on a Red Pitaya FPGA platform using Vivado. The system automatically optimizes the piezo drive parameters for cavity tuning. This contribution presents the current progress of the automated compensation algorithm and the cavity simulator developed for testing
and evaluation.

Speakers: Mathieu Omet (High Energy Accelerator Research Organization), Dr Rishabh Bajpai (High Energy Accelerator Research Organization)

165 Development of high power energy recovery absorbing load for large scale accelerators

For large particle accelerators, the radio-frequency (RF) power source system constitutes the most significant portion of total energy consumption. A substantial fraction of the RF energy not utilized for charged particle acceleration is directed to an absorption load at the output of the accelerating structure, where it is converted into thermal energy and dissipated. To use this otherwise wasted energy, RF-DC rectification technology presents a viable solution for converting the RF power back into usable DC electricity. Historically, the performance of this technology has been constrained by the limited high-frequency and high-power handling capabilities of transistors. Therefore, although it has an attractive concept, this method has not been implemented in experiments or engineering applications when reaching the GHz level.
However, the recent advent of fourth-generation transistors based on Gallium Nitride (GaN) has significantly advanced these capabilities, renewing the experimental prospects of this energy recovery method. This work is dedicated to investigating the feasibility of this GaN-based RF rectification scheme.

Speaker: yang zhao (Institute of High Energy Physics, Chinese Academy of Sciences)

166 Development of L-Band 10MW High Efficiency Multibeam Klystron

This paper presents the design and simulation of a high-efficiency 10 MW RF power source including the complete electron gun, electromagnet focusing system, RF interaction structure and output window. At an accelerating voltage of 115 kV, the designed electron gun produces a total space-charge-limited beam current of 132 A while maintaining an average cathode loading below 3.36 A/cm², which is suitable for safe and efficient operation. The calculated maximum surface electric field in the beam optics region remains below 5.8 kV/mm, while the electric field at the high-voltage ceramic seal is limited to 1.17 kV/mm. These values indicate that the structure operates within acceptable electrical stress limits, thereby reducing the risk of breakdown and improving long-term device reliability in 2D and 3D software's. The static beam analysis shows that the electron beam, with an average beam radius of 5 mm, is successfully focused and transported to the interaction cavity.The beam ripple is maintained at less than 5%.Beam dynamics analyses were conducted using 1D AJDISK, 2D KLYC, 2.5D EMSYS, and 3D CST simulation tools, which predicted efficiencies of 75%, 74%, 72%, and 72%, respectively.

Speaker: NOMAN HABIB (Institute of High Energy Physics)

167 DEVELOPMENT OF NORMAL CONDUCTING HEAVY ION LINAC IN CHINA

The research on heavy ion linac was began more than ten years ago initially aim to improve the HIRFL operation at IMP. In China, a continuous wave (CW) heavy ion linac,SSC Linac, working at 53.667MHz was developed as the SSC injector. The ion particle can be accelerated to 1.48MeV/u with the designed A/q=5.17. At present stage, this CW linac has been put into operation and the Uranium has been accelerated to 1.48MeV/u successfully. To satisfy the continue requirements, a compact 162.5MHz heavy ion linac operating in pulse mode was developed. The “KONUS” beam dynamics design was adopted and the heavy ions can be accelerated to 4MeV/u with A/q≤3. The SESRI linac was another pulse machine which was built at Harbin. In this linac, both of the heavy ions and proton beam can be accelerated by this linac to 2MeV/u and 5.6MeV, respectively. In this paper, the status of these three heavy ion linacs and their beam commissioning results were presented.

Speakers: Fu Ma (Institute of Modern Physics), Xuejun Yin (Institute of Modern Physics), Zhongshan Li (Institute of Modern Physics)

168 Driving the SIBAF Project: Physics Design of a 108.408 MHz Heavy-Ion RFQ Injector with A/Q up to 8.5 for Fusion Material Irradiation

A dedicated heavy-ion Radio Frequency Quadrupole (RFQ) accelerator is currently under development at GSI for the SIBAF (Superconducting Ion accelerator as BAsis technology for Fusion research) project. Operating at 108.408 MHz, the RFQ is designed to accelerate heavy ions with a mass-to-charge ratio (A/q) of up to 8.5, from an injection energy of 4 keV/u to a final energy of 300 keV/u. Given that the subsequent main linac utilizes superconducting structures, the RFQ must deliver exceptionally high beam quality to minimize losses and ensure stable operation. This paper details the physics design concepts, beam dynamics optimizations, and comprehensive simulation results for the SIBAF RFQ.

Speaker: Holger Podlech (Goethe University Frankfurt)

169 EEX-based methods towards nanometer-scale modulation and brightness enhancement

Emittance exchange (EEX) is an attractive approach for generating high-frequency bunch trains from transverse modulations. Ongoing efforts aim to explore the limits of longitudinal modulations achievable with EEX beamlines and methods for enhancing radiation brightness for a given beam. One project investigates the generation of nanometer-scale longitudinal modulation using a transmission electron microscope (TEM) grid combined with a quadrupole demagnifier that controls the period of the transverse density modulation. Another project explores the feasibility of generating a sawtooth correlation—known to maximize radiation brightness from a single bunch--using transverse wigglers. We present the goals and status of these projects. This includes the design of an EEX beamline compatible with nanometer-scale modulation and a transverse wiggler system for producing sawtooth correlations.

Speaker: Buse Naz Temizel Ozdemir (Northern Illinois University)

170 Electromagnetic design study of a 500 MHz sub-harmonic buncher cavity for the PLS-II linac

The PLS-II is considering nonlinear-kicker (NLK) injection to reduce stored-beam perturbations. This scheme requires the linac to deliver a dominant bunch with a reduced energy spread. However, the present S-band pre-buncher and buncher generate multiple bunches, leading to RF-phase-dependent capture conditions and possible injection instability. A previous study using a 500 MHz sub-harmonic buncher (SHB) model based on 2D SUPERFISH calculations showed that replacing the pre-buncher reduced the rms energy spread from 10 MeV to 1.1 MeV and produced a dominant bunch at the end of the simulated injector section. To support further evaluation, this work develops a simulation-based electromagnetic model of a 500 MHz SHB cavity. The cavity is designed using eigenmode simulations and is evaluated in terms of the resonant frequency, effective gap voltage, shunt impedance, intrinsic quality factor, transit-time factor, and peak surface field. The cavity-derived longitudinal field is used in particle tracking to assess its effect on bunching and energy spread. This study provides the electromagnetic design basis for evaluating a 500 MHz SHB option for the PLS-II linac.

Speaker: Mr Geunwoo Kim (Pohang University of Science and Technology)

171 ESS Beam Current Monitor System: Technical Challenges and Improvements from Seven Years of Operation

With the restart of beam commissioning activities at the European Spallation Source (ESS) in January 2026, the Beam Current Monitor (BCM) system has been in operation for more than seven years. During this period, several beam monitoring and machine protection functions have been added to the system, including beam mode and destination consistency checks, as well as differential beam loss measurements. The overall system accuracy is about 0.1%, requiring reliable analog signal transmission over long cables, low-noise electronics and fast digital signal processing. These aspects are particularly important to minimize the impact of electromagnetic interference (EMI) from RF and other high-power pulsed equipment, thereby improving beam availability. This paper presents an overview of the ESS BCM functions, the technical challenges encountered during beam commissioning, and the solutions implemented to improve system performance and availability.

Speaker: Hooman Hassanzadegan (European Spallation Source)

172 Full 4D Reconstruction of Phase Space via Maximum Entropy Theory for Slit-Based Beam Diagnostics

Emittance is a key parameter that characterizes beam quality and its behavior under given optics. Conventional emittance measurement methods reconstruct the beam phase-space based on Twiss parameters calculated from beam profiles, and are therefore based on Gaussian beam optics. To overcome this limitation, tomography techniques have been introduced to reconstruct the phase-space distribution using projection data measured at various phase-space angles. In this study, we reconstruct the phase-space distribution using the Maximum Entropy Theory (MENT) with data from the slit-based Virtual Pepper-Pot (VPP) diagnostics at the Beam Test Stand (BTS) of the Korea Multipurpose Accelerator Complex (KOMAC). The conventional multi-optics tomography method is improved by combining it with MENT. To avoid nonlinear effects such as space charge, a single-optics configuration is also established using a fixed quadrupole setting, with angular projection data obtained by introducing additional diagonal scans and multi-screen scans. Using X-suite simulations, the two methods are quantitatively compared in terms of total variation distance (TVD) and emittance error.

Speaker: DAON LEE (Kangwon National University)

173 Gain and beam quality degradation in a transverse gradient undulator in the large signal regime

The transverse gradient undulator (TGU) is a key component for realizing diffraction-limited storage-ring-based X-ray free-electron laser oscillators (XFELOs), as it can compensate for the large energy spread in storage ring electron beams. Previous studies have mainly focused on the small-signal gain of the TGU in such a setup. However, under large-signal conditions, the gain can deviate significantly from the small-signal gain. In this contribution, we investigate the TGU gain in the large-signal regime using three-dimensional simulations. We also examine the effects of large-signal interaction on beam quality, in particular the increase in beam emittance.

Speaker: Xingguang Liu (Chinese Academy of Sciences)

174 Generation and Application of Stripped Proton Beams at the CSNS Linac

The CSNS linac delivers a primary H⁻ beam to the RCS while also providing stripped proton beams generated through two mechanisms: foil stripping and intra-beam stripping. Carbon foil collimators selectively strip halo particles from the beam periphery, reducing the transverse emittance of the H⁻ beam, which allows a larger painting range during RCS injection and reduces beam loss. Intra-beam stripping is an unavoidable byproduct of high-intensity H⁻ transport whose effects will become more prominent at the higher beam power of the CSNS-II upgrade, and this work presents initial studies of its mechanisms. The intra-beam stripping generated proton beam has been used for detector calibration, while the higher-intensity foil-stripped proton beam can be used for isotope production. This work demonstrates a dual-beam operation design at the CSNS linac, turning stripped proton beams from a source of beam loss into new applications.

Speaker: Zhiping Li (Institute of High Energy Physics)

175 Generation of Local Vertical Dispersion in a Long Straight Section of SAPS Storage Ring

A promising direction for fourth-generation light sources is the integration of a free-electron laser (FEL) oscillator to achieve higher spectral brightness. This approach imposes stringent requirements not only on the FEL oscillator parameters but also on the storage ring's performance. Preliminary studies at the Southern Advanced Photon Source (SAPS) indicate that the optimal gain for an oscillator occurs when the vertical dispersion in a long straight section is approximately 1 cm. To realize this condition, we explore methods to introduce a local vertical dispersion in the SAPS storage ring lattice. Several approaches are under consideration, such as applying a bending angle to a longitudinal gradient dipole within a DBA-like cell to generate the desired vertical dispersion, with subsequent correction using a dipole in the next cell. This paper discusses the principles for generating such local vertical dispersion and evaluates its potential impact on the overall ring performance.

Speaker: Yu Zhao (Institute of High Energy Physics)

176 Intra-Pulse Feedback for Short RF Pulses in LLRF Systems

LLRF control of accelerating cavities with microsecond-scale pulses is challenging because short pulses limit the effectiveness of FPGA-based intra-pulse feedback, restricting control to pulse-to-pulse corrections. This is often insufficient to compensate RF-chain-induced jitter and achieve the required field stability. We propose a novel intra-pulse feedback scheme for short pulses, featuring autoconfiguration and support for advanced pulse shaping, including SLED systems.
An implementation of this novel feedback concept was developed and deployed at the INFN SPARC_LAB facility, representing the first realization of its kind. It is now routinely operated with state-of-the-art performance, demonstrating significantly improved phase stability compared with conventional pulse-to-pulse control.
We present here a new implementation for short-pulse operation, based on a different architecture that simplifies system integration. This paper describes its design and experimental validation, including measurements at INFN SPARC_LAB. The proposed solution extends the Libera LLRF platform and has strong potential for short-pulse accelerator applications.

Speaker: Borut Baricevic (Instrumentation Technologies (Slovenia))

177 Intrabeam Scattering studies in Free Electron Lasers with RF-Track

Intrabeam Scattering (IBS) has recently been recognized as a limiting factor for free electron laser (FEL) performance, making it a critical concern for the linear accelerator community. There is a growing need for accurate numerical tools to compute IBS and integrate it with other collective effects, as most previous studies assumed Gaussian beams, which are not representative of FEL conditions. In response, the tracking code RF-Track has been enhanced with a novel kinetic-hybrid Monte Carlo algorithm for IBS calculations. This contribution reports on IBS studies for several FELs, including SwissFEL at PSI and FERMI at Elettra. For SwissFEL, simulation results are benchmarked against experimental measurements. Benchmarks of emittance growth are compared with other tracking codes, and predictions for IBS impact on future facilities are discussed.

Speaker: Paula Desire Valdor (European Organization for Nuclear Research)

178 Introduction of co-deposition method for improvement of quantum efficiency and lifetime of Cs-Te photocathodes in KU-FEL

Cs-Te photocathodes are widely used in photoinjectors for free electron lasers owing to their high quantum efficiency (QE). At KU-FEL, an infrared oscillator-type FEL in Kyoto University, a 1.6-cell RF gun with CsBr-coated Cs-Te photocathode has been developed for high-bunch-charge (~1 nC) multi-bunch operation. However, the QE and lifetime of the cathode in our RF gun are insufficient for practical use. In 2024, CERN group reported that the QE of Cs-Te photocathode made by co-deposition has significantly higher than that made by sequential deposition*. Therefore, we are planning to introduce the co-deposition method to our system to increase the QE and lifetime of the cathode. Right now, a co-deposition source compatible with our UHV chamber was designed and fabricated. Co-deposition experiments are planned in May 2026. Results with co-deposition and sequential deposition of Cs-Te photocathodes in our system will be reported in the conference.

Speaker: Mr Yutaro Kubo (Kyoto University)

179 JINR DLNP Linear Accelerator: Commissioning Results and Preparations for the Official Startup

Last preparations for operation for users are ongoing at the new basic facility of the Laboratory of Nuclear Problems of the Joint Institute for Nuclear Research — the LINAC (formerly LINAC-200) accelerator. The facility can provide electron beam with a wide range of energies (5 to 200 MeV), pulse durations (0.25 to 3 us) and charges (240 nC to single electrons per pulse). The maximum pulse repetition rate is 25 Hz. The facility can also provide beams of gamma rays (by installing tungsten converter in the beamline) and neutrons (beryllium converter). Commissioning results and last facility upgrades are presented.

Speaker: Mikhail Nozdrin (Joint Institute for Nuclear Research)

180 LINAC BEAM PHYSICS DESIGN UPDATE for CSNS POWER UPGRADE PROJECT

The China Spallation Neutron Source (CSNS) officially initiated its power upgrade project(CSNS-Ⅱ) in 2024, aiming to raise the accelerator beam power from 100kW to 500kW. The CSNS accelerator consists of an 80 MeV normal conducting linear accelerator and a 1.6 GeV rapid cycling synchrotron. To increase the peak beam intensity from 10mA to 40 mA, we plan to replace the front end system of the linear accelerator. Meanwhile, a superconducting linear accelerator will be implemented to boost the beam energy from 80 MeV to 300 MeV. This paper presents the upgraded linac lattice design and corresponding commissioning results developed for high intensity beam operation.

Speaker: Jun Peng (Institute of High Energy Physics)

181 Longitudinal Acceptance Improvement via RF Phase Retuning in RAON Superconducting Linac Beam Commissioning

The RAON superconducting linac consists of quarter-wave resonator (QWR) and half-wave resonator (HWR) sections and is designed to accelerate ion beams from protons to uranium, with a uranium beam energy of up to 18.5 MeV/u. During the 2026 beam commissioning, three QWR cavities and eight HWR cavities were not available for operation. The absence of multiple cavities can disturb the longitudinal beam dynamics by changing the energy gain and synchronous phase profile from the nominal lattice. This may reduce the longitudinal acceptance and increase the risk of beam loss. To mitigate this effect, RF phases of the cavities both upstream and downstream of the inactive cavities were retuned to keep the beam within the stable RF bucket. In this work, simulation and experimental studies on this phase-retuning method are presented. The results show that appropriate RF phase adjustment can compensate for missing cavity operation, improve the longitudinal acceptance, and enhance beam transmission during superconducting linac commissioning.

Speaker: Ji-Ho Jang (Institute for Basic Science)

182 Longitudinal phase space reconstruction via acceptance scans in high-current hadron linacs

Optimizing lattice and beam tuning in high-current hadron linacs requires reliable characterization of the full three-dimensional phase space. However, longitudinal diagnostics in linacs are inherently sparse, leading to limited observability and ambiguities in phase space. In J-PARC linac, only a few bunch shape monitors are available, and their use is constrained by operational limitations, making them insufficient for routine high-precision longitudinal matching. As an alternative, we develop a measurement scheme based on longitudinal acceptance. By sampling the effective acceptance under multiple conditions—either at different locations or with varied upstream longitudinal focusing—and analyzing the transmitted beam, the longitudinal phase space can be inferred even in the presence of space charge and nonlinear effects. The reconstructed phase space enables more reliable beam tuning and provides insight into transverse–longitudinal coupling, particularly in the context of phase-space “temperature” control. This is directly relevant to the mitigation of intra-beam stripping (IBSt) and distributed beam loss in high-intensity H⁻ linacs, as demonstrated in recent J-PARC operations.

Speaker: Yong Liu (High Energy Accelerator Research Organization)

183 Low-Level RF and timing systems of the laser driven RF gun test bench at JINR DLNP

Low-Level RF and timing systems are of primary importance to operate laser-driven RF-Gun. The laser oscillator piezo feedback synchronizes the phase between laser pulse and accelerating field. The laser pulse picking is conducted by the acousto-optic modulator in order to generate from single shot to tens pulses per facility machine cycle. The acousto-optic modulator operation is synchronized by the trigger pulses arrival time. The trigger pulses generation and delay are controlled by the digital time delay modules, which are locked to the accelerating field clock signal. Both systems are being commissioned at the laser-driven RF-Gun test-bench at the Laboratory of Nuclear Problems, Joint Institute for Nuclear Research. The test-bench Low-Level RF and timing systems current status is presented in this report. Moreover, the laser oscillator piezo feedback analogue and digital signal processing chains, including algorithms, are demonstrated in details.

Speaker: Dr Konstantin Popov (Joint Institute for Nuclear Research, Institute of Nuclear Physics)

184 Machine learning-based calibration and surrogate modeling of the photoinjector at PAL-XFEL

To achieve a high-brightness X-ray free-electron laser (FEL), it is essential to perform precise tuning of electron beam parameters at the photoinjector section, where the intrinsic emittance is determined. At PAL-XFEL, injector tuning is typically performed via manual, parameter-scan-based emittance optimization, which can be time-consuming. In addition, simulation-based beam matching often shows discrepancies with measured data, making beam prediction more challenging. To address this issue, we have developed a machine learning-based surrogate model to calibrate the simulation model and represent injector beam dynamics. The model is initially trained using particle tracking simulation data that include realistic UV laser distributions. This initial training is then refined through transfer learning with measured data. The resulting surrogate model enables fast prediction of beam parameters and can be used to guide beam tuning. This approach is expected to reduce tuning time and support more efficient accelerator optimization.

Speaker: Won Jang (Pohang University of Science and Technology)

185 Maintenance strategies and high-power RF testing of ESS RFQ power couplers and DTL RF windows

Following the Beam on Dump (BOD) and BOD2 campaigns, the European Spallation Source (ESS) is preparing for the subsequent BOD3 and Beam on Target (BOT) phases, which require higher levels of accelerator reliability, availability, and stability. Ensuring continuous operation demands not only effective maintenance but also advanced strategies for managing critical components.

This work focuses on RFQ power couplers and DTL RF windows, key elements for RF power transmission and vacuum integrity, exposed to significant electromagnetic, thermal, and vacuum stresses. Beyond maintenance, the study presents dedicated test stands for high-power RF testing and conditioning in a controlled environment.

Main issues encountered during testing, such as multipacting, RF arcing, and contamination, are analyzed. These efforts aim to reduce risks, improve reproducibility, and ensure the availability of ready-to-use spare components, minimizing machine downtime.

This work shows that integrating maintenance with dedicated testing infrastructure is essential to enhance RF system reliability and support future high-power ESS operation.

Speaker: Andrea Passarelli (European Spallation Source)

186 Medical FLASH facilities

In 2019, the annual number of cancer cases exceeded 19 million, resulting in 10 million deaths worldwide. Radiation therapy stands out as one of the most effective methods for cancer treatment. Electron beams in the 100-MeV range can reach even deep-seated tumors without the need for surgical intervention. Thanks to novel high-gradient acceleration technologies, clinical facilities for high-energy electron–based irradiation are actively under development. In this talk, we give an overview of the existing low-energy electron and Very-High-Energy Electron (VHEE) machines capable of reaching ultra-high dose rates, thus enabling exploration of the potential FLASH effect. Furthermore, we shine a light on the planned VHEE UHDR medical facilities coming on stage in the next decade. We conclude by emphasizing the unsolved challenges associated with the exploitation of the FLASH effect, with special emphasis on the temporal structure of the delivered irradiation.

