Cavity Fabrication and Surface Preparation
Cavity Clean Assembly and Testing
Cryomodule Design and Testing
In this tutorial an introduction to Low Level Radio Frequency (LLRF) is given. The tutorial is divided into two parts. First, after explaining the purpose of LLRF, an introduction to the theoretical background is given. This covers the modeling of accelerating RF cavities, the deduction of fundamental equations, and short peaks into signal processing and controller theory. This part also...
Superconducting Radio Frequency (SRF) technology relies on cryogenics to achieve and maintain the ultra-low temperatures required for efficient accelerator operation. This tutorial introduces the essential principles of cryogenics for SRF applications, aimed at providing participants with a foundation to support their work in the field. Topics include the role of cryogenics in SRF technology,...
The RIKEN superconducting heavy-ion linac, so-called SRILAC, has been successfully operating for almost five years, and continuously deliver a heavy ion beam for a super-heavy-element synthesis experiment by fixing minor and major hardware troubles. The effects of a broken coupler in the early days and four years of operation have resulted in increased X-ray emission levels in several...
Materials imperfections in Nb-based superconducting quantum circuits—in particular, two-level-system (TLS) defects—are a major source of decoherence, ultimately limiting the performance of quantum computation and sensing. Thus, identifying and understanding the microscopic origin of possible TLS defects in these devices will help developing strategies to eliminate them and is key to...
The Electron-Ion Collider (EIC) is being implemented at Brookhaven National Laboratory (BNL) in a special partnership with Thomas Jefferson National Accelerator Facility. EIC is designed to collide electrons and protons/Heavy Ions with energies of 5-18 GeV, 2.5 A in the Electron Storage Ring (ESR) and 41-275 GeV/u, 1 A in the Hadron Storage Ring (HSR). The interaction region with a crossing...
A five-year project (MEXT advanced Accelerator element Technology Development (MEXT-ATD)) funded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) began at KEK in FY2023. The goal is to manufacture, construct and test a cryomodule (CM) that satisfies the ILC (International Linear Collider Project) specifications and conduct cooling tests. The MEXT-ATD program is...
This talk will describe the most recent advances and progress in building an SRF cavity-based quantum computing facility at the Fermilab SQMS center. Several technical challenges had been successfully overcome to preserve the highest quality factors of SRF cavities in the presence of the sapphire chip holding the transmon qubit inside the cavity. The record values of the attained multicell...
The SCL is an in kind contribution to ESS by IJCLAB (spoke cavities and cryomodules), INFN (Medium Beta Cavities), STFC (High Beta cavities) and CEA (all elliptical cryomodule assembly). Spoke cryomodules have been tested at FREIA facility in Uppsala (Sweden) and elliptical cryomodules have been tested at the ESS Test Stand 2 in Lund. The installation of 27 cryomodules (13 spokes, 9 medium...
The Linac Coherent Light Source superconducting linac (LCLS-SC) at SLAC National Accelerator Laboratory, built during the LCLS-II project, has now been in operation for the past three years, with user experimental delivery commencing in 2024. In 2026, the LCLS-II-HE project will add 23 additional 1.3 GHz cryomodules, bringing the LCLS-SC maximum electron beam energy from 4 GeV to 8 GeV. This...
FRIB is the first heavy-ion accelerator facility to deploy a large number of Half-Wave Resonators (220 HWRs) and operate at 2 K in its superconducting drive linac. As of today, FRIB delivered the world’s highest uranium beam power (>18 kW) on target and will continue its power ramp-up in the next few years in parallel to support user science program. The technologies that have sustained the...
Recently, the SHINE Linac layout has been modified to use fewer cryomodules (CMs) to reach 8 GeV, bene-fiting from the higher performance of high-Q cavities and CMs. The mass production of SHINE cavities and CMs is currently underway. To date, more than 100 mid-T baked cavities and 100 N-doped cavities have been vertically tested. Most of them have been assem-bled into cryomodules, achieving...
The superconducting heavy ion HELmholtz LInear ACcelerator (HELIAC) is designed to meet the needs of the Super Heavy Element (SHE) research and material sciences user programs at GSI in Darmstadt. The HELIAC is planned for construction at GSI in Darmstadt. The beam energy can be varied smoothly between 3.5 and 7.3 MeV/u, with an average current of up to 1 emA and a duty cycle of 100 %....
The superconductor linear accelerator LINAC of SPIRAL2 at the GANIL facility is in operation since October 2019. The 26 superconducting quarter wave resonators (QWR) of the LINAC are integrated into 19 cryostats and cooled down at 4 K by a dedicated refrigeration system. These superconducting cavities are operated at a nominal gradient of 6.5 MV/m but most of the cavities can be operated up to...
A 591 MHz superconducting RF cavity is designed for the Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC), providing an accelerating voltage of up to 4 MV. Based on the requirements for Robinson stability and suppression of multipacting effects, four key physical parameters are specified: the fundamental mode frequency should be 591 MHz ± 0.1 MHz; the R/Q of the fundamental mode...
The European Spallation Source (ESS) superconducting proton linac is currently undergoing commissioning. During the initial operation phase, the final beam energy will be about 800 MeV, reaching a 2 MW power. High reliability and availability are crucial for the success of the ESS science programs and thus operations will be maintained even with failures of main linac components such as...
The main accelerator of Shanghai High Repetition Rate X-ray FEL and Extreme Light Facility (SHINE) is an 8 GeV CW superconducting RF linac, which constructed by superconducting modules (8 X 9-cell 1.3 GHz TESLA type cavities). This article introduces the cavities progress that Beijing HE-Racing Technology Co., Ltd. (HERT) fabricated for SHINE.
The CEPC (Circular Electron-Positron Collider) is a 100-kilometer circular collider designed to operate at center-of-mass energies ranging from 90 GeV to 360 GeV, with the primary physics program targeting Z and W bosons, Higgs bosons, and top-quark pair (ttbar) production. Following the publication of its Technical Design Report (TDR) in 2024, the project has now entered the Engineering...
Since 2018, IJCLab is involved in PIP-II project on the design, development and qualification of accelerator components for the SSR2 (Single Spoke Resonator type 2) section of the superconducting linac. All pre-production components (cavity, coupler and tuner) have been fabricated and qualified either at IJCLab (tuner and cavity) and/or at FNAL (coupler and cavity). This paper will summarize...
Next-generation, thin-film surfaces employing Nb3Sn, NbN, NbTiN, or other compound superconductors are essential for reaching enhanced RF performance levels in SRF cavities. However, optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University developed and commissioned a chemical...
The power upgrade project of the China Spallation Neutron Source(CSNS-II) was officially launched in 2024. It will upgrade the accelerator complex five times its current beam power capability, from 100 kW to 500 kW. A key component of the project is the superconducting linac(SCL), designed to accelerate an H- beam of 43 mA peak current from 80 MeV to 300 MeV. The SCL is composed of two...
The development of compact, SRF-based accelerators for applications beyond research is experiencing notable advancements due to the use of cryocoolers for conduction cooling instead of traditional liquid cryogens. Following the successful demonstration of a single-cell cavity operated through conduction cooling with three two-stage cryocoolers, Jefferson Lab has made strides in the operation...
The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA joined the international collaboration in 2018 and will deliver 10 low-beta cryomodules as In-Kind Contributions to the PIP-II project, with cavities supplied by LASA-INFN (Italy) and VECC-DAE (India), and...
Thermal management of high-power input couplers is a critical challenge in conduction-cooled superconducting accelerators. This work presents a low thermal load input coupler design featuring a detachable electromagnetic shield, effectively directing microwave-induced heat toward the 50K region. RF and thermal simulations confirm its efficient power transmission and reduced heat load at...
A high-power input coupler was developed to transmit 100 kW-class RF power in continuous wave (CW) mode to a 1.3 GHz conduction-cooled superconducting accelerator. Both RF and thermal design optimizations were carried out to ensure efficient performance and compatibility with cryogenic constraints. Results of RF simulations showed a reflection coefficient of S1,1 = −44 dB at 1.3 GHz and a...
The Chinese initiative Accelerator Driven Subcritical System (CiADS) proposed by the Insitute of Modern Physics (IMP) will use 58 650 MHz input power couplers for low β and high β elliptical superconducting cavities, for continuous wave power up to 130 kW. Pre-design of 650 MHz couplers has been completed. In order to validate the performance of these couplers and effectively eliminate soft...
High-power, compact, continuous-wave (CW) linear electron accelerators with beam energies of up to 10 MeV are being considered for possible industrial applications. Conduction-cooled, superconducting radio-frequency (SRF) technology allows operating such machines at high electrical efficiency, thereby reducing the operating cost significantly. A prototype conduction-cooled SRF cryomodule has...
The Compact Linear Collider (CLIC) Damping Rings (DRs) must generate ultra-low emittance bunches to achieve high luminosity. This requires many wigglers with high energy loss, compensated by the RF system. The resulting strong beam loading transients pose a major challenge for RF system design. A novel 2 GHz SRF cavity with an ultra-low R/Q below 1 Ω is proposed to minimize these transients....
