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Alan Schwettman (Stanford University)24/08/2026, 08:55Session 1: First Lasing and Special TopicsInvited Oral Presentation
Place holder for the Special talk in memoriam for Todd Smith (Stanford).
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Kelly Gaffney (SLAC National Accelerator Laboratory)24/08/2026, 09:25Session 1: First Lasing and Special TopicsInvited Oral Presentation
Place holder for Kelly's talk.
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Hitoshi Tanaka (RIKEN SPring-8 Center)24/08/2026, 10:30
The Compact X-ray Free-Electron Laser (SACLA) initially faced severe criticism that it would be unable to achieve effective laser amplification. However, SACLA smoothly achieved laser amplification after its construction and has become one of the world’s most widely used FEL facilities, capable of conducting independent experiments simultaneously with its three FEL beamlines. This presentation...
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Toru Hara (RIKEN SPring-8 Center)24/08/2026, 10:55
Since the commissioning in 2011, SACLA has made continuous efforts to improve stability and XFEL performance with a focus on user operation. A variety of XFEL operation modes have been offered to users, such as two-color, self-seeded and attosecond XFEL. In parallel with XFEL operation, SACLA has been also playing an unique and important roll as a low-emittance injector of a storage ring,...
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Takashi Tanaka (RIKEN SPring-8 Center)24/08/2026, 11:20
Recent advancements in FEL science and technologies have made it possible to generate attosecond pulses in many FEL facilities by means of various methods. Such "attosecond FELs" definitely contribute to the progress of ultrafast science, by improving the temporal resolution in time-resolved measurements; however, we should recall that human desires are limitless! The next target may probably...
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Dr Philipp Dijkstal (Paul Scherrer Institute)24/08/2026, 11:45
Wakefield structures can generate strong transverse chirps (beam tilts) and thereby enable time-resolved beam diagnostics similar to transverse deflecting rf structures, but at a much reduced cost. Electron beam current and FEL power profile measurements using rectangular corrugated structures are routinely performed at SwissFEL and other facilities. Some of the data analysis methods required...
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Sven Reiche (Paul Scherrer Institute)24/08/2026, 14:00Session 3: FEL theory and Machine LearningInvited Oral Presentation
We present studies on enhanced SASE at the soft X-ray beamline Athos at SwissFEL. The generation of a series of current spikes with 790 nm spacing is injected into the Athos undulator beamline. Due to strong space charge forces the optimum performance occurs with a strong positive taper of the undulator field. There is a clear modal structure in the observed spectra, indicating the presence of...
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Dr Giovanni Perosa (European X-Ray Free-Electron Laser)24/08/2026, 14:25Session 3: FEL theory and Machine LearningInvited Oral Presentation
We derive a resonant effective action for the time-dependent free-electron laser. The action treats longitudinal time dependence and finite-bunch effect within a single self-consistent framework. After canonical normalization, the action is shown to be homogeneous under Pierce parameter rescaling. Such property directly yields scaling laws for the field, without explicitly finding or solving...
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Seongyeol Kim (Pohang Accelerator Laboratory)24/08/2026, 14:50Session 3: FEL theory and Machine LearningInvited Oral Presentation
Control of 6-dimensional beam phase space is one of the most important steps for high-brightness X-ray Free Electron Lasers (XFELs). Such beam manipulation can be properly performed through accurate beam diagnostics. Recently, generative phase space reconstruction (GPSR) based on neural networks and differentiable simulations has been developed for robust phase space diagnostics, including...
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Auralee Edelen (SLAC National Accelerator Laboratory)24/08/2026, 15:15Session 3: FEL theory and Machine LearningInvited Oral Presentation
Author will add more later
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Pardis Niknejadi (Deutsches Elektronen-Synchrotron DESY)24/08/2026, 16:00
Modern software systems increasingly require modular, reusable components that scales across diverse application domains. In accelerator physics, machines often rely on specialized simulation codes tailored to distinct segments of the accelerator, making integrated start-to-end studies complex and fragmented. Here, we introduce GEIST (Genesis–Elegant Interface Simulation Toolset), an...
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Primoz Rebernik Ribic (Elettra-Sincrotrone Trieste S.C.p.A.)24/08/2026, 16:00
With the completion of the early phase of the FERMI 2.0 upgrade program, the FERMI facility has significantly increased its flexibility, enabling the extension of its operational capabilities. The new FEL-1 layout, supporting both HGHG and EEHG, has substantially broadened the FEL-1 tuning range. This advancement is accompanied by improved spectral brightness and enhanced stability, achieved...
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Aaron Reed (SLAC National Accelerator Laboratory)24/08/2026, 16:00
At LCLS, attosecond xFEL pulses (“XLEAP” mode) allow users to probe electronic process on their natural timescale.* However, XLEAP is much more sensitive than conventional SASE operation to drifts and jitter in the RF phases, laser timing, bunch charge, and beam orbit. As a result, XLEAP setup and pulse energy optimization is highly variable and difficult to replicate even minute-to-minute,...
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Longdi Zhu (École Polytechnique Fédérale de Lausanne)24/08/2026, 16:00
We investigate attosecond spike formation in an x-ray free-electron laser driven by sign-reversing chirped undulator tapering in a strongly non-adiabatic regime. When the total detuning changes appreciably over one gain length, the longitudinal dynamics is most transparently described through slice-resolved bunching evolution. We introduce a reduced physical picture that organizes the process...
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Dr Hao Sun (Institute of Advanced Light Source Facilities Shenzhen)24/08/2026, 16:00
Generating and synchronizing two-color attosecond x-ray pulses is vital for ultrafast electronic studies. We propose a novel dual chirp-taper free-electron laser scheme exploiting bunching inheritance to generate attosecond pulse pairs. An electron beam with a laser-induced sinusoidal energy chirp traverses tapered main and afterburner undulators. This produces two-color pulses separated by...
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David Cesar (SLAC National Accelerator Laboratory)24/08/2026, 16:00
Attosecond FEL pulses can be generated by limiting lasing to a single high-current spike with a duration comparable to the FEL coherence length. At LCLS-II, the XLEAP program generates such a distribution by overlapping a short laser pulse onto the conventional cathode drive laser. Here, we demonstrate that this initial density perturbation drives a pair of counter-propagating space-charge...
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Yosuke Honda (High Energy Accelerator Research Organization)24/08/2026, 16:00
Energy-Recovery Linac (ERL) based Free-Electron Laser (FEL) has been a promising solution for the high-power EUV light source for future semiconductor lithography. KEK has been developing the key components of the accelerator system and designing the prototype machine. Beam optics design is important for realizing the required beam performance in the FEL section, for safely transport the beam...
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Zihan Zhu (SLAC National Accelerator Laboratory)24/08/2026, 16:00
Control of the longitudinal phase space (LPS) of electron beams is essential for the flexible operation of X-ray free-electron lasers, but remains challenging because the measured beam distribution is high dimensional, noisy, and sensitive to machine drift. We develop and experimentally demonstrate a latent-space approach for online LPS shaping at the Linac Coherent Light Source.
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Nicholas Sudar (SLAC National Accelerator Laboratory)24/08/2026, 16:00
The photon energy range of the LCLS-HE upgrade relies heavily on the achievable longitudinal beam brightness. The final peak current and correlated energy spread are both limited by the longitudinal phase space at the exit of the injector, non-linear compression, and collective effects. The initial charge distribution off the cathode effects all of these factors. However, determining an ideal...
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Dr Philipp Dijkstal (Paul Scherrer Institute), Wenxiang Hu (Paul Scherrer Institute), Sven Reiche (Paul Scherrer Institute)24/08/2026, 16:00
X-ray free electron lasers (XFELs) are modern photon sources which generate widely tuneable, high-brilliance, ultrafast laser pulses. External seeding schemes transfer the coherence properties of optical laser sources to the FEL pulses, while performing a photon energy upconversion. In this contribution, we show the latest external seeding results from the soft X-ray beamline at SwissFEL,...
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Ji Qiang (Lawrence Berkeley National Laboratory)24/08/2026, 16:00
Lithography is a critical component of chip manufacturing in the semiconductor industry. The conventional laser-produced plasma (LPP) approach is energy-inefficient and poses potential environmental issues. In contrast, an energy recovery linac (ERL) based free-electron laser (FEL) offers a cleaner, more efficient alternative by recycling electron beam energy after FEL radiation. In this...
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Mikhail Krasilnikov (Deutsches Elektronen-Synchrotron DESY)24/08/2026, 16:00
The Photo Injector Test Facility at DESY in Zeuthen (PITZ) is developing a THz free electron laser (FEL) as a potential source for pump–probe experiments at the European XFEL. In a recent proof-of-principle experiment using the LCLS-I undulator and a 17 MeV/c electron beam from the PITZ injector, pulse energies exceeding 100 μJ at 3 THz were demonstrated for bunch charges up to 2.4 nC. These...
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Chang-Kyu Sung (Pohang Accelerator Laboratory)24/08/2026, 16:00
High-brightness free-electron laser (FEL) generation critically depends on both the transverse and longitudinal properties of the electron beam, such as transverse emittance, slice energy spread. These beam parameters can be significantly degraded due to collective effects, e.g., wakefield, coherent synchrotron radiation. Such effects are pronounced due to the high current spikes, so-called...
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Dr Hao Sun (Institute of Advanced Light Source Facilities Shenzhen)24/08/2026, 16:00
We report the experimental demonstration of direct-amplification enabled harmonic generation in an ultraviolet free-electron laser (FEL) driven by a low-intensity seed laser. By employing a versatile undulator configuration that enables seed amplification and harmonic generation within a unified setup, we achieved over 100-fold energy gain of the seed and observed exponential growth at the...
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Amir Weinberg (Tel Aviv University)24/08/2026, 16:00
Here we present an analytical model theory for time domain analysis and design of Tapering Enhanced Superradiant (TES) FEL at zero-slippage condition. The model is implemented for optimization of an ongoing experimental project of a THz radiation source based on the 6 MeV ORGAD RF-Accelerator at Ariel University.