Speaker: Alexander Malyzhenkov (European Organization for Nuclear Research)

187 Multiphysics-Based Optimization of Cooling Structure for Drift Tubes in a High-Intensity Proton Linac

The Alvarez-type drift tube linac (DTL) is critical for high-intensity proton accelerators. Higher RF duty factors impose severe cooling demands on drift tubes (DTs). However, DTs embedded with electromagnetic quadrupoles (EMQs) have extremely limited space for water channels due to complex fabrication. This problem is more critical in higher-energy DTL sections, where the heat flux density at the DT nose cone is substantially higher and harder to dissipate. To address this, a multi-physics approach is established. Heat source distribution from electromagnetic simulations is transferred to CFD for conjugate heat transfer analysis, followed by thermal-deformation and frequency-shift evaluation. Key cooling parameters—heat flux distribution, flow path, and flow velocity—are analyzed. Based on these, the water circuit is optimized. The optimized design significantly reduces maximum DT temperature and the resulting steady-state frequency shift, while pressure drop and manufacturing complexity remain within acceptable limits. This method provides a practical cooling solution for high-duty-factor DTL drift tubes and offers a reference for other high-intensity linac projects.

Speaker: Ahong Li (Institute of High Energy Physics, Spallation Neutron Source Science Center)

188 NEW COMPACT HOM DAMPER FOR SRF CAVITIES

SRF technology enables particle accelerators to operate with greater average beam currents and higher duty cycles. In these regimes parasitic excitation of the cavity High Order Mode (HOM) spectrum becomes the limiting factor due to extra RF losses and the beam instabilities. We discuss the limitations of HOMs for large accelerator projects such as the Fermilab MI upgrade and the proposed future circular and linear colliders EIC and ILC. A new compact HOM damper concept would provide required HOM suppression. The idea is based on using an oversized coaxial line with a half-septum insert directly connected to the axial region of the SRF cavity. Such radially sectioned coaxial acts as a low-pass filter for the operating mode, while remaining transparent for the HOMs. Implementations of this design for the accelerating and crab cavities developed for the ILC, MI and EIC machines, respectively, are discussed. We pay particular attention to evaluating limiting factors such as multipactor phenomena in the coaxial line, suppression of arbitrary polarizations of dipole HOMs, and the possibility of integrating the proposed designs with proven solutions for broadband HOM absorbers.

Speaker: Andrei Lunin (Fermi National Accelerator Laboratory)

189 No parametric instabilities in actual high-intensity linear accelerators except the envelope instability

Parametric instabilities have been long known to the community and studied intensively. However, simulations with the realistic distributions find that no parametric instabilities are manifested except the envelope instability. Moreover, the effect of the envelope instability is less for realistic distribution than Gaussian distribution. Onset of the envelope instability is delayed significantly and the emittance growth is reduced. On the other hand, the effect of the fourth-order particle resonance is more for realistic distributions.

Speaker: Dong-O Jeon (Institute for Basic Science)

190 Operation Status of Scintillator-based Beam Loss Monitors for KOMAC DTL tanks

Beam loss monitor (BLM) is a key device for protecting accelerator systems, as it measures secondary radiation produced by a particle beam colliding with the inner wall of the accelerator. Therefore, in the KOMAC 100 MeV proton accelerator, BLMs were installed on the 20 MeV DTL (Drift Tube Linac) and 100 MeV DTL tanks for the purpose of machine protection. These BLMs are scintillator-based radiation detectors capable of operating in high-radiation environments, with two or more devices installed on each DTL tank. In this study, the nonlinearity between BLM signal intensity and beam loss was analyzed to demonstrate that considering not only beam current but also other conditions are essential for calibrating BLMs.

Speaker: Gyuhaeng Jo (Korea Multi-purpose Accelerator Complex)

191 Overview of Beam Tuning Development Using Machine Learning at ATF

At the Accelerator Test Facility (ATF) at KEK, research and development of beam control and diagnostic techniques is being carried out toward the realization of nanometer-scale beams required for the International Linear Collider. Since nanobeam tuning requires the adjustment of many parameters under limited machine time and human resources, efficient optimization methods are essential. In this work, we have developed and implemented a beam tuning method based on Bayesian optimization. The results confirm more efficient tuning than conventional manual operation. In parallel, a big-data analysis framework is also being developed to organize and utilize operational data for improving machine understanding and future automated tuning. This presentation gives an overview of these machine-learning-based developments at ATF and discusses their potential for efficient beam operation.

Speaker: Motoki Sato (High Energy Accelerator Research Organization)

192 Phase matching of longitudinal hollow electron beam and ion beam in a storage ring

In the cooling storage ring, a low-temperature electron beam from the electron cooling device overlaps with a high-temperature ion beam in the storage ring. The overlap occurs at the same average velocity for a certain distance. Through Coulomb interaction, electrons absorb excess energy from ions. This reduces the transverse emittance and longitudinal momentum spread of the ion beam, and increases its phase space density. When cooling a Gaussian-distributed pulsed ion beam with a longitudinal hollow electron beam, the pulses must match at the longitudinal center. This article introduces a phase match scheme for longitudinal hollow electron beams and ion beams. The scheme includes pulse measurement, triggering delay, phase match monitoring, and future feedback for automatic correction. This ensures the pulses are always synchronized. The scheme will be used in longitudinal hollow electron beam cooling experiments and will support future investigations into the cooling process.

Speakers: Fu Ma (Institute of Modern Physics, Chinese Academy of Sciences), Prof. Xiaodong Yang (Institute of Modern Physics, Chinese Academy of Sciences)

193 Physics design of a full cryogenic test platform at IHEP

High-brightness, ultra-low emittance electron beams are essential for XFELs, UED, and UEM. Cryogenic RF copper structures enable higher breakdown thresholds and accelerating gradients, opening new possibilities for ultra-bright sources.
We present the design and optimization of a compact, fully cryogenic injector integrating a C-band (5712 MHz) RF gun and accelerating structure at 77 K, representing a first concept of an all-cryogenic beam test facility. Beam dynamics optimization was performed using ASTRA with the NSGA-II algorithm, targeting low emittance and high peak current. The effects of RF gradient and laser pulse shaping were investigated.A normalized transverse emittance of 0.126 mm·mrad was achieved at 100 pC. Sensitivity to RF jitter and misalignment was also evaluated. These results demonstrate the potential of all-cryogenic injectors for compact XFELs and advanced accelerators.

Speaker: Zhongtian Liu (Chinese Academy of Sciences)

194 Plasma Processing Developments for Medium- and High-Beta Cavities in the ESS Linac

Plasma processing is increasingly recognized as an effective technique for mitigating field emission and restoring the performance of SRF cavities. A collaboration between CEA, ESS and INFN is currently working to adapt and optimize this method for the medium- and high-beta elliptical cavities installed in the ESS linac.
This contribution summarizes ongoing efforts to implement plasma processing both in cavities assembled in cryomodules and in cavities prepared for vertical testing. The work presents electromagnetic analyses performed to identify the modes that best allow processing of the cavities, together with the conceptual design of the vacuum system for the experimental setup. Results obtained on a 704 MHz medium-beta cavity equipped with different couplers are also reported, along with preliminary investigations carried out on the 704 MHz high-beta cavity.

Speaker: Andrea Passarelli (European Spallation Source)

195 Pole Shape Optimization of a Tunable Permanent Magnet Quadrupole for Future Accelerator Beamlines

Next-generation storage rings require low emittance and high brilliance, and their quadrupole magnets must provide both high magnetic gradients and stringent multipole field quality. Conventional electromagnetic quadrupoles consume substantial electrical power and require cooling systems because of Joule heating. In this study, a permanent magnet quadrupole (PMQ) that generates its magnetic field without an excitation power supply and allows the gradient to be varied mechanically was designed.
Starting from a two-dimensional pole shape and an end-edge chamfer angle determined in previous work, the geometry was extended to a three-dimensional model that accounted for a 2 mm longitudinal pole extension at each end, introduced during fabrication to clamp the poles to the aluminum yoke. This extension altered the fringe-field distribution and degraded the integrated multipole content. A parametric sweep of the chamfer angle was therefore performed over the machinable range, and the angle minimizing the integrated harmonic content was selected.
The resulting geometry satisfies the field quality criteria for next-generation storage rings, with allowed multipole components below $5\times 10^{-5}$, forbidden components at the $10^{-5}$ level, and a field uniformity of 0.1% at $r_{ref} = 3 mm$. These results demonstrate the feasibility of a high-quality PMQ that provides a variable magnetic gradient without steady-state power consumption or cooling.

Speaker: Junwon Choi (Kangwon National University)

196 Preliminary Linac Design Options for the CSNS Phase‑III Upgrade

The China Spallation Neutron Source (CSNS) passed national acceptance in 2018. Construction of the Phase‑II upgrade began in 2024 and will increase the beam‑on‑target power from 100 kW to 500 kW and raise the linac exit energy from 80 MeV to 300 MeV. The planned Phase‑III upgrade will replace the current drift‑tube linac (DTL) downstream of the radio‑frequency quadrupole (RFQ) with a superconducting linac, and will add further superconducting accelerating sections at the end of the Phase‑II linac to raise the linac beam energy above 1 GeV. Depending on the chosen upgrade scenario, the accelerator beam power could be increased into the 2–10 MW range. This paper presents several preliminary linac design options for the CSNS Phase‑III upgrade and outlines their basic beam‑physics design.

Speaker: Yue Yuan (Institute of High Energy Physics)

197 Progress of S-band high efficiency periodic permanent magnet klystron

High-efficiency klystrons can significantly reduce the operational costs of particle accelerators. However, for the of low-duty-factor klystrons commonly used in linear accelerators, the power consumption of electromagnetic focusing coils remains non-negligible. This paper presents the progress of an S-band 50 MW high-efficiency klystron employing periodic permanent magnet (PPM) focusing aiming to achieve high conversion efficiency while minimizing auxiliary power consumption. Due to the relatively large dimensions of S-band tubes, the focusing structure is constrained and the beam rigidity is limited. These factors impose stringent requirements on beam dynamics design and require coordinated optimization of the magnetic field configuration and electron bunching process.. Simulation results validate the feasibility of applying PPM focusing to a high-efficiency S-band klystron, with an overall tube efficiency of 54%.The proposed S-band PPM klystron provides a promising approach for improving the efficiency and reducing the operational cost of high-power RF sources in accelerator application.

Speaker: Han Xiao (Institute of High Energy Physics)

198 Progress Update on the ATLAS Multi-User Upgrade at Argonne

The ongoing multi-user upgrade of the superconducting ion linac, ATLAS at Argonne, will enable simultaneous acceleration and delivery of two different ion beams to different experimental areas. One nearly continuous stable beam from the ECR ion source and one pulsed radioactive beam from the EBIS charge breeder of nuCARIBU will be interleaved in time via an electrostatic deflector at injection and accelerated through the first two sections of the linac. At that point, one of the beams is deflected via kicker magnet to a lower energy experimental area while the other is sent for further acceleration in the third section of the linac and delivered to a higher energy experimental area. In addition to enhancing the nuclear physics program at ATLAS, this upgrade will also increase the availability of beam time for some applications. While the construction and installation of the new pulsed injection beamline is now complete, the design of the extraction beamline has changed. The original chicane designed to bypass the existing 40-deg bend has been replaced by simple kicker-septum magnet system. Details of the final design and progress made on the kicker and septum will be presented.

Speaker: Brahim Mustapha (Argonne National Laboratory)

199 Pseudo six-dimensional + 1 phase space reconstruction with a Convolutional Neural Network

In particle accelerators, full knowledge of the six-dimensional (6D) beam phase space is crucial but difficult to obtain with conventional beam diagnostics. We have developed a two-stage convolutional neural network (CNN) that reconstructs the 6D phase space from only sixteen transverse x − y screen images taken at a place with dispersion by different phase space rotation angles. With these images, we reconstruct the 6D phase space distribution at the cathode surface and visualize it as 15 two-dimensional images covering all pairwise coordinate combinations. Compared to existing 6D beam imaging measurement techniques such as tomography, it significantly reduces measurement time and required computational resources, enabling the provision of a more practical 6D phase space measurement method.

Speaker: Zachary Liptak (Hiroshima University)

200 Radio-frequency cavity field measurements through free falling bead

A novel bead-falling measurement method is proposed for precise and efficient electromagnetic field mapping in RF cavities for particle accelerators. Unlike the conventional bead-pull technique, which uses a complex wire-pulley system prone to perturbations and mechanical errors, this method employs free-falling beads to simplify the setup and significantly improve accuracy.A compact portable device integrating an automated bead release and detection system connected to a vector network analyzer (VNA) was developed. The technique was validated on a three-gap buncher cavity and a scaled Alvarez-type cavity, showing excellent precision and stability even under low signal-to-noise ratios and environmental vibrations.This method offers superior accuracy, reliability, and efficiency, making it a promising new standard for RF cavity diagnostics and tuning.

Speaker: Dr Xiaonan Du (GSI Helmholtz Centre for Heavy Ion Research)

201 Recent progress in additive manufacturing of linear accelerator components

Compared with subtractive manufacturing methods such as CNC machining, additive manufacturing (AM) enables the fabrication of highly complex monolithic geometries. As a result, AM can improve functionality and reduce manufacturing costs. For linear accelerator (linac) components, this potential has been demonstrated in a growing number of studies and prototype developments. At the same time, recent advances in AM, particularly in metal powder-based processes, have significantly reduced earlier limitations related to linac-specific requirements such as vacuum outgassing and RF electrical conductivity. AM has therefore become a promising approach for the fabrication of linac components. It enables designs that are difficult or impossible to produce by conventional methods, including highly complex cooling structures and multimaterial components. Despite these advantages, conventional fabrication methods are still often preferred. This short review summarizes recent progress in the additive manufacturing of linac components. It discusses several successfully manufactured prototypes and shows which linac-specific requirements can already be fulfilled by AM today.

Speaker: Michael Mayerhofer (Universität der Bundeswehr München)

202 Recent progress in PWFA research at FACET-II

Emittance preservation is one of the biggest challenges in beam-driven plasma wakefield acceleration (PWFA), demanding extremely precise control of the transverse aspect of the electron beam. We will talk about recent experimental progress in transverse control and optimization for the PWFA experiment at FACET-II in order to demonstrate a collider-quality PWFA stage. We will talk about various novel diagnostics: slice BPM dispersion measurement, beam reconstruction and optimization, etc. We will talk about the application of ML-based optimization based on beam-only measurements and plasma performance.

Speaker: Yiheng Ye (SLAC National Accelerator Laboratory)

203 Reconstruction of beam transverse parameters in the Fermilab side-coupled linac using a normalized coordinate framework

Quadrupole scans are a commonly used tool for beam second moment reconstruction. Limitations in the strength of the magnets and layout of the beamline elements frequently preclude simple quadrupole-drift-detector scans from collecting sufficient data for reconstruction. Using a normalized coordinate framework, we characterize the prerequisites for a robust simple quadrupole scan and expand these prerequisites to reconstruction from more complex optics. The beam second moments are investigated at two locations in the Fermilab Side-Coupled Linac under simple and complex optics, using this framework to maximize information gained from wire scanner profile measurements.

Speaker: Erin Chen (Fermi National Accelerator Laboratory)

204 Research on Locally Focusing Atmospheric Muon Source

Atmospheric muon imaging has low efficiency due to low flux (~70 m⁻²·s⁻¹·sr⁻¹ at 0° zenith), requiring long acquisition. This paper proposes two magnetic focusing systems to enhance muon flux and reduce collection time: a three-section superconducting solenoid and a triplet quadrupole lens (short- and long-range focusing). The solenoid has inlet (1m/0.5m/5.5T), middle (0.75m/1m/3.5T), outlet (0.5m/0.5m/5.5T). At 0.5m from outlet, flux magnification is 2.17 for 0.6–1.2 GeV/c muons. The quadrupole lens gives magnifications of 2.10 (1m short-range) and 2.91 (20m long-range) for 1.4–3.0 GeV/c muons. Data based on sea-level muon flux. These enhancements cut collection time nearly in half. The long-range quadrupole is especially suitable for localized imaging in large facilities. A dynamically adjustable, noninvasive, economical locally enhanced imaging system is also proposed. This work establishes focusing methods for atmospheric muons, improving efficiency in archaeology, volcanology, and nuclear security.

Speaker: Liang Lu (Sun Yat-sen University)

205 Research on very high intensity laser ion source with a inner-assembled solenoid

The laser ion source (LIS) features a compact design, straightforward operation, and ease of maintenance. In this work, an inner-assembled solenoid is employed to confine the ion beam, thereby mitigating plasma expansion and reducing ion loss. The influence of laser power density on peak current, pulse width (FWHM) and total charge of Al, Cu, Fe and Ni ion beams in the range of 350 mJ-1450mJ is studied. The results indicate that increasing laser power enhances the peak current and ion energy, with Ni exhibiting a pronounced threshold behavior. With the application of an inner-assembled solenoid, the beam intensity of different ions at 540 mm and 900 mm increased by 2 to 5 times. The peak currents for Al, Fe, Cu, and Ni are 167 mA, 113.9 mA, 108.4 mA, and 111.5 mA, respectively, accompanied by prolonged pulse durations and enhanced total charge. Velocity distribution analysis confirms that the magnetically confined plasma still adheres to a Maxwellian distribution.

Speaker: Liang Lu (Sun Yat-sen University)

206 Resonance Control of an 81.25MHz RFQ with Dual Power Couplers at IRIS

The Institute for Rare Isotope Science (IRIS) has developed and is operating an 81.25 MHz Radio Frequency Quadrupole (RFQ) equipped with two power couplers. Due to small installation errors, the two couplers exhibit slightly different coupling factors (β). As a result, the reflected powers from two couplers become unbalanced depending on the operating temperature of the Resonance Control Cooling System (RCCS).
The RCCS was originally designed to regulate the coolant temperature within ±0.1 °C. However, because the current high-power RF system has limited capability to tolerate reflected power, simultaneous minimization of the reflected power from both couplers is required by optimizing the RCCS operating temperature.
To improve operational stability under the existing RF system conditions, the PID gains of the RCCS were optimized, and the temperature control resolution was refined from 0.1 °C to 0.01 °C. Through these improvements, the reflected RF power from both couplers could be effectively minimized, enabling stable RFQ operation under reduced reflection conditions.

Speaker: Bum-Sik Park (Institute for Basic Science)

207 RF design of a spherical-cavity-type pulse compressor for muon linac

The development of a muon-dedicated traveling-wave disk-loaded structure (DLS) is in progress at the Japan Proton Accelerator Research Complex (J-PARC). Accelerating ultraslow muons to relativistic energies preserves low beam emittance and improves penetration capability, enabling new opportunities in precision particle physics experiments and muon imaging. However, unlike electrons, muons undergo substantial velocity changes during acceleration, even at high energies, requiring precise phase synchronization between the beam and RF fields. This requirement becomes more critical when using pulse-compressed RF power with temporal variation.
In this work, we present the RF design of a spherical-cavity-type pulse compressor (SCPC) for a DLS. Two degenerate $\mathrm{TE_{112}}$ modes with a 90-degree phase difference are utilized at 2592 MHz. RF performance was optimized using 3D electromagnetic simulations to achieve the target frequency characteristics and controlled mode degeneracy. Based on the RF loss distribution, thermal analysis evaluated temperature rise and cooling requirements, while structural simulations assessed deformation to estimate frequency detuning.

Speaker: Yuga Nakazawa (High Energy Accelerator Research Organization)

208 S-band high-gradient low β single-periodic magnetically coupled standing-wave accelerating structure

A novel 3 GHz single-periodic magnetically coupled standing-wave accelerating structure for β=0.26 particles with an optimized nose cone and six coupling holes was proposed for the compact proton therapy linac under development at the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). High-power tests demonstrated that the accelerating structure could operate stably at an effective input power of approximately 5.7 MW, achieving an accelerating gradient of 38 MV/m at the pulse length of 5 μs and the repetition rate of 70 Hz. Further increasing the duty factor to 0.1%, the accelerating gradient decreased to 24 MV/m due to the uneven cooling of each single cell. Cavity design, optimization, manufacture, rf measurement, and high-power test are discussed in this paper.

Speaker: Wei Qin (Institute of Modern Physics, Chinese Academy of Sciences)

209 SARAF Cryomodules Status

SNRC and CEA are collaborating on developing SARAF Phase 2 to deliver 5 mA CW proton and deuteron beams up to 40 MeV. CEA is responsible for the design, fabrication and commissioning of the linac downstream of the RFQ. The linac includes four superconducting cryomodules (CM), comprising two low-β (β = 0.09) and two high-β (β = 0.18) units. All four cryomodules were successfully assembled and tested at Saclay, including cryogenic, vacuum, RF cavity and solenoid characterization. All four CMs have been delivered to SNRC. CM1 and CM4 are already installed in the tunnel and their integration is ongoing. This contribution presents the integration and qualification results of the cryomodules at Saclay, the current status of their installation at SNRC and a comparison to the Phase I prototype superconducting module.