Thomas Jefferson National Accelerator Facility (JLab) is leading the design and fabrication of all superconducting radiofrequency (SRF) cryomodules for the Electron-Ion Collider (EIC), to be built at Brookhaven National Laboratory (BNL). To achieve head-on luminosity at the interaction point, the EIC will employ SRF Radiofrequency Dipole (RFD) crab cavity cryomodules to compensate for the 25...
High-Pressure Rinsing (HPR) is one of the most im-portant processes in achieving high performance of SRF cavities. The geometry of SSR cavities differs significant-ly from that of HWR and QWR cavities. To upgrade the HPR process of SSR cavities, it is important to under-stand how much of the inner surface area can be effective-ly reached by the waterjet from HPR nozzles. HPR simu-lation...
In new-generation synchrotron light sources, triple-radio-frequency (triple-RF) systems are proposed to meet larger bunch lengthening requirements and enable specific longitudinal injection conditions. In this talk, we will present beam dynamics analysis for the superconducting triple-RF system designed for the Hefei Advanced Light Facility (HALF) storage ring. We will demonstrate that a...
The introduction of zirconium to niobium SRF cavities suggests a promising alloy with lower RF losses, higher critical magnetic fields, and a higher endurance to gradients. However, difficulties in fabrication of a ZrNb alloy, especially on the irregular surface of SRF cavities, have slowed the applicatory study of this potential improvement. We utilize a newly commissioned chemical vapor...
At the electron accelerator for beams with high brilliance and low emittance (ELBE), the second version of a superconducting radio-frequency (SRF) photoinjector was brought into operation in 2014. After a period of commissioning, a gradual transfer to routine operation took place in 2017, so that now up to 1800h of user beam are generated every year. In addition to this standard mode with a...
Comprehensive RF characterization of superconducting materials in a large range of multiparameters plays a pivotal role in research both on exploring material limits and understanding RF loss mechanism. This is particularly critical for emerging thin-film superconductors such as Nb₃Sn and superconducting-insulator-superconducting (SIS) heterostructures (e.g., NbTiN-AlN-Nb). The Quadrupole...
The SHINE project is a high-repetition-rate hard X-ray Free Electron Laser (XFEL) facility driven by a superconducting RF linear accelerator with an energy exceeding 8.0 GeV. The linear accelerator (LINAC) of SHINE consists of six hundred 1.3 GHz 9-cell cavities for acceleration, producing photons with energies ranging from 0.4 to 25 keV. This study focuses on the first single-cavity...
Niobium films are crucial for superconducting radiofrequency cavities and two-dimensional superconducting transmon qubits. However, performance issues such as the medium-field Q-slope in Nb film cavities and microwave dissipation in qubits persist. To identify the limiting factors in Nb film performance, we used DC biased high-power impulse magnetron sputtering to deposit niobium films onto a...
Field emission and multipacting are critical factors that limit the achievable operational gradient of superconducting radio frequency (SRF) cavities. Plasma processing has been demonstrated as an effective in-situ technique for mitigating hydrocarbon-induced field emission and multipacting across a range of cavity geometries. In this work, we present the initial development and subsequent...
The superconducting Radiofrequency Dipole (RFD) crab cavities for the Large Hadron Collider’s High-Luminosity upgrade (HL-LHC) incorporate hook-style Horizontal Higher-Order Mode (HHOM) couplers to extract and damp HOMs, minimizing beam-cavity interactions. These couplers, fabricated from high-purity niobium, must maintain superconductivity under operational conditions at 2 K. As part of the...
This paper presents the key aspects of the cryogenic integrated control system for the ESS superconducting linear accelerator and its importance during the first operational experience in a LINAC configuration, enabling 2 MW beam power and beyond. This unified system is controlled by a master PLC managing the full CMDS (Cryomodules and Cryogenic distribution System) consisting of 43 cells,...
Plasma ignition studies have been initiated at IJCLab since 2022. These are focusing on “in situ” plasma decontamination of SRF cavities with complex geometries as Quarter Wave Resonator (QWR) and Single Spoke Resonators (SSR). IJCLab being strongly involved in PIP-II project and in particular in the qualification test of SSR1- and SSR2-type resonators, the vertical cryostat has been upgraded...
High-performance SRF cavities are of central importance for many future projects and can only be realized through international collaboration. A key challenge is the standardization of parameters for chemical etching, heat treatment, and vertical testing. We have observed small but significant differences in the parameters defined locally across laboratories. In parallel with collaborative...
Field emission is a major parasitic phenomenon that limits the performance of superconducting RF (SRF) cavities. It leads to the generation of dark currents and bremsstrahlung gamma rays, which in turn cause increased cryogenic load, local heating, and in severe cases, cavity quench. Moreover, the high dose rates produced in the proximity of the cavity can result in material damage and...
The grinding process plays a crucial role in the fabrication of sub-components for 325 MHz spoke SRF cavities. During the forming and manufacturing stages, various defects can occur, which are addressed through grinding. This study aims to examine the effect of different grit sizes and explore how these sizes correlate with defect measurements. Optical microscopy and scanning electron...
Medium Grain Niobium (MG Nb) is a cost-effective material compared to Fine grain Nb (FG Nb) that has isotropic mechanical properties and can clear the high-pressure gas safety criteria for a 1.3 GHz 9-Cell jacketed Tesla cavity. At KEK, various high Q – high G surface treatments have been applied to the 1-Cell MG Nb cavities and its performance has been measured via vertical tests, with and...
Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) is an experimental accelerator-driven system in development at SCK-CEN. It will allow fuel developments, material developments for GEN IV systems, material developments for fusion reactors and radioisotope production for medical and industrial applications. First phase of the project called MINERVA currently in...
High-Q three-dimensional (3D) superconducting cavities are often used for quantum application including dielectric constant measurement, quantum memory[1], and dark matter detection[2]. In these experiments, a high-Q cavity is integrated with a superconducting qubit, which yields circuit-based Quantum Electrodynamics (cQED) architecture. The cavity geometry employed for quantum applications is...
The Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) project has entered its construction phase. This state-of-the-art facility includes an 8 GeV electron linear accelerator, which utilizes superconducting radio frequency (SRF) cavities. Each cryomodule within the accelerator comprises eight standard TESLA 1.3 GHz 9-cell superconducting cavities with two Higher Order Modes...
Recently, 1.3 GHz 3-cell superconducting cavities were proposed for the injector of the high-brightness free electron laser based on the energy recovery linac scheme. In the injector section, three cavities are required to accelerate a 10 mA electron beam to 10 MeV. The diameter of the beam pipe is increased to 100 mm to damp higher order modes (HOMs), which may lead to beam quality...
CEPC is engineered to function in four distinct operational modes (Higgs, W, Z-pole, and t-tbar), supporting a broad spectrum of beam parameters. The collider's beam energy ranges from 45.5 to 180 GeV, with a beam current varying from 5.6 mA to 1.4 A, and a synchrotron radiation (SR) power output ranging from 30 to 50 MW. The collider is a double-ring with shared cavities for Higgs operation...
Cylindrical shell silicon carbide (SiC) higher-order-mode (HOM) beamline absorbers (BLA) were developed and high-power tested for the 591 MHz single-cell superconducting radio frequency (SRF) cavities in the Electron Storage Ring of the Electron-Ion Collider. The material properties of the BLA are crucial for HOM damping and wakefield performance. However, discrepancies were observed between...
Medium-temperature baking (Medium-T Baking) has emerged as a key technique for enhancing SRF cavity performance, with multiple studies attributing its efficacy to oxide decomposition and oxygen diffusion. In-situ high-resolution transmission electron microscopy (HRTEM) enables real-time, atomic-scale visualization of dynamic structural changes, providing an ideal platform for probing Nb oxide...
This contribution outlines the current status and recent progresses of INFN LASA’s in-kind contribution to the PIP-II project at Fermilab. It focuses on key manufacturing activities, on preliminary inspection results on sub-components and on upgrades to cavity testing infrastructures. The production of the 38, 5-cell, β = 0.61 SRF cavities designed by INFN LASA for the LB650 section of the...
Two Prototype 1.5 GHz fundamental power couplers for the VSR (Variable pulse length Storage Ring) DEMO project at Helmholtz Zentrum Berlin (HZB), were produced by Research Instruments (RI) and Thales, with the aim to reach 16 KW CW. To allow for conditioning of the couplers in cold a dedicated coupler test stand was designed, installed and commissioned, creating a testing environment that...
Niobium-3 tin Nb3Sn is a promising material for next-generation superconducting RF cavities due to its high critical temperature and high theoretical field limit. There is currently significant worldwide effort aiming to improve Nb3Sn growth to push this material to its ultimate performance limits. In this paper, we present the first results of deposition of Sn on different Nb samples in...
The first commissioning run of the superconducting cryomodules at the European Spallation Source (ESS) provided important insights into the performance of the cryogenic systems. This paper reviews the cryogenic operations, with a focus on cooldown processes, pressure control, temperature stability, and overall system reliability. The effectiveness of individual helium bath pressure regulation...