The design of the setup is based on a twenty-period planar undulator made of...
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Jingyi Tang (Stanford University)24/08/2026, 16:00
We present a differentiable 1D free-electron laser (FEL) simulation framework based on automatic differentiation. In contrast to conventional FEL codes that provide only forward simulation, the differentiable formulation enables efficient evaluation of gradients of FEL observables with respect to beam, undulator, and model parameters. This makes it possible to apply gradient-based methods to...
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Kiley Gruenberg (SLAC National Accelerator Laboratory)24/08/2026, 16:00
Machine-learning surrogate models for accelerators require compact beam representations that preserve physically meaningful structure while remaining useful for predictive and tuning tasks. In this work, multi-projection beam images from simulated LCLS injector data are studied as a representation-learning problem. The goal is to evaluate how ML model architecture choices impact the degree to...
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Ahmed Osman (SLAC National Accelerator Laboratory)24/08/2026, 16:00
Laser heaters are commonly used in free-electron laser (FEL) injectors to suppress microbunching instabilities by increasing uncorrelated slice energy spread. We investigate using a third-harmonic laser–undulator interaction in the LCLS-I injector for this purpose. Measurements of the central slice energy spread as a function of laser power are performed for both fundamental and third-harmonic...
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Trey Guest (European X-Ray Free-Electron Laser)24/08/2026, 16:00
![Scheme for simultaneous MHz operation of beamline endstations based on electron and photon beam steering.][1]
The European XFEL comprises three SASE beamlines that branch to eight endstation instruments. Each beamline currently operates a single instrument exclusively, fundamentally limiting the total beamtime available for experiments. In this talk, we propose an electron beam steering...
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Dr Henry Freund (University of Maryland, College Park)24/08/2026, 16:00
The Ming Xie* formula for shot noise has been widely used to estimate the performance of SASE free-electron lasers and has been compared with various simulation codes with great success. However, the formula is directly applicable only to a single slice of the electron beam and it would be useful to generalize the formula to treat arbitrary temporal bunch shapes. Ming’s formula applies...
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Arnav Swaroop (SLAC National Accelerator Laboratory, University of California, Berkeley)24/08/2026, 16:00
Coherent undulator radiation from pre-bunched electron beams can generate carrier-envelope phase (CEP) stable radiation pulses. Leveraging the development of multi-bunch concepts and pulse-by-pulse bunch shaping, we propose using CEP-stable coherent undulator radiation to seed the FEL instability and generate fully coherent phase-stable radiation pulses via double reflection. In this poster,...
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Chang-Kyu Sung (Pohang Accelerator Laboratory)24/08/2026, 16:00
We present the experimental results on the generation of fresh-slice self-seeded hard X-ray free-electron laser (FEL) pulses at PAL-XFEL. The self-seeding scheme significantly enhances the spectral brightness of FELs and has therefore been extensively verified and widely applied in user science over the years, whereas the fresh-slice technique enables higher pulse power by reducing the pulse...
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Alex DeSimone (Northern Illinois University)24/08/2026, 16:00
We present a method that uses transverse wigglers to impart arbitrary correlations in transverse phase space. This approach becomes particularly powerful when combined with emittance exchange, which converts the transverse phase space into the longitudinal phase space. In contrast to conventional single-sinusoidal correlations, a sawtooth correlation can maximize the fraction of particles...
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MyungHoon Cho (Pohang Accelerator Laboratory), Chi Hyun Shim (Pohang Accelerator Laboratory), Dr Philipp Dijkstal (Paul Scherrer Institute), Wenxiang Hu (Paul Scherrer Institute)24/08/2026, 16:00
First tunable, phase-locked, ultrafast hard X-ray (PHLUX) pulse pairs were generated at PAL-XFEL. A fresh-bunch self-seeded FEL, driven by an electron beam that was shaped with a slotted foil and a corrugated wakefield structure, generates coherent radiation that is intensity-modulated on the femtosecond time scale. We measure a stable frequency comb generated by a phase-locked pulse pair (to...
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Aliaksei Halavanau (SLAC National Accelerator Laboratory)24/08/2026, 16:00
In recent years there is a growing interest in FEL-based generation of very soft x-rays, due to increased scientific and industrial applications. In this proceeding, we investigate the feasibility of very soft x-ray generation at the Linac Coherent Light Source (LCLS). We focus on the mechanisms of FEL tuning, diagnostics, and practical aspects of user delivery of such light. We demonstrate...
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Dr William Fawley (Lawrence Berkeley National Laboratory)24/08/2026, 16:00
The venerable GINGER code (first virtual light in 1985) has been extensively updated and extended with new features including an ADI-based Cartesian radiation field solver, a more robust, transversely-resolved, longitudinal space charge solver, and a new Python-based, GUI-oriented post-processor (XG3DpyPP). Serious efforts have been directed toward optimizing run times including support for...
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Dr Philipp Dijkstal (Paul Scherrer Institute)24/08/2026, 16:00
One goal of the recently proposed SwissFEL facility upgrade
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(SwissFELplus) is to enable the generation of longitudinally coherent
FEL pulses across a large photon energy range at the the hard X-ray
beamline Aramis. We consider to implement the Forward Bragg Diffraction self-seeding approach, where a diamond crystal in transmission geometry filters the SASE signal generated in the first... -
Lingjun Tu (Institute of Advanced Light Source Facilities Shenzhen)24/08/2026, 16:00
Broadband tunability is a key pursuit for terahertz (THz) free-electron lasers, yet it is often constrained by the narrow energy acceptance of laser modulators in prebunched schemes. Here, we propose a harmonic modulation scheme to decouple this constraint. Taking the Electron Source Test Facility at Dalian as a specific case study, our simulations demonstrate that by matching the laser field...
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Ingmar Hartl (Deutsches Elektronen-Synchrotron DESY)24/08/2026, 16:00
We present recent progress on the SLASH laser system, a high-repetition-rate tunable femtosecond UV laser developed for external seeding of the FLASH free-electron laser (FEL). The system features a dual-branch architecture: a third-harmonic generation arm (343 nm) and a tunable OPCPA-based arm (297–317 nm), enabling flexible pulse control for advanced seeding schemes like echo-enabled...
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Xiujie Deng (Tsinghua University)24/08/2026, 16:00
Microbunching enables laser-like radiation generation from charged particle beam,
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and is one of the main driving forces advancing accelerator light sources in the past
decades. The most prominent example is free-electron laser. A natural approach of microbunching
creation is to imprint a coherent phase space correlation on the electron
beam using a conventional quantum laser, whose... -
Zhangfeng Gao (Shanghai Synchrotron Radiation Facility)24/08/2026, 16:00
Shanghai soft X-ray free electron laser facility(SXFEL) is the first coherent X-ray light source in China with a wavelength covering the water window. With the help of elliptically polarized undulators(EPU), the output laser can be switched between linear polarization and circular polarization, meeting the needs of different users. After tuning the planar undulators upstream and adjusting the...
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Jingyi Tang (Stanford University)24/08/2026, 16:00
Digital twins and online physics models are becoming increasingly important for the operation of modern X-ray free-electron lasers, where high-brightness beam delivery depends on precise control of the longitudinal phase space. At LCLS and LCLS-II, small RF phase drifts in the early linac can produce large changes in bunch compression, causing discrepancies between offline model predictions...
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Amir Weinberg (Tel Aviv University)24/08/2026, 16:00
The 6MeV ORGAD Accelerator at Ariel University is driving a THz Superradiant FEL. The radiation is emitted superradiantly (in proportion to the number of electrons squared) in a rectangular waveguide-undulator section. The condition for the spontaneous emission to emit superradiantly is that the duration of the electron bunch σ_t is much shorter than the optical period (2π/ω) of the radiation...
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Cheng-xin Wu (Institute of Advanced Light Source Facilities Shenzhen), Zhenbiao Sun (Institute of Advanced Light Source Facilities Shenzhen)24/08/2026, 16:00
Four-dimensional (4D) transverse phase space (TPS) reconstruction of electron beam is an important issue in accelerator beam diagnosis, since the 4D-TPS is vital for beam manipulation and cannot be directly determined from limited two-dimensional screen measurements. A machine-learning-based differentiable reconstruction framework is developed to infer the hidden phase-space distribution, and...
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Lanpeng Ni (Shanghai Institute of Applied Physics)24/08/2026, 16:00
High-gain harmonic generation (HGHG) is known to be critically sensitive to residual group-delay dispersion (GDD) and third-order dispersion (TOD) in the seed laser, which distort the temporal profile and degrade the harmonic up-conversion spectrum. The feasibility of the direct-amplification enabled harmonic generation (DEHG) scheme has been experimentally demonstrated [Phys. Rev. Lett.,...
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Samuel Sahel-Schackis (SLAC National Accelerator Laboratory, Stanford University)24/08/2026, 16:00
X-ray free-electron lasers enable femtosecond-resolution probing of photoinduced chemical dynamics. Interpreting these experiments requires atomistic simulations of excited-state systems on matching timescales - a task where ab initio molecular dynamics remains prohibitively expensive. We present a Neural Network Quantum Molecular Dynamics (NNQMD) framework that bridges this gap by training...
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Kookjin Moon (Pohang Accelerator Laboratory)24/08/2026, 16:00
Forward Bragg diffraction (FBD)-based hard X-ray self-seeding (HXRSS) is a promising method for producing narrow-bandwidth and stable hard X-ray FEL pulses. However, the pulse-energy stability of self-seeded FELs can be influenced by several temporal effects, including the FBD filter response, the electron bunch duration, the seed-pulse overlap, and the self-seeding chicane delay. In this...
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Naoto Yamamoto (High Energy Accelerator Research Organization)24/08/2026, 16:00
Ions produced by collisions between high-energy electron beams and residual gas molecules can be trapped along the beam trajectory by the strong electric potential well of the electron beam, leading to detrimental effects on beam dynamics. Ion trapping is therefore a relevant issue for high-duty continuous-wave (CW) machines, such as energy recovery linacs intended for use as...