Speaker: Jonathan Dumas (Commissariat à l'Energie Atomique)

210 Single-shot 3D spatiotemporal visualization of THz electromagnetic wave packet

Precise characterization of the vectorial properties of THz electromagnetic wave packet serves as the essential foundation for materials electromagnetics research and accelerator physics. The complete vectorial properties of THz electromagnetic waves encompass the complex amplitude, the polarization, and the magnetic field characteristics. However, few current methods enable the complete visualization of the THz electromagnetic field.
Here, we develop a method for visualizing the complete THz electromagnetic wave packet. This approach utilizes the electric-optic sampling in conjunction with the high-dimensional one-shot optical field compressive sensing (HOOCS) system [1]. We employ this method to characterize both the 3D homogeneous THz field generated via the optical rectification, and the 3D radially polarized electric field produced by relativistic electron bunch (30MeV at the University of Osaka), consequently permitting the 3D reconstruction of the relativistic electron bunch. This work establishes a novel framework for high-dimensional THz detection, with potential applications in THz ellipsometry and real-time electron dynamics observation.

Speaker: Yaodan Hu (Huazhong University of Science and Technology)

211 Stable Double-Bunch Beam Generation for Plasma Wakefield Accelerators Via CSR-Tolerant Isochronous Beamlines

Beam-driven plasma wakefield acceleration (PWFA) is a promising strategy for future high-energy electron–positron colliders. A critical challenge remains the generation of high-charge, highly stable double-bunch beams, as current methods often suffer from significant charge loss or charge limitations. In this paper, we propose a coherent synchrotron radiation (CSR)-free beam-merging scheme utilizing twin isochronous beamlines that share a common dipole magnet. This design enables the generation of high-charge double-bunches with superior stability. Numerical simulations demonstrate that the scheme produces a 5 nC / 1 nC electron double-bunch without charge loss. The emittance growth for both bunches is constrained to approximately 0.1 mm·mrad, while the inter-bunch timing jitter is maintained below 2 fs. We further evaluate the robustness of this scheme and highlight its potential for large-scale accelerator facilities to provide high-quality drive beams for plasma wakefield acceleration.

Speaker: Wei Li (Institute of High Energy Physics)

212 Status of the FAIR Proton LINAC

The proton linear accelerator (p-LINAC) is envisaged as the injector for the antiproton physics program at the FAIR facility in Darmstadt, Germany. The p-LINAC is designed to deliver a beam current of 70 mA at an energy of 68 MeV with a repetition rate of 4 Hz. The ion source has been developed in collaboration with CAE. The Ladder RFQ was designed by IAP Frankfurt, as were the normal-conducting coupled CH cavities (CCH). The construction was carried out by local industrial partners and has been completed for the Ladder RFQ as well as for the first CCH cavity.
The proton driver—together with the antiproton production chain at FAIR—has been postponed due to a re-prioritization within the FAIR project and is currently in a frozen state.
In this paper, we describe the ongoing and planned high-power RF tests of the Ladder RFQ and the CCH cavities. Furthermore, we present the status of the RF systems, including the clystrons and the modulator. The preparation and maintenance of the test setup will ensure a smooth transition when the p-LINAC project is resumed.

Speaker: Maximilian Schuett (GSI Helmholtz Centre for Heavy Ion Research)

213 Status of the LOEWE-3 RFQ at IAP Frankfurt

The IAP (Institute for Applied Physics) of the Goethe University Frankfurt has a long experience in the development of 4-Rod RFQs. In the course of a project funded by the Hessen Agentur as part of LOEWE funding line 3, the basic design of the 4-rod RFQs is now to be further developed. The aim is to investigate whether an improvement in Q-Value and vacuum can be achieved through new production and construction methods, as well as through fundamental adjustments to the basic geometric structure of the 4-Rod RFQ design.
Higher quality is achieved through increased contact pressure between the individual components, along with improved vacuum performance due to the use of metal seals. The paper describes the measurements performed on the fully assembled LOEWE-3 demonstrator and compares them with the simulated values.

Speaker: Dr Klaus Kuempel (Goethe University Frankfurt)

214 Status of the SRF Cavity Tuner for the ILC Prototype Cryomodule at KEK

An ILC prototype cryomodule is presently being assembled at KEK, incorporating eight superconducting 1.3 GHz TESLA cavities. Accurate tuning and stable control of the resonance frequency of these narrow-bandwidth cavities, both prior to and during operation, require dedicated cavity tuners. The tuner concept is derived from the LCLS-II design. The specific requirements of the ILC prototype cryomodule, combined with the current market conditions, have necessitated an almost complete redesign. Owing to limited resources, full system-level validation prior to installation is not feasible. Therefore, targeted qualification tests of individual components are being performed. This contribution summarizes the current status of tuner development and production. Furthermore, two novel test approaches for the slow actuator (stepper motor with gearbox) and the fast actuator (piezo actuator) under cryogenic vacuum conditions are introduced, along with initial measurement results.

Speaker: Mathieu Omet (High Energy Accelerator Research Organization)

215 Status of the Vacuum System for the High-Energy Linear Accelerator Section of RAON

The Rare Isotope Accelerator Complex for ON-line (RAON) under the Institute for Basic Science (IBS) is currently operating the low-energy linear accelerator section successfully, and is preparing for the construction of the high-energy linear accelerator section. The fabrication of superconducting (SC) cryomodule prototypes is underway. In conjunction, the cryogenic, RF, magnet, and vacuum systems are being prepared for integration and operation in alignment with the construction schedule. This paper describes the current status of the vacuum system for the high-energy linear accelerator section and details its auxiliary components, specifically the non-evaporable getter (NEG) and the cold cathode gauge (CCG).

Speaker: Myung Ook Hyun (Institute for Basic Science)

216 Study of Beam Mismatch Effects in a 2.5-MeV 200-MHz 4-Vane RFQ for Neutron Generation

A beam dynamics study was carried out for a compact proton accelerator system under development for accelerator-driven neutron source applications in Hungary. The accelerator consists of a proton ion source, a low-energy beam transport line, and a 200-MHz 4-vane RFQ linac.
Numerical simulations were performed to evaluate beam transport and acceleration from the ion source extraction region to the upstream section of the neutron production target. Particular attention was paid to the influence of input beam mismatch on RFQ transmission, emittance growth, and beam loss characteristics. The maximum accelerable beam current was also estimated under realistic operating conditions.
In addition, a tolerance study was carried out to evaluate the acceptable operating range for stable accelerator operation. The sensitivity to transverse mismatch and injection parameter deviations was investigated systematically, and the resulting beam quality degradation and generation of off-specification beam components were analyzed quantitatively.

Speaker: Masahiro Okamura (Brookhaven National Laboratory)

217 Sub-femtosecond electron-bunch generation via two-dimensional beam compression

Sub-femtosecond electron beams would provide a powerful probe of ultrafast electronic and nuclear dynamics, but their generation with both high beam energy and pC-level charge remains challenging. Conventional longitudinal compression requires a large energy chirp and becomes increasingly impractical for hundred-MeV beams, whereas low-energy approaches are strongly limited by space-charge effects and typically operate at very low charge. Here, we propose a two-dimensional beam-compression scheme based on transverse–longitudinal coupling. In this scheme, the compressed bunch length is governed by the beam geometric emittance, allowing the small transverse emittance of modern electron beams to be exploited for ultrashort bunch generation. Start-to-end simulations show that sub-femtosecond bunches with hundred-MeV beam energy and pC-level charge can be produced. This approach offers a potential route toward compact, high-energy attosecond electron beams and may enable sub-femtosecond radiation sources based on undulator radiation or inverse Compton scattering.

Speaker: Weihang Liu (Institute of High Energy Physics)

218 Tandem Accelerator Complex UKP-2-1 Operation Status and Applications

The tandem accelerator complex UKP-2-1 is double-ended electrostatic accelerator located at Kazakhstan. The accelerator complex contains 2 independent beamlines, which share a common 1 MV high voltage terminal, nitrogen pressure vessel and gas stripper. The first beamline is dedicated to supply continuous proton beam for surface and depth distribution analysis. The analysis is conducted at the ion beam analysis end-station equipped with Rutherford Backscattering Spectrometry (RBS), Particle-Induced X-Ray Emission (PIXE), Nuclear Reaction Analysis (NRA) techniques. The second beamline purpose is to provide continuous heavy ion beam for irradiation and implantation purposes. The proton beam and heavy ion sources are based on duoplasmatron and multi-cathode cesium sputter (MC-SNICS), correspondingly, which are capable to supply the beam current up to 10 μA.
This report presents the accelerator complex UKP-2-1 current operation status and facility research program. This work was supported by the Program #BR23891530 “Development of integrated scientific research in nuclear and radiation physics on the basis of Kazakhstan’s accelerator complexes” of the Ministry of Energy, Kazakhstan.

Speaker: Konstantin Popov (Institute of Nuclear Physics)

219 The design of the ferroelectric based fast tuner

In this paper, the design of a ferroelectric fast reactive tuner for superconducting cavities has been presented.

Speaker: Cong Zhang (Institute of High Energy Physics)

220 The High Brilliance Neutron Source (HBS-I)

Neutrons are an essential tool for studying the structure and dynamics of matter. The High Brilliance Neutron Source (HBS) project aims to develop a scalable Compact Accelerator-driven Neutron Source that will enable neutron fluxes at the corresponding instruments comparable to existing fission-based or spallation neutron sources. After positive project evaluation in 2025, the German Science Council recommends strongly the construction of the first project stage (HBS-I). HBS-I uses pulsed 100 mA high-current proton beams to generate neutrons through a low-energy nuclear reaction at 20 MeV. The HBS-I Linac consists of a proton source, a 4-solenoid LEBT with chopper, two 4-Rod RFQ accelerators and a chain of 20 room temperature CH-cavities operated at 176 MHz. The maximum RF duty factor is 25%, resulting in a thermal load of up to 30 kW/m. The technology of this Linac is derived from the cw operated MYRRHA injector. The paper describes the status of the HBS-I proton Linac.

Speaker: Prof. Holger Podlech (Goethe University Frankfurt, HFHF - Helmholtz Research Academy Hesse for FAIR, Campus Frankfurt)

221 The static error analysis for the linac of CSNS-II

The CSNS is undergoing a beam power upgrade from 100~kW to 500 kW. In order to adapt this beam power upgrade, the beam current in the linac has to be increased from 10 mA to 40~mA and the beam energy has to be increased from 80 MeV to 300 MeV. Therefore, the ion source, RFQ and will be replace and 44 new superconducting cavities will be installed. During the new element installation, there is unavoidable alignment errors that will degrade the beam performance. In this paper, a static error analysis for the linac of CSNS upgrade project is presented.

Speaker: Yanliang Han (Institute of High Energy Physics)

222 Xray tests of ESS icBLM system

The European Spallation Source (ESS) in Lund, Sweden, is a pulsed neutron source based on a proton linac. During beam commissioning in 2025, the 870 MeV protons of 6 mA current, 5 microsecond pulse length and 1 Hz repetition delivered to tuning beam dump.  
Beam Loss Monitoring (BLM) system is to protect the accelerator from beam-induced damage and unnecessary activation of the components.  The one of ESS BLM detector is ionization chamber (icBLM) . All 266 chambers are installed, connected, powered. There was performed a several tests : the leakage current tests at CERN and ESS labs, self-integration, DAQ, HV tests in tunnel of whole chain of system, calibration test at HiRadMat facility at CERN. This contribution focuses on the results from acceptance and calibration campaigns made at end of 2025 and in 2026 by BLM team with help of DEKRA Xray gun for readiness for beam on target commissioning.

Speaker: Viatcheslav Grishin (European Spallation Source)

Wednesday 19 August

WE1A - Invited Talks

223 Post-Mortem Insights into the SNS RFQ: Implication and Paths Forward for high beam power operation

The first Radio-Frequency Quadrupole (RFQ01) at the Spallation Neutron Source (SNS) operated in both the main accelerator and the Beam Test Facility for a combined period of approximately 20 years. Over this time, the performance of RFQ01 declined significantly, with beam transmission decreasing from about 90% to 70% or less. RFQ01 is currently undergoing a comprehensive post-mortem analysis. Initial visual inspections revealed substantial erosion on the low-energy side of the vane tips. To characterize the erosion profile with high precision, a 3D microstructural surface replication was produced using an in-house, 6-inch-long mold along with full 3D CST model. Additional borescope inspections identified further vane erosion in the middle and downstream sections of the first segment. The final phase of the post-mortem study will involve full disassembly of the structure to expose the entire length of each vane for complete laser scanning. The CST 3D model will then be updated to incorporate the full erosion profile. The results of these studies will help clarify the underlying degradation mechanisms and inform implications and paths forward for reliable high beam power operation.

Speaker: Haitao Ren (Oak Ridge National Laboratory)

224 Overview and current status of the IFMIF-DONES accelerator systems

Overview and current status of the IFMIF-DONES accelerator systems is presented.

Speaker: Dr Ivan Podadera (Consorcio IFMIF-DONES España)

225 A SURVEY OF THE GLOBAL SCIENTIFIC KLYSTRON MARKET AND ITS FUTURE

The continued high-quality scientific output of many research facilities depends directly on their reliable operation and, in taking a wider view, a market that can provide a stable supply. In the late 2010s and early 2020s, market irregularities were amplified in large part because of the COVID-19 pandemic and the disruption it caused in resource availability. Though COVID-19 has been resolved for some time, the instabilities in the klystron market persist. Recently, the Spallation Neutron Source, the European Spallation Source, Argonne National Laboratory, and SLAC National Accelerator Laboratory formed a committee to assess the current state of the scientific klystron market and determine how best to stabilize it for the future. To that end, the committee decided to start with a global workshop that explicitly included not just end-users, but, importantly, klystron suppliers as well. The first “Long-Pulse and Continuous Wave (CW) Klystron Workshop” was held at the Oak Ridge National Laboratory’s Spallation Neutron Source in late September 2025. This presentation summarizes the findings, actions, and progress against those actions determined by the workshop attendees.

Speaker: John Moss (Oak Ridge National Laboratory)

226 Status of the HIAF Linacs (canceled)

IMP is constructing two major projects near Huizhou. Both involve the installation of superconducting hadron linacs with equipment that has been developed by IMP over the last decade or more. The presentation should summarize progress on the two projects.

Speaker: Weilong Chen (Institute of Modern Physics, Chinese Academy of Sciences)

227 TRANSFORMING THE BNL 200 MeV H⁻ LINAC: 10³ LOWER LOSSES, 2× HIGH-CURRENT TRANSMISSION, AND 2× LOWER EMITTANCE

Abstract
The Brookhaven National Laboratory (BNL) 200 MeV Drift Tube Linac (DTL) operates at 6.67 Hz, delivering H⁻ beams for both the polarized proton program at RHIC and isotope production at BLIP. Over the past two decades, targeted upgrades—especially within the low-energy and medium-energy beam transport (LEBT and MEBT) sections—have dramatically enhanced linac performance. Beam transmission for high-current isotope production has improved by more than 100%, while transverse emittance has been halved for polarized proton operation. Moreover, beam losses have been reduced by three orders of magnitude, significantly lowering radiation levels and enabling higher current delivery. These upgrades translate into increased beam intensity to BLIP and superior quality and stability to EIC, marking a transformative step for the linac’s long-term operational reliability and scientific output.

Speaker: Deepak Raparia (Brookhaven National Laboratory)

228 High-Current Heavy-Ion Acceleration Above 100 mA in a Four-Rod RFQ

We report on the achievement of a world-record peak beam current for heavy ions through the acceleration of fully stripped carbon ions (C⁶⁺) using a 100-MHz four-rod radio-frequency quadrupole (RFQ) accelerator combined with a Direct Plasma Injection Scheme (DPIS) driven by a laser ion source.
A peak beam current of 105 mA was successfully accelerated to an output energy of 300 keV/u. The beam current was measured downstream of the analyzing magnet for charge-state selection, confirming transport and acceleration of the high-intensity C⁶⁺ beam. This result represents the highest peak current achieved to date for heavy-ion RFQ acceleration.

Beam commissioning demonstrated stable RF operation and robust beam transmission at record current levels. The accelerator performance, space-charge behavior, and operational limits are discussed, together with the implications for next-generation high-current heavy-ion injectors and accelerator-driven applications in the >100 mA regime.

Speaker: Masahiro Okamura (Brookhaven National Laboratory)

10:30 Coffee Break

WE2A - Plenary Talk

229 Laser-plasma accelerator driven radiation generation and applications

Laser-plasma accelerators hold great promise for a range of radiation generation applications due to their high accelerating gradients, which can result in significant reductions in facility size and cost. They are also capable of producing electron beams with novel and tunable properties, including ultrashort bunch durations. Recent work has demonstrated several advances in secondary radiation generation, achieving high performance with stable operation over extended periods.

This talk will present an overview of recent breakthroughs in compact radiation sources based on laser-plasma accelerators at the BELLA Center, Lawrence Berkeley National Lab. Highlights include stable, high-gain operation of compact free-electron lasers over several hours (S. Barber et al., PRL 2025; F. Kohrell et al., PRAB submitted; K. Jensen et al., PRAB submitted), compact generation of directional multi-GeV muon beams (D. Terzani et al., PRAB 2025), Thomson scattering for monochromatic gamma-ray production (H.-E. Tsai et al., PRAB in prep), and advanced imaging applications using LPA betatron radiation (M. Balcazar et al., Nature Communications 2025).

Speaker: Jeroen van Tilborg (Lawrence Berkeley National Laboratory)

WE2A - Invited Talks

230 Status of the NEWGAIN Project: The New Heavy Ion Injector for SPIRAL2

The NEWGAIN (NEW GAnil INjector) project is now in the construction phase at GANIL. This major upgrade, driven by the integration of the new ASTERICS superconducting ECR ion source, aims to expand the capabilities of the SPIRAL2 accelerator by enabling the acceleration of heavy ions with an $A/q$ ratio of up to 7. With this enhancement, SPIRAL2 will provide high-intensity beams ranging from protons to uranium, significantly strengthening GANIL’s international competitiveness in both fundamental research and multidisciplinary applications.
This communication provides a detailed update on the construction progress and outlines the key milestones achieved and forthcoming. The layout of the new injector features two ECR ion sources—including ASTERICS, for which the superconducting coil is currently under fabrication—and two LEBT lines. The system also includes a new RFQ, with mechanical sections currently being received at GANIL, followed by a MEBT section designed to inject the beam into the existing SPIRAL2 MEBT and subsequent superconducting LINAC.

Speaker: Frederic Chautard (Grand Accélérateur Nat. d'Ions Lourds)

231 Breaking the Cryoplant Barrier: Conduction-Cooled Nb₃Sn SRF Linacs for Industrial and Environmental Applications

Superconducting linacs have traditionally required large cryogenic infrastructures, while compact accelerators relied on normal-conducting technology. This divide is narrowing. At Fermilab’s IARC, Nb₃Sn-coated cavities operating near 4 K, combined with cryocooler-based conduction cooling and solid-state RF power, enable compact SRF linacs for high-duty-factor operation outside traditional facilities. Systems under construction target environmental remediation and medical device sterilization at approximately 10 MeV, where efficiency and life-cycle cost are critical. These machines use multi-cell elliptical cavities at 650 MHz and 1.3 GHz, operating at 7–10 MV/m under conduction cooling with industrial cryocoolers. Eliminating liquid-helium plants shifts SRF from facility-scale installations to application-oriented platforms, thereby extending superconducting technology into regimes that have not been economically viable.

Speaker: Jayakar Thangaraj (Fermi National Accelerator Laboratory)

232 Bringing Coherent X-Ray Science to the Lab: The ASU Compact XFEL

Arizona State University is developing a compact, room-sized x-ray free electron laser (CXFEL), a far smaller and more affordable alternative to conventional XFELs. The design combines an X-band linac with precise electron-beam phase-space control and an optical undulator to produce coherent x-rays via inverse Compton scattering. This talk will provide an overview of the project, including the currently operating incoherent device and the coherent ICS facility under construction. https://www.photonics.com/Articles/Arizona-State-University-Builds-Compact-X-Ray/a70832

Speaker: Mark Holl (Arizona State University)

Social Outing

Thursday 20 August

TH1A - Invited Talks

233 25 years of FEL operation at FLASH (DESY)

First SASE lasing at DESY's FLASH Free-electron laser (FEL) - that time called as TESLA Test Facility FEL - was in February 2000. It was the first FEL worldwide producing SASE radiation at VUV wavelengths. Since then, over more than two decades, FLASH has provided high peak and average brilliance XUV and soft X-ray FEL radiation for photon science experiments.

In order to operate FLASH as a state-of-the-art FEL, it has been continuously refurbished and upgraded. The most recent upgrade FLASH2020+ increased the electron beam energy of the superconducting linac to 1.35 GeV and reconstructed the FLASH1 undulator beamline. The new external seeded FLASH1 will provide fully coherent radiation at up to MHz bunch repetition rate (burst). Moreover, thanks to the new APPLE-III type undulators, a full polarization control is possible. As before, FLASH1 hosts also a THz source. FLASH2 continues in SASE operation.

This paper provides an overview of FLASH's evolution from a test facility for superconducting accelerator technology to a trailblazing and innovative FEL user facility, very successfully operated for the photon science community.