The ILC Technology Network (ITN) in Europe, in close collaboration with KEK and key institutions including CEA, CERN, INFN, is actively driving the development of advanced superconducting radiofrequency (SRF) technologies to support the realization of the International Linear Collider (ILC). The ITN-EU initiative focuses on developing and validating cost-effective, high-performance cavity...
The trapping of magnetic flux during the transition of a superconducting radio frequency (SRF) cavity can substantially increase RF dissipation in the cavity walls, leading to a reduction in Q0, that in turn can increase cryogenic costs. The impact of trapped magnetic flux can be reduced by either suppressing the ambient magnetic field or by limiting/removing the influence of pinning sites in...
The successful development of Nb3Sn/Cu coatings for the SRF cavities of next generation particle accelerators would allow for the operation of the SRF system at 4.5 K, resulting in a reduction of the needed cryogenic power by a factor 3 with respect to what normally needed for bulk Nb cavities, operated at 2 K. In the framework of I.FAST and ISAS collaborations, an optimized recipe for Nb3Sn...
Taiwan Light Source (TLS) is a third-generation synchrotron light source located at NSRRC in Taiwan, operating at an electron energy of 1.5 GeV. The original RF system of TLS utilized two normal-conducting Doris cavities. In 2005, these were replaced with a single CESR-B type superconducting RF (SRF) module, which significantly improved the system's stability and enabled an increase in the...
The pulsed linac at EuXFEL, operated by DESY, is de-signed to deliver up to 2700 electron bunches during a beam delivery time of 600 µs within an RF flat-top time of 650 µs. The user community would like to have more photon pulses. This can be done only by increasing RF flat-top length. The whole RF pulse length at the linac is limited by several factors, primarily the RF pulse length in the...
The qualification of 325 MHz Single Spoke Resonators type 2 (SSR2) jacketed cavities to meet technical requirements represents a significant milestone in the development of the SSR2 cryomodules for the PIP-II Project at Fermilab. This poster reports the procedures and lessons learned in processing and preparing these cavities for horizontal cold testing prior to integration into a cavity...
Nb3Sn SRF cavities have attracted increasing attention as a candidate for next-generation accelerators due to their potential to achieve high Q-values even at 4.2 K, enabling operation with conduction cooling. Since 2019, KEK has been developing Nb3Sn single-cell cavities via the vapor diffusion method using Sn and SnCl2 sources. In parallel, a dedicated small-scale coating system was...
To meet the stringent requirements of high-current energy recovery linacs (ERLs), a 1.3 GHz 7-cell superconducting cavity was designed and optimized. The RF design employed multi-objective optimization to balance accelerating mode performance with higher-order mode (HOM) damping, achieving effective HOM suppression without compromising the fundamental mode performance. Key RF components,...
Double Quarter Wave (DQW) superconducting crab cavities will be employed to compensate for the vertical crossing angle in the High-Luminosity LHC (HL-LHC). Four DQW series cavities were manufactured and tested at the CERN vertical test facility. Each cavity undergoes a sequence of cold tests, starting from the bare cavity and progressing to the cavity in its final configuration, with all...
RF testing and performance analysis of low beta superconducting cavity cryomodules are in progress for the two facilities: High Intensity Heavy Ion Accelerator (HIAF) and Chinese initiative Accelerator Driven System (CiADS). This poster describes the status and progress of RF conditioning, plasma cleaning, key cavity parameter identification, cavity operation limits testing, and stability...
As part of the High Luminosity LHC (HL-LHC) project, crab cavities will be installed around CMS and ATLAS experiments of the LHC. To accommodate the different crossing angle planes, two cavity designs have been selected: the RF Dipole (RFD) and the Double Quarter Wave resonator (DQW).
Two prototype RFD cavities were fabricated and successfully tested at CERN. Subsequently, the cavities were...
Sustainability and cost reduction are key factors for the development of future large particle accelerators. This has led INFN LASA to start an INFN-funded R&D program dedicated to studying and improving the performance of SRF Nb cavities in terms of quality factor (High-Q) and accelerating gradient (High-G). Moreover, the R&D program is also pushed by the INFN LASA contribution to...
STFC is responsible for delivering 20 high-beta 650 MHz cavities for the PIP-II project, with industry partners now producing series cavities. Both pre-series cavities have set world records in performance and cleanliness, meeting the project’s stringent requirement for field emission-free operation, accelerating gradient, and Quality factor. Achieving this milestone required an...
650 MHz multicell superconducting radio frequency (SRF) elliptical cavities are developed for stable acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities with optimum beta equal to 0.62 and 0.82, respectively, were proposed to boost the beam energy from 175 MeV to 500 MeV, with the capabilities to upgrade the energy...
The 650 MHz high power coupler has been designed and developed by IMP for medium-high beta elliptical superconducting cavities in the Chinese Initiative for Accelerator Driven Subcritical Systems (CiADS) project, delivering an average power of 130 kW. The coupler incorporates a door knob conversion structure, 75 ohm coaxial structure and dual warm window structure to achieve long term stable...
The European Spallation Source (ESS), as one of the complex accelerators require installation and commissioning of many systems and components. One of them is the accelerator line which is composed with the cryomodules uses to accelerate of the particles. Taking into account that ESS is one of the most technological advanced accelerators in Europe we can expect also that accelerator line is...
A heavy-ion accelerator facility was constructed for the Rare Isotope Science Project (RISP) at the Institute for Rare Isotope Science (IRIS) in Daejeon, Korea. The cryomodule with quarter-wave resonators (QWRs) and half-wave resonators (HWRs) was installed in the SCL (Superconducting Linac) 3 tunnel, and the beam commissioning (Beam energy = 16.4 MeV/u, 40Ar8+) has been completed. The...
The relationship between crystal orientation and the strength of single-crystal niobium was evaluated. First, several single-crystal blocks were cut from a niobium ingot, and bar tensile testing specimens were taken from each block. In previous studies, a niobium ingot was sliced to produce a disk, from which a small single-crystal flat specimen was cut; however, this time, round bar specimens...
The high-purity niobium material used in the superconducting cavities is an ingot produced by electron beam melting, and is a polycrystalline with a grain size of 10 to 200 mm. Niobium sheets sliced from ingots contain large grains and called as large grain (LG). Superconducting cavities made from LG niobium have the advantages of a high maximum acceleration gradient, Q value, and low...
Niobium-based superconducting radio-frequency (SRF) cavities are crucial for particle accelerators, yet their performance is limited by native niobium oxide formation, which contributes significantly to increased residual surface resistance. This oxidation challenge is similarly critical in superconducting quantum circuits, where niobium oxide layers adversely impact coherence times and device...
The testing and delivery of 86 704 MHz high-beta superconducting RF (SRF) cavities as part of an In-Kind-Contribution (IKC) by Accelerator Science and Technology Centre (ASTeC) for the European Spallation Source (ESS) facility in Lund, Sweden has just been completed. The cavities have been manufactured by industry, Research Instruments in Germany, and have been tested at Daresbury Laboratory...
The precise and efficient testing of the RF performance of superconducting radio frequency (SRF) samples under superconducting conditions serves as the fundamental support for developing new SRF materials. The traditional SRF material RF performance testing systems have technical bottlenecks such as strong dependence on liquid helium, long testing cycles, and high operating costs. In this...
The collaboration research is conducted according to the ITN (ILC Technology Network). As a part of research into the manufacturing methods for SRF cavities used in ILC (International Linear Collider), two 1.3 GHz single-cell cavities were fabricated by utilizing fine and medium grain size niobium materials, respectively. Those cavities are manufactured by KAT Co., Ltd. in Korea under the...
The study of higher order modes (HOM) excited in the pulse mode superconducting Linac of CSNS-II is presented in this paper. The effects of cryogenic losses and influences on beam dynamics caused by the HOMs have been investigated.
The China Spallation Neutron Source II (CSNS - II) necessitates 10 cryomodules equipped with double - spoke cavities and 8 cryomodules equipped with elliptical cavities to achieve the acceleration of H⁻ ions from 80 MeV to 300 MeV. Prior to their installation into the tunnel, each cryomodule must undergo horizontal testing and obtain certification. This paper will elaborate on the results of...
Stainless steel bellows are used to connect the 197 MHz superconducting crab cavities, to compensate for the cavity displacement due to cryogenic temperature changes. The impedance of the bellows should be evaluated for both wakefield effects and the potential high order trapped modes. In the nominal bellows one longitudinal trapped mode was found at 2252 MHz, located between two nearby...
INFN-LASA has successfully completed its in-kind contribution to the European Spallation Source Eric, delivering 36 superconducting medium beta cavities for the ESS Linac. These cavities are designed to increase the energy of the proton beam from 216 MeV to 571 MeV. In addition, four spare cavities are being fabricated. This article outlines the performance of the cavities delivered so far and...