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Jack Hirschman (Stanford University)24/08/2026, 16:00
High-repetition-rate x-ray free-electron lasers operating at MHz rates generate data volumes that preclude offline analysis as a sole experimental strategy, demanding streaming diagnostics capable of real-time decision support. We present a hybrid neural architecture for online characterization of attosecond x-ray pulses from angular-streaking diagnostics* at LCLS-II, integrating...
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Zhenbiao Sun (Institute of Advanced Light Source Facilities Shenzhen)24/08/2026, 16:00
Shenzhen Superconducting Soft X-Ray Free Electron Laser (S3FEL), a superconducting accelerator facility aimed at providing soft X-ray FEL pulses with a repetition rate of 1 MHz, is currently under construction. These FEL pulses originate from the electron beam with an energy of 2.5 GeV generated in a continuous-wave superconducting linear accelerator. This paper comprehensively describes the...
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Vladimir Ognivenko (National Science Centre Kharkiv University)24/08/2026, 16:00
The radiation friction force acting on a relativistic electron in incoherent fields of spontaneous undulator radiation of other beam electrons moving in a spatially periodic magnetic field of the undulator is considered. An expression for the radiation friction force, both for the initial stage of the pre-Brownian motion of electrons and for the kinetic stage is obtained. Considering a helical...
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Matthias Scholz (Deutsches Elektronen-Synchrotron DESY)24/08/2026, 16:00
Following the long installation and maintenance period in the second half of 2025, the European XFEL accelerator complex was successfully recommissioned and returned to user operation. During the shutdown, numerous modifications and upgrades were implemented across the accelerator and associated infrastructure, including improvements to the cryogenic system, the injector and the undulator...
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Seongyeol Kim (Pohang Accelerator Laboratory)24/08/2026, 16:00
Precise beam manipulation and preservation of beam quality along the beamline are essential to produce high-brightness X-ray Free Electron Lasers (XFELs). These tasks can be effectively carried out through accurate beam diagnostics. In addition, a calibrated simulation model enables investigation of the optimal beamline conditions against collective effects such as coherent synchrotron...
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Namra Aftab (Deutsches Elektronen-Synchrotron DESY)24/08/2026, 16:00
Development of a high-power, tunable THz source for pump–probe experiments at the European XFEL is currently underway at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). With the present PITZ setup, FEL radiation in the 1–5 THz range can be generated using an LCLS-I undulator. Proof-of-principle experiment has been successfully demonstrated with high-charge electron beams of several...
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Hiroyuki Hama (Tohoku University)24/08/2026, 16:00
The Smith-Purcell effect is a well-known radiation emitted when an electron beam propagates the vicinity of a diffraction grating surface. Apparently, the surface current model* successfully interprets the process of Smith-Purcell radiation (SPR) generated through an Eshellet-type grating with a small blazing angle. According to the surface current model, the SPR intensity rapidly increases...
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Alex DeSimone (Northern Illinois University)24/08/2026, 16:00
Transverse deflecting cavities (TDCs) have always been interesting beamline elements that couple a particle’s longitudinal position and transverse coordinates. While they have been widely adopted for longitudinal diagnostics and other specialized purposes, such as emittance exchange, several longitudinal manipulation methods using TDCs have been introduced during the last six years. These...
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David Dunning (Science and Technology Facilities Council)24/08/2026, 16:00
UK scientists are amongst the leading users of XFELs, which enable revolutionary atomic-level imaging and ultrafast time resolution far beyond other methods. Looking to the future, the UK community have developed a science and technology case and a conceptual design for a next-generation XFEL. Such a facility will be able to leverage maturing technologies to deliver vast increases in research...
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Evgeny Schneidmiller (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 08:30
Reverse undulator taper is a unique method allowing to strongly suppress radiation intensity at the exit of SASE undulator while maintaining microbunching at a significant level. Recently, it was used to generate high-purity circularly polarized radiation from dedicated afterburners (Apple-X at the European XFEL and Apple-III at FLASH, the latter operates at the 3rd harmonic of SASE...
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Eito Iwai (Japan Synchrotron Radiation Research Institute, RIKEN SPring-8 Center)25/08/2026, 08:50
We demonstrate sub-femtosecond hard X-ray free-electron laser (XFEL) pulse generation at SACLA, achieved through a robust and flexible scheme for additional electron bunch compression. The method leverages a reverse-energy chirp, driven by wakefields within the accelerating structures and longitudinal space charge effects. By employing a tunable R56 optics in a two Double Bend Achromat (DBA)...
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Ingmar Hartl (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 09:10
The recently commissioned dual NEPAL photocathode laser systems at EuXFEL and FLASH enable the generation of twin electron bunches with unprecedented flexibility. Each laser pulse can be independently tuned in pulse energy, temporal and longitudinal profile, and relative timing, allowing for electron bunch production in the same or any two 0.77 ns spaced RF buckets. This capability unlocks...
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Alexander Malyzhenkov (European Organization for Nuclear Research), Eduard Prat (Paul Scherrer Institute), Gian Luca Orlandi (Paul Scherrer Institute), Sven Reiche (Paul Scherrer Institute), Tobias Weilbach (Paul Scherrer Institute)25/08/2026, 09:30
Standard x-ray free-electron lasers (FELs) generate pulses with total durations of tens of femtoseconds and with time and spectral profiles consisting of multiple randomly distributed spikes. Strongly compressing an electron beam is a typical approach to produce shorter and coherent FEL pulses. We have advanced this method by starting at the injector of the FEL facility with electron beams...
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Christopher Zimmer (SLAC National Accelerator Laboratory)25/08/2026, 09:50
Driven by a continuous-wave superconducting linear accelerator, a high-repetition-rate x-ray FEL has been build at SLAC. After commissioning in 2022 and 2023, early user operation was started in 2024. By the end of 2025, the machine was operated with up to 93,000 Hz beam rate, supporting 3 soft x-ray user stations. We will report the beam and FEL performance, operation observations and...
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Primoz Rebernik Ribic (Elettra-Sincrotrone Trieste S.C.p.A.)25/08/2026, 10:30
We will present the first results of an experiment performed at the FERMI FEL to generate few-femtosecond extreme-ultraviolet (XUV) pulses using a recently developed slippage-compensation scheme in externally seeded free-electron lasers. Building on this approach, we will also show the results of a theoretical study aimed at extending the scheme to generate multiple few-femtosecond XUV pulses,...
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Zheng Qi (Shanghai Advanced Research Institute)25/08/2026, 10:55
First lasing and stable operation of a direct-amplification enabled harmonic generation free-electron laser were achieved, with the harmonic number up to 12th from a single-stage modulation and 30th from two-stage modulations employing the beam-echo effect. This work demonstrates for the very first time that high harmonic FEL generation can be facilitate using only one single seed laser with...
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Jenny Morgan (SLAC National Accelerator Laboratory)25/08/2026, 11:20
We propose and simulate a scheme for generating coherent short-wavelength radiation exploiting the intrinsic coherence of emission from a compressed, high-current electron beam. When the bunch length is shorter than the resonant wavelength, the undulator radiation is temporally coherent. This radiation is extracted and optically refocused onto a second, longer electron beam, acting as a...
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Matthias Scholz (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 11:36
The first high-repetition-rate hard X-ray self-seeding system was installed on the SASE2 beamline of the European XFEL in 2019. It has since been used to deliver self-seeded radiation pulses in burst mode over the photon-energy range from 6 to 18 keV, reaching a maximum spectral density of approximately 2 mJ/eV at 7.5 keV. User operation started in 2021, and an increasing fraction of user time...
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Ye Hong (SLAC National Accelerator Laboratory)25/08/2026, 11:52
To overcome the thermal load challenges at the high-rep rate HXR self-seeding FELs, we summarize the recent design and experimental test progress. The LCLS-II-HE is designed to have cryo-cooled HXRSS system. To validate the design and prototype, experiment tests have been carried out on the diamond and the related mounting and clamping schemes. Wavefront sensors and single-shot spectrometers...
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Maurizio Vannoni (European X-Ray Free-Electron Laser)25/08/2026, 14:00Session 6: FEL Oscillators and Infrared FEL (IR-FEL)Invited Oral Presentation
Classical optical lasers provide intense, coherent light in the visible and infrared regions, but extending this concept to X-rays has been particularly challenging due to a lack of suitable gain media and mirrors. Current hard X-ray free-electron laser (XFEL) facilities overcome this difficulty using a relativistic high-peak-current electron bunch as gain media for a self-amplified...
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Kaiqing Zhang (Shanghai Synchrotron Radiation Facility)25/08/2026, 14:30Session 6: FEL Oscillators and Infrared FEL (IR-FEL)Invited Oral Presentation
High-power, continuously tunable narrowband terahertz (THz) sources are essential for advancing nonlinear optics, THz-driven material dynamics, and ultrafast spectroscopy. Conventional techniques typically impose a trade-off between pulse energy and frequency tunability. Here, we demonstrate a novel free-electron laser approach that overcomes these limitations by pre-modulating a relativistic...
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Aliaksei Halavanau (SLAC National Accelerator Laboratory), Zhirong Huang (SLAC National Accelerator Laboratory)25/08/2026, 15:00Session 6: FEL Oscillators and Infrared FEL (IR-FEL)Contributed Oral Presentation
The cavity-based XFEL (CBXFEL) is a novel X-ray source based on an X-ray Free-Electron Laser (XFEL) encased in an optical cavity. This concept, when built, will offer substantial improvements in X-ray brightness and coherence compared to existing high-gain SASE sources. A joint project is underway at SLAC National Accelerator Laboratory, in collaboration with Argonne National Laboratory and...