Speaker: Katja Honkavaara (Deutsches Elektronen-Synchrotron DESY)

234 Compact and efficient CW electron LINACs for industrial and environmental applications

Compact, efficient and high-power sources of electrons are of growing interest for a wide range of applications including materials processing, medical device and food sterilization, wastewater and soil treatment. Electron energy from <1MeV to 10 MeV and beam power from kW to MW levels are desirable. We describe a compact modular system being developed at JLab starting with a gridded thermionic electron gun and using an initial graded-beta copper CW linac to capture and form the beam, followed by one or more beta=1 CW linac sections to increase the energy. These sections may be normal conducting or conduction-cooled superconducting cavities depending on the energy and power levels required. CW operation allows for reliable high average power at modest gradient using cost-effective, highly efficient industrial magnetrons for the RF sources. We describe the design and development of these component along with plans for an integrated system to demonstrate CW beam operation.

Speaker: Robert Rimmer (Thomas Jefferson National Accelerator Facility)

235 Intrabeam Scattering and 6D Brightness: Modelling, Measurement, and the Road to a Brighter SwissFEL electron source

Intrabeam scattering (IBS) in the SwissFEL injector has emerged as a critical performance-limiting phenomenon, manifesting as a significantly larger slice energy spread than previously anticipated. By combining detailed numerical simulations with a newly developed analytical model, we achieve excellent agreement with experimentally measured slice energy spreads, validating our approach. These results naturally prompt the question of how IBS-induced degradation can be mitigated, both in future SwissFEL operation and in next-generation facilities. Leveraging the insights gained from our study, we identify key design principles for X-ray free-electron laser (XFEL) injectors aimed at suppressing slice energy spread growth. Furthermore, guided by this improved understanding, we propose and evaluate novel operational schemes for the electron source that enhance XFEL performance in the presence of IBS.

Speaker: Thomas Lucas (Paul Scherrer Institute)

236 Technical commissioning of the ESS linac cavities for the Beam on Dump Phases

The ESS linac has been commissioned in two different operation phases operation on the 12 kW commissioning beam dump. In 2025 the linac was operated at full duty cycle in the NCL section (up to 90 MeV) and at reduced duty cycle in the SCL section (up to 870 MeV), due to limitations in the cooling infrastructure and staged implementation of LLRF functionalities. In the present phase the whole linac has been operated up to its full duty cycle at 14 Hz and 3.2 ms RF pulses, showing LFD capabilities with long RF pulses in SRF structures.
This contribution summarizes the staged technical commissioning phases, presenting the conditioning experience and the setup for operation at nominal RF performances.

Speaker: Marten Koopmans (European Spallation Source)

237 Status of the CiADS Linac

IMP is constructing two major projects near Huizhou. Both involve the installation of superconducting hadron linacs with equipment that has been developed by IMP over the last decade or more. The presentation should summarize progress on the two projects.

Speakers: Yuan He (Institute of Modern Physics, Chinese Academy of Sciences), Zhijun Wang (Institute of Modern Physics, Chinese Academy of Sciences)

238 Progress in the LIPAc Validation and the roadmap towards SRF Linac Beam Commissioning

The Linear IFMIF Prototype Accelerator (LIPAc), jointly developed by Europe and Japan, aims to validate the acceleration of a 125 mA deuteron beam in continuous‑wave operation up to 9 MeV. In the 2024 campaign, LIPAc achieved a major milestone by demonstrating high‑duty RFQ operation with a 119 mA deuteron beam and a duty cycle approaching 10%, marking the highest‑performance operation to date. Building on this progress, preparation for the SRF Linac commissioning has advanced steadily.
The cryomodule assembly is now on track for completion in early 2026, following the resolution of several technical challenges that had previously constrained the schedule. Subsequent integration activities—including beamline installation and the connection of electrical and cryogenic systems—will pave the way toward the first SRF Linac cooldown, targeted for late 2026 to early 2027.
This contribution highlights the key achievements of Phase B+, details the ongoing preparation for SRF Linac integration and check‑out activities, and presents the roadmap leading to the first beam commissioning of the SRF Linac.

Speaker: Keitaro Kondo (National Institutes for Quantum Science and Technology)

10:30 Coffee Break

TH2A - Invited Talks

239 Development of the composite structure SRF cavities for pursuing high operational stability at IMP

The on-line operating instability of the bulk Nb superconducting cavity is mainly attributed to the following factors: Lorentz force detuning, mechanical vibration, thermal breakdown induced by the electron loading effect and the enhanced heat dissipation at defects etc. Theoretically, the copper-niobium / aluminum-niobium composite superconducting cavities have excellent potential for high thermal and mechanical stability, which can make full use of the high-gradient surface processing recipes developed for the bulk niobium cavity, the thick copper/ aluminum layer’s high thermal conductivity and rigidity, thereby enhancing the operational stability of the bulk niobium cavities. In this contribution, we present the status of development of the CuNb composite and AlNb composite superconducting cavities at IMP, including the technical challenges, the RF and mechanical test results at cryogenic temperature, etc.

Speaker: Shichun Huang (Institute of Modern Physics)

240 Operation challenges of large-scale low-beta SC cavities in heavy ion linac

The FRIB has extensive experience operating large amounts of low-beta (quarter-wave and half-wave) superconducting resonators. This talk will report overcoming challenges in supporting the SRF system with nearly 100% availability.

Speaker: Sang-hoon Kim (Facility for Rare Isotope Beams)

241 A Universal Power Coupler Developed for Three Superconducting Linear Accelerators at IMP

"The Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS) is scheduled to complete the construction of three superconducting linear accelerators (CiADS, HIAF, and IP-SAFE) between 2024 and 2026.These accelerators incorporate 7 types of superconducting cavities with operating frequencies ranging from 81.25 MHz to 650 MHz, 10 types of cryomodules, and nearly 400 power couplers in total.
To shorten the development cycle and improve engineering reliability, we have developed a universal dual warm-window power coupler that is compatible with various cavity types, features a broad frequency range, and supports a wide power span. This universal coupler helps reduce the time spent on process development, such as copper plating and ceramic window brazing, and facilitates quality control in mass production.
In addition, we have developed a dual-port input resonant ring with extremely high gain for the conditioning and testing of power couplers. Over the past 50 months, we have completed the fabrication and high-power conditioning of 295 such universal dual warm-window power couplers, among which 174 units have been put into operation and are performing well."

Speaker: TIANCAI JIANG (Institute of Modern Physics)

Student Prizes

12:30 Lunch

TH1P - Invited Talks

242 Progress on Staging of laser-plasma accelerators

Multi-stage coupling of two or more laser-plasma accelerators is as a key technology for future high-energy physics applications of plasma-based accelerators, including TeV-scale collders. Single laser-plasma accelerators stages have demonstrated accelerating gradients orders of magnitude beyond conventional RF technology, high beam quality, and acceleration to 10 GeV. However, scaling to collider-relevant energies requires the efficient coupling of multiple plasma stages with beam quality preservation and minimal charge loss.
Currently, demonstrations of staging have been limited to energy gains at the ~100 MeV level, with low charge transport between the stages (Steinke, Nature 2016). At the BELLA Center, multi-stage coupling of laser-plasma accelerators at the GeV level is being investigated. This talk will present an overview of recent progress towards high quality multi-stage coupling including stable, high quality injectors, active plasma lenses, and plasma mirrors.

Speaker: Dr Aodhan McIlvenny (Lawrence Berkeley National Laboratory)

243 Experimental Generation of Extreme Electron Beams for Advanced Accelerator Applications

Published in PRL. Demonstration of experimental generation of high energy (10 GeV), ultrashort (femtosecond-duration), ultrahigh current (∼0.1  MA), petawatt peak power electron beams in a particle accelerator. These extreme beams enable the exploration of a new frontier of high-intensity beam-light and beam-matter interactions broadly relevant across fields ranging from laboratory astrophysics to strong field quantum electrodynamics and ultrafast quantum chemistry. We demonstrate our ability to generate and control the properties of these electron beams by means of a laser-electron beam shaping technique. This experimental demonstration opens the door to on-the-fly customization of extreme beam current profiles for desired experiments and is poised to benefit a broad swath of cross-cutting applications of relativistic electron beams. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.085001

Speaker: Claudio Emma (SLAC National Accelerator Laboratory)

244 Simultaneous boost of electron beam energy and brightness in a plasma wakefield accelerator

(based on recently published Nat. Commun. 16, 10719 (2025)).

Demonstrating that a plasma-wakefield accelerator operating in the nonlinear regime acts as a transformer to simultaneously boost the energy and brightness of an electron bunch injected from the plasma. Using a 10-GeV drive bunch and a three-stage meter-scale plasma source, electron bunches exceeding 20 GeV with sub-percent energy spread, 2 mm·mrad normalized emittance, and multi-kA peak current were observed. Other important features including high energy-conversion efficiency, an energy transformer ratio exceeding two, and a brightness enhancement over an order of magnitude were also observed

Speaker: Douglas Storey (SLAC National Accelerator Laboratory)

THOP - Oral Posters

245 Identifying Anomalies at CEBAF via Singular Value Decomposition of Cross-Plane Covariance

We present a method for detecting and characterizing anomalies in a nominally decoupled, recirculating linac accelerator, such as the Continuous Electron Beam Accelerator Facility (CEBAF). Proposed future accelerators of this type include PERLE and LHeC. The method computes the zero-lag cross-plane covariance from samples of beam position data, and analyzes its singular value decomposition (SVD). Each singular triplet of the SVD spectrum produces paired spatial patterns and a strength that quantify where and how the two planes move together at the same instant. Projecting each array of positions at a given time onto the spatial singular vectors indicates when the coupled pattern is active. Large modes provide direct evidence of dispersion, skew optics, position feedback cross-feed, scraping, or faults that introduce coupled beam motion. The construction is formalized, differentiability is discussed, and data from observed anomalies such as magnet failures and known optic modulation are presented.

Speaker: Ryan Bodenstein (Thomas Jefferson National Accelerator Facility)

246 Phase and Amplitude Setup of the RF Cavities of the ESS Linear Accelerator

The European Spallation Source (ESS) aims to be the world's brightest neutron source, designed to delivering 2 GeV protons at 5 MW to a rotating Tungsten target via a 600 m-long superconducting linear accelerator. At the present installation phase, with 82 of the total 146 cavities available in the superconducting linac, a beam of 800 MeV (2 MW) can be produced. During the first half of 2026, a second commissioning run for the full accelerator had the goal to improve the setup of the machine and to increase the beam power above the levels used during the first run in 2025.
One of the first steps required at the start of each run is to find the amplitudes and phases for each of the cavities for correct acceleration. This paper will give an update on the methods presently used for setup of both the normal conducting and the superconducting part of the machine.

Speaker: Daniel Noll (European Spallation Source)

247 Beam Dynamics Challenges and Solutions for a High-Current Electron Cooler Linac at the EIC

The Electron-Ion Collider at Brookhaven National Laboratory requires high-current, high-brightness electron beams for efficient ion beam cooling. We present the design and beam dynamics optimization of a normal-conducting electron linac for the Low-Energy Cooler (LEC), building on operational experience from the Low Energy RHIC Electron Cooler (LEReC) and extending performance toward the demanding EIC parameter regime.
The accelerator is designed to generate 1 nC electron bunches with average beam current up to 80 mA and final energy of 13 MeV while maintaining normalized transverse emittance below 1.5×10^(-6)m and relative energy spread better than 3×10^(-4). Start-to-end beam dynamics studies, including injector, accelerating sections, long transport, and 180 m cooling sections, were performed using PARMELA code and benchmarked against IMPACT-T and GPT codes.
The results demonstrate the feasibility of achieving an electron beam quality required for future EIC cooling applications using a normal-conducting RF accelerator approach, with potential relevance to other high-current electron beam facilities.

Speaker: Dmitry Kayran (Brookhaven National Laboratory)

248 Single-Shot Extraction Efficiency Evaluation of an Infrared FEL Oscillator via simultaneous measurement of electron energy evolution with and without FEL lasing

Extraction efficiency is a key parameter for oscillator FELs. To evaluate it in a single macro-pulse, both electron beam energy evolution with and without FEL lasing must be known. Previously, we developed a secondary electron emission monitor (SEEM) to measure the temporal energy evolution after the undulator with and without FEL lasing. Since SEEM requires separate measurements with and without FEL lasing, its accuracy is limited. To improve accuracy, we utilize a beam position monitor (BPM) in the dispersive section upstream of the undulator at KU-FEL*, where horizontal beam position strongly correlates with beam energy. Thus the BPM can provides the temporal energy evolution before (or without) FEL lasing. By simultaneously acquiring SEEM and BPM in the same macro-pulse, we can obtain both energy distributions with and without FEL lasing in a single shot. We will present the experimental setup including signal processing, calibration results, and single-shot extraction efficiency measurements. This approach enables high-precision single-shot extraction efficiency measurement and facilitates further optimization of FEL operation.

Speaker: Zhuang Bi (Kyoto University)

249 RF Energy Recovery Power Conversion for Particle Accelerators

To enhance the energy efficiency and cost-effectiveness of large-scale particle accelerator facilities, energy recovery has emerged as a key research direction. From the perspective of radio frequency (RF) power sources, this article reports on the latest research progress in this field at IHEP. First, the fundamental principles of energy recovery based on RF power sources are elaborated, covering three aspects: energy recovery klystrons based on multi-stage depressed collectors, high-power RF energy recovery systems, and studies on high-efficiency power recovery devices.
The article highlights recent key technological breakthroughs, including:
(1) Research on energy recovery schemes, which are expected to increase klystron efficiency to over 90%;
(2) RF energy recovery, detailing advancements in RF devices and RF-to-DC conversion technologies;
(3) Design and preliminary experiments of energy recovery devices, demonstrating recent progress in efficiency improvement and energy recovery.

Speaker: Jindong Liu (Chinese Academy of Sciences)

250 Development of high-gradient booster linac for multi-GeV proton radiography at LANSCE

Increasing energy of proton beam at the Los Alamos Neutron Science Center (LANSCE) from 800 MeV to 3-5 GeV will improve radiography resolution ten-fold. This energy boost can be achieved with a compact cost-effective linac based on normal conducting high-gradient (HG) RF accelerating structures operating at liquid nitrogen temperatures (cryo-cooled). Such an HG booster is feasible for proton radiography (pRad), which requires short beam pulses at very low duty. The pRad booster starts with a short L-band section to capture and compress the 800-MeV proton beam from the existing linac. The main HG linac will be based on S- and C-band cavities. An L-band de-buncher at the booster end can reduce the beam energy spread if needed for pRad experiments. We are developing proton cryo-cooled HG standing-wave structures with distributed RF coupling for the booster. Prototype cavity structures at S- and C-band are designed and will be tested cryo-cooled to measure breakdowns at high gradients. The booster linac beam dynamics design options and preliminary proton radiography simulations will also be presented.

Speaker: Sergey Kurennoy (Los Alamos National Laboratory)

251 Additive Manufacturing of Copper and Copper-Alloy 4-Rod RFQs with Gyroid-Enhanced Cooling for High-Power CW Operation

Additive manufacturing (AM) offers new possibilities for the design and fabrication of radio-frequency quadrupoles (RFQs), particularly in enabling complex internal geometries that are difficult or impossible to realize with conventional machining. In this work, the application of AM to the production of 4-rod RFQ structures made from pure copper and copper alloys is investigated.

A key focus is the integration of gyroid-based lattice structures within the cooling channels to enhance heat transfer and improve thermal stability under high RF load. A 4-stem RFQ prototype is designed and manufactured to evaluate the feasibility of this approach.

The primary goal is to assess the potential for stable continuous-wave (CW) operation, to explore the achievable increase in power handling capability compared to conventionally manufactured RFQs, and to evaluate the potential for reductions in manufacturing cost enabled by additive manufacturing.

The results aim to demonstrate that AM-enabled design, combined with advanced cooling concepts, can provide a viable pathway toward next-generation high-power RFQ systems.

Speaker: Julius Storch (Goethe University Frankfurt)

252 Power Efficiency Estimations for a High Intensity Proton Linac

The Accelerator community needs to evolve to more efficient
technologies and support R&D to reduce total energy consumption. This requires a change in culture - we need to focus on energy
efficiency with the same priority as achieving higher performance. Some linac installations like those for Accelerator Driven Systems (ADS) are advertised as being powered by the nuclear energy they produce with the surplus power going to the grid. In this case power efficiency is a key parameter in the design. Power usage can be impacted by various factors including temperature of operation and rf surface resistance. This paper presents modeling exercise to motivate future R%D towards improving power efficiency and in particular focused on accelerator used to drive ADS.

Speaker: Robert Laxdal (TRIUMF)

253 Experience with a pulsed gas stripper from first user beamtimes at GSI

The efficiency of stripping heavy ions like uranium into a single charge state at 1.4 MeV/u using a gas target can be increased significantly by applying hydrogen instead of nitrogen, thereby narrowing the resulting charge state spectrum. However, pulsed injection into a dedicated interaction chamber will be required to reduce the load of the vacuum pumping system to an acceptable level. Such a setup was developed, a prototype constructed and studied thoroughly in various dedicated machine development beamtimes at GSI/Germany. During the last two user beamtimes, the prototype setup was operated under regular operating conditions with nitrogen, while hydrogen operation is restricted to machine studies due to necessary safety measures still under completion. Several ion species have been stripped in the course of the beamtimes and valuable data on stripping efficiencies have been measured with both gases. An overview of the technical challenges encountered, operational experience and results obtained so far, and an outlook towards regular operation with hydrogen will be presented.

Speaker: Peter Gerhard (GSI Helmholtz Centre for Heavy Ion Research)

254 4D transverse coupling measurements of an 18 MeV photo-injector electron beam at PITZ

At the Photo-Injector Test facility at DESY in Zeuthen (PITZ), the horizontal and vertical phase spaces of electron beams are measured to characterize the performance of L-band photo-electron sources. These measurements are taken use a using the slit-screen method located 5.27 m downstream of the photo-cathode after acceleration to 18 MeV by a 14-cell booster cavity. The beamlet images from x and y plane slit scans can then be combined using a Virtual Pepper Pot (VPP) to reconstruct the full 4D transverse phase space. This technique has enabled detailed characterization of the x-y coupling originating from the electron source. Notably, the VPP analysis shows the x-y coupling is not uniform across the entire beam, instead one corner is significantly more coupled than the rest of the beam. While the cause of this effect is still under investigation, it can be reduced using a skew quadrupole near the exit of the gun.

Speaker: Christopher Richard (Deutsches Elektronen-Synchrotron DESY)

255 Progress in Nb3Sn SRF cavity development at KEK after furnace relocation

Nb$_3$Sn is one of the most promising materials for next-generation superconducting radio-frequency (SRF) cavities, as it enables high-Q operation at 4 K. This feature opens the possibility of conduction-cooled SRF systems without liquid helium. At KEK, Nb$_3$Sn coating development based on the Sn vapor diffusion method has been in progress since 2019, with continuous improvements in cavity performance. Last year, the coating furnace was dismantled, relocated, and recommissioned. After the relocation, cavity development was resumed with verification of coating reproducibility, achieving stable coating and improved cavity performance. In parallel, coating studies using a coupon cavity equipped with sample holders have been initiated. This approach enables preparation of samples that reproduce the Nb$_3$Sn film formed on the cavity inner surface, allowing more detailed surface characterization than in conventional sample studies. We will report recent progress in Nb$_3$Sn cavity development after furnace relocation, together with the results of surface characterization using these samples.

Speaker: Hayato Ito (High Energy Accelerator Research Organization)

THPO - Poster Session

256 4D transverse coupling measurements of an 18 MeV photo-injector electron beam at PITZ

At the Photo-Injector Test facility at DESY in Zeuthen (PITZ), the horizontal and vertical phase spaces of electron beams are measured to characterize the performance of L-band photo-electron sources. These measurements are taken use a using the slit-screen method located 5.27 m downstream of the photo-cathode after acceleration to 18 MeV by a 14-cell booster cavity. The beamlet images from x and y plane slit scans can then be combined using a Virtual Pepper Pot (VPP) to reconstruct the full 4D transverse phase space. This technique has enabled detailed characterization of the x-y coupling originating from the electron source. Notably, the VPP analysis shows the x-y coupling is not uniform across the entire beam, instead one corner is significantly more coupled than the rest of the beam. While the cause of this effect is still under investigation, it can be reduced using a skew quadrupole near the exit of the gun.

Speaker: Christopher Richard (Deutsches Elektronen-Synchrotron DESY)

257 A 16-Channel Wideband BPM for Transverse Profile and Temporal Distribution Measurements at RAON

Non-destructive beam profile monitoring is a critical diagnostic capability for tuning modern heavy-ion accelerators. In this study, we present the design of a 16-channel wideband Beam Position Monitor (BPM) system for non-destructive transverse profile and temporal distribution measurements, specifically targeted for the ~10 MeV/u beamlines at the RAON heavy-ion accelerator facility. To facilitate accurate temporal distribution measurements, the BPM structure is optimized to achieve a broad frequency response with a bandwidth exceeding 8 GHz. High-frequency signal acquisition is performed utilizing a wideband sampling oscilloscope, capturing the transient beam signals directly in the time domain.

Speaker: Prof. Ji-Gwang Hwang (Kangwon National University)

258 Additive Manufacturing of Copper and Copper-Alloy 4-Rod RFQs with Gyroid-Enhanced Cooling for High-Power CW Operation

Additive manufacturing (AM) offers new possibilities for the design and fabrication of radio-frequency quadrupoles (RFQs), particularly in enabling complex internal geometries that are difficult or impossible to realize with conventional machining. In this work, the application of AM to the production of 4-rod RFQ structures made from pure copper and copper alloys is investigated.