As part of the upgrade of the Elettra synchrotron ring to Elettra 2.0, an upgrade and expansion of the helium liquefaction plant is also planned. The current cryogenic system is based on a Kaeser He compressor and a Helial 1000 cold box liquefier/refrigerator, with a Siemens S7-00 PLC-based control system, currently connected exclusively to the superconducting third harmonic cavity...
A novel vertical test facility (VTF) has been in operation at the UKRI-STFC Daresbury Laboratory since 2019. This VTF tests jacketed SRF cavities in a horizontal configuration at 2 K. Originally designed and operated for 704 MHz high-beta cavities for ESS, the facility has now been upgraded and expanded to test 650 MHz high-beta cavities for PIP-II, including fast cooldown capability (>20...
To support the ILC Technology Network (ITN) Cryomodule project at KEK, we have constructed and assembled six single cell cavities, four fine grain (FG) and two medium grain (MG) for vertical testing (VT). A series of surface treatment were applied to the cavities using the proposed recipe for the construction of the International Linear Collider (ILC). This recipe consists of four steps: bulk...
There is increasing awareness within the global community of the need for meaningful actions on energy consumption and sustainability. High energy physics installations consume large quantities of energy and non-recoverable resources. Existing operation is being challenged to reduce consumption and new projects are being scrutinized for a full life cycle impact. Future developments of...
IMP is currently constructing three major SRF linacs: the High Intensity Heavy Ion Accelerator (HIAF), the China Initiative Accelerator Driven System (CiADS), and the Isotope Platform based on a high current superconducting linac (IP-SAFE), and operating one superconducting linac for Super Heavy Elements (CAFE2). This talk will report recent progress of these projects with emphasis on SRF...
The European XFEL is in operation since 2017 with a maximum energy of 17.5 GeV in short-pulse (SP) mode, consisting of 0.65 ms-long bunch trains at 10 Hz repetition rate. The accelerator can deliver up to 2700 electron bunches every 100 ms, with a spacing between bunches of 220 ns. After eight years of successful operation the accelerator team, with strong support from the XFEL strategy...
The China Spallation Neutron Source (CSNS) is the fourth pulsed accelerator-driven neutron source in the world. Meanwhile, it is one of the core large-scale scientific facilities of the Guangdong-Hong Kong-Macao Greater Bay Area Comprehensive National Science Center. The planned China Spallation Neutron Source Phase II (CSNS-II) started construction in 2024 and is scheduled to be completed in...
A specialized setup was designed to carry on a mid-T baking of SRF niobium cavities. It utilizes resistive heaters installed on the outer cavity walls, with a cryostat serving as a vacuum vessel. Based on our material studies with the real-time in-situ synchrotron XPS, a single-cell 1.3 GHz cavity was thermally treated in the regime providing contamination-free oxygen doping of niobium. RF...
The heat treatment of SRF cavities at medium temperature (250 °C to 350 °C), also known as “mid-T heat treatment”, is one of the R&D activities at DESY towards a high-duty-cycle (HDC) upgrade of the European XFEL. Such treated cavities exhibit an improvement in the quality factor Q0 (3E10 to 5E10) at a moderate accelerating electric field strength Eacc (10 MV/m to 20 MV/m) compared to EuXFEL...
Theories predict that Superconducting-Insulating-Superconducting (SIS) multilayers delay vortex penetration allowing for operation gradients more than twice of bulk Nb cavities and significantly higher Q-values [1]. The University of Hamburg focuses on Atomic Layer Deposition (ALD) as the most promising technique to coat SIS multilayers. A proof-of-principle experiment to coat cavities with an...
This talk will make a report on investigating performance of Nb thin films and in particular: effect of sequential heat treatments on mid field Q-slope and quench of Nb thin films effect of film vs bulk vs the Nb oxide in losses of the films in the quantum regime. This innovative study investigates a thin film of HiPIMS niobium deposited on a bulk niobium cavity. Measurements at FNAL...
KEK has performed R&D toward Nb3Sn accelerator. Investigation is carried out to optimize coating parameters, such as amount of Sn, process of nucleation, coating and annealing, toward realize higher performance of cavity. Simultaneously study on conduction cooling by cryo-cooler and design of Nb3Sn cryomodule are ongoing. Currently horizontal cryostat for Nb3Sn cavity is under construction and...
Hydrofluoric acid (HF)-free bipolar pulsed electropolishing (BPEP) offers an environmentally sustainable alternative to conventional Buffered Chemical Polishing (BCP) and Electropolishing (EP) techniques for superconducting radiofrequency (SRF) cavities. Recent studies at Jefferson Lab have demonstrated that a single-cell 1.3 GHz niobium cavity processed using HF-free BPEP achieved an...
The performance of superconducting radio frequency (SRF) cavities is critically influenced by surface preparation. Traditionally, electropolishing (EP) has been employed to achieve a clean, low-roughness surface on both niobium (Nb) and copper (Cu) substrates, despite requiring harsh and corrosive acids. Since 2019, our research at LNL has focused on an alternative approach: Plasma...
Improvement in SRF accelerator performance after in-tunnel plasma processing has been seen at SNS and CEBAF. Plasma processing development for FRIB quarter-wave and half-wave resonators (QWRs, HWRs) was initiated in 2020. Plasma processing on individual QWRs (beta = 0.085) and HWRs (beta = 0.53) has been found to significantly reduce field emission. A challenge for the FRIB cavities is the...
Plasma processing has emerged as a powerful tool for restoring and sustaining the performance of SRF cavities over long-term operation. While well-established for elliptical cavities, its application to low-beta structures presents new challenges due to their complex geometries. To address this, we developed optimized plasma processing techniques for a quarter-wave resonator (SPIRAL2 QWR) and...
Specific heat treatments applied to superconducting radio-frequency (SRF) cavities, such as nitrogen infusion or Mid-T baking, aim to improve the quality factor (Qo) at medium accelerating fields (~10–20 MV/m). These treatments reduce the BCS surface resistance by tuning the mean free path of niobium over a few hundred nanometers, either by diffusing oxygen from the native oxide layer or by...
Electron-Ion Collider (EIC) is a next generation particle accelerator to be built at Brookhaven National Laboratory, in partnership with Thomas Jefferson National Accelerator Facility. In Electron Storage Ring (ESR), 18 single-cell 591 MHz SRF cavities are required to compensate for energy loss from synchronic radiation. Effective damping of higher-order-modes (HOMs) is also critical to ensure...
In modern particle accelerators, multiple superconducting cavities are often driven simultaneously by one high-power klystron, thereby reducing the cost of the power supplies. The CEPC TDR specifies 96 cryomodules for 650 MHz 2-cell cavities, with each cryomodule originally housing two cavities. During the horizontal testing phase, however, we plan to simultaneously drive six superconducting...
Superconducting Radio Frequency (SRF) technology is a key component in many particle accelerators operating in a continuous wave, or high duty cycle, mode. The on-line performance of SRF cavities can be negatively impacted by the gradual reduction in the accelerating gradient that can be attained within a reasonable field emission level. Conventional cleaning procedures are both time- and...
As for all superconducting radio-frequency (SRF) cavities preserving the performance during accelerator operation is even more essential for an SRF gun, because the accelerating field is typically very high and cannot be compensated by a neighboring cavity. One of the main limiting factors remains field emission, that is originating either from particulates or hydrocarbon contaminants on the...
The Linear IFMIF Prototype Accelerator (LIPAc) is a deuteron linear accelerator (linac) designed to validate the acceleration of a 125-mA beam up to 9 MeV in continuous wave (CW) operation, contributing to the realization of the IFMIF project. The 125-mA deuteron beam is initially accelerated to 5 MeV by a radio-frequency quadrupole (RFQ) and subsequently to 9 MeV by a superconducting...
During the present technical commissioning run of the ESS linac several measurements were taken to extract beam properties (e.g. phase and current) on the base of beam transient induced voltage and comparing with beam diagnostic based measurements.
High-intensity accelerators, particularly Accelerator-Driven Systems (ADS), require high availability and reliability for proper operation. For superconducting linear accelerators, the ability to continue operating even when one of the RF cavities fails is key to achieving the required availability, known as cavity compensation. Beam dynamics studies of the JAEA-ADS linear accelerator have...
Coating Nb with thin superconducting layers (with or without insulating layers, i.e., SS or SIS) with longer penetration depth λ can enhance the accelerating gradient by maintaining the Meissner state above each layer’s superheating field Bsh, due to reduced surface screening currents and interfacial energy barriers. We review previously published studies using radioactive beam-based...
In the last years, low frequency gravitational waves (GWs) have been consistently measured by the LIGO-Virgo collaboration, but little to no attention has been paid to higher frequencies GWs in the range of 10 kHz to 100 MHz, at which confirmation for current theories or even new physics could be hidden. The MAGO 2.0 project aims at filling this gap in the parameters space using...
The Linear IFMIF Prototype Accelerator (LIPAc) is designed as a high-current deuteron linear accelerator (linac) capable of accelerating a 125-mA beam up to 9 MeV in continuous wave (CW) mode. The RFQ linac and subsequent beam transport lines equipped with several diagnostics successfully commissioned a 119-mA deuteron beam with an 8.75% duty cycle. The superconducting RF (SRF) linac is the...