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Ryoichi Hajima (National Institutes for Quantum Science and Technology)25/08/2026, 15:20Session 6: FEL Oscillators and Infrared FEL (IR-FEL)Contributed Oral Presentation
High harmonic generation (HHG) has emerged as a powerful method for producing coherent femtosecond-to-attosecond light in the VUV, EUV, and X-ray regions. Since the harmonic cutoff energy and the upconversion phase matching limits increase with the driving laser wavelength, mid-infrared (MIR) drivers are uniquely advantageous for extending the emission toward soft X-ray wavelengths, and...
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David Dunning (Science and Technology Facilities Council)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
We present a software framework for digital shadows (one‑way data flow) and digital twins (two‑way closed‑loop synchronisation) for particle accelerators, linking physical machines with virtual counterparts to enable predictive modelling, automated control and improved facility design. The architecture comprises a coherent chain of tools that maintain a unified description of the accelerator....
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Emmanuel Aneke (Northwestern University)25/08/2026, 16:00
We demonstrate that a hard X-ray storage ring free-electron laser oscillator (SRFELO) with steady-state output is feasible using nominal APS-U parameters. Numerical simulations using a planar undulator yield a 5.2 keV configuration that exceeds 6% gain, even within a strict 5-meter insertion device limit. We present a comparative study between results using an Elegant and Genesis-based python...
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Michael Ehrlichman (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The accelerator modeling ecosystem at SLAC automates much of the work involved in generating the information that feeds survey & alignment teams, engineering groups, and the controls system. Starting from the same lattice files and modeling codes used to develop Twiss optics and calculate beam properties, quantities including beam stay clears and element locations are produced. These...
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Jingyi Tang (Stanford University)25/08/2026, 16:00
Cavity-based X-ray free-electron lasers (CBXFELs) are promising sources of fully coherent, stable, high-brightness hard X-rays, but practical implementation at LCLS-II-HE must account for beam-power and beam-dump limitations. In previous work, we proposed an active Q-switched X-ray regenerative amplifier FEL, where electron-beam phase-space manipulation controls the effective cavity quality...
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Dr Henry Freund (University of Maryland, College Park)25/08/2026, 16:00
Regenerative amplifier x-ray free-electron lasers constitute alternative configurations for fourth generation light sources which are typically operated in self-amplified spontaneous emission (SASE) mode. However, SASE exhibits relatively large fluctuations in the power and spectral properties from shot to shot, whereas XRAFELs provide a much more stable source of hard x-ray photons. Here, we...
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Matthias Scholz (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
Modern FEL operation increasingly relies on advanced software tools, automation, and data-driven optimization methods. At the European XFEL, a strategy is being developed to improve operational efficiency, overall FEL performance, and to reduce the dependence on experts during non-standard operation modes.
Recent developments include automated scanning and tuning procedures, the use of...
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Dylan Kennedy (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
Characterizing the full 6-dimensional phase-space distribution of beams from the LCLS-II photoinjector is essential for understanding and optimizing downstream accelerator performance. Long-term monitoring of this distribution is equally important for detecting drifts in machine state and implementing timely corrective actions. Continuous phase space characterization during routine operation...
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Ming-Chang Chou (National Synchrotron Radiation Research Center)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The energy and energy spread of electron beams from the NSRRC photoinjector were studied for the generation of ultrashort bunches using velocity bunching for a superradiant THz source. A dipole-magnet-based spectrometer was employed to measure the beam energy and relative energy spread from the energy-dispersed beam profile observed on a downstream diagnostic screen. To achieve high energy...
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Qika Jia (University of Science and Technology of China)25/08/2026, 16:00
In the article of Rui Prazeres [Phys. Rev.Accel. Beams 19, 060703 (2016)], hereafter the article and the authors, one of the conclusions drawn by the author of the article is that there is a limit to the length of the waveguide, exceeds which a phenomenon of “mode disorder” appears in the cavity. Our analysis indicates that the phenomenon should be caused by the instability of the optical...
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Konstantin Kruchinin (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
Diagnosing the longitudinal profile of ultrashort electron bunches, now reaching femtosecond and attosecond durations in modern Free Electron Lasers and Laser Wakefield Accelerators remains a major challenge, as conventional tools, such as Transverse Deflecting Cavities, lack the required temporal resolution. Coherent radiation spectroscopy provides an attractive alternative. Radiation,...
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Makoto Asakawa (Kansai University)25/08/2026, 16:00
We report on the development of a sheet-beam electron source for terahertz Smith–Purcell radiation experiments. A photoemission-based electron gun driven by a femtosecond Ti:sapphire laser produces an elliptical beam of approximately 0.1 mm × 8 mm at 5 keV.
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To control beam divergence along the short axis, a focusing electrode was introduced. Beam profiles were measured using a microchannel... -
Sergei Kladov (University of Chicago)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
Microbunching damping in relativistic electron beams is strongly influenced by inverse dispersive transport terms that couple transverse phase-space coordinates to the longitudinal displacement. In this work, we investigate the use of microbunching damping as a diagnostic and optimization tool for lattice tuning in linear accelerators. In particular, residual dispersion is minimized by...
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Dr Henry Freund (University of Maryland, College Park)25/08/2026, 16:00
Recent progress in short wavelength FELs from the EUV through x-rays has opened new avenues for industrial and research applications. Most such FELs rely on SASE in which the optical pulse grows from noise in a single pass through the undulator. However, this results in significant shot-to-shot fluctuations in the power and spectrum. Oscillators are under consideration to stabilize the noise...
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Rasmus Ischebeck (Paul Scherrer Institute)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
In addition to the standard FEL operation of SwissFEL, we are developing several advanced FEL modes, where we tailor the phase space of the electron beam before sending it into the undulator. This includes ultra-short pulse and large-bandwidth modes, echo-enabled harmonic generation, and a scheme to generate trains of attosecond FEL pulses.
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These modes require beams with a high 6d phase space... -
Sean OTool (Stanford University)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The Linac Coherent Light Source (LCLS) enables pioneering studies of ultrafast phenomena by producing X-ray pulses with attosecond durations and continuously tunable wavelengths. However, X-ray pump-probe experiments are limited by achievable time delays. While existing magnetic chicanes offer wide delay ranges, they introduce a minimum slippage of 300 as for harmonic schemes, which grows to 5...
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J. Michael Klopf (Helmholtz-Zentrum Dresden-Rossendorf)25/08/2026, 16:00
In an FEL oscillator, it is not uncommon to see spectral content at the 3rd and even 5th harmonic of the fundamental lasing wavelength. This arises from on-axis emission from the undulator at the fundamental and odd harmonics. Under proper conditions, FEL oscillations also at the 2nd harmonic are possible, but even harmonics are strongly suppressed due to off-axis emission from the...
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Zhen Zhang (SLAC National Accelerator Laboratory)25/08/2026, 16:00
High-repetition-rate free-electron laser (FEL) facilities such as LCLS-II rely on continuous-wave (cw) injectors to deliver high-quality electron beams to multiple undulator lines simultaneously. Ensuring injector reliability under nonideal conditions is critical for sustained user operations. In this work, we investigate the fault tolerance of a representative cw photoinjector by analyzing...
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Mauro Siebeneichler Leffever (University of Nevada, Las Vegas, Varian Medical Systems (United States))25/08/2026, 16:00
This work investigates the feasibility of using commercial medical
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linear accelerators as electron sources for compact free electron laser
systems in the mid infrared regime. Representative beam parameters were
defined using product specifications and engineering estimates, then
compared with the infrared free electron laser at the Fritz Haber
Institute. Resonance conditions and Pierce... -
Ming-Chang Chou (National Synchrotron Radiation Research Center)25/08/2026, 16:00
NSRRC has been dedicated to providing the superradiant THz free electron laser (FEL) for scientific research users in recent years. Linac-based coherent superradiant THz FELs produced by the NSRRC high brightness photoinjector, which has been installed in the Accelerator Test Area (ATA), is served for users. Users in different research fields have different requirements for THz FEL...
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Mikhail Krasilnikov (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 16:00
A new generation of normal-conducting 1½-cell L-band RF photoguns (Gun5) has been developed at DESY for long-pulse operation at the European XFEL. Compared to the previous generation (Gun4), Gun5 supports RF pulses up to 1 ms at 10 Hz while maintaining an accelerating gradient of 60 MV/m at the cathode (~70 kW average RF power in the gun cavity). Key design improvements include an elliptical...
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Frank Stephan (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The Photo-Injector Test facility at DESY in Zeuthen (PITZ) is designed to characterize and optimize L-band photo-electron sources. As such, it has many diagnostics and tools available to measure the beam quality close to the gun. To ensure all components near the gun are properly aligned, four pairs of fiducial magnet nests were installed around the gun; approximately 50 cm from the beam axis....
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Heishun Zen (Kyoto University)25/08/2026, 16:00
A new 1.6-cell photocathode RF gun has been installed at the Kyoto University Free-Electron Laser (KU-FEL) facility to increase its peak power for high-harmonic generation (HHG) in gas. During the 2022 Phase I commissioning, which utilized a copper photocathode, the electron bunch charge was limited to 60 pC due to low quantum efficiency (QE). To address this, a semiconductor thin film (CsTe...
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Zhen Zhang (SLAC National Accelerator Laboratory)25/08/2026, 16:00
We present a robust method for generating custom-shaped, coherent hard X-ray pulses in regenerative amplifier free-electron lasers (RAFELs) using laser-induced energy modulation of the electron beam. A temporally shaped optical modulation imprints an optical-wavelength energy pattern on the beam, which interacts with the recirculated seed in the X-ray cavity to generate spectral sidebands....
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Ankur Dhar (SLAC National Accelerator Laboratory)25/08/2026, 16:00
One pathway to producing high brightness electron beams for future light sources is to use a radio-frequency (rf) driven high field photogun to rapidly accelerate photoemitted electrons to the relativistic regime and preserve the brightness. However, the highest attainable field is limited by rf breakdowns of materials used in a photogun. Shortening rf pulse duration feeding into a photogun...