A key focus is the integration of gyroid-based lattice structures within the cooling channels to enhance heat transfer and improve thermal stability under high RF load. A 4-stem RFQ prototype is designed and manufactured to evaluate the feasibility of this approach.

The primary goal is to assess the potential for stable continuous-wave (CW) operation, to explore the achievable increase in power handling capability compared to conventionally manufactured RFQs, and to evaluate the potential for reductions in manufacturing cost enabled by additive manufacturing.

The results aim to demonstrate that AM-enabled design, combined with advanced cooling concepts, can provide a viable pathway toward next-generation high-power RFQ systems.

Speaker: Julius Storch (Goethe University Frankfurt)

259 An Ionization Profile Monitor for Transverse Beam Profile Measurements at GSI/FAIR

A control and acquisition system for ionization profile monitor (IPM) stations at GSI/FAIR has been implemented and deployed, providing real-time, simultaneous transverse beam characterization in both planes without disturbing the beam. Built on FESA (Front-End Software Architecture), the system uses dedicated classes to manage the cameras, high-voltage control, and digital I/O. Image correction and noise filtering are applied before the beam position, beam width, and profile integral are extracted from the resulting profiles. Automatic high-voltage reduction protects the detector under overload conditions. Acquisition is synchronized with the accelerator cycle via a White Rabbit timing receiver, supporting frame rates of up to 300 fps. Acquired images and computed profiles are saved per machine cycle in an XML-based format. A JavaFX operator interface provides guided setup, live visualization with historical data overlay, and expert configuration options. Designed to support multiple IPM stations at GSI/FAIR, the system is currently in operational use at SIS18 (heavy-ion synchrotron) and ESR (Experimental Storage Ring).

Speaker: Ziga Kroflic (Cosylab)

260 Attosecond Structuring of MeV Electron Beams via Two-Color Laser Modulation

The ability to resolve electronic motion on attosecond timescales is central to advancing ultrafast science. Ultrafast electron diffraction (UED) with attosecond electron pulses offers a direct route to this goal, yet generating such pulses at relativistic energies remains challenging. Here, we investigate a two-color laser modulation scheme for producing attosecond electron pulse trains via velocity bunching. Three-dimensional particle-tracking simulations show that the two-color laser fields form a copropagating traveling-wave modulation that imposes optical-cycle-scale energy modulation on a relativistic electron beam, leading to the formation of a train of attosecond microbunches. Including space-charge effects reveals a trade-off between bunch charge and temporal compression, whereby higher charge reduces the modulation amplitude and broadens the microbunch duration. Using the HUST-UED facility as a representative platform, we systematically analyze the key parameters governing attosecond beam formation. Our results establish two-color laser modulation as a viable route to attosecond electron beams and provide a pathway toward extending MeV UED into the attosecond regime.

Speaker: Jiapeng Li (Huazhong University of Science and Technology)

261 Beam Dynamics Challenges and Solutions for a High-Current Electron Cooler Linac at the EIC

The Electron-Ion Collider at Brookhaven National Laboratory requires high-current, high-brightness electron beams for efficient ion beam cooling. We present the design and beam dynamics optimization of a normal-conducting electron linac for the Low-Energy Cooler (LEC), building on operational experience from the Low Energy RHIC Electron Cooler (LEReC) and extending performance toward the demanding EIC parameter regime.
The accelerator is designed to generate 1 nC electron bunches with average beam current up to 80 mA and final energy of 13 MeV while maintaining normalized transverse emittance below 1.5×10^(-6)m and relative energy spread better than 3×10^(-4). Start-to-end beam dynamics studies, including injector, accelerating sections, long transport, and 180 m cooling sections, were performed using PARMELA code and benchmarked against IMPACT-T and GPT codes.
The results demonstrate the feasibility of achieving an electron beam quality required for future EIC cooling applications using a normal-conducting RF accelerator approach, with potential relevance to other high-current electron beam facilities.

Speaker: Dmitry Kayran (Brookhaven National Laboratory)

262 Beam dynamics simulation and lattice optimization for the Siam Photon Source injector

The Siam Photon Source (SPS) injector, comprising a pre-injector linac and a low-energy beam transport line (LBT), delivers a 40 MeV electron beam to a booster synchrotron for acceleration to 1.2 GeV. While this system has operated in its original configuration since commissioning, prior machine studies (in 2006 and 2016) revealed that overall beam transmission efficiency had degraded to below 30%. To address these losses without disrupting ongoing user beam services, start-to-end beam dynamics simulations were developed to serve as an optimization model. The model integrates space-charge tracking in the pre-injector (using ASTRA) with beam optics matching and multi-particle tracking through the LBT lattice (using ELEGANT). By benchmarking the simulated beam parameters against both the original conceptual design and recent measurements, several discrepancies were identified. This paper details the simulation methodology and proposes machine corrections—including the optimization of RF power and phase in the bunching components, and quadrupole tuning and polarity adjustments—to control the beam envelope and increase the transmission efficiency.

Speaker: Dr Thakonwat Chanwattana (Synchrotron Light Research Institute)

263 Beam dynamics studies and commissioning of the first proton RFQ linac prototype developed by CNPEM

The Brazilian Center for Research in Energy and Materials (CNPEM) has initiated a proton linear accelerator development program aimed at broadening its expertise in accelerator technologies to enable future applications in radioisotope production and proton therapy. As a first step in this initiative, a 1 MeV Proton Radio Frequency Quadrupole (RFQ) operating at 476 MHz was designed, manufactured, assembled, and commissioned in Brazil. This work discusses aspects of the beam dynamics, RF design, vane modulation design, vacuum system, and beam measurements of the prototype. Emphasis is given to beam performance comparisons between simulations and experimental measurements of both the ion source extraction line and the accelerated beam, including transmission, phase-space evolution, emittance, einzellens scanning, and spectrometer-based beam characterization. The comparisons provide insights to the team and increase overall confidence in engineering solutions adopted during the development, including a vacuum sealing strategy based on 3D O-rings. Finally, future developments planned for this initiative are outlined.

Speaker: Mr Tarik Ventorini de Oliveira (Brazilian Center for Research in Energy and Materials, Universidade Estadual de Campinas (UNICAMP))

264 Beam extraction study of Kr and Xe Ions from 14.5 GHz ECR Ion Source at RAON

The RAON 14.5 GHz ECR ion source has been used for beam conditioning and beamline commissioning with relatively lighter-mass ion beams such as Argon and Neon. As demand for beams with various A/q values has recently increased, the operational range of the ion source has needed to be extended to heavier noble gas beams such as krypton (Kr) and xenon (Xe). In ECR ion source operation, the extracted beam current and charge state distribution are affected by RF power, main and support gas injection conditions, bias disk conditions, and extraction parameters. In this study, Kr and Xe beam tuning was performed by varying these operating conditions while monitoring the extracted beam. These results provide operational reference data for the extraction of heavy noble gas beams from the RAON 14.5 GHz ECR ion source.

Speaker: Dr Eunhun Im (Institute for Basic Science)

265 Beam-Dynamics Design of a Zero-Phase Accelerating Linac with Electrode-Based Focusing

Conventional linacs operated at the zero synchronous phase offer high acceleration efficiency but usually lack intrinsic transverse focusing, requiring additional magnetic elements and increasing system complexity, size, power consumption, and cost. We propose a novel beam-dynamics concept, Simultaneous zerO-phase Focusing and Acceleration (SOFA), based on planar accelerating electrodes. Theoretical analysis indicates that the transverse focusing force is proportional to sin(phi0 + psi), where phi0 is the synchronous phase and psi is an effective focusing phase determined by electrode boundary conditions. Thus, even at phi0 = 0, a non-zero focusing force can be generated, enabling simultaneous acceleration and focusing. Using a multi-gap cumulative focusing strategy, preliminary 3D field-based simulations for a 12C4+ beam show stable periodic transverse envelope evolution and acceptable normalized transverse acceptance. Without embedded magnets, SOFA may improve accelerating gradient and shunt impedance while reducing RF power and cost, making it promising for cancer therapy and compact ion-beam applications.

Speaker: guangxian li (Institute of Modern Physics)

266 BEPCII Linac upgrade plan with a new damping ring

IHEP is exploring potential schemes for BEPCII to adopt the crab-waist scheme to further increase luminosity and conduct relevant experimental research. Considering that BEPCII is an existing machine, the upgrade and modification must accommodate the existing tunnel geometry and detector spatial arrangement. It is preferable to make only local adjustments or modifications to the lattice. We plan to simultaneously modify both the collision region and the inner ring injection region of the existing BEPCII, aiming to achieve 10 times luminosity increase in the 1.0 GeV to 1.89 GeV energy range while retaining the BESIII detector. A small damping ring has been considered in the existing Linac tunnal to reduce the emittance of the injection beam, and hence to support the crab waist scheme in the colliding ring. By adding a compact damping ring to the linear accelerator, we also hope to achieve the physics operation in a new energy range below 1 GeV.

Speaker: Dou Wang (Institute of High Energy Physics, Chinese Academy of Sciences)

267 Characterization and optimization of the PAL-UED facility

Ultrafast Electron Diffraction (UED) is an imaging technique used to observe the atomic structure of matter and its dynamics through the scattering of a pulsed electron beam.
The performance of a UED beamline depends on electron beam parameters such as beam size, bunch length, bunch charge and beam energy which are affected by UED machine parameters including strength of solenoid and RF phase. However, these beam parameters cannot be optimized simultaneously due to their mutual correlations and trade-offs, such as those caused by space-charge effects.
At PAL, an MeV-UED facility for both solid and gas-phase imaging was constructed. In this paper, we introduce the current status of the MeV-UED apparatus at PAL-eLABs together with measurements of several key laser and electron beam parameters. Additionally, we discuss the implementation of an online optimization process using constrained multi-objective Bayesian optimization. We also compare this with multi-objective regionalized Bayesian optimization, which restricts the search for the next observation point to a hyperrectangular trust region whose center and width vary during the optimization process.

Speaker: Minseo Jung (Pohang University of Science and Technology)

268 Commissioning of the BEPCII Linac as the Injector for PWFA Accelerator

The Beijing Electron Positron Collider II (BEPCII) is a key large scientific installation for high-energy physics research in China, with its linear accelerator (Linac) serving as the core injector system responsible for generating and accelerating high-quality electron/positron beams to the designed energy for collider operation. Recently, this linac has been updated to serve as a high-performance electron injector for the Plasma Wakefield Acceleration (PWFA) experiment. This paper presents a complete set of beam commissioning, optimization, and performance validation for the BEPCII Linac to meet the strict beam requirements of PWFA. The commissioning focuses on beam energy stability, orbit quality, emittance control, and timing synchronization, aiming to provide a high-stability, low-emittance electron beam for PWFA-driven acceleration. Through orbit correction, RF parameter tuning, magnet system calibration, optics matching, and pulse stability optimization, the BEPCII Linac achieves excellent beam performance: energy stability better than ±0.1%, beam orbit fluctuation below 0.5 mm and normalized emittance below 0.4 mm·mrad.

Speaker: Lei Du (Institute of High Energy Physics)

269 Compact Dual-Harmonic RF Kicker for High-Charge Bunch Tail Mitigation at ATLAS

An RF kicker is being developed to mitigate high-charge bunch tails that can induce quenches in the superconducting magnets of the Argonne Tandem Linear Accelerator System (ATLAS). Building on previous design, the dual-harmonic kicker incorporates an additional harmonic mode to minimize the kick to the bunch core while maintaining effective tail removal. The resonant structure has been redesigned to reduce the coil size, resulting in a more compact assembly, and to implement the coupling and tuning schemes compatible with dual-harmonic operation. This paper presents the recent mechanical layout refinements, updated electromagnetic simulations, and outlines the next steps toward prototype fabrication and experimental validation.

Speaker: Deeksha Sinha (Northern Illinois University)

270 Conceptual Design and Development Status of a Spare Ion Source for RAON

RAON (Rare Isotope Accelerator for ON-line experiment) is a heavy-ion accelerator developed through the Rare Isotope Science Project (RISP) from 2011 to 2023, and has been providing beams to users since 2024. Currently, stable isotope beams such as argon, oxygen, neon, and other ion species are supplied using an Electron Cyclotron Resonance Ion Source (ECRIS). In addition, radioactive isotope (RI) beams have recently been delivered to users via the Isotope Separator On-Line (ISOL) system.

To ensure stable beam operation, RAON aims to operate three ion sources. At present, a 14.5 GHz ECRIS is in operation, while a 28 GHz ECRIS is under development. Furthermore, an additional 14.5 GHz ECRIS is being developed to enable pre-testing of various beams and to enhance the operational flexibility of the accelerator.

This paper presents the conceptual design and current development status of the additional 14.5 GHz ECRIS as a spare ion source, and discusses its potential applications.

Speaker: Jeongil Heo (Institute for Basic Science)

271 Construction Status of the ILC Prototype Cryomodule at KEK

Within the framework of the MEXT-ATD program and the ILC Technology Network (ITN), an ILC prototype cryomodule is presently being designed and assembled at KEK. The module will comprise eight superconducting 9-cell 1.3 GHz TESLA cavities. In parallel, the necessary infrastructure for cryomodule testing and operation is being set up. This contribution presents the current status of the cryomodule components, including the superconducting radio-frequency cavities, fundamental power couplers, cavity frequency tuners, magnetic shielding, the superconducting quadrupole magnet, and the cryomodule vacuum vessel. Furthermore, the status of the associated external systems and infrastructure is described, including the refrigeration system, high-power and low-level RF systems, the bunker, and clean-room facilities for cryostring assembly.

Speaker: Mathieu Omet (High Energy Accelerator Research Organization)

272 Deep Learning-Based Surrogate Model for 4D Phase-Space Reconstruction in the RAON LEBT

Precise measurement of the 4D phase-space distribution (x, x', y, y') is essential for optimizing accelerator performance and ensuring stable operation. However, the prolonged measurement time of traditional scanning-based diagnostics limits their application in real-time tuning. In this study, we propose a deep learning-based surrogate model for the rapid reconstruction of heavy-ion beam distributions in the Low Energy Beam Transport (LEBT) section at RAON.
Deep learning integrated with physics simulations was adopted in this study to achieve physically reasonable prediction. This method enables the reconstruction of the 4D phase-space distribution at the exit of the ion source, providing a robust framework for real-time diagnostics and autonomous tuning for accelerator systems. The model is trained and validated using high-fidelity particle tracking simulations to ensure numerical stability and minimize statistical bias. This approach significantly reduces the computational overhead compared to conventional tracking codes, allowing for instantaneous beam characterization required for dynamic machine protection and optimization.

Speaker: Woohyeong Kim (Gangneung–Wonju National University)

273 Design and Developement of the Superconducting Linac for IP-SAFE project

IP-SAFE is an isotope production facility based on superconducting linac located at Lanzhou. The facility is composed of a 115 MeV, 2 mA proton superconducting linac, two target stations, a chemical speration system, radioactive waste treatment systems and auxiliary support systems. The superconducting linac is designed and constructed in last 3 years. In the talk, the design, construction, and early commissioning result of IP-SAFE linac will be presented.

Speaker: Huan Jia (Institute of Modern Physics, Chinese Academy of Sciences)

274 Design and Fabrication of a 4 kW RF Solid State Power Amplifier for SCL3 Heavy Ion Accelerator

The Superconducting Linac 3 (SCL3) of the RAON heavy ion accelerator uses quarter wave resonator (QWR) cavities at 81.25 MHz and half wave resonator (HWR) cavities at 162.5 MHz. Each cavity is driven by a dedicated 4 kW solid state power amplifier (SSPA). This paper presents the design and fabrication of a domestically developed spare SSPA unit for SCL3. The amplifier uses six 900 W power amplifier (PA) pallets, and their outputs are combined through low loss combiners to produce 4 kW continuous wave (CW) and pulsed RF output. A dual circulator protection structure is used to protect the amplifier under full reflection conditions at any reflection phase. This structure includes 1 kW circulators at the PA pallet level and a 5 kW circulator at the system output stage. In addition, EPICS based real time monitoring and dual channel interlock functions are implemented to improve operational reliability. Performance test results confirm that the fabricated SSPA satisfies the main requirements for output power, efficiency greater than 45%, phase stability, and amplitude stability.

Speaker: Ki Taek Son (Institute for Basic Science)

275 Design and optimization of a compact THz-FEL oscillator with planar undulator

In a THz FEL oscillator, the undulator and optical cavity are the key components for radiation. In this paper, we present an integrated optimization of the systematical parameters under the requirement of high compactness. The joint influence of the undulator and resonator on the FEL performance introduces a multi-parameter coupling that complicates the design. To address this, we simplify the optimization through dimensionality reduction, and then globally tune both sets of parameters to maximize the micropulse and macropulse energy. The joint GENESIS and OPC simulations show that, with an electron energy of 15 MeV and beam current of 100 A, the output micropulse and macropulse powers could reach 2.5 MW and 4.8 kW respectively, and the wavelength could be tuned continuously across the range of 30-100μm.

Speaker: Ruiying Luo (Huazhong University of Science and Technology)

276 Design and Progress of the Beamlines for PWFA at IHEP

Beam-driven plasma wakefield acceleration (PWFA) holds considerable promise for next-generation electron-positron colliders and high-energy free-electron lasers, owing to its ultrahigh accelerating gradients. To address fundamental physics and technical challenges associated with both electron and positron acceleration in PWFA, the Institute of High Energy Physics (IHEP) has established a plasma wakefield acceleration experimental platform based on the Beijing Electron-Positron Collider (BEPCII). The platform comprises two beamlines and a petawatt laser system. Beamline I deliver electron and positron beams from BEPCII to the experimental area, while Beamline II is a newly constructed 150 MeV high-performance linear accelerator. Together, these beamlines support a range of plasma acceleration experiments, including positron acceleration, electron-cascade acceleration, high transformer-ratio electron acceleration, and external-injection electron acceleration. Notably, Beamline II is capable of generating electron beams with a bunch charge exceeding 5 nC and a peak current above 10 kA. This paper presents a detailed overview of the physics design and current progress of beamlines.

Speaker: Dr Cai Meng (Chinese Academy of Sciences)

277 Design and stability analysis of a quadrupole demagnifier for emittance exchange-based transverse-to-longitudinal density modulation frequency upshift

A project is underway to explore the generation of sub-micron longitudinal beam modulations—with the long-term goal of building a compact X-ray source. Our system uses a transmission electron microscope (TEM) grid to impose a transverse density modulation on the initial beam, and an emittance exchange (EEX) beamline to convert that transverse modulation into a longitudinal modulation. However, the TEM grid alone results in too large of a longitudinal modulation. We present the design of a quadrupole demagnifier that reduces the modulation period and prepares the beam for injection into the EEX beamline. The tunability and operational stability of the demagnifier optics are analyzed, and the impact of errors on the final longitudinal modulation is evaluated. Simulations were performed using General Particle Tracer (GPT) and ELEGANT.

Speaker: Buse Naz Temizel Ozdemir (Northern Illinois University)

278 Design of a C-band Spherical Pulse Compressor for the CEPC Linac

This work presents the design, simulation, and validation plan of a C-band spherical pulse compressor for the CEPC linac. The study is based on the RF power scheme in which one 80 MW klystron drives four accelerating structures. To meet this requirement, the compressor is designed to achieve an energy multiplication factor of M ≥ 1.9, enabling stable operation at 64 MW input power and supporting the 40 MV/m accelerating-gradient target.
Compared with conventional pulse compressors, the spherical structure provides a compact geometry, high unloaded quality factor, relatively uniform surface field distribution, and improved high-power reliability. The research includes CST-based optimization of a dual-mode 3 dB circular-polarization coupler, eigenmode analysis of the TE₁₁₄ spherical cavity modes, integrated frequency- and time-domain simulations, machining-error analysis, and multiphysics evaluation. Fabrication, cold testing, and high-power testing will be conducted to verify the prototype performance.

Keywords: C-band; spherical pulse compressor; CEPC linac; 80 MW klystron; energy multiplication factor.

Speaker: hengjun cao (Institute of High Energy Physics)

279 Design of a Superconducting Cavity for an EUV Energy Recovery Linac

An energy recovery linac (ERL) is an accelerator in which electron bunches are decelerated in the linac after generating radiation to recover their energy. Through this process, the ERL can achieve high energy efficiency while maintaining a high beam current. Due to these advantages, the ERL is an attractive candidate for a next-generation extreme ultraviolet (EUV) light source in lithography. EUV lithography is a critical procedure in the semiconductor fabrication process. Since an EUV-ERL can produce higher power than other conventional methods, it is more cost-efficient in terms of both construction and operation.
For efficient energy recovery, superconducting radio-frequency (SRF) cavities are used in the linac of the ERL. To design an SRF cavity, several factors and phenomena, such as peak electric and magnetic fields, higher-order mode (HOM) damping, and multipacting, should be considered simultaneously.
In this paper, we designed and optimized an L-band SRF cavity for an EUV-ERL. For the optimization of the cavity, machine learning was employed, utilizing the cavity dimensions as input parameters and the impedances of HOMs as the objectives.