The BESSY Variable pulse-length Storage Ring (VSR) Demo project aimed to provide short and long pulses simultaneously in the BESSY II storage Ring. To achieve this goal HZB has developed high current Continuous Wave (CW) Superconducting Radio Frequency (SRF) cavities operating at 1.5 GHz for 300 mA beams with large damping capabilities to cope with the HOM powers expected. This paper presents...
The design of the ten additional CEBAF Upgrade Cryomodules leads to significantly higher fault rates than the 40 original cryomodules, due to sensitivity to microphonics. Cartridges that compress pellets of boron nitride nanotubes (BNNT) are mounted in parallel to the SRF cavities of two refurbished Upgrade Cryomodules. Now substituted into CEBAF, these cryomodules exhibit significant...
Previous research has shown that Nb3Sn cavities with tin-rich grain boundaries tend to show significant Q-slope behavior, while cavities with grain boundaries of the “ideal” 25 %-tin composition have higher quality factors and reach higher quench fields. In this paper, we make the case that it is possible to improve the properties of Nb3Sn grain boundaries even further. We use...
The RF accelerating module is crucial for imparting kinetic energy to particle beams in accelerators. Superconducting RF (SRF) technology offers key advantages over conventional room-temperature RF systems, including lower operational costs, reduced beam loss, and higher accelerating power. The superconducting cavity, SRF's core component, requires ultra-low temperatures. While liquid helium...
This report presents the design of an MTCA.4-based low-level radio frequency (LLRF) tuning controller for the Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL). A standard 1.3 GHz cryomodule at S3FEL comprises eight superconducting cavities, each requiring one slow tuner motor control, two fast piezoelectric actuator (PZT) controls, and an additional motor control for high-power...
A 5-year project called MEXT Advanced Accelerator element Technology Development began in FY2023 at KEK. The goal of this project is to manufacture one cryomodule (CM) that meets the requirements of International Linear Collider (ILC) and to test completed CM at cryogenic temperature. ILC model CM consists of nine cell superconducting cavities, magnetic shields, power couplers, tuners, cooling...
The QWR/HWR cavity cryomodules have been designed for High Intensity heavy-ion Accelerator Facility (HIAF) at the Institute of Modern Physics (IMP) of the Chinese Academy of Science (CAS). There are 17 cryomodules operating at 2 K&3130 Pa of HIAF linac, which consist of 6 QWR007 cryomodules and 11 HWR015 cryomodules, respectively. These cryomodules are being processed in the vendor currently....
The superconducting linac is proposed for effective acceleration of proton beam in a new project of China Institute of Atomic Energy. A 975MHz superconducting radio frequency cavity is designed to accelerate the H+ ion beam in the energy range from 500 MeV to 1000 MeV. This paper will present the design and simulation， including the multi-parameter electromagnetic design and optimization,...
RF testing is a key element in the development of super-
conducting thin film coated cavities. In order to optimize the
deposition process, tests initially focussed on flat samples,
before moving on to RF cavity tests, however the jump from
flat samples to cavities is large and often requires signifi-
cant changes to the deposition process. In order to develop a
multi-step approach to...
Nb₃Sn in the form of thin film on copper is one of the most promising routes in the field of superconducting radio-frequency accelerating cavities for future colliders. At INFN – Legnaro National Laboratories, thin films of Nb₃Sn have been successfully deposited on small copper samples via DC magnetron sputtering the process enabled the production of films with critical temperature > 17 K, at...
SPIRAL2 is a state-of-the-art superconducting linear accelerator for heavy ions. The radiofrequency operation of the linac can be disrupted by anomalies that affect its reliability. This work leverages fast, multivariate time series postmortem data from the Low-Level Radio Frequency (LLRF) systems to differentiate anomaly groups. However, interpreting these anomalies traditionally relies on...
Fermilab is one of the leaders in development of vapor diffused Nb3Sn films inside niobium cavities. This material has a higher critical temperature (Tc) than niobium, enabling cavity operation at 4.2 K. This higher operational temperature significantly reduces the infrastructure required for cooling compared to 2 K systems, making superconducting radio-frequency (SRF) technology more...
Electropolishing (EP) is used for the surface treatment of Nb cavities used in superconducting accelerators. The electrolyte for Nb material EP is a mixture of hydrofluoric acid and sulfuric acid, which makes EP work in Nb cavities very expensive. In this study, the development of a new EP method for Nb cavity using fluoride salts and organic solvents will be reported. The organic solvents...
A new surface treatment method is being developed, wet nitrogen doping, in which nitric acid is added during electro-polishing (EP). In the first trial on a FRIB beta = 0.53 half-wave resonator (HWR), a high quality factor (Q0 = 8E10) was observed at 2 K at low field (accelerating gradient ≤ 0.5 MV/m) without an anti-Q slope. It is known that the Q0 can be increased by shortening the mean...
The International Linear Collider (ILC) is a future linear collider that uses superconducting accelerating cavities. In the scope of the ILC Technology Network (ITN), an ILC prototype cryomodule featuring 8 cavities is being developed and built at KEK. The cavities will be driven by a 10 MW multibeam klystron located about 200 m away from the test stand. The WR650 and WR770 are commonly used...
HZDR has done pioneering work in the field of the superconducting photoelectron source (SRF gun). The development began more than 20 years ago with the first proof of concept experiment. This was the first time worldwide that electrons were generated from a normal-conducting semiconductor photocathode within a superconducting half-cell resonator [1]. Convinced by this success the work was...
As the application of superconducting cavities becomes increasingly widespread, the development of cost-effective coatings with enhanced performance has become a focal point for researchers. This study primarily focuses on depositing niobium-niobium-tin (Nb3Sn) multilayer thin films on the inner surface of a 6 GHz copper half-cell via the co-sputtering method. The emphasis is on preparing...
In the context of future accelerator studies, niobium coating of copper-based cavities plays a key role in achieving an optimal balance between radio-frequency performance and cost-effectiveness.
Recent advancements have focused on the development of bulk-machined elliptical cavities, featuring a seamless, weld-free equator. By optimizing the design of machining tools, the machining...
Field emission (FE) remains a significant hurdle for achieving optimal performance and reliability in superconducting radiofrequency (SRF) cavities used in accelerator cryomodules. A thorough understanding of the generation and propagation of FE-induced radiation is therefore essential to mitigate this problem. The absence of standardized measurement protocols further complicates the...
Particulate contamination in SRF cavities is known to trigger field emission, a phenomenon where electrons tunnel out from the surface of the cavities due to high electric fields. These rogue electrons limit the achievable accelerating gradient, affecting the final beam energy delivered by the accelerator. The TRIUMF e-Linac and ISAC-II heavy ion accelerators see a progressive onset of field...
The development of an easy and inexpensive Nb sheet preparation process, based on metallographic polishing has been presented earlier [1,2]. The aim is to remove the damage layer issued from the rolling process on the sheet in order to reduce the length of surface treatment on completed cavities. The process has been applied on a QPR sample and tested in RF, without any surface chemistry. Its...
In EIC Electron Storage Ring (ESR), 18 single-cell 591 MHz SRF cavities are required to compensate for up to 10 MW energy loss from synchronic radiation. There are two FPCs to deliver 800 kW RF power to each cavity. The FPC was design and under prototyping. This paper presents the FPC design and manufacture progress of FPC.
The SRF community has shown that high temperature annealing can improve the flux expulsion of niobium cavities during cooldown. The required temperature will vary between cavities and different batches of material, typically around 800 C and up to 1000 C. However, for niobium with a low residual resistance ratio (RRR), even 1000 C is not enough to improve its poor flux expulsion. The purpose...
At the Superconducting RIKEN Linear Accelerator (SRILAC), auxiliary control and monitoring tasks for the RF system, such as RF voltage and power readout, feeder control, and tuner adjustments, are managed using a Mitsubishi MELSEC iQ-R series programmable logic controller (PLC). This PLC is directly connected to the FPGA-based LLRF controller, forming an integrated system for low-level RF...
In order to reduce the cost of superconducting cavities, research has been actively conducted in recent years to realize inexpensive cavities by making the cavity body out of copper and coating the inside with niobium to induce superconductivity. The inner surface of the accelerating cavity must be smooth, and a seamless cavity is ideal as a base for the coating. We came up with the idea of...
A method to enhance ATLAS low-beta superconducting cavities has been developed at Argonne National Laboratory in collaboration with MSU/FRIB, Fermilab, IJCLab, JLab, and BNL. At the center of the accelerator, a cryostat containing seven 72 MHz QWR installed in 2014 has world-leading performance for ion linacs at v/c~0.1, though performance has been reduced by ~20 % over the past decade due to...
A dedicated series of tests on the superconducting Medium-Beta and High-Beta cavities has been proposed to determine various parameters critical for future LINAC and LLRF system operation. These studies include measurement of the cavity stiffness coefficient (expressed as the Lorentz Force Detuning factor), evaluation of piezo tuner range and polarity, investigation of piezo capacitance as a...