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Heishun Zen (Kyoto University)25/08/2026, 16:00
The post-compression of femto-second pulsed lasers utilizing spectral broadening in solid and gas is now commonly used for obtaining few-cycle pulses. In the long-wavelength infrared (LWIR) region, solid targets such as ZnSe, and KRS-5 has been utilized*. I performed spectral broadening experiment with a 3-mm-thick KRS-5 plate at the FEL wavelength of 11 micro-m to see what would happen when...
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Mikhail Krasilnikov (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 16:00
Beam dynamics studies have been performed to optimize the brightness of a superconducting radio-frequency (SRF) photoinjector for the CW option of the European XFEL. A superconducting L-band 1.6-cell cavity is considered as a high-brightness electron source capable of CW operation and meeting stringent beam quality requirements. Due to the limited achievable accelerating gradient in the SRF...
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Sebastian Aderhold (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The Linac Coherent Light Source superconducting linac (LCLS-SC) at SLAC National Accelerator Laboratory, built during the LCLS-II project, has been in operation since 2023, with user experimental delivery commencing in 2024. In 2026, the LCLS-II-HE project is adding 23 additional 1.3 GHz cryomodules, bringing the LCLS-SC maximum electron beam energy from 4 GeV to 8 GeV. This poster will...
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Heishun Zen (Kyoto University)25/08/2026, 16:00
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...
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J. Michael Klopf (Helmholtz-Zentrum Dresden-Rossendorf)25/08/2026, 16:00
FELs have a long history of delivering intense tunable narrowband THz and IR radiation for a vast array of applications. Nearly all THz/IR FELs are oscillators that utilize an optical resonator to achieve the extremely high spectral brightness of transform-limited optical pulses. Due to the dynamics of the FEL process, FEL-oscillators must operate with an optical resonator “detuned” from...
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Tyler Kabana (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
As the SLAC high-level applications environment begins migrating towards Python-based frameworks, rigorous validation against legacy tools is critical for operational continuity. We present a comprehensive benchmarking study comparing a new Python wire scanner analysis framework (slac-tools) against legacy MATLAB software at LCLS using 379 historical datasets from routine operations since...
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Federico Vismarra (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
We propose a novel photoelectron streaking technique for free-electron laser facilities, enabling simultaneous, in situ characterization of attosecond soft X-ray pulses and the relativistic electron beam that generates them*.
Our device combines solid-state valence photoemission driven by FEL soft-X-ray pulses with co-propagating, THz-like transient electric field of the electron beam...
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Qika Jia (University of Science and Technology of China)25/08/2026, 16:00
The infrared free electron laser project FEL-HMF of Anhui university was launched in May 2022. The facility integrate free electron laser, strong magnetic field, and low-temperature environment for material science research and other research. The project is scheduled to commission and lasing this year. The progress and the current status (results of the commissioning) of the project are reported here.
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Sona Chandran P (Raja Ramanna Centre for Advanced Technology)25/08/2026, 16:00
The Infrared Free Electron Laser (IR-FEL) at the Raja Ramanna Centre for Advanced Technology (RRCAT) is the first operational FEL based user facility in India, delivering radiation in the wavelength range of 12.5-50 µm. At a repetition rate of 2 Hz, a CW average power >20 mW, micro-pulse peak power ~ 10 MW, micro-pulse energy ~100 µJ and peak spectral brightness up to...
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Timothy Suzuki (Michigan State University)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
Potassium tantalate niobate (KTN) is a paraelectric perovskite crystal with a strong quadratic electro-optic effect near its Curie temperature, making it a promising material for high-speed optical beam deflection*. Electrode design strongly influences the electric-field uniformity, drive voltage, fringe fields, and dielectric-breakdown risk in KTN deflectors. Based on electrostatic...
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Ingmar Hartl (Deutsches Elektronen-Synchrotron DESY)25/08/2026, 16:00
The recently installed NEPAL photocathode lasers at FLASH, PITZ and the European XFEL, deliver exceptional stability, reliability, and flexibility for XFEL operation. Their programmable spectral filter enables precise control of intensity and phase of the near-infrared seed-laser pulses which are then nonlinearly amplified and wavelength converted to UV. We developed an adaptive pulse-shaping...
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Jinguo Wang (Shanghai Advanced Research Institute)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The Shanghai High Repetition Rate XFEL and Extreme Light Facility (SHINE) requires a facility-wide synchronization system with femtosecond-level stability to support high-brightness FEL operation and ultrafast pump–probe experiments. This paper presents the design of the optical synchronization system developed for SHINE. A mode-locked optical master oscillator is employed as the central...
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Senlin Huang (Peking University)25/08/2026, 16:00
The construction of a platform for terahertz (THz) radiation research at Peking University has been completed recently. The platform consists of a DC-SRF-II photocathode gun, an superconducting radio-frequency (SRF) linac equipped with two 9-cell TESLA-type cavities, a magnetic chicane for electron bunch compression, and a 40-period undulator with taper control. By integrating with an...
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AKASH CHANDRA BEHERA (Fritz Haber Institute of the Max Planck Society)25/08/2026, 16:00
The infrared free-electron laser (IR-FEL) at the Fritz Haber Institute recently commissioned a two-color upgrade, enabling simultaneous lasing with two IR FEL oscillators with independently tunable wavelength. This is realized by employing a high-frequency kicker cavity to feeding alternating electron bunches from within the 1GHz bunch train into the two separate IR FEL oscillators. Within...
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Kevin Eckrosh (Arizona State University, Biodesign Institute)25/08/2026, 16:00
Recent years have seen a growing interest in developing x-ray sources that are cheaper and more compact than conventional XFELs and synchrotrons. The Compact X-ray Light Source (CXLS) at Arizona State University achieves this using Inverse Compton scattering to produce a high-brightness, short pulse duration x-ray beam. This source operates in blowout mode, meaning a high-charge, short-bunch...
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Levi Fisher (University of Hawaiʻi at Mānoa)25/08/2026, 16:00
Cavity desynchronization is important in FEL oscillators, especially in the IR and THz regimes where optical slippage is significant and laser lethargy can reduce gain under perfect synchronism. Because fast mechanical cavity tuning is difficult, several facilities have implemented dynamic desynchronization by sweeping the electron bunch repetition rate through upstream RF phase control,...
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Dr Francesca Addesa (Paul Scherrer Institute)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
At the Paul Scherrer Institute (PSI), nanotechnology has been successfully employed to develop minimally invasive Wire Scanners with sub-micrometer spatial resolution for monitoring the transverse beam size at SwissFEL during lasing operation. The devices consist of a monolithic low-stress Si₃N₄ structure with a C-shaped silicon fork, integrating two perpendicular wires for full transverse...
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Franz-Josef Decker (SLAC National Accelerator Laboratory)25/08/2026, 16:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsPoster Presentation
The energy of the beam is 5 to 10 times more stable than the beam powered by the LCLS Copper Linac due to the continuous wave (CW) operation of the superconducting (SC) Linac. Transversely, we have identified Injector Laser movements on the cathode of RF Gun (low frequency to a few Hz). Some 60 Hz lines from spreader kicker were seen and corrected by timing adjustments of the kicker pulse....
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Yuri Shvyd'ko (Argonne National Laboratory)25/08/2026, 16:00
Cavity-based X-ray free-electron lasers (CBXFELs) require tunable X-ray crystal cavities to broaden their practical utility. However, the previously proposed four-crystal bow-tie design has a lateral footprint comparable to the undulator length, limiting its deployment in accelerator tunnels. Here, we introduce a compact, broadly tunable X-ray cavity comprising six Bragg-reflecting crystals...
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Madison Singleton (SLAC National Accelerator Laboratory)25/08/2026, 16:00
Cavity-based X-ray free-electron lasers (CBXFELs), including the X-ray regenerative amplifier FEL (XRAFEL) and the XFEL oscillator (XFELO), have been proposed as sources of highly coherent and stable hard X-rays. XRAFELs can generate high-peak-power X-ray pulses with bandwidths limited by Bragg-crystal filtering, whereas XFELOs provide much narrower bandwidths but at substantially lower peak...
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Theodore Vecchione (SLAC National Accelerator Laboratory)25/08/2026, 16:00
Significant progress has been made in the performance of the LCLS-II photoinjector and its photocathode subsystem. Cs₂Te photocathodes are now routinely produced with uniform, high initial quantum efficiency (QE) and Coulomb-level lifetimes. However, unexpected photocathode dynamics have emerged as an operational challenge. Over longer timescales, initially uniform QE develops spatial...
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Yanwen Sun (SLAC National Accelerator Laboratory)26/08/2026, 08:30Session 11: Undulators and Photon Beamline InstrumentationInvited Oral Presentation
I will present the design and commissioning results of a broadband hard x-ray delay line for generating attosecond pulse pairs. The system utilizes an unconventional delay adjustment mechanism, in which the relative path length between the two beams is controlled through the rotation of an x-ray mirror pair. The exit beam pointing stability is guaranteed by the mirror-pair...
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Dr Jan Grünert (European X-Ray Free-Electron Laser)26/08/2026, 08:55Session 11: Undulators and Photon Beamline InstrumentationInvited Oral Presentation
European XFEL is commonly providing user operation with self-amplified spontaneous emission (SASE) and hard x-ray self-seeding (HXRSS), ref [1]. A facility-internal project had been started to demonstrate operation of a cavity-based XFEL (CB-XFEL), ref [2], which promises to improve spectral purity and brightness significantly. The first demonstration of a CBXFEL was achieved in May 2025, ref...
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Marco Calvi (Paul Scherrer Institute)26/08/2026, 09:20Session 11: Undulators and Photon Beamline InstrumentationInvited Oral Presentation
To provide fully controllable elliptical polarisation to all experimental stations of the SwissFEL facility, spanning soft to hard x-rays, the PSI ID group is developing a novel undulator concept based on HTS REBCO tapes. The proposed design enables the superposition of right-handed and left-handed helical fields with comparable strength, allowing the generation of horizontal and vertical...