Speaker: Minseo Jung (Pohang University of Science and Technology)

280 Design of SR Kicker Power Supplies for Kicker Magnets at Korea-4GSR

Prototype kicker power supplies have been designed for the storage ring beam injection of the Korea 4th generation storage ring (Korea-4GSR). The kicker power supplies drive four bump magnets to maintain field balance and synchronized kick of the beam. The pulsed magnetic field of kickers should be synchronized within a timing jitter of 5 ns and an amplitude difference of ± 0.2%. To fulfill the performance requirements of the kicker power supplies, the pulse-shape matching mechanism among four kickers, and handling two kicker magnets by using one kicker power supply as a parallel driver will be adapted to reduce fluctuation of the kick and the trajectory offset. Specifications of the kicker magnet power supply are the pulse width of 5 us, 200ns flattop width, a half-sinusoidal waveform with the peak current of 7 kA, and 2 Hz repetition rate. In this paper, the circuitry applied to the design of the power supply and circuit simulation will be discussed.

Speaker: Sang-Hee Kim (Pohang Accelerator Laboratory)

281 Development of a relativistic vortex electron source: current status and first results

Vortex electron beams are quantum states carrying quantized orbital angular momentum (OAM). Their extension to relativistic energies remains an open challenge, as experimental realizations so far are limited to electron microscopes at a few hundred keV. Such beams are of growing interest in accelerator physics, as OAM-carrying electrons may provide complementary tools for studies of nucleon structure and spin-related phenomena in scattering experiments.

We pursue the generation of MeV-scale vortex beams within a classical RF photoinjector. OAM is transferred from structured laser radiation to photoelectrons at emission, followed by rapid acceleration in a standard RF gun over a short distance, enabling controlled low-charge operation with reduced space-charge effects. The approach is compatible with established photoinjector technology.

This report demonstrates classical beam dynamics for sub-pC bunch charge operation simulation results. Moreover, a theoretical study of the evolution of a Laguerre-Gaussian electron wave packet in realistic accelerating fields is presented.

Speaker: Dr Konstantin Popov (Joint Institute for Nuclear Research)

282 Development of capacitive bellows tuner for low-beta single spoke cavity

We are now developing a capacitive bellows tuner to increase a frequency tuning range of low-beta single spoke cavity. By inserting a length-adjustable niobium bellows electrode from the outer conductor of a coaxial (half-wavelength) superconducting cavity toward the inner conductor electrode, a larger tuning range than conventional methods is realized. The bellows electrode is fabricated from high-purity niobium material. The fabricated tuner is incorporated into the superconducting spoke cavity under development at J-PARC, and the resonance frequency of the cavity is measured. Fabrication of the bellow tuner and frequency measurement is presented.

Speaker: Yasuhiro Kondo (Japan Atomic Energy Agency)

283 Development of high-gradient booster linac for multi-GeV proton radiography at LANSCE

Increasing energy of proton beam at the Los Alamos Neutron Science Center (LANSCE) from 800 MeV to 3-5 GeV will improve radiography resolution ten-fold. This energy boost can be achieved with a compact cost-effective linac based on normal conducting high-gradient (HG) RF accelerating structures operating at liquid nitrogen temperatures (cryo-cooled). Such an HG booster is feasible for proton radiography (pRad), which requires short beam pulses at very low duty. The pRad booster starts with a short L-band section to capture and compress the 800-MeV proton beam from the existing linac. The main HG linac will be based on S- and C-band cavities. An L-band de-buncher at the booster end can reduce the beam energy spread if needed for pRad experiments. We are developing proton cryo-cooled HG standing-wave structures with distributed RF coupling for the booster. Prototype cavity structures at S- and C-band are designed and will be tested cryo-cooled to measure breakdowns at high gradients. The booster linac beam dynamics design options and preliminary proton radiography simulations will also be presented.

Speaker: Sergey Kurennoy (Los Alamos National Laboratory)

284 Development of Medical Alpha-Emitting Radioisotope Production Using the 70 MeV Cyclotron and ISOL System at IRIS

Radioisotopes such as ²¹³Bi, ²²³Ra, ²²⁵Ac, and ²²⁷Th are alpha emitters and are regarded as among the most promising candidates for targeted cancer radiotherapy, owing to the high linear energy transfer, ~100 keV/μm, and their short path length in biological tissue, typically 50–100 μm. Recently, IRIS initiated a project to develop ²²⁵Ac production by irradiating ²³²ThO₂ targets with protons in the energy range of 40–70 MeV.

Based on theoretical estimates, irradiation of a 3-mm-thick ²³²ThO₂ target with 70 MeV protons at a beam current of approximately 100 μA for two days is expected to produce about 100 mCi of ²²⁵Ac, which could be used for preclinical evaluation of radiopharmaceuticals.

In addition, the ISOL facility, combined with the operation of the 70 MeV cyclotron, could provide several high-purity radioisotopes using a high-resolution separator. The ISOL project reached a major milestone in August 2024, when the first RI beam was extracted from the cyclotron and accelerated to 16 MeV/u by the superconducting LINAC at IRIS. This talk will present a brief overview of recent research activities related to the ISOL system and the 70 MeV cyclotron at IRIS.

Speakers: Bum-Sik Park (Institute for Basic Science), Dr Yeongheum Yeon (Institute for Basic Science)

285 Development of Resonant Kicker(RK) LLRF for PAL-XFEL

PAL-XFEL has been operating two beamlines simultaneously since 2021. The simultaneous operation method involves generating and accelerating single bunch of electrons at 60 Hz to provide 30 Hz beams to the hard X-ray(HX) and soft X-ray(SX) beamlines, respectively. It is intended to switch to a method developed by SwissFEL, which is capable of providing 60 Hz beams to both the HX and SX beamlines. To implement this, the two adjacent electron bunches are spaced 25ns apart, and the operating frequency is designed so that the RK operates at 20 MHz. We chose a method of driving the RK using a combination of LLRF and SSA. Currently, the LLRF prototype is in devleopment, and we would like to share the progress of the prototype LLRF.

Speaker: Jinyul Hu (Pohang Accelerator Laboratory)

286 Development status and field qualification of the latest 80 MW S-band klystron for Pohang Accelerator Laboratory

Development status of the latest domestically produced 80 MW S-band klystron for Pohang Accelerator Laboratory (PAL) is reported, with emphasis on the VK4 tube now under field qualification at the PAL-XFEL. Earlier prototypes reached the target RF power at low repetition rate but were limited to 30 Hz by frequent gun arcing. Breakdown studies identified clump-assisted discharge in the diode region and electron multiplication from the ceramic triple point as the dominant mechanisms. Based on these findings, improved electrode polishing and cleaning and a triple-point electrostatic shield were implemented in VK4 and VK5. In laboratory processing, VK4 demonstrated stable operation at 80 MW, 4 us, and 60 Hz, while VK5 showed a further reduction of total HV arc rate by about 59%, confirming the benefit of improved gun preparation. To verify accelerator readiness, site testing of VK4 is being carried out with stepwise HV and RF qualification up to 400 kV, 80 MW, 4 us, and 60 Hz. Initial field-test results and implications for routine accelerator operation will be presented.

Speaker: Dr Sung-Ju Park (Pohang Accelerator Laboratory)

287 Diagnostics and RF Monitoring Tools for Routine Operation of the TPS 150 MeV Linac and LTB

The 150 MeV electron linear accelerator (LINAC) serves as the primary injector for the Taiwan Photon Source (TPS), requiring high-precision beam stability and reliability to maintain top-up operation performance. Since the commencement of operation, the diagnostic systems—including integrating current transformers (ICTs), wall current monitors (WCMs), and profile monitors—have played a critical role in beam commissioning and routine maintenance. This paper presents an updated overview of the integrated diagnostic and RF monitoring infrastructure for the TPS 150 MeV LINAC. We discuss the current diagnostic layout and focus on the latest refinements in RF phase and amplitude monitoring, which are essential for controlling energy jitter and beam loading effects. Finally, we report on the current operational status and outline future strategies for further enhancing diagnostic resolution and system responsiveness to ensure the continued stability of the TPS injector.

Speaker: Chunyi Wu (National Synchrotron Radiation Research Center)

288 Electrostatic Pre-buncher for Enhancing the Fast neutron Time-of-Flight Capabilities in SARAF

Soreq Applied Research Accelerator Facility (SARAF) aims to deliver up to 5 mA CW proton/deuteron beams at energies up to 40 MeV. Neutron TOF experiments at SARAF were initially enabled through a novel electrostatic fast-chopper system installed in LEBT, to allow single RFQ bunch acceleration. More recently, a two-gap electrostatic pre-buncher has been designed, constructed, and installed in the SARAF LEBT. The pre-buncher can compress up to ~18 βλ section of the incoming DC beam to converge into a single RF cycle at the RFQ entrance, while the chopper is operated in synchronization to deflect all unwanted beam portions. Preliminary measurements demonstrate successful single-bunch selection and a good agreement with simulation results, yielding a two-fold enhancement of the charge per bunch for protons for a 5 mA peak current. For the low current of 0.1 mA the corresponding enhancement factor was of the order of 20. This enhancement is limited by space charge effects and expected to improve for deuteron beams. In this talk, we will present the design, simulations, and beam measurement results. The limitations of the approach and possible mitigations will also be discussed.

Speaker: Mr Ilya Polikarpov (Soreq Nuclear Research Center)

289 Enhancing the Operational Lifetime and Reliability of the ALBA Linac

The design of an upgrade of the ALBA synchrotron, known as ALBA II, is currently underway. The injector of the ALBA II facility will preserve the existing ALBA injector, based on a 100 MeV linac and a full energy 3 GeV booster, in operation since 2012. To extend the operational lifetime of the linac and improve its reliability throughout ALBA II operation, several consolidation activities have been initiated while preserving full compatibility with the existing accelerator infrastructure. This paper presents a detailed description of these activities, including operational experience with the recently implemented single klystron mode at 80 MeV, as well as planned actions to replace and upgrade critical components that may fail or become obsolete in the coming years.

Speakers: Davide Lanaia (ALBA Synchrotron (Spain)), Raquel Muñoz Horta (ALBA Synchrotron (Spain))

290 Envelope optics for a beam in a traveling-wave linac

We present a second-order Hamiltonian formulation describing a beam in a traveling-wave rf structure.
With the infinitesimal transfer matrix formalism, the linear optics about the accelerating reference particle are computed. The spatial phase advance is obtained from complex electromagnetic field data by extracting the accumulated phase and differentiating it to determine the local wave number k(s), providing a systematic reduction from full field descriptions to a reduced-order beam dynamics model.
The model is implemented in the first order envelope code TRANSOPTR, with its results benchmarked against a particle tracking code ASTRA. The TRANSOPTR model provides a practical framework for efficient tuning and optimization of systems incorporating traveling-wave linacs.

Speaker: Emma Ghelfi (TRIUMF)

291 ESS Ion Source and LEBT Test Stand

The injector of the European Spallation Source (ESS), comprising the ion source, low energy beam transport (LEBT), and radio frequency quadrupole (RFQ), will deliver a 62.5 mA proton beam in 2.86 ms pulses a at repetition rate of 14 Hz at 5 MeV beam energy for further acceleration in the normal and superconducting RF structures. The ion source and LEBT parameters are critical for the parameters of the beam, which is injected into the RFQ. In addition to the beam properties itself, reliability and lifetime are key parameters of ion source performance and need to be carefully assessed. For this purpose, a dedicated ion source and LEBT test stand is installed. In general, the test stand features components for an identical setup as the configuration in the main Linac. However, the test stand is also foreseen as a testbed for dedicated ion source and LEBT studies in settings or configurations, which are not feasible in the main machine. This paper presents an overview of the test stand design, reports on the progress of the project and gives an update about the recent milestones, including first plasma in the ion source, high voltage testing, and first beam extraction.

Speaker: Marten Koopmans (European Spallation Source)

292 Experience with a pulsed gas stripper from first user beamtimes at GSI

The efficiency of stripping heavy ions like uranium into a single charge state at 1.4 MeV/u using a gas target can be increased significantly by applying hydrogen instead of nitrogen, thereby narrowing the resulting charge state spectrum. However, pulsed injection into a dedicated interaction chamber will be required to reduce the load of the vacuum pumping system to an acceptable level. Such a setup was developed, a prototype constructed and studied thoroughly in various dedicated machine development beamtimes at GSI/Germany. During the last two user beamtimes, the prototype setup was operated under regular operating conditions with nitrogen, while hydrogen operation is restricted to machine studies due to necessary safety measures still under completion. Several ion species have been stripped in the course of the beamtimes and valuable data on stripping efficiencies have been measured with both gases. An overview of the technical challenges encountered, operational experience and results obtained so far, and an outlook towards regular operation with hydrogen will be presented.

Speaker: Peter Gerhard (GSI Helmholtz Centre for Heavy Ion Research)

293 Experimental Validation of an X-Band LLRF Prototype for High-Gradient Linear Accelerators

Low-Level RF (LLRF) systems are essential for maintaining amplitude and phase stability in modern linear accelerators, directly affecting beam quality and operational reliability. The increasing use of X-band technology in compact, high-gradient linacs enables ultra-short RF pulses and higher accelerating fields, while also increasing sensitivity to phase noise, timing jitter, and thermal effects. To address these challenges, a dedicated X-band LLRF prototype has been developed within the framework of the EuPRAXIA Doctoral Network for application in next-generation X-band linear accelerators. The system combines a high-speed RF front-end with FPGA based digital back-end optimized for fast pulsed operation, low-latency processing, and precise amplitude and phase control. After extensive laboratory testing, the prototype has been validated on a real accelerator test bench. This paper presents the system's concept and experimental results, including pulse-to-pulse stability and phase noise performance. The results confirm the feasibility of the proposed X-band LLRF approach for future high-gradient linac applications.

Speaker: Mr Phani Deep Meruga (Instrumentation Technologies (Slovenia), Sapienza University of Rome)

294 Fast beam chopping and emittance control in Low-Energy Beam Transport Lines

In high-intensity proton accelerators such as the China Spallation Neutron Source (CSNS), emittance control in the low-energy beam transport (LEBT) section is essential for improving beam quality and achieving high transmission efficiency. The electrostatic beam chopper originally installed in the CSNS LEBT has been shown to increase beam emittance by disrupting space charge compensation (SCC). To address this issue, a novel chopper scheme featuring a faster rising edge with minimized SCC destruction is proposed and experimentally tested. Furthermore, barrier electrodes are introduced to axially confine compensation ions by shielding the effect of local potential well. Both experimental measurements and simulations demonstrate that the barrier electrodes effectively suppress beam emittance growth. These findings provide effective strategies for high-intensity beam transport with fast chopping capability in the LEBT section.

Speaker: Dr Hui Liao (China Spallation Neutron Source)

295 First Beam Demonstration in Hand-Portable Battery-Operated 2 MeV Ku-band Linac

This talk reports on the design, fabrication, and beam testing of a novel 2 MeV Ku-band (15.14 GHz) traveling wave electron linear accelerator developed by RadiaBeam Technologies for a battery-powered, hand-portable X-ray generator intended for field radiography and non-destructive testing (NDT). The goal is to replace hazardous isotopes, such as Ir-192, Cs-137, and bulky betatrons with a compact, adjustable, and safer radiation source.
The system achieves dramatic miniaturization by combining several innovations: use of a 250 kW peak power air-cooled magnetron for reduced accelerator size while maintaining sufficient beam energy; a split accelerating structure fabrication method, machining both halves of the structure in one piece to eliminate the need for post-brazing tuning, reduce manufacturing errors, and improve vacuum conductance; and an ultra-compact solid-state Marx modulator, weighing ~1.2 kg, operable from two Li-Ion batteries.

Speaker: Sergey Kutsaev (RadiaBeam Technologies (United States))

296 Flexible multi bunch injection at Diamond light source

Diamond Light Source has, since the start of operation, run with both single bunch and multi bunch injection. Due to limitations in functionality and jitter in multi bunch mode, Diamond has been running with an upgraded gun pulser for the past 3 years. This pulser enables flexible modulation of the gun cathode in multi bunch mode by generating voltage waveforms from an arbitrary waveform generator (AWG). Single bunch operation was implemented using a separate supply to replicate the old pulser, allowing simple injection while providing scope for development of the multi bunch circuit. Leveraging the flexibility of the new pulser, fill patterns can be selected and injected with fewer shots and improved repeatability, leading to, among other things, faster fill times. Details of the functionality, design, and operation will be presented, along with results and issues related to reproducibility.

Speaker: Anton Tropp (Diamond Light Source)

297 FPGA-Based Frequency Shift Correction for Linear Accelerators

The muon high-precision (g-2)/EDM experiment, which is planned at the J-PARC, utilizes the world’s first dedicated muon linear accelerator (linac), requiring stringent Radio-Frequency (RF) field stability. The Radio Frequency Quadrupole (RFQ), the linac's initial stage, experiences frequency shifts that cause operation outside the RFQ bandwidth. Due to budget constraints, conventional tuning methods are impractical. This study presents a real-time digital feedback system developed within a Low-Level RF (LLRF) framework to maintain frequency-shifted operation and to correct IQ time variations caused by the frequency shifts, which was implemented on a Field-Programmable Gate Array (FPGA), proving a cost-effective and compact solution. This approach eliminates the need for additional external hardware such as dedicated tuners. Following the successful validation using a simulation test cavity, the system was integrated with the actual RFQ. This system met the stability requirements for achieving muon beam acceleration tests. This LLRF-based approach ensures beam integrity and represents a significant milestone towards achieving the precision goals of the J-PARC experiment.

Speaker: Osman Emre Delialioglu (The Graduate University for Advanced Studies, SOKENDAI)

298 Generation of scanning electron beams in one millisecond for FLASH-RT and spatially fractionated radiation therapy at PITZ

The photoinjector test facility at DESY in Zeuthen (PITZ) is developing a dedicated R&D platform for electron FLASH radiation therapy, known as FLASHlab@PITZ. Benefiting from the long RF pulse (1 ms at 1–10 Hz) of the accelerator and the flexible time structure of the photocathode drive laser, an exceptionally wide range of dose rates—from 0.05 Gy/s to beyond 10¹² Gy/s—can be achieved using 20 MeV electron beams with tunable bunch charges from sub-pC to several nC. In particular, both uniform and spatially fractionated radiation fields can be produced by scanning the electron beam within a single RF pulse. This capability is enabled by an inductive kicker providing vertical deflection on the microsecond timescale and a stripline kicker for horizontal deflection on the sub-microsecond timescale. These features allow systematic investigations of the FLASH effect as well as spatially fractionated radiation therapy (SRFT) in biological samples. In this contribution, we present the design performance of the kicker system along with measurement results from beam-scanning experiments, with particular emphasis on the delivered electron beam and dose distributions.

Speakers: Dr Anne Oppelt (Deutsches Elektronen-Synchrotron DESY), Christopher Richard (Deutsches Elektronen-Synchrotron DESY)

299 Hierarchical CMA-ES Framework for Multi-Parameter Multi-Objective Optimization of High-Intensity RFQ Beam Dynamics Design

Abstract: To resolve the strong parameter coupling and competing objectives in high-intensity RFQ beam-dynamics design, this paper presents a hierarchical optimization framework based on the Covariance Matrix Adaptation Evolution Strategy. A 14-knot parameterization reduces the problem from more than 600 dimensions to a tractable 42-dimensional optimization problem.Piecewise Cubic Hermite Interpolating Polynomial is then used to ensure physically smooth and monotonic axial profiles. A multi-stage search strategy is employed, including Latin hypercube sampling with K-means clustering for global exploration, CMA-ES local refinement with IPOP restarts, narrow-range re-optimization, coordinate-descent fine-tuning, and Gaussian perturbation search. This framework is applied to design a 162.5 MHz RFQ which will accelerate the He²⁺ from 50 keV/u to 2 MeV/u with 120emA. The beam dynamics simulation results show that the beam transmission efficiency can be improved from 90% to 99% comparing with the conventional four-section design strategy. This work provides an efficient and automated tool for high-intensity RFQ design and can be extended to other high-current accelerator design.

Speaker: mengxue li (Institute of Modern Physics, Chinese Academy of Sciences)

300 Identifying Anomalies at CEBAF via Singular Value Decomposition of Cross-Plane Covariance

We present a method for detecting and characterizing anomalies in a nominally decoupled, recirculating linac accelerator, such as the Continuous Electron Beam Accelerator Facility (CEBAF). Proposed future accelerators of this type include PERLE and LHeC. The method computes the zero-lag cross-plane covariance from samples of beam position data, and analyzes its singular value decomposition (SVD). Each singular triplet of the SVD spectrum produces paired spatial patterns and a strength that quantify where and how the two planes move together at the same instant. Projecting each array of positions at a given time onto the spatial singular vectors indicates when the coupled pattern is active. Large modes provide direct evidence of dispersion, skew optics, position feedback cross-feed, scraping, or faults that introduce coupled beam motion. The construction is formalized, differentiability is discussed, and data from observed anomalies such as magnet failures and known optic modulation are presented.