The LCLS-II-HE project has completed qualification testing of the 9-cell 1.3 GHz cavities and has completed construction and testing of 22 out of 24 new cryomodules. All but 9 cavities out of over 200 tested have met the qualification requirements in vertical test. The cryomodules have met specifications, exceeding the required accelerating voltage by an average of 25 MV per module. Here we...
Field emission (FE) is one of the main issues limiting the performance of superconducting cavities. Various studies have been conducted to mitigate FE using methods such as computer simulations, microscopic surface analysis, plasma processing, and X-ray or temperature mapping. Among these, X-ray and temperature mapping are the most direct methods for localizing FE emitters. However, due to...
A vibrating sample magnetometer (VSM) is being developed with the capability to measure field penetration on ellipsoidal superconducting samples intended for use in superconducting radio frequency cavities. The explicit goal of this machine is to perform field penetration measurements on atomic layer deposition (ALD) coated niobium ellipsoids (ie., thin film MgB2, Nb3Sn on Nb), as well as on...
As the demand for more efficient SRF technology continues to rise, so does the need to improve the performance of Nb3Sn, the most promising alternative to niobium. Leveraging recent breakthroughs in Nb3Sn research from Cornell University and Fermilab, namely the electrochemical synthesis-based growth of Nb3Sn and the centrifugal barrel polishing (CBP) technique to smoothen the final Nb3Sn...
A fundamental-mode power coupler (FPC) for the 591 MHz superconducting RF (SRF) cavities is currently being designed and prototyped for use in the Electron Storage Ring of the Electron-Ion Collider. Due to limitations in power source availability and in consideration of the FPC fabrication schedule, the initial high-power tests of the prototyped FPCs are planned to be conducted using a 704 MHz...
Nb3Sn has great potential to be the next generation superconducting material on the inside of Cu superconducting radiofrequency cavities (SRF) due to its relatively high critical temperature Tc ≈ 18 K compared to other low temperature superconductors e.g., Nb with Tc ≈ 9 K. For Axion detection, cavities might operate below 100 mK, and copper bodies are preferred. Here, we report methods to...
Nb3Sn is a promising alternative to bulk niobium (Nb) for superconducting radio-frequency (SRF) cavities due to its higher critical temperature and superheating field. In this study, Nb3Sn thin films were deposited via DC magnetron sputtering from a stoichiometric Nb:Sn alloy target onto various substrates, including diamond-turned Cu, bulk Nb, and Cu with a Nb bilayer. The influence of...
Thread-mounted cathode installation directly at the backwall of the gun cavity allows cavity cleaning following cathode installation and thus beneficial for RF performance of the injector. Recent vertical tests of the CW L-band SRF gun cavity with a copper cathode installed demonstrated world-record high axial electric fields (up to 50 MV/m). While beneficial for RF performance, photoemissive...
The 82 SRF cavities of the present 2 MW configuration of the ESS Linac have been operated up to their specification during the first technical commissioning run on the temporary beam dump. Operational experience and comparison of cavity performances between vertical tests at the project in kind members and those measured at the cryomodule test stands and in the tunnel is described.
Bogorad et al. proposed Superconducting Radio-Frequency (SRF) cavities with high quality factors as a platform for detecting axions, which are a dark matter candidate, as well as low-energy QED corrections that give rise to photon-photon scattering [1]. The idea is to use the cubic nonlinearity of axion-electrodynamics to detect the axion field by measuring photons at a signal frequency ω3 = 2...
Plasma Electrolytic Polishing (PEP) is under active development at INFN-LNL as a flexible, environmentally friendly alternative to conventional electropolishing (EP). Since 2019, our research has focused on optimizing PEP for a variety of accelerator-relevant materials and geometries, ranging from standard planar samples to complex components, including parts fabricated via Additive...
Plasma treatment has emerged as an effective method for mitigating field emission and recovering the performance of superconducting radiofrequency (SRF) cavities. A collaborative effort involving CEA, ESS, FNAL, and INFN is currently focused on applying this technique to low-beta elliptical cavities for both the ESS and PIP-II linacs. This paper reports on the ongoing work aimed at developing...
Point Contact Tunneling Spectroscopy (PCTS) is a powerful technique ideal for investigating the surface superconducting properties of materials. Since it utilizes the oxides present on the sample’s surface to probe the superconducting density of states, this tool is valuable for studying superconducting devices such as qubits and SRF cavities, where a native or engineered oxide layer is...
Here we investigate the magnetic phase behaviour of an impure superconductor, and predict the critical fields of the Meissner/vortex state in the presence of impurities. To do this, we derive the Gibbs free energy of an impure superconductor immersed in an external magnetic field. We then use this Gibbs free energy to derive modified Ginzberg-Landau equations, which if solved describe the...
A high beam brightness is an important requirement for an electron linear accelerator, with the electron source setting the lower limit for the achievable brightness. A superconducting radio-frequency photoelectron injector (SRF gun) ) stands out as an advanced electron source capable of delivering beams with superior properties compared to other continuous-wave injectors. Currently, SRF guns...
Researches on preparation of Nb3Sn superconducting cavities has been carried at Peking University. Nb3Sn films were prepared by tin vapor method with a high vacuum furnace. We proposed a coating scheme of 1.3 GHz single cell Nb3Sn cavity with three tin sources inside. Nb3Sn films with a tin content of more than 25 % were obtained. The vertical tests show the Q of the prepared Nb3Sn cavities...
Powerful Energy Recovery Linac for Experiments (PERLE) is a compact three-pass ERL project based on SRF technology, being as a new generation machine targeting the 5 MW beam power regime. PERLE will serve as a hub for the validation and exploration of a broad range of accelerator phenomena in an unexplored operational power regime serving for the development of ERL technology for future energy...
We present further progress on a theoretical model linking nanohydride formation to mid- and high-field Q-slope in SRF cavities. Using time-dependent Ginzburg-Landau theory, we calculate Q-vs-E curves for cavities with a range of hydride distributions corresponding to different global hydrogen concentrations and different distributions of hydride nucleation sites. We show that hydrides smaller...
The native oxides of niobium cause surface losses during cavity operation arising from two-level systems/defects (TLS). These losses dominate the quality factor at low accelerating gradients (Eacc < 0.1 MV/m). In particular, the amorphous Nb2O5 is identified as a prominent host for the TLS. Nb2O5 dissociates when the material is baked above 200 °C for several hours in vacuum (the so-called...
At KEK, an International Linear Collider prototype cryomodule containing eight TESLA-type cavities is currently under development and is scheduled for testing in 2028. To evaluate the performance of the low-level RF (LLRF) system, a Red Pitaya-based cavity simulator is being developed. The simulator will also be used at the STF VT stand to support the development of the digital LLRF system,...
Robotic R&D for SRF started from FY2022 at KEK. Some works related to auto-cleaning and assembly in clean room have been done in FY2023. In FY2024, a simulator ‘ROBOGUIDE’ was introduced, enabling precise orbit development and positioning, moreover, any 3D models developed by CAD became available on ROBOGUIDE. In FY2025, assembly between mock-up cavity and mock-up coupler will be demonstrated,...
Research of Nb3Sn superconducting radio-frequency (SRF) cavities was conducted at the Institute of High Energy Physics Chinese Academy of Sciences (IHEP), in order to improve the intrinsic quality factor (Q0) and accelerating gradient (Eacc). Various recipes of coating were attempted at SRF cavities and samples made of Nb, which resulted in different Sn content. It was found that the Sn...
We report on the easily accomplished, in situ measurement of individual SRF Cavity dissipation in CEBAF cryomodules at the Thomas Jefferson National Accelerator Facility (JLab). Calculated Q0s from the data allows assessing the health of cryomodules over time. A 2022 SBIR Grant from the Office of Nuclear Physics, DOE Office of Science, to Hyperboloid LLC enabled development. JLab provided the...
Nb3Sn thin film cavities are new generation of superconducting cavities, which have the potential to replace traditional pure niobium cavities owing to their superior theoretical radio frequency (RF) performance. Higher theoretical acceleration gradient and quality factor give Nb3Sn cavities more possibilities in the future. There have been relatively high success in producing such cavities by...
From the production and testing of Nb/Cu elliptical cavities by hydroforming, it was found that there is a problem of poor surface roughness due to the large plastic deformation of the copper substrate. To improve this problem, we are trying to apply Plasma Electrolytic Polishing (PEP), which has been developed by INFN-LNL. PEP has the features of extremely high polishing speed compared to...
Dark matter with masses much less than 1 eV/c² is treated as a classical field, commonly referred to as wavelike dark matter. Among the leading candidates is the axion, which may have a mass on the order of μeV and can be converted into ordinary microwave photons of minuscule amplitude under a strong magnetic field. Leading wavelike dark matter searches often employ SRF cavities as detectors...
A five-year project (MEXT advanced Accelerator element Technology Development (MEXT-ATD)) funded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) began at KEK in FY2023. The goal is to manufacture, construct and test a cryomodule (CM) that satisfies the ILC (International Linear Collider Project) specifications and conduct cooling tests. The MEXT-ATD program is...