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Veronica Guo (Stanford University)26/08/2026, 09:40Session 11: Undulators and Photon Beamline InstrumentationContributed Oral Presentation
Probing the ultrafast motion of electrons that drive chemical reactions and determine material properties requires state-of-the-art light sources with attosecond pulse duration. Soft X-ray pulses can probe electronic densities with atomic-site specificity. The advent of X-ray free-electron lasers (XFELs) has increased the per-pulse flux of attosecond sources by orders of magnitude, enabling...
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Naresh Kujala (European X-Ray Free-Electron Laser)26/08/2026, 09:55Session 11: Undulators and Photon Beamline InstrumentationContributed Oral Presentation
The European X-ray Free Electron Laser facility in Germany delivers pulses with femtosecond pulse lengths at repetition rates up to 4.5 MHz. The X-ray photon diagnostics group provides reliable measurement devices and feedback systems for monitoring and controlling the properties of the FEL radiation which is created by the Self Amplified Spontaneous Emission (SASE) process. The stochastic...
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Ichiro Inoue (The University of Tokyo)26/08/2026, 10:30
We report on the realization of damage-free diffraction and spectroscopy using attosecond hard X-ray pulses from LCLS, European XFEL, and SACLA. By compressing the X-ray pulse duration to the attosecond regime, X-ray–induced electronic and structural damage is effectively suppressed during the interaction, enabling the probing of pristine atomic structures and electronic states in matter. We...
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Gregor Knopp (Paul Scherrer Institute)26/08/2026, 10:55
Coherent nonlinear light–matter interaction with X-rays gives access to a regime in ultrafast spectroscopy in which atomic resolution meets femtosecond and attosecond timescales. Particularly X-ray four-wave mixing, involving several resonant transitions in a single coherent nonlinear process, has the potential to provide information on the electronic states coupling, coherent electron...
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Laura Foglia (Elettra-Sincrotrone Trieste S.C.p.A.)26/08/2026, 11:20
Progress in nanoscience increasingly depends on our ability to control light at spatial and temporal scales matching those characteristic of nanostructures. In particular, controlling the polarization of light is essential for investigating materials whose properties depend not only on light intensity, but also on the specific orientation of the electric field. Such polarization-sensitive...
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Taran Driver (SLAC National Accelerator Laboratory)26/08/2026, 11:45
Author will add more on the abstract
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Yi Jiao (Chinese Academy of Sciences)26/08/2026, 14:00
Magnetic bunch compressor is an indispensable component in free-electron laser facilities. Recently, breakthrough progress has been made in the physical modeling, understanding, and analytical analysis of the bunch compressor, enabling effective bunch compression while avoiding emittance growth induced by coherent synchrotron radiation effects. In this reivew, we will report latest progress in...
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Philipp Amstutz (Deutsches Elektronen-Synchrotron DESY)26/08/2026, 14:25
To generate ultra-short photon pulses in a free-electron laser (FEL) accurate control of the longitudinal phase space density of the electron bunch that drives the FEL process is required. A novel laser-based technique to manipulate the longitudinal phase space density (T. Tanaka, 2019) has been explored at FLASH. An ultra-short current spike is created by compressing part of an electron bunch...
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Giovanni Campri (Elettra-Sincrotrone Trieste S.C.p.A.)26/08/2026, 14:50Session 8: Electron Beam DynamicsContributed Oral Presentation
We report on recent experimental sessions at FERMI FEL, characterizing the electron beam longitudinal phase space and the HGHG FEL, in single and double compression scheme. The impact of microbunching instability on the beam dynamics and lasing is recorded, and succesfully compared with predictions from a MBI instability integral model incorporating intrabeam scattering. With the addition of...
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Zhen Zhang (SLAC National Accelerator Laboratory)26/08/2026, 15:15Session 8: Electron Beam DynamicsContributed Oral Presentation
Beam halo formation poses a critical challenge for high-repetition-rate continuous-wave (CW) free-electron lasers (FELs), directly affecting beam quality and machine protection, as observed during the LCLS-II commissioning. We identify and experimentally validate a previously unrecognized three-step mechanism for halo generation in the photoinjector, arising from coupled...
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Yu NAKATA (The University of Tokyo, RIKEN SPring-8 Center)26/08/2026, 17:00
Recent advances in X-ray free-electron lasers (XFEL) have opened new opportunities for X-ray nonlinear optics and transient dynamics in condensed matter*. Tight focusing of XFEL pulses is essential for generating the high intensities required for nonlinear X-ray processes and for achieving high-spatial-resolution imaging of ultrafast dynamics. However, 100-nm focusing of soft X-rays remains...
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Nicholas Matlis (Arizona State University)26/08/2026, 17:00
The Compact X-ray Light Source (CXLS) at Arizona State University is a compact inverse-Compton-scattering (ICS) facility designed to provide femtosecond hard X-rays in a university laboratory environment. CXLS has entered commissioning and early-science operation, demonstrating stable operation of a 9.3 GHz X-band accelerator, synchronized picosecond laser systems, and femtosecond hard X-ray...
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Maofei Qian (Argonne National Laboratory)26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
A 13.5-nm SASE FEL based on a force-neutral, phase-adjustable undulator (FNAPU) with integrated FODO focusing has been simulated. For an undulator period of 28 mm and K = 2.32, simulations assuming a 1-GeV electron beam with 0.5-mm·mrad normalized emittance and 3-kA peak current show that the integrated focusing maintains an rms beam size of approximately 20 μm, enabling saturation in about 6...
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Adil Ansari (Arizona State University)26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
X-ray free-electron lasers (XFELs) provide exceptional brightness and ultrafast capabilities but face high demand for beamtime. Compact X-ray light sources (CXLS) aim to reduce facility size and cost, enabling broader access to a subset of XFEL experiments and complementing large-scale facilities.
We present the development of a digital twin for key CXLS components, designed for system...
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Liubov Samoylova (European X-Ray Free-Electron Laser)26/08/2026, 17:00
We present results of modeling of the FEL radiation used in pump probe experiment at BL3 at SACLA free electron laser. 160 pC, 8 GeV electron bunch produces two photon pulses with different photon energies (color1: 8 keV and color 2: 9 keV) when consecutively passing two undulator sections. First color is filtered by Si111 monochromator to the bandwidth of 0.02% (pulse energy is 0.1 uJ)....
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John Walters (Stanford University)26/08/2026, 17:00
We use attosecond interferometry to diagnose the temporal profile of attosecond pulse trains generated with a seeded free electron laser. A harmonic train is generated using the FERMI free electron laser with a seeding field of 266 nm. This harmonic pulse train is overlapped with a second 266 nm pulse at the Low Density Matter beamline. Two color photoemission in helium was analyzed using a...
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Dr Ekaterina Jung (WAIV FTIR GmbH)26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
Spectral diagnostics of infrared and THz free electron lasers typically rely on either laser-based techniques or large benchtop FTIR systems, making alignment and beamline integration time-consuming. We present AURA, the most compact broadband FTIR spectrometer developed by WAIV FTIR GmbH, covering a continuous spectral range from 3 to 600 µm (100 THz to 0.5 THz). The instrument fits in a 130...
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Fumio Shishikura (Nihon University)26/08/2026, 17:00
Free-electron lasers (FELs) are valuable light sources for examining the biological effects of mid-infrared radiation on living organisms. We investigated the compound eyes of two arthropod species, crayfish (Procambarus clarkii, Crustacea) and crickets (Gryllus bimaculatus, Insecta), using LEBRA-FEL (3–6 μm) and KU-FEL (3.4–26 μm) as radiation sources. In both cases, the...
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Zoltán Tibai (University of Pecs)26/08/2026, 17:00
Efficient acceleration has been demonstrated using dielectric waveguides driven by multi-cycle THz pulses. Further improvements were achieved by employing sequential THz sources and waveguide structures, enabling cascaded acceleration* . The cascaded THz-driven dielectric electron accelerator proposed here provides enhanced acceleration efficiency while enabling electron bunch compression. A...
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Xiujie Deng (Tsinghua University)26/08/2026, 17:00
In this paper, we will report the property of SSMB radiaiton, like the power, bandwidth, and spectral brightness.
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Mario Balcazar (SLAC National Accelerator Laboratory)26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
We present results from the commissioning of the X-ray optics motion and photon diagnostics systems for the cavity-based X-ray free-electron laser (CBXFEL) project, a partnership among Argonne National Laboratory (ANL), SLAC National Accelerator Laboratory, and RIKEN SPring-8. The project aims to demonstrate CBXFEL technology using X-rays produced in the first seven hard X-ray undulators of...
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Ji Qiang (Lawrence Berkeley National Laboratory)26/08/2026, 17:00
High-brightness X-ray Free Electron Lasers (FELs) are transformative tools for scientific discovery. However, most existing FELs are kilometer-scale facilities with high construction costs and low repetition rates, limiting their accessibility and throughput. This paper proposes a compact, high-repetition-rate (MHz) EUV to 1 nm soft X-ray FEL with a footprint of less than 100 meters. The...
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Philippe Piot (Argonne National Laboratory)26/08/2026, 17:00
Increasing the number of X-ray free electron laser (XFEL) facilities and capabilities across the United States is critical to keep pace with the growing demand from the user community. We are exploring a novel concept based on two-beam acceleration technology, with a focus on delivering coherent X-ray pulses with agile and customizable properties. The Coherent Agile Pulse at Argonne X-ray...
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Federico Vismarra (SLAC National Accelerator Laboratory)26/08/2026, 17:00
Soft-X-ray attosecond spectroscopy at FELs provides direct access to ultrafast electronic dynamics in matter with simultaneous sub-femtosecond resolution and atomic-site specificity*. By exploiting core-level transitions, these approaches offer a localized and phase-sensitive probe of electronic coherence, extending attosecond science beyond valence dynamics into the regime of strongly...
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Dr Henry Freund (University of Maryland, College Park)26/08/2026, 17:00
The application to FELs has become a research interest after improvements in laser-plasma-accelerator (LPA) beam quality and reliability, [1,2]. The goal is for more compact light sources due to the high gradients in the LPA. However, the FEL output from ultra-short LPA electron bunches (at the 20-fs level) is dominated by the rapid slippage of the beam behind the optical pulse in two LPA-FEL...