Speaker: Ryan Bodenstein (Thomas Jefferson National Accelerator Facility)

301 IFMIF-DONES Advanced Machine Protection System: Interlock Signal Optimization

The International Fusion Materials Irradiation Facility-DEMO-Oriented Neutron Source (IFMIF-DONES), a cutting-edge accelerator-based neutron source for fusion materials research. IFMIF-DONES Facility Project involves a particle accelerator that produces a deuterons beam of 40 MeV and 125 mA, impacting on a flowing liquid lithium target, generating the neutron source by nuclear stripping reaction, therefore a robust central control system for safe and efficient operation.
The current Machine Protection System (MPS) Interlock Signal List comprises more than 3,600 interlock signals distributed across 42 systems. This work presents an optimization approach where each Local MPS generates, as a general rule, only one Functional Interlock Event upstream to the Satellite Units, while only a few systems may generate up to three different Functional Interlock types. This reduces the upstream signals from over 3,600 to a range between 42 and approximately 52 signals, significantly simplifying cabling and system complexity while maintaining full flexibility for future expansions.

Speaker: Ruben Lorenzo Ortega (IFMIF-DONES Spain Consortium)

302 Implementation and operational experience of an EtherNet/IP-based device interface in RILAC toward the RIBF Facility Upgrade Project

A reliable device interface is essential for long-term accelerator operation. In the RIKEN Radioactive Isotope Beam Factory (RIBF) control system, many devices are integrated with Experimental Physics and Industrial Control System (EPICS) input/output controllers (IOCs) through TCP/IP-based socket communication. Although this approach is flexible and cost-effective, reconnection after an unexpected power loss or restart of a device or network switch is not always successful, and recovery may require restarting the IOC. To improve reliability and maintainability, Ethernet-based industrial field networks, such as EtherCAT and EtherNet/IP, were proposed for the future RIBF Facility Upgrade Project*. Following a recommendation from the CSR1 Technical Advisory Committee to evaluate the proposed technologies in an existing accelerator facility, EtherNet/IP was implemented in the RIKEN linear accelerator (RILAC) control system as one of the candidate field networks. The system currently consists of one scanner and 16 adapters with a requested packet interval of 10 ms and is used for Faraday cup, beam attenuator, and vacuum control. The existing EPICS process variable names and graphical user interfaces were retained without modification. The system was used in routine RILAC operation, including beam operation for experiments using the superconducting RIKEN linear accelerator (SRILAC), from September 2025 through July 2026. During this period, except during scheduled maintenance, the IOC was not rebooted, and no interruption of device control attributable to EtherNet/IP communication occurred. Automatic recovery after planned power cycling was also confirmed.

Speaker: Akito Uchiyama (RIKEN Nishina Center)

303 Integrated Digital RF Protection and Control Platform for 100-MeV Proton Linac Operation at KOMAC

High-power RF systems in proton linear accelerators require reliable protection against abnormal conditions such as RF arcing and excessive reflected power. At KOMAC, the existing analog RF interlock system was upgraded to a digital platform based on a Zynq System-on-Chip architecture to improve operational flexibility and system integration.
The developed system digitizes forward, reflected, and pickup RF signals using simultaneous-sampling ADCs and performs real-time RF power and VSWR calculations in FPGA logic. Arc sensors, vacuum faults, and external protection signals are integrated into the digital interlock framework. Timing-critical functions are implemented in programmable logic, while control and monitoring are supported through an EPICS-based environment.
Experimental verification confirmed stable waveform acquisition and reliable interlock generation within the required protection time. Compared with the analog system, the digital platform improves maintainability, remote operation, and centralized monitoring while preserving fast protection performance.

Speaker: Dr Young-Gi Song (Korea Multi-purpose Accelerator Complex)

304 Investigation of the Operational Aspects of Ferroelectric Fast Reactive Tuners (FE-FRTs)

Integrating ferroelectric fast reactive tuners (FE-FRTs) into SRF cavities offers a promising route to mitigate microphonics. This work reports the design and characterisation of an FE-FRT coupled to a 1.3 GHz two-cell cavity, supported by a lumped element equivalent circuit model and 3D CST simulations. From this framework, external Q-factors, FPC specifications, and generator power requirements are derived, including power loss estimates to identify optimal working points. The tuner’s non-linear response to RF current is characterised, accounting for higher-order modes (HOMs) in both the cavity and the tuner resonator. By appropriate resonant frequency choice, monopole HOMs in the tuner can be kept away from harmonics of the fundamental mode; however, the permittivity variation in the FE wafers during operation could shift a HOM close to the third harmonic at 3.9 GHz, potentially coercing the stable operating range. In our example design, the two monopole HOMs below the fourth harmonic exhibit fields mainly on the sapphire window rather than on the FE wafers, thereby strongly reducing direct excitation by the fundamental field and mitigating associated risks for LINAC operation.

Speaker: Maleesh Shehan Rathnasiri Dissanayake Mudiyanselage (Lancaster University)

305 JINR DLNP Laser-driven RF-Gun Test Bench Commissioning Status

A laser-driven RF-Gun test-bench development and commissioning is ongoing at the Dzhelepov Laboratory of Nuclear Problems (DLNP) at the Joint Institute for Nuclear Research (JINR). Bench primary purpose is to investigate the possibility of replacement the JINR DLNP electron linac thermionic gun with the laser-driven RF-Gun. Another important task is the relativistic vortex electron beams generation study*. This report shows the laser-driven RF-Gun test-bench layout, commissioning results and facility future plans.

Speaker: Mikhail Nozdrin (Joint Institute for Nuclear Research)

306 LLRF-based multistage phase reversal feed for RF pulse compressor

High-gradient radio-frequency (RF) pulses are fundamental to the operation of linear accelerators. In a typical linac, such pulses are generated by a klystron or magnetron. To obtain higher peak power, RF pulse compressors are widely employed. A relatively long, low-power pulse with a specifically tailored amplitude and phase profile can be transformed by the compressor into a short pulse with several times the original power, thereby increasing energy efficiency and reducing the cost of the microwave source. In the present work, two compressors are cascaded to achieve two-stage pulse amplification. To this end, the low-level radio-frequency (LLRF) system generates a multiple-phase-reversal waveform that can be edited in real time. In our implementation, a 1.5-μs pulse is compressed to 50 ns by employing ten phase reversals. Iterative learning control (ILC) is applied to modulate the waveform and compensate for imperfections in the electronics. The resulting LLRF output is fed into a simulated model of the two-stage compressor, and the results show that this method can achieve a power amplification factor of 15.

Speaker: Yiming Xu (Shanghai Synchrotron Radiation Facility)

307 LORASR-Designer: a graphical interface for linac beam dynamics design and simulation based on LORASR

LORASR-Designer is a graphical user interface for linac beam dynamics design and simulation based on the LORASR simulation code developed at IAP. It extends existing LORASR workflows by enabling interactive configuration, parameterization, and validation of RF linac layouts. Instead of direct input-file editing, accelerator sections and design parameters are represented in a structured internal model, including section configuration, phase settings, longitudinal design modes, and aperture-related quantities. This improves consistency in model definition, supports backward-compatible handling of legacy configurations, and enables reproducible project-based workflows. LORASR-Designer is integrated into the LINAC-Multitool, where it adds design functionality while using the existing structures for visualization and evaluation of beam dynamics results.

Speaker: Peter Braun (Goethe University Frankfurt)

308 Mitigation of high voltage arc-downs of the LANSCE H- 80 keV pre-injector column

The LANSCE H- beam ultimately reaches 800 MeV to serve its user programs. The H- beam originates in a filament arc-driven plasma cesiated-surface-conversion H- ion source, and is initially accelerated to 80 kV via a three-stage accelerating column. A prime source of H- beam instabilities at LANSCE come from high voltage arc-downs of the 80 keV Column. These arc downs are primarily due to the cesium in the H- source, which can quench the hydrogen plasma, or over-cesiate and short the converter surface. Excessive 80 kV arc-downs lead to failure on the 80 kV column components, further increasing downtime.
Recent upgrades were made to mitigate these arc-downs, and to protect the 80 kV column components. Mitigation of source-based arc-downs involves current limiting the converter with a high-power resistor, and adding FPGA based fast electronics that turns off the beam gate on over-currents on the plasma or converter current. Equipment protection upgrades involve implementing block/clamp diodes for power supply protection, and calibrated spark gaps to ensure proper arc-downs to ground. The design, implementation and results of these upgrades will be discussed.

Speakers: David Kleinjan (Los Alamos National Laboratory), Isaac Wiens (Los Alamos National Laboratory)

309 New type of HOM absorber for CLIC accelerating structure based on resistive coating

Accelerating cavities are commonly equipped with RF loads to absorb energy deposited by the beam into higher-order modes (HOMs). These modes generate electromagnetic wakefields that can induce transverse and longitudinal kicks in the beam, potentially leading to beam instabilities.
This work investigates a novel type of HOM absorber based on resistive coatings deposited on dielectric substrates. The shape of the dielectric and the resistivity of the coating have been optimized to improve the load performance and integration in X-band accelerating cavities for the Compact Linear Collider (CLIC). The study includes experimental characterization of NEG coatings with the target surface resistance of 200 Ω/□ applied to alumina substrates, as well as low-power RF measurements. In addition to room-temperature applications, this approach is also explored as a potential solution for RF loads operating at cryogenic temperatures, where conventional lossy dielectrics are not suitable.

Speaker: Pablo Martinez Reviriego (European Organization for Nuclear Research)

310 Online Beam Alignment System Design for the STCF Injector Main Linac

The STCF injector Main Linac comprises 36 constant-gradient traveling-wave structures. Equipment misalignments and orbit distortions severely degrade beam quality. This paper presents the design and simulation of its online beam alignment system. First, the spatial layout of dual-plane correctors and beam position monitors (BPMs) is optimized for long-distance transmission. Second, dual-plane corrector magnets are designed and electromagnetically optimized to ensure magnetic performance and structural stability. Finally, an error transfer model evaluates beam dynamics under various installation and orbit errors, quantifying their impacts and verifying the system's trajectory correction efficacy. This study provides a vital engineering reference for the STCF, ensuring high-precision stable beam operation.

Speaker: Hao Hu (Huazhong University of Science and Technology)

311 Operational Achievements and 2026 Upgrades of the SC-RFQ Linac at KAHIF for High-Dose Nuclear Material Irradiation

he KAERI Heavy-ion Irradiation Facility (KAHIF) is a linear-accelerator-based infrastructure designed to emulate neutron-induced displacement damage in next-generation nuclear and fusion structural materials [1-3]. KAHIF consists of a 25.96 MHz Split-Coaxial Radio-Frequency Quadrupole (SC-RFQ) operating at 178 keV/u, and a 51.92 MHz Interdigital H-mode (IH) drift tube linac capable of accelerating heavy ions up to 1.09 MeV/u. In 2025, KAHIF achieved a critical operational milestone by successfully establishing a high-flux solid metal ion beam [4-6]. By optimizing a Metal Ions from Volatile Compounds (MIVOC) system using ferrocene at room temperature, the facility stably extracted and accelerated an Fe13+ ion beam to 9.68 MeV.
This paper outlines the operational performance of KAHIF faciliy for high-dose irradiation. To further advance extreme material testing capabilities, 2026 strategic upgrades include rebuilding the Medium Energy Beam Transport (MEBT) line for precise beam diagnostics, installing a 950°C ultra-high-temperature target chamber, and developing a He/Fe simultaneous dual-beam irradiation architecture.

Speaker: Seunghyun Lee (Korea Atomic Energy Research Institute)

312 Overview of the FACET-II facility at SLAC

FACET-II is a National User Facility offering unique capabilities for the advancement of accelerator science. Utilizing high-energy electron beams, it enables state-of-the-art research in advanced acceleration methods, ultra-high-brightness beam generation, and novel radiation sources. Here, we provide an overview of the FACET-II facility and highlight its experimental infrastructure, which is accessible to the scientific community through a competitive user program.

Speaker: Ivan Rajkovic (SLAC National Accelerator Laboratory)

313 Partial discharge-based condition assessment of high-voltage capacitors

Insulation imperfections in high-voltage capacitors can trigger partial discharge (PD) activity, driving degradation and ultimately causing failure. This study investigates the relative assessment of PD activity in high-voltage capacitors, combining experimental PD measurements on two distinct capacitor types with the visual inspection of a failed unit. Due to the limited suitability of PD threshold values for long-term operational assessment, the analysis is limited to relative comparison. Accordingly, the investigated type is compared with a reference capacitor of comparable design. The PD measurements confirm discharge activity in both capacitor types, with the investigated type exhibiting a greater number of higher-amplitude discharges than the reference. Analysis of PD characteristics suggests the presence of void- or surface-related discharges, supported by visual inspection of a failed capacitor in which voids in the resin insulation were identified. These findings are consistent with the PD behaviour and failure of the inspected unit and highlight the role of void-related defects in PD activity and insulation failure.

Speaker: Victor Cajus Kröger (Deutsches Elektronen-Synchrotron DESY)

314 Performance of 2-Step Baked Niobium Cavities for the ITN Cryomodule

To support the ILC Technology Network(ITN) Cryomodule project at KEK, we have constructed and assembled six single cell cavities and one 9-cell cavity for vertical testing (VT). A series of surface treatment were applied to the cavities using the proposed recipe for the construction of the International Linear Collider (ILC). This recipe consists of four steps: bulk electropolishing (EP), annealing, cold EP, and finally two step baking. Using this recipe, we can consistently exceed the ILC specifications. We analyze the performance and characteristics of these cavities using Q vs E and temperature mapping measurements. We also analyze the effect of cold EP and HPR on the maximum quench field and quality factor of the cavities.

Speaker: Eric Viklund (High Energy Accelerator Research Organization)

315 Phase and Amplitude Setup of the RF Cavities of the ESS Linear Accelerator

The European Spallation Source (ESS) aims to be the world's brightest neutron source, designed to delivering 2 GeV protons at 5 MW to a rotating Tungsten target via a 600 m-long superconducting linear accelerator. At the present installation phase, with 82 of the total 146 cavities available in the superconducting linac, a beam of 800 MeV (2 MW) can be produced. During the first half of 2026, a second commissioning run for the full accelerator had the goal to improve the setup of the machine and to increase the beam power above the levels used during the first run in 2025.
One of the first steps required at the start of each run is to find the amplitudes and phases for each of the cavities for correct acceleration. This paper will give an update on the methods presently used for setup of both the normal conducting and the superconducting part of the machine.

Speaker: Daniel Noll (European Spallation Source)

316 Physics studies for the Muon Collider target system.

The target system for a proposed Muon Collider must withstand multi-MW pulsed proton beams, at 5 GeV for 2 MW or 10 GeV for 4 MW scenarios, to produce muons through pion decay. It must also maintain long-term reliability while providing the required particle yield, with performance depending on its ability to sustain high thermal and radiation loads.
This study presents optimised pion-to-muon production yields and investigates radiation-induced heat loads for the tungsten powder (W jet) target system across a 1 − 20 GeV kinetic energy scan range, using FLUKA, to determine the optimal target design for use within the collider. Idealised physics geometries are used throughout this work, with engineering feasibility estimated from the design constraints.

Speaker: William Bishop (University of Warwick, Science and Technology Facilities Council)

317 Physics-Informed Multi-Objective Genetic Optimization for High-Intensity RFQ Design

RFQ design involves strong parameter coupling, multi-physics interactions, and multiple optimization constraints. To address these challenges, this work develops a physics-informed genetic optimization framework for RFQ beam dynamics and electromagnetic design.
By incorporating evolutionary rules associated with modulation factor, synchronous phase, and focusing strength, the framework improves optimization efficiency and physical reliability. The method has been validated for several RFQ configurations, including heavy-ion, proton, compact CW, and He²⁺ RFQs. The optimized LEAF, ADS Injector-II, PAFA, and SYSU-IFCEN HeRFQs achieved transmission efficiencies of 98.7%, 99.8%, 99.8%, and 97.4%, with RFQ lengths of 575.85 cm, 409.56 cm, 351.98 cm, and 143.42 cm, respectively. Typical optimization tasks required 80–300 core-hours using 20–70 generations with 100 individuals.
The framework was also applied to RFQ electromagnetic design using surrogate-model-assisted optimization. For a C⁴⁺ RFQ cavity, the optimized design achieved an approximately 10% increase in the Q value.
These results demonstrate an efficient approach for automated RFQ optimization and accelerator design.

Speaker: Yulin Ge (Sun Yat-sen University)

318 POLARIZED ION SOURCE DEVELOPMENTS FOR EIC AT BNL*

Abstract
The OPPIS has undergone multiple upgrades since 2000, with the most recent completed in 2022. Improvements to the Rb and Na cells have reduced vapor dispersion in the beamline, significantly lowering consumption and improving source stability. Plasmatron modifications extended component lifetimes. These upgrades enabled reliable Run-24 operation, with a mean current of 350 µA, 300 µs pulse width, and ~80% polarization delivered at the 200 MeV linac exit.
Development is also underway for a high-intensity (2×10¹¹ ions/pulse) polarized ³He⁺⁺ source for the future EIC. The approach uses metastability-exchange optical pumping of high-purity ³He gas in a strong magnetic field, followed by ionization in EBIS. In tests with an “open” cell, 80–85% polarization has been achieved. The final gas cell configuration is now being tested with a 5 T EBIS solenoid magnet.

Speaker: Deepak Raparia (Brookhaven National Laboratory)

319 Power Efficiency Estimations for a High Intensity Proton Linac

The Accelerator community needs to evolve to more efficient
technologies and support R&D to reduce total energy consumption. This requires a change in culture - we need to focus on energy
efficiency with the same priority as achieving higher performance. Some linac installations like those for Accelerator Driven Systems (ADS) are advertised as being powered by the nuclear energy they produce with the surplus power going to the grid. In this case power efficiency is a key parameter in the design. Power usage can be impacted by various factors including temperature of operation and rf surface resistance. This paper presents modeling exercise to motivate future R%D towards improving power efficiency and in particular focused on accelerator used to drive ADS.

Speaker: Robert Laxdal (TRIUMF)

320 Preliminary Beam Dynamics Studies on SDTL for 200 MeV energy upgrade at KOMAC

The proton accelerator, operational since 2013, has consistently achieved over 3,000 annual operating hours, providing 100 MeV proton beams to users. Increased demand from the semiconductor industry for testing and evaluation necessitates an energy upgrade to 200 MeV, aiming to enhance performance and support advanced materials industries.
The design for this extended linac is based on a normal-conducting separated-drift tube linac (SDTL) structure, chosen for its efficiency within limited space, including some building extension. The SDTL design maintains the DTL structural configuration without quadrupole magnets, utilizing a doublet focusing structure between tanks instead.
Preliminary beam dynamics studies compared 5-cell and 6-cell SDTL options, considering space constraints. This paper presents the beam dynamics results, providing insights into the feasibility of an efficient SDTL configuration for the 200 MeV upgrade.

Speaker: Seunghyun Lee (Korea Multi-purpose Accelerator Complex)

321 Progress in Nb3Sn SRF cavity development at KEK after furnace relocation

Nb$_3$Sn is one of the most promising materials for next-generation superconducting radio-frequency (SRF) cavities, as it enables high-Q operation at 4 K. This feature opens the possibility of conduction-cooled SRF systems without liquid helium. At KEK, Nb$_3$Sn coating development based on the Sn vapor diffusion method has been in progress since 2019, with continuous improvements in cavity performance. Last year, the coating furnace was dismantled, relocated, and recommissioned. After the relocation, cavity development was resumed with verification of coating reproducibility, achieving stable coating and improved cavity performance. In parallel, coating studies using a coupon cavity equipped with sample holders have been initiated. This approach enables preparation of samples that reproduce the Nb$_3$Sn film formed on the cavity inner surface, allowing more detailed surface characterization than in conventional sample studies. We will report recent progress in Nb$_3$Sn cavity development after furnace relocation, together with the results of surface characterization using these samples.

Speaker: Hayato Ito (High Energy Accelerator Research Organization)

322 Progress on Feedback Control for Transverse Wiggler-Based Sawtooth Correlation Generation

We present progress on a feedback control system for real-time optimization of five transverse wigglers to generate a sawtooth phase-space correlation. A recently proposed transverse wiggler-based correlation control method requires simultaneous tuning of 5-10 wigglers, each with three control variables (phase, amplitude, and period), which makes the tuning challenging. An upcoming experiment to demonstrate bunching factor enhancement using a sawtooth correlation will implement five wigglers. For a successful demonstration, we are developing a closed-loop framework that will use single-shot, projection-based transverse phase-space diagnostics to iteratively update wiggler parameters. The system will support remote control and real-time adjustment during operation.

Speaker: Buse Naz Temizel Ozdemir (Northern Illinois University)

323 Restoring High-Brightness Electron Beams via Correction of Transverse Coupling

High brightness and low transverse emittance are essential for achieving high signal-to-noise ultrafast electron diffraction (UED). In practice, however, asymmetries in the RF gun cavity and misalignments of the focusing solenoid introduce residual stray quadrupole fields, leading to transverse phase-space coupling that degrades beam quality and limits UED performance.Here we use a compact correction scheme based on a combination of normal and skew quadrupoles, enabling the synthesis of a compensating quadrupole field with tunable strength and rotation to systematically suppress multi-source stray fields. Guided by the HUST-UED parameters, we design and implement a dedicated corrector and perform four-dimensional transverse phase-space measurements. The results show effective decoupling of the horizontal and vertical phase spaces and a marked reduction of coupling-induced aberrations.Following the correction, the beam brightness is significantly enhanced, demonstrating the effectiveness and practicality of the approach for high-brightness electron sources. This work paves the way for higher signal-to-noise and improved spatiotemporal resolution in ultrafast diffraction imaging.