Field emission is one of the main problems that is difficult to completely avoid in superconducting accelerator project, and it is usually considered to be caused by particles or chemical residuals. Although careful assembly and cleaning can minimize or eliminate this issue, field emission may still occur to some extent. This report focuses on the field emission problem faced in the SHINE...
All elliptical cryomodules are tested at the ESS Test Stand in Lund before their installation in the linac. In June 2024 21 of the 30 cryomodules have been tested, 8 more are being prepared for test. This contribution presents a review of the testing experience, success rate, non-conformities encountered, and their resolution.
Currently a prototype cryomodule for the International Linear Collider featuring eight 1.3 GHz TESLA-type superconducting radio frequency cavities is being designed and built at KEK. In this contribution we report on the status of the development and production of the cavity frequency tuner. The design of the tuner body was finalized and the procurement of the first four series units is...
The Helmholtz Linear Accelerator HELIAC is a superconducting (sc) continuous wave linear accelerator for heavy ions currently under development at GSI in Darmstadt. In order to fully test the new cryomodules a new area was set up. The construction started already in 2018 by clearing the necessary space for a radiation protection bunker near the existing pre-accelerator HLI at GSI. Because of a...
As a practical technique to mitigate field emission effect of superconducting cavities on-line, plasma processing has been developed for CSNS-II superconducting Linac. Experimental platform has been set up and experiments of plasma ignited in various cavities with different frequencies have been conducted. The details of the research will be presented in the paper.
A Ferro Electric Fast Reactive Tuner(FE-FRT) for UK-XFEL superconducting Tesla Cavities is under development, which is used to suppress the microphonics of the superconducting cavities, a fast dynamic detuning. The EF-FRT tuner doesn't have moving parts and so has an extremely fast tuning process to compensate the microphonics. The RF design of the FRT includes the optimization of the Figure...
The LCLS-II project has installed a new superconducting linac at SLAC National Accelerator Laboratory to enable free electron laser science at repetition rates up to 1 MHz. The installed 35 1.3 GHz cryomodules produce an electron beam with energy of up to 4 GeV. Commissioning of the superconducting linac began in mid-2022, leading to the achievement of first light in 2023 and subsequent user...
Superconducting radio frequency (SRF) cavities which are made from bulk niobium and operated at cryogenic temperatures around 2 K, are essential components in modern particle accelerators. Due to the sustainability issues related to niobium, which is considered a critical metal, and the huge power consumption of accelerator facilities, the community has discussed alternative...
For the sustainable accelerators in the future, we need to develop extremely high performance superconducting cavities. This would require collaboration between physicists and engineers towards the same goal. In this hot topic, the internationally distinguished panel members and the audience will discuss state-of-the-art of superconducting cavities and overview the perspective of research...
The Future Circular Collider (FCC) will employ 400 MHz elliptical cavities with niobium coating on copper substrates. Since the performance requirements of the FCC are higher than those of the Large Hadron Collider, which has similar operating conditions, a “seamless” substrate without welding seams is being investigated to achieve these requirements. Hydroforming is one of the methods to...
Nb3Sn has been identified as the most promising next-generation superconducting material for accelerator cavities. This is due to the higher critical temperature of Nb3Sn (Tc = 18 K) compared to niobium (Tc = 9.2 K), which leads to greatly reduced RF losses in the cavity during 4.5 K operation. This allows two important changes during cavity and cryomodule design. First, the higher Tc leads to...
The design, fabrication, and validation progress towards a ferroelectric fast reactive tuner (FE-FRT) as a demonstrator of a high-power tuner for beam loading compensation at LHC injection settings is presented. Such compensation is referred to as transient detuning compensation and involves discrete frequency switching of an LHC cavity configuration on sub-microsecond time scales. The FE-FRT...
Operational experience of the LHe-Free (LHe-free) Nb3Sn demo SRF electron linac over the past year will be reported. A statistical analysis was conducted on beam loss-induced irradiation effects on the Nb3Sn thin film of the superconducting cavity inner surfaces, with subsequent assessment of their impact. An irradiation terminal facility was constructed to conduct experiments on electron beam...
A CEBAF-style quarter cryomodule with two Nb3Sn coated 5-cell CEBAF-style SRF cavities was tested successfully in the cryomodule test facility (CMTF) at JLab in 2024. Efforts continued since then toward a beam test of that cryomodule in the upgraded injector test facility (UITF) at JLab. In this talk, we will report on the beam test results and the planned future steps in further developing...
Recent improvements in Nb3Sn cavity and commercial cryocooler performance have made the fabrication of conduction-cooled cryomodules for SRF cavities feasible, which drastically expands SRF applications to medical imaging, water purification, and security. Cornell has developed a turn-key, conduction-cooled cryomodule to operate a 1.3 GHz Nb3Sn SRF cavity by optimizing the cooling output of...
Recent developments in the high Q and high gradient frontier of SRF cavities have focused on altering the surface impurity profile through in-situ baking, furnace baking, and doping to introduce and diffuse impurities such as O, N and C. However, the precise role of each impurity in improving performance is not fully understood. We take a materials-focused approach to identifying the...
A program of quantitative measurements of magnetic flux expulsion on flat macroscopic samples has been used to assess and categorise magnetic expulsion efficiency. The measurement setup is a magnetic flux lens based on closed-topological heating/cooling through the material’s superconducting transition. This offers systematic and repeatable expulsion measurements for bulk, thin film and...
Two-level systems (TLS) have long been a catch-all explanation for RF loss and quantum decoherence in superconducting devices. In our study, the first to directly link TLS losses to a specific physical mechanism, we demonstrate that oxygen vacancies in the naturally formed Nb₂O₅ on oxidized niobium are a major driver of such dissipation. We performed sequential in situ vacuum-baking treatments...
We present trapped flux data of Nb3Sn samples prepared with sputtering and via bronze route. The data shows that during cooldown magnetic fields with magnitudes several times that of the earth’s magnetic field can be generated. As the sample becomes superconducting the fields are trapped and can be directly measured by our setup. In the data a correlation between field magnitude and the...
Measuring fundamental RF field limits of candidate superconductors for SRF cavities is challenging as local defects and thermal heating can lead to premature quench at field well below the ultimate limit of a superconducting material. Cornell has developed, fabricated, and commissioned a unique sample host cavity that allows for exposing superconducting material samples to very high RF fields...
Trapped vortices in superconductors introduce residual resistance in superconducting radio-frequency (SRF) cavities and disrupt the operation of superconducting quantum and digital electronic circuits. Understanding the detailed dynamics of trapped vortices under oscillating magnetic fields is essential for advancing these technologies. We have developed a near-field magnetic microwave...
SRF cavities are a critical technology both for particle accelerators, where they enable high energies and efficient operation, and superconducting quantum circuits, where they enable large coherence times for qubits. In both applications, the need for better performing cavities with higher quality factors is clear. The native oxide that forms on the surface of niobium may be the source of...
Copper-based Nb3Sn cavity is a promising candidate for next generation accelerator applications in the field of superconducting radio frequency (SRF). It combines the excellent thermal conductivity of copper and the superior superconducting properties of Nb3Sn, and has the potential to greatly improve the performance of the SRF cavity. The electrochemical and thermal synthesis (ETS) bronze...
The successful development of Nb3Sn/Cu coatings for the SRF cavities of next generation particle accelerators would result in the reduction of the needed cryogenic power by a factor 3 with respect to what normally needed for bulk Nb cavities, while maintaining operation at 4.5 K. In the framework of the I.FAST and ISAS collaborations, research activities are carried out at INFN-LNL to develop...
The sensitivity of compound superconductors to gradient-limiting defects is well established. To overcome this challenge and develop recipes for enhanced-Tc surfaces that approach their fundamental limits, we take a multi-pronged theoretical approach: we identify material systems where low-Tc or normal-conducting defects are less likely to occur, where bulk superconducting properties favor...
Niobium-based bulk SRF cavities have demonstrated exceptional performance. To further improve niobium cavity performance, we present studies involving a novel surface engineering process designed to prevent the formation of amorphous niobium oxides on the surface. This is achieved by encapsulating the niobium surface using thermal Atomic-Layer-Deposition (ALD). This technique has been shown to...
In the SRF community, the origin of the anti-Q-slope in bulk niobium cavities and the Q-slope in niobium-coated copper cavities remains an open question. In this contribution, we propose a theoretical framework explaining both phenomena through a unified approach. The distribution function of quasiparticles may play a crucial role in the response of a superconductor exposed to radio-frequency...
The anti-Q-slope observed in superconducting RF (SRF) cavities has been a longstanding puzzle. Previous studies by Gurevich [1] and Kubo-Gurevich [2] linked this phenomenon to the smearing of the density of states under high RF current. However, the experimentally observed trend of a more pronounced anti-Q-slope with increasing frequency remains unexplained. Recent theoretical investigations...