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Johann Eduardo Baader (SLAC National Accelerator Laboratory)26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
A magnetic measurement test stand has been developed to reduce the workload and time required for the final tuning of the LCLS-II-HE soft X-ray undulators. The test stand includes a touch probe for mechanical measurements, a Hall probe for local field measurements, and a stretched wire system for field integral measurements. The test stand enables early magnetic alignment and magnetic field...
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Rafi Hessami (SLAC National Accelerator Laboratory)26/08/2026, 17:00
The ongoing Plasma-driven Attosecond X-ray source experiment (PAX) at FACET-II aims to produce coherent soft X-ray pulses of attosecond duration using a plasma wakefield accelerator [1]. These X-ray pulses can be used to study chemical processes where attosecond-scale electron motion is important. For this first stage of the experiment[KS1.1], PAX plans to demonstrate that <100 nm bunch length...
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Zhaoheng Guo (École Polytechnique Fédérale de Lausanne, Paul Scherrer Institute)26/08/2026, 17:00
We demonstrate the generation of both soft and hard X-ray attosecond pulses at SwissFEL, based on the temporal shaping of the photocathode laser pulses. Through flexible bunch compression schemes, the electron beam current profile evolves from a double-Gaussian shape with 10 ps duration into a femtosecond-scale isolated high-current spike in the core of a tens-of-femtosecond-long electron...
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Claudio Emma (SLAC National Accelerator Laboratory)26/08/2026, 17:00
FACET-II is a National User Facility at SLAC focusing on research in the areas of advanced acceleration and coherent radiation techniques with high-energy electron beams [1]. This contribution summarizes recent experimental results relevant for FEL and high brightness beam applications including the generation of extremely high current beams through laser-electron phase space manipulation [2],...
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Nathan Burger (RadiaBeam Technologies (United States))26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
Conventional variable gap undulators rely on mechanically complex, force intensive support systems that limit tuning speed, alignment stability, and operational reliability—challenges that are increasingly critical for next generation free electron lasers (FELs). In collaboration with Argonne National Laboratory (ANL), RadiaBeam Technologies is advancing ANL’s Force Neutral Adjustable Phase...
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Paris Franz (xLight)26/08/2026, 17:00
Harmonic lasing is an advanced FEL concept to produce short wavelengths with a low-energy electron beam by developing lasing at an odd harmonic of the FEL fundamental wavelength. Harmonic lasing self-seeded (HLSS) FEL uses a two-stage high-gain FEL with the first stage being a harmonic lasing FEL to produce the coherent seed for the second stage which serves as a high-gain FEL amplifier. HLSS...
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Chance Ornelas-Skarin (Stanford University)26/08/2026, 17:00
The microscopic structure and dynamics of valence electrons determine many of a material's properties, including its optical ones. Conventional x-ray scattering can resolve the angstrom-scale electronic structure, but it is difficult to separate the valence electrons from the more localized core electrons. Here we report nonlinear x-ray scattering measurements from optically-driven valence...
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Csaba Nemeth (SLAC National Accelerator Laboratory)26/08/2026, 17:00Session 11: Undulators and Photon Beamline InstrumentationPoster Presentation
Polarization control of high-intensity coherent X-ray light is essential for many experiments, including magnetic spectroscopy and studies of chiral molecular structure. However, most free-electron laser facilities rely on planar undulators for light generation, which are generally unable to provide polarization tunability. Counterintuitively, analytical solutions of Maxwell's equations...
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Pardis Niknejadi (Deutsches Elektronen-Synchrotron DESY)26/08/2026, 17:00
A theoretical framework for understanding and controlling mode selection in echo-enabled harmonic generation (EEHG) free-electron lasers (FELs) at high harmonic numbers is presented. In EEHG, adjacent harmonics naturally exhibit comparable microbunching amplitudes, creating a unique opportunity to work with different spectral components. To capture this process, we benchmark orthogonal...
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Samuel Barber (Lawrence Berkeley National Laboratory)26/08/2026, 17:00
Several demonstration experiments of laser plasma accelerator (LPA) driven free electron lasers (FEL) have emerged in the past 5 years [1,2] and are paving the path towards compact light sources. The electron beams generated in plasma accelerators differ significantly from those produced in RF-based photoinjectors and linear accelerators, which drive all existing XFELs. LPAs exhibit larger...
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Haoyuan Li (Linac Coherent Light Source)26/08/2026, 17:00
Ultrafast optical laser-based techniques have enabled the probing of atomistic processes at their intrinsic temporal scales with femto- and attosecond resolution.
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However, the long wavelengths of optical lasers have prevented their interrogation and manipulation with nanoscale spatial specificity.
Advances in hard X-ray free-electron lasers have enabled progress in developing X-ray... -
Simone Di Mitri (Elettra-Sincrotrone Trieste S.C.p.A.)26/08/2026, 17:00
The systematic comparison of two semi-analytical models of microbunching instability affecting electron beams in single pass or recirculating linear accelerators is reported. The comparison is comprehensive of numerous features of the instability, and enriched by three different expressions to calculate intrabeam scattering. The inclusion of this effect allows the recovery of agreement with...
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Suren Karabekyan (European X-Ray Free-Electron Laser)26/08/2026, 17:00
The variable polarization afterburner at the European XFEL was successfully commissioned in early 2024. It consists of four APPLE-X undulators installed behind the SASE3 planar undulator system, generating the free-electron laser pulses for the soft X-ray beam lines. The afterburner has now become an integral part of the European XFEL and is used for various experiments. These include...
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Cagri Erciyes (Max Planck Institute for Nuclear Physics)26/08/2026, 17:00
Free-electron lasers (FELs) deliver the brightest coherent X-ray pulses for atomic-resolution ultrafast science, yet scaling to extreme peak powers and attosecond durations faces a fundamental barrier: in the ultrahigh-current regime, longitudinal space-charge fields impose slice-dependent energy detuning that suppresses gain and confines efficient lasing to a small bunch fraction. We...
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Kelly Swanson (SLAC National Accelerator Laboratory)26/08/2026, 17:00
Electron bunches with attosecond-scale bunch durations and high peak currents would enable new opportunities for next-generation light sources. However, to generate such short bunches requires novel compression techniques. Here we consider plasma-based compression, a method which exploits the inherently large accelerating fields in a plasma wakefield accelerator, to add an energy-time...
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Lingen Huang (Helmholtz-Zentrum Dresden-Rossendorf)26/08/2026, 17:00
Heating and ionization are among the most fundamental processes in relativistic laser--solid interactions; however, their spatiotemporal evolution remains challenging to capture experimentally. Here we present detailed diagnosis of high-intensity laser interactions with wire targets, leveraging the extreme spectral brightness of an X-ray free-electron laser in sub-picosecond time-resolved...
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Melanie Murillo (Stanford University)26/08/2026, 17:00
We present a Dielectric Laser Accelerator concept for achieving tunable interactions with electron beams using silicon photonic integrated circuits to program laser phase fronts. Our photonic circuit is an 8x8 binary tree mesh of Mach-Zehnder Interferometers (MZIs), enabling routing, splitting, and recombination of light via adjustable thermal phase shifters. We couple 2.2 um, 330 fs FWHM...
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Jack Hirschman (Stanford University, SLAC National Accelerator Laboratory)26/08/2026, 17:00
Next-generation x-ray free-electron lasers operating at MHz repetition rates require fast, flexible source-level actuators for adaptive and autonomous operation.* The photoinjector drive laser, mapping directly onto the electron beam's initial longitudinal phase space, represents a powerful and largely unexplored upstream handle. Here we present the first demonstration of programmable...
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Simone Di Mitri (Elettra-Sincrotrone Trieste S.C.p.A.)26/08/2026, 17:00
An update version of the brilliance plot in units of 0.01% relative bandwidth is proposed, including most recent planned and running 4th generation multi-bend storage ring light sources. It is then shown that, in order to match experimental and simulated data, the calculation has to take into consideration a non-uniform electron current profile in self-amplified spontaneous emission, and the...
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Federico Vismarra (SLAC National Accelerator Laboratory)26/08/2026, 17:00
Attosecond pump-probe experiments are a long-sought tool to observe electronic processes on their natural timescales; however, slippage during FEL amplification complicates the ability to set short delays. At LCLS, we have recently demonstrated pump-probe measurements with sub-fs delays by using harmonic pulse pairs (w/2w). A soft x-ray delay line will enable general two-color operation, but...
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Jenny Morgan (SLAC National Accelerator Laboratory)26/08/2026, 17:00
We present simulations demonstrating single-cycle waveform control of undulator radiation using an ultrashort electron beam produced by a plasma wakefield accelerator. By operating in a regime where the resonant radiation wavelength exceeds the effective bunch length of the compressed current spike, the emitted electric field closely follows the structure of the undulator magnetic field. This...
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Yuri Shvyd'ko (Argonne National Laboratory)26/08/2026, 17:00
Momentum-resolved inelastic x-ray scattering (IXS) probes the dynamical structure factor S(Q,ω) in solids, liquids, biological systems, and quantum materials, providing access to phonons, magnons, and charge, orbital, and valence excitations on meV energy scales and nm$^{−1}$ momentum scales. Although IXS is a well-established technique at storage-ring sources, its broader impact is limited by...
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Tehya Andersen (Lawrence Berkeley National Laboratory, University of California, Berkeley)26/08/2026, 17:00
Free-electron lasers (FELs) driven by electron beams generated by laser-plasma-accelerators (LPAs) offer an attractive avenue towards compact, high brightness and short wavelength coherent light sources. The BELLA Center LPA FEL facility at the Lawrence Berkeley National Laboratory delivers few fs-duration, 40-80 pC electron bunches of 100 MeV energy, 4% FWHM energy spread, at a 1Hz repetition...