Speaker: Changda Peng (Huazhong University of Science and Technology)

324 RF Design of an S-band HEM11 Transverse Deflecting Cavity for an Electron Linac Test Facility

S-band transverse deflecting cavity (TDC) system is being developed at Pohang Accelerator Laboratory (PAL) using its in-house brazing facility. This TDC will be employed for the longitudinal phase-space characterization of electron beams in the eLABs at PAL. Low-power RF tuning is required before high-power conditioning because the input-coupler response and deflecting-mode field distribution must be evaluated together. This work reports the RF design and low-power characterization of the brazed TDC using complex S11 measurements and electromagnetic simulations. During mechanical tuning, phase changes at three characteristic mode frequencies were mapped to a simulation-equivalent coupler-cell radius. The measured and simulated phase changes agreed with an RMS residual of 1.3 degrees. At the 2pi/3-mode frequency, iris-centered perturbation yielded a phase advance of 239.7 degrees, compared with 158.7 degrees for cell-centered perturbation over equal axial intervals. Fixed-frequency three-dimensional field integration also showed larger normalized local Slater terms at iris positions, and low-power RF tuning is ongoing.

Speaker: Mr Geunwoo Kim (Pohang University of Science and Technology)

325 RF design of broadband high-power coaxial HOM extractors for the FCC-ee 400 MHz cavities

The higher-order mode (HOM) power generated in the 2-cell 400 MHz superconducting cavities and associated auxiliary components of the FCC-ee at the Z working point, with a beam current of 1.28 A, is estimated to reach approximately 60 kW per four-cavity cryomodule. Efficient extraction of this power is essential to ensure stable operation and to limit the thermal load on the cryogenic system. In this work, the HOM damping requirements for Z operation are reviewed, and the RF design of broadband high-power coaxial HOM extractors is presented. The proposed extractors are normal-conducting devices located in the inter-cavity regions of the cryomodule, each capable of handling kilowatts of HOM power while keeping the heat load to the cryogenic system within acceptable limits. The extracted HOM energy is taken outside the cryomodule and dissipated in RF loads at room temperature. A ceramic window is used to isolate the load from the beam vacuum, with optimized RF matching to minimize reflections. The performance of the proposed design is evaluated and compared with alternative HOM damping schemes, such as beamline absorbers and waveguide dampers.

Speaker: Shahnam Gorgi Zadeh (European Organization for Nuclear Research)

326 RF Energy Recovery Power Conversion for Particle Accelerators

To enhance the energy efficiency and cost-effectiveness of large-scale particle accelerator facilities, energy recovery has emerged as a key research direction. From the perspective of radio frequency (RF) power sources, this article reports on the latest research progress in this field at IHEP. First, the fundamental principles of energy recovery based on RF power sources are elaborated, covering three aspects: energy recovery klystrons based on multi-stage depressed collectors, high-power RF energy recovery systems, and studies on high-efficiency power recovery devices.
The article highlights recent key technological breakthroughs, including:
(1) Research on energy recovery schemes, which are expected to increase klystron efficiency to over 90%;
(2) RF energy recovery, detailing advancements in RF devices and RF-to-DC conversion technologies;
(3) Design and preliminary experiments of energy recovery devices, demonstrating recent progress in efficiency improvement and energy recovery.

Speaker: Jindong Liu (Chinese Academy of Sciences)

327 Simulation study on beam dynamics of two-beam acceleration in RFQ

The Radio Frequency Quadrupole (RFQ) accelerator is a compact linear ion accelerator for high-current low-energy beams, widely used in particle physics, medical treatments, material research, and other fields. Currently, the RFQ primarily accelerates a single type of ion, utilizing only half a cycle of the input high-frequency power. Theoretically, the RFQ can also achieve two-beam acceleration by accelerating ions of opposite charge with the same charge-to-mass ratio during the other half-cycle. In this study, we developed a beam dynamics simulation program for the RFQ using the IBSimu package. The single-beam simulation results align with the widely used TOUTATIS code, enabling the program's application to two-beam simulation studies. This work investigates the differences between single-beam and two-beam acceleration in the RFQ, as well as the effects of varying beam currents and beam proportions on two-beam acceleration, providing data support for future RFQ upgrades and optimizations in linear accelerators.

Speaker: Dr Hui Liao (China Spallation Neutron Source)

328 Simulation‑based analysis of geometric imperfections and tuning for a BNCT‑RFQ

Boron neutron capture therapy (BNCT) is attracting increasing attention. This paper presents the structural design and error analysis of a radio frequency quadrupole (RFQ) accelerator currently being fabricated for BNCT applications. The RFQ is designed to accelerate a 15 mA proton beam to 2.5 MeV, with a total length of 4.7 m divided into four segments, each approximately 1.2 m long. Various types of machining imperfections may inevitably exist after the final assembly of the cavity. Since these imperfections can significantly affect the RF performance and field distribution of the RFQ, tuners are provided on the cavity to compensate for such manufacturing errors. To predict the potential impact of these errors on cavity performance and to evaluate the effectiveness of the tuners, several possible structural error patterns were modeled in a CST simulation environment based on the RFQ cavity model. The simulation results reveal how these errors affect the high-frequency and electromagnetic characteristics of the RFQ and confirm the effectiveness of a proposed tuning algorithm.

Speaker: Zhiqiang Ren (Sichuan University)

329 Single-Shot Extraction Efficiency Evaluation of an Infrared FEL Oscillator via simultaneous measurement of electron energy evolution with and without FEL lasing

Extraction efficiency is a key parameter for oscillator FELs. To evaluate it in a single macro-pulse, both electron beam energy evolution with and without FEL lasing must be known. Previously, we developed a secondary electron emission monitor (SEEM) to measure the temporal energy evolution after the undulator with and without FEL lasing. Since SEEM requires separate measurements with and without FEL lasing, its accuracy is limited. To improve accuracy, we utilize a beam position monitor (BPM) in the dispersive section upstream of the undulator at KU-FEL*, where horizontal beam position strongly correlates with beam energy. Thus the BPM can provides the temporal energy evolution before (or without) FEL lasing. By simultaneously acquiring SEEM and BPM in the same macro-pulse, we can obtain both energy distributions with and without FEL lasing in a single shot. We will present the experimental setup including signal processing, calibration results, and single-shot extraction efficiency measurements. This approach enables high-precision single-shot extraction efficiency measurement and facilitates further optimization of FEL operation.

Speaker: Zhuang Bi (Kyoto University)

330 Steady-state and transient simulations of an RF cavity fed via multiple ports

High-power radio-frequency (RF) cavities, such as RFQs, may require multiple input couplers to circumvent the breakdown limit. With advances in semiconductor amplifiers, each coupler is often connected to a single source. Although all amplifiers are synchronized in amplitude and phase by an LLRF system, calibration or control errors may persist. These errors, along with disparities in the external Q-factor, affect the amplitude and phase of the voltage seen by the beam and, consequently, the energy gain. An imbalance between the different RF sources can also lead to excessive reflected power at the couplers. This article presents a numerical simulation method based on the open-source Scilab/Xcos software, capable of predicting not only the steady-state behavior but also the transient behavior of such a system: it is applied to the ESS RFQ and to a new RFQ developed at CEA Saclay for industrial purposes. As an example of the results, the reflected power is distributed uniformly in steady-state and transient between the couplers when the external Q-factors differ, provided that all sources deliver signals of equal amplitude and phase. Countless failure scenarios can be investigated.

Speaker: Pierrick Hamel (CEA, Paris-Saclay University)

331 Study of RF Beam Separation and Scanning Uniformization Techniques for High Power Particle Accelerators

High-power particle accelerator beams have important applications in many fields. Multi-terminal beam delivery can improve beam utilization, while the extremely high peak current density on the target surface limits the safe and stable operation of target stations. To meet the demand for simultaneous multi-terminal beam delivery, RF beam separation was studied. A scheme based on a RF deflecting cavity and septum magnets was used to distribute the beam among different target stations. Beam dynamics simulations show that this scheme can achieve loss-free transport. After separation, the beam emittance increases significantly, mainly due to RF-field nonlinearity. To address the peak current density limitation on a single target, beam scanning uniformization was studied. A technical scheme based on point scanning and circular scanning was adopted to achieve beam uniformization on the target surface. Numerical simulations show that the peak current density is reduced to 8.62 μA/cm². Beam dynamics simulations show that point scanning can inject the beam spot into the target center, and circular scanning enables the beam spot to form a circular distribution on the target.

Speaker: Jie Zeng (Institute of Modern Physics, Chinese Academy of Sciences)

332 The fundamental power coupler for CSNS-Ⅱ elliptical cavities

The China Spallation Neutron Source upgrade project (CSNS-Ⅱ) uses 24 elliptical cavities in the LINAC section. Each cavity is equipped with a coaxial fundamental power coupler featuring a characteristic impedance of 50 Ω and a fixed coupling antenna. The coupler must withstand a minimum peak power of 600 kW with 5% duty factor and an equivalent average power of at least 40 kW. This paper details the multiphysics design, which encompasses electromagnetic optimization, multipacting analysis, and thermal -stress simulations. Additionally, the high-power conditionning results for the first batch of power couplers are presented.

Speaker: Dr MengXu Fan (Institute of High Energy Physics, China Spallation Neutron Source)

333 Toward an optimization framework for RFQ and DTL cavities: a study of black-box methods and inverse-design formulations

The design optimization of RFQ and DTL cavities involve expensive black-box simulations, difficult constraints coming from simulation failures and the absence of reliable derivative information. These characteristics make derivative-free optimization methods particularly interesting, yet their practical performance in a conjoint RFQ-DTL cavity design optimization remains insufficiently studied. This contribution presents a prototype optimization framework connecting the execution of established accelerator codes, automating post-processing and derivative-free optimization methods. This work discusses the performance of the derivative-free method MADS comparing it to commonly used Bayesian approaches in black-box optimization. The framework under development also aims to study an inverse-design formulation: instead of only evaluating a proposed design, we study a way for the optimizer to search for feasible input configurations that reproduce a selected target output while still trying to preserve the optimality of the point.

Speaker: Eduardo Moraes Ferrari (Brazilian Center for Research in Energy and Materials)

334 Transient Field Evolution in Traveling-Wave Disk-Loaded Structures for Muon Acceleration under Pulse-Compressed RF Excitation

This study investigates the transient evolution of accelerating fields in traveling-wave disk- loaded structures for muon acceleration driven by realistic RF pulse waveforms generated by a spherical cavity pulse compressor. Such compressed RF pulses may deviate significantly from an ideal flat-top profile due to transient effects associated with the energy storage and release process in the pulse compression cavity.
Transient field evolution in traveling-wave accelerating structures designed for particle acceleration with evolving velocity has not been systematically studied under realistic pulse- compressed RF excitation.
A transient analysis is performed to investigate the time-dependent evolution of the accelerating fields under these conditions. Particular attention is given to how the compressed RF waveform affects the formation and stability of the accelerating fields within the structure. The obtained results are expected to provide a basis for future beam dynamics studies and to guide the design and optimization of traveling-wave accelerating structures driven by pulse-compressed RF systems for muon acceleration.

Speaker: Yusuke Takeuchi (Nagoya University)

335 Tunable photocathode two-bunches mode for advanced accelerator application

Generation and control of two electron bunches to achieve desired drive and witness quality is crucial for plasma-wakefield acceleration (PWFA) experiments. One scheme to generate two electron beams with desired spacing is to apply two laser pulses with ps delay on the photocathode and co-accelerated two electron beams in the same RF bucket. Such a method is used in e.g. two-color FEL and PWFA experiments.

We will talk about the dynamic, operation, and control aspects of the photocathode two-bunches configuration with nC bunch charge, asymmetric bunch charge ratio, kA peak current, and multi-stage compression. We will talk about experimental performance, and benchmark it against simulation and analytic theory incorporating wakefield effect. We demonstrate excellent longitudinal simulation-experiment agreement using XTCAV measurements, and show that photocathode two bunches provide sufficient flexibility and tunability for various advanced accelerator applications.

Speaker: Yiheng Ye (SLAC National Accelerator Laboratory)

336 Using Stretching-Modulation-Compression Effect to Generate Femtosecond MeV Electron Bunches

We propose a scheme for generating femtosecond to sub-femtosecond ultrafast electron bunches by combining undulator technology with terahertz (THz) modulation. A theoretical model has been developed to describe the transport dynamics of relativistic electrons interacting with THz modulation fields and longitudinal space charge effects within the bunch. The proposed scheme successfully produces isolated ultrafast electron bunches with kinetic energy ~3 MeV, bunch length ~6 fs (rms), and charge up to 0.1 pC, as well as microbunch trains with ~800 as length, ~2 fC charge, and tunable ~200 um spacing. By adjusting upstream and downstream longitudinal dispersion, the bunch structure and microbunch length can be effectively controlled. We provide scaling relations for key parameters with respect to initial bunch charge and analyze the influence of various physical quantities on final bunch length and arrival time. This theoretical model and scheme may offer valuable insights for generating few-femtosecond or attosecond electron bunches in accelerator-based ultrafast facilities.

Speaker: Qiao Luo (Huazhong University of Science and Technology)

Conference Banquet

Friday 21 August

FR1A - Invited Talks

337 A Very compact Inverse Compton scattering gamma-ray source at Tsinghua University

The inverse Compton scattering (ICS) source based on the collision between high-quality electron beams and laser can generate high-brightness quasi-monoenergetic γ-rays. Our labs have developed a compact MeV quasi-monoenergetic γ-ray ICS source and has successfully commissioned. The VIGAS can generate gamma ray beam with energy can be adjusted from 0.2-4.8MeV, and flux about 10^8 phones/second. A high-quality compact electron linear accelerator, which integrated S-band (gun, buncher and pre-accelerator) and X-band (main accelerator) structures, has been successfully operating with electron beams energy higher than 320 MeV within 9.7 meters. A low-level radio frequency (LLRF) system featuring high-precision synchronization has been successfully developed and has demonstrated stable operation. We have started the investigation of VIGAS applications and is currently conducting the preliminary experiments such as high energy phase contrast imaging.

Speaker: Chuanxiang Tang (Tsinghua University)

338 Low-emittance muon beam acceleration using a radio frequency quadrupole for the J-PARC muon g−2/EDM Experiment

At Japan Proton Accelerator Research Complex (J-PARC), a low-emittance muon beam based on a linear accelerator is being developed for precision measurements of the muon anomalous magnetic moment (g-2) and electric dipole moment (EDM), as well as for non-destructive imaging applications. In the low-velocity section of the muon linac, a 324-MHz radio-frequency quadrupole linac (RFQ) is employed to bunch and accelerate muons from thermal energy to 340 keV.
In this study, a muon-beam cooling and RFQ acceleration experiment is being conducted at J-PARC. Thermal muons are produced via laser ionization of thermal muonium emitted from a room-temperature silica aerogel target, electrostatically extracted to 5.7 keV, and injected into the RFQ. The muons are accelerated to 340 keV, and their longitudinal and transverse beam profiles are being characterized at the RFQ exit.
This work demonstrates an in-situ implementation of a full-scale RFQ for the world’s first muon linac in the dedicated g−2/EDM experimental area at J-PARC. The experimental concept, beamline configuration, commissioning status, and outlook toward establishing a low-emittance muon linac are presented.

Speaker: Yuga Nakazawa (High Energy Accelerator Research Organization)

339 New-type high-voltage pulse generator with wide-band rf amplifiers: The principle and application for particle accelerators

A new-type high-voltage pulse generator by means of a method of frequency-segmented power amplification was proposed and developed. A seed pulse is divided into several lines that have bandpass filters, variable delay lines, variable power attenuators, and main rf amplifiers to correct the frequency-dependent group delays and gain of the amplifier circuit and to perform fine-tuning of the pulse structure. The high-voltage pulse was finally obtained by combining them with the rf power combiners. We introduced it for the new beam chopper of low-emittance thermionic electron gun at the X-ray free-electron laser SACLA. Flat and stable pulses with a 2-ns width, a 0.8-kV height in 50-ohm impedance, and peak-to-peak flattop variation of 0.6% were successfully generated, and the system has already been in operation at the SACLA injector. It can also generate an electron beam with multi-bunch structure. Recently, we succeeded in generating double-bunch XFEL lights with a 10-keV photon energy, 0.5-mJ pulse energies each, and 8.4-ns bunch separation. This type of pulse generator will play important roles not only in particle accelerators but also in other fields such as optical lasers.

Speaker: Dr Kazuaki Togawa (RIKEN SPring-8 Center)

340 Development of MW-Level Compact P-Band Metamaterial Klystrons at CSNS

The CSNS has newly developed a metamaterial based 324 MHz klystron with R&D launched in 2021 and successful hot testing in June 2025. The metamaterial-loaded cavities enable 55% shorter structure length, and the integrated second harmonic bunching cavity achieves high efficiency， With 3 MW peak output power and 53.1% efficiency. this report shares the latest development of the metamaterial klystron.

Speaker: Zhencheng Mu (Institute of High Energy Physics)

341 Status and Overview of the CLEAR Facility at CERN

CLEAR (CERN Linear Electron Accelerator for Research) is a versatile electron beam user facility operating at CERN, providing beams with energies up to 200 MeV across a broad range of bunch charges, emittances, and timing configurations.
The facility serves a diverse and growing internal and external user community, supporting a wide experimental program spanning multiple domains of accelerator research and applications.
In this paper, we present an overview of the current status of CLEAR, summarizing the breadth of experiments conducted across recent operational runs and the key developments of the facility.
We further report on the installation and commissioning of the second beam line, a new beamline branch featuring a dog-leg section, a set of slits in both dispersive and non-dispersive regions, and larger aperture focusing elements, which have the potential to significantly expand the facility's experimental capabilities and accessible beam parameter space.
The continued development of CLEAR's infrastructure and the steady growth of its user base consolidate its role as a unique and flexible platform for accelerator research and technology demonstration at CERN.

Speaker: Antonio Gilardi (European Organization for Nuclear Research)

342 Demonstration of cavity field mapping by falling drops of liquid

Experimental mapping of the electric field of a cavity is usually through bead-pull measurements. These require quite long times to align the bead and are generally restricted to the beam axis. Here, the bead has been replaced by drops of liquid falling through the cavity. Together with efficient compression and noise reduction techniques, the method allows for fast and precise measurements. The launching position of the droplets is controlled by a motor driver, thus allowing for automated 3d-field mapping around the axis. Results from mapping a 36 MHz buncher cavity are presented.

Speaker: Lars Groening (GSI Helmholtz Centre for Heavy Ion Research)

10:30 Coffee Break

FR2A - Plenary Talks

343 Linacs for lithography

Light drives innovation – the wavelength, the power, the intrinsic qualities. From the mask shop to the packaging fab, from lithography to metrology, each technology node has relied on light invention to enable scaling, process control, reliability, and even ensuring supply chain security. However, the increasing cost and complexity of new light sources to meet industry demands has become prohibitive, leading to stagnation in technology development and reliance on the status quo in terms of the light available and the applications it permits. Now, a leap is required to develop the new generation of light source that will serve the semiconductor industry indefinitely, providing low-cost EUV as well as any wavelength required for manufacturing or R&D applications. xLight is building an accelerator-based light source to drive the semiconductor industry into the next decade and beyond, providing high power, quality light to any application and delivering light as a utility.

Speaker: Erik Hosler (GlobalFoundries (United States))

344 Linac Facilities for Single Event Effects Testing

Modern electronic systems are required to provide various degrees of radiation hardness against performance and lifespan degradation due to the natural environment, man-made radiation sources, and their mission or use case. Solar coronal mass ejections (CME) and galactic cosmic rays (GCR) are two sources of naturally-occurring radiation fields with sufficient flux and energy to disrupt sensitive electronic systems. Single event effects (SEE) are a primary cause of failures in electronics due to energy deposited by high energy ions. Accelerator-based sources of ion irradiation are now commonly used to explore device interactions with ions of 10’s MeV/AMU kinetic energies. With the evolution of requirements from the electronics community to ions in the 100’s MeV/AMU to GeV/AMU energy regime, new accelerator architectures are being considered. Linac-based facilities offer several advantages over other architectures. In this talk we will discuss the requirements and opportunities for accelerator-based radiation sources for SEE testing, and the tradeoffs between various architectures. Current and proposed linac-based facilities will be presented and discussed.

Speaker: Steven Lidia (Facility for Rare Isotope Beams)

FR2A - Closing Talk

345 Linacs for Societal Applications: A Journey from an Accelerator Center to Society

Linear accelerators have long been central to research and industrial applications. This talk examines how developments at accelerator centers can be translated into applications in healthcare, advanced material testing, and other emerging fields. Drawing on selected case studies, it highlights pathways by which technologies originating in high-energy physics are adapted to address real-world needs. The role of interdisciplinary collaboration and structured technology transfer mechanisms is emphasized as a key enabler in this process. By connecting technical advances with their broader applications, it offers a perspective on how linac technologies contribute to societal progress.

Speaker: Benjamin Frisch (European Organization for Nuclear Research)

Closing

Facility Tour