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Jenny Morgan (SLAC National Accelerator Laboratory)26/08/2026, 17:00
There has been significant interest in generating orbital angular momentum (OAM) pulse pairs at free-electron lasers, either through direct OAM seeding schemes or via harmonic emission in helical undulators. In such schemes the pulses are temporally separated; while coherent superpositions of OAM modes can be identified from their transverse interference patterns, this approach fails when the...
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Aliaksei Halavanau (SLAC National Accelerator Laboratory), Dr Claudio Pellegrini (SLAC National Accelerator Laboratory)26/08/2026, 17:00
We report on the progress of the design and development of an X-ray Laser Oscillator (XLO) based on population inversion, to be driven by the LCLS-II-HE free-electron laser currently under construction at SLAC National Accelerator Laboratory. The XLO concept exploits the brightness, high repetition rate (up to 1 MHz), and tunability of LCLS-II-HE photon beam to generate population inversion in...
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Xiujie Deng (Tsinghua University)26/08/2026, 17:00
In this paper, we propose to combine two promising research topics in accelerator physics, i.e., optical stochastic cooling (OSC) and steady-state microbunching (SSMB). Our study shows that such an OSC-SSMB storage ring with a circumference of 50 m and beam energy of several hundred MeVs using present technology can deliver kilowatt radiation at 100 nm wavelength. A more ambitious application...
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Nicholas Matlis (Arizona State University)26/08/2026, 17:00
We investigate generation of structured X-rays at ~9 keV energies via inverse Compton scattering (ICS) of 1030 nm structured light from ~20 MeV electrons. Structured light at X-ray photon energies enables entirely new ways of probing and controlling matter at the atomic and nanoscale, including accessing chiral, magnetic, and orbital-selective interactions that are invisible to conventional...
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XINGYU SU (The University of Tokyo)26/08/2026, 17:00
Nonlinear spectroscopy in the XUV and soft-X-ray regions offers a unique route to combine the symmetry sensitivity of optical nonlinear processes with the element and orbital selectivity of core-level resonances. We present an experimental platform for time-resolved XUV-to-soft-X-ray nonlinear spectroscopy at FEL sources, using second-harmonic generation as a representative nonlinear probe....
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Hankai Zhang (École Polytechnique Fédérale de Lausanne, Paul Scherrer Institute)26/08/2026, 17:00
Ultrafast imaging enables the investigation of nanoscale dynamics in single particles using individual X-ray pulses. Accurate interpretation of such images requires understanding the strong interaction between the X-ray pulse and the sample, particularly when the electronic structure effects is of interest.
We investigate ultrafast X-ray--induced dynamics in sodium iodide (NaI)...
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Dr Wei-Yuan Chiang (National Synchrotron Radiation Research Center)26/08/2026, 17:00
Laser wakefield accelerators (LWFAs) have emerged as promising compact drivers for free-electron lasers (FELs), owing to their ability to produce femtosecond electron beams with high peak current over centimeter-scale acceleration distances. However, their relatively large energy spread remains a key challenge for achieving high-gain FEL operation. While magnetic compression can effectively...
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Feng Zhou (SLAC National Accelerator Laboratory)27/08/2026, 08:30
LCLS-II has transitioned to users operation since 2023 and recently ramped the beam rate up to 93 kHz. This paper will present LCLS-II injector operational progresses and challenges.
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Gongxiaohui Chen (Argonne National Laboratory)27/08/2026, 09:00
Normal-conducting accelerating structures capable of supporting GV/m-scale electric fields offer a compelling pathway toward compact accelerator systems. Achieving such fields in photocathode RF guns is equally essential for the production of high-brightness electron bunches. Our group has recently demonstrated ~0.4 GV/m peak electric fields on the photocathode surface of an X-band (11.7 GHz)...
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Nikhil Bachhawat (Stony Brook University)27/08/2026, 09:30
The generation of high-quality continuous-wave (CW) electron beams with parameters suitable for hard X-ray free-electron lasers (FELs) has so far not been demonstrated experimentally. Traditionally, photoinjectors operating at very high accelerating gradients are considered necessary to meet the stringent beam-quality requirements of hard X-ray FELs. While high-gradient guns have been...
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HAO ZHANG (University of California, Los Angeles)27/08/2026, 09:50
Generating high-brightness electron beams with optimized longitudinal phase space is essential for driving next-generation free-electron lasers (FELs). However, accelerator-induced distortions often degrade beam quality and lasing performance. Here, we present a novel approach to counteract these effects by manipulating the photoemission laser’s temporal distribution*. By introducing a...
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Andrei Trebushinin (European X-Ray Free-Electron Laser)27/08/2026, 10:30Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsInvited Oral Presentation
We report the observation of transverse intensity fluctuations (spikes) in synchrotron radiation from a single undulator cell at the European XFEL after monochromatization [1]. Autocorrelation analysis of the recorded events confirms that these fluctuations originate from the partial transverse coherence of the radiation. By calculating the second-order autocorrelation function, we determined...
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Gian Luca Orlandi (Paul Scherrer Institute)27/08/2026, 11:00Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsInvited Oral Presentation
Monitoring the electron pulse duration is crucial for setting up and stabilizing the lasing in a linac-driven Free-Electron-Laser (FEL). Bunch-Compressor-Monitors (BCMs) allow for a non-invasive - albeit uncalibrated – monitoring of the electron pulse duration at the exit of a magnetic chicane by detecting and fully integrating the radiation energy emitted by the electron beam around the...
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Keigo Kawase (National Institutes for Quantum Science and Technology)27/08/2026, 11:30Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsContributed Oral Presentation
To demonstrate the stabilization of the carrier-to-envelope phase (CEP) of the free-electron laser oscillator via injection seeding, we are developing a fiber-laser-based, passively CEP-stabilized difference-frequency-generation mid-infrared source. The external injection seeding into the FEL requires a synchronized laser pulse with the electron bunch driving the FEL. Thus, we introduce a...
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Sean OTool (Stanford University)27/08/2026, 11:50Session 10: Electron Diagnostics, Timing, Synchronization, and ControlsContributed Oral Presentation
Accurate characterization of 3D space-charge fields in ultrashort electron beams is crucial for next-generation accelerators. The complex, transient 3D space-charge and CSR fields that ultimately shape and limit high-brightness beams have yet to be directly measured, leaving critical dynamics unobserved. A compact diagnostic for the direct measurement of the field itself thus remains a key...
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Samuel Barber (Lawrence Berkeley National Laboratory)28/08/2026, 08:30Session 9: Novel Accelerator and FEL ConceptsInvited Oral Presentation
Compact free-electron lasers (FELs) based on plasma-based accelerators have been envisioned for many years. While recent milestone experiments have demonstrated their feasibility, further progress is required to establish laser-plasma-accelerator-driven FELs as reliable light sources. Demonstrating both full FEL saturation and operational reliability comparable to conventional FEL facilities...
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Andrea Frazzitta (Paul Scherrer Institute)28/08/2026, 08:55Session 9: Novel Accelerator and FEL ConceptsInvited Oral Presentation
The plasma discharge undulator (PDU) has recently been proposed as a compact, tunable, fully plasma-based undulation device. In the PDU, a high-current discharge within a capillary generates an azimuthal magnetic field providing strong linear focusing, while a controlled periodic modulation of the discharge axis acts as a geometric driving term, producing well-defined undulator oscillations at...
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YANJUN GU (The University of Osaka)28/08/2026, 09:20Session 9: Novel Accelerator and FEL ConceptsInvited Oral Presentation
Free-electron lasers (FELs) provide ultrashort, coherent, and wavelength-tunable radiation for a wide range of scientific applications. Here, we present the demonstration of a laser-wakefield-acceleration (LWFA)-driven FEL operating at a central wavelength of 40 nm. By using a compact 0.8 J laser system and carefully optimizing the plasma density, electron injection, laser wavefront, and...
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Fei Li (Institute of High Energy Physics)28/08/2026, 09:45Session 9: Novel Accelerator and FEL ConceptsInvited Oral Presentation
With the development of plasma-based accelerators as a novel acceleration technology, beam phase space manipulation techniques based on plasma wakefields have also gradually begun to be applied, demonstrating their unique advantages in flexibility and device miniaturization compared to traditional beam manipulation techniques. Here, we demonstrate the saturation of a soft X-ray FEL driven by...
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Wenxiang Hu (Paul Scherrer Institute, ETH Zurich)28/08/2026, 10:30
X-ray free-electron lasers (FELs) are powerful photon sources offering a wide wavelength range, subfemtosecond pulse duration, and high brightness. Most X-ray FELs are based on self-amplified spontaneous emission (SASE). SASE-FEL radiation has excellent transverse but only limited longitudinal coherence, with power and spectral profiles consisting of multiple randomly distributed spikes.
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River Robles (Stanford University)28/08/2026, 11:00
Attosecond science with XFELs is a rapidly growing field. Nearly half of soft X-ray LCLS user experiments now use attosecond pulses. In this talk, I will present recent advances in the generation and characterization of attosecond pulses at the LCLS and LCLS-II, focusing on three main topics:
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1. First direct observation of attosecond pulses in the hard X-ray domain.
2. Attosecond lasing in... -
Yin Kang (Shanghai Advanced Research Institute, Chinese Academy of Sciences)28/08/2026, 11:30
A comprehensive framework for the generation and diagnostics of X-ray and THz OAM beams has been successfully established at the Shanghai Soft X-ray Free-Electron Laser (SXFEL) facility. This work effectively bridges the gap between advanced orbital angular momentum (OAM) physics and the stringent beam quality requirements of a high-performance XFEL facility. The ability to produce soft X-ray...
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Jingyi Tang (Stanford University)28/08/2026, 11:50
We propose a novel and simple scheme for generating tunable, phase-locked hard-X-ray pulse pairs in cavity-based free electron lasers. A short electron bunch first amplifies one temporal slice of a long coherent cavity field; after a magnetic delay, the same bunch overlaps a fresh seed slice in a second undulator section, producing a second pulse locked to the same optical reference. The...
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