Achieving optimal performance in SRF (Superconducting Radio Frequency) cavity assembly relies heavily on precise cleanroom processing, where contamination poses significant risks. Human activities, a major source of particle emissions in cleanrooms, not only threaten cavity cleanliness but also contribute to labor intensity and noise exposure. To mitigate these challenges, recent advancements...
The performance of superconducting RF (SRF) cavities is extremely sensitive to contamination by particles on the SRF surface. To mitigate this, high-pressure rinsing (HPR) with ultra-pure water is performed after surface treatment, and cavity assembly is conducted in a cleanroom environment. However, even when cleanroom suits are worn, human involvement in these processes can still introduce...
The performance of SRF cavities is critically dependent on the integrity of their inner surfaces. However, traditional inspection methods are limited by the geometry of these cavities. To overcome this challenge, a novel automated defect detection system has been developed at CERN. This system utilizes a short-focus imaging system mounted on a scanning robotic arm, enabling comprehensive and...
A superconducting radio-frequency photo-injector (SRF-PI) can in principle operate in continuous-wave (CW) mode at high gradients with ultra-high vacuum. Using low mean-transverse-energy photocathodes, SRF-PIs could provide high-brightness, high- repetition-rate beams with long cathode lifetimes. For these reasons, an SRF-PI has been adopted for the proposed Low Emittance Injector addition to...
A future upgrade of the European XFEL foresees High-Duty-Cycle (HDC) operation which requires a new electron beam injector. The centerpiece of such a photoinjector is a continuous wave (CW) L-band superconducting radio frequency (SRF) cavity developed at DESY. This cavity demonstrated world record peak axial electric field values of up to 50 MV/m with a copper (Cu) cathode, thread mounted to...
After about a decade of research, development and construction work, the bERLinPro Energy Recovery Linac project at HZB changed over into the commissioning phase and started the operation of the SRF photo-injector with the injection line of the accelerator. This system had already produced beam from a metal photo-cathode in 2018 [1] in a dedicated test environment and was assembled in the...
The commissioning of LIPAc (Linear IFMIF Prototype Accelerator) is ongoing at QST Rokkasho Institute for Fusion Energy within the engineering validation of the accelerator system up to 9 MeV/125 mA in continuous wave under international collaboration between Japan and Europe. Several SRF cryomodules will be required for IFMIF to accelerate deuterons from 5 MeV to 40 MeV. The prototype of the...
A new cryogenic facility for the RF testing of thin film coated SRF cavities has been designed and built at Daresbury Laboratory. This facility uses a pulse-tube cryocooler providing 2.7 W of cooling power at 4.2 K and enables cavity tests at: 1.3, 3 and 6 GHz. The cryostat has been constructed and has successfully passed initial vacuum and cryogenic tests. The primary focus of this facility...
Within the ITN (ILC Technology Network) activity led by KEK, the so-called "Medium Grain Niobium" is investigated with respect to its possible application for a large-scale SRF cavity production for the International Linear Collider ILC [1-3]. In the framework of the KEK-DESY collaboration, the niobium material for two 1.3 GHz single-cell cavities was supplied by KEK. After fabrication and...
Additive Manufacturing (AM) offers a unique way of fabricating components with intricate geometries and enables the use of materials that are otherwise difficult to machine or process due to high melting points. Within this context, recent work at INFN-LNL and INFN-Padova focused on the fabrication of a seamless 6 GHz copper cavity using AM techniques. This study investigates the feasibility...
In complement to the development activities for fusion reactors (JT-60SA & ITER), Fusion for Energy contributes to the R&D for material characterisation facilities. The LIPAc, technical demonstrator for the production and acceleration of a D+ beam, will be used for neutron production by nuclear stripping reaction on a liquid Li target. Since its first beam in 2014, the LIPAc construction and...
In this work a method to include the effects of beam loading in FEM solvers for electromagnetic problems, such as CST and HFSS, is considered. The method involves using transmission line models of a beam-loaded and beamless resonant cavity to determine an effective surface resistance and tuning angle for the beamless cavity to produce the same reflection as the beam-loaded case. The cavity,...
RAON is a heavy ion accelerator consisting of a cryomodule containing a superconducting cavity in the SCL3 section and a warm section with a quadrupole magnet and a diagnostic chamber. Two types of superconducting RF cavities are utilized, arranged in three types of cryomodules: the 81.25 MHz quarter-wave resonator (QWR) and the 162.5 MHz half-wave resonator (HWR). In 2024, beam commissioning...
Accurate monitoring of beam dynamics in superconducting linear accelerators (linacs) is important for minimizing beam losses and maintaining stable operation. In superconducting sections, however, destructive diagnostics must be avoided to prevent issues such as particulate contamination and outgassing, which makes direct beam envelope measurements particularly difficult. This work introduces...
During vacuum commissioning and operation of large superconducting accelerators, gas flow may induce the dust particle within pipelines, causing intolerable particulate contamination in superconducting radio frequency (SRF) cavities. Investigating the transport behavior of microscale solid particles within accelerator pipelines is critical for understanding and solving particulate...
Crystal defects, such as dislocations and low-angle boundaries, provide sources of magnetic flux trapping in the Nb materials used for superconducting radio frequency (SRF) resonating cavities. Improving the performance of SRF cavities, as measured through the quality factor, requires reducing these defects. SRF cavity production involves deformation processing, such as rolling and forming,...
Recent advances in additive manufacturing promise interesting possibilities for the design and fabrication of superconducting radio frequency (SRF) cavities. Cold Spray Additive Manufacturing (CSAM) is one candidate that would allow for rapid built times, realization of integral cooling structures, deposition of different materials and an easy upscaling with available equipment. As it is the...
Superconducting QUantum Interference Devices (SQUID)s are superconducting loops broken by one or more Josephson junctions and act as RLC circuits with a resonant frequency that can be tuned by an applied magnetic field. A microwave metamaterial can be created by positioning many of these SQUIDs in an array such that such that their spacing is much less than that of the microwave wavelength. In...
The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA joined the international collaboration in 2018 and will deliver 10 low-beta cryomodules as In-Kind Contributions to the PIP-II project, with cavities supplied by LASA-INFN (Italy) and VECC-DAE (India), and...
This work presents a state-of-the-art design of a Ferroelectric Fast-Reactive Tuner (FE-FRT), capable of modulating high reactive power in TESLA type cavities on a microsecond time scale. The Mainz Energy-Recovering Superconducting Accelerator employs superconducting radio frequency cavities operating at 1.3 GHz, achieving quality factors on the order of 10^10. However, detuning of +/-25 Hz...
1.3 GHz 3-cell superconducting cavities were proposed for the injector of the high-brightness free electron laser based on energy recovery linac scheme. The average beam current is 10 mA and injector energy is 10 MeV. The beam tube of the cavity is enlarged to damp higher-order modes (HOMs) and to keep beam stability. Three cavities have been fabricated. An intrinsic quality factor of 2.0 ×...
The Institute of High Energy Physics (IHEP) developed the 1.5 GHz high -order harmonic cavity system for the Hefei Advanced Light Facility (HALF) project. This paper primarily introduces the design and development of the 1.5 GHz high-order harmonic superconducting cavity and cryomodule. The structure of the harmonic cavity has been simplified, and an integral welding method for the cavity with...
IJCLab has been contributing to several SRF accelerators in the world (SPIRAL2, ESS, PIP-II) and in particular was in charge of the design, surface preparation and qualification in vertical cryostat of low beta (i.e. complex 3D shape) resonators as Quarter-Wave Resonators (QWR) and Spoke Resonators. One of the main challenges of these complex geometries is the final surface cleaning by High...
The introduction of thin film structures into superconducting cavities is theoretically predicted to improve performance, and experimental verification is now required. In this study, we are developing a relatively small and easy-to-handle niobium-made 3 GHz single-cell cavity to verify the effects of introducing thin film structures. We performed vertical measurements on the 3 GHz single-cell...
Bulk Nb superconducting radio-frequency (SRF) cavities are widely utilized in particle accelerators, however, their accelerating gradient and overall performance are limited by the superheating field (Bs). To overcome this theoretical limit, we aim to develop innovative multilayer structures. Iron-based superconductors are considered promising coating materials for such multilayer structures,...
Superconducting thin film (TF) technology for Superconducting readio-frequency(SRF) applications is under intense development in many research centres around the world. TF SRF technology can not only drastically reduce cryogenic costs but also opens the door to simplified alternative cooling schemes with reduced helium inventory. Up to today, TF development have been considered within two High...
Recent advancements in Nb₃Sn cavity development have enabled the design of SRF accelerators utilizing compact mechanical cryocoolers instead of helium liquefiers, simplifying system architecture and reducing costs. In this background, our company has released a high-efficiency, high-capacity 4 K GM-JT (Gifford-McMahon-Joule-Thomson) cryocooler system with 10 W-class cooling capacity at 4.2 K....
Superconductor MgB2 has a Tc of 40 K, and its materials parameters suggest that SRF cavities with higher Q, higher gradient, and higher operation temperatures than Nb cavities can potentially be made from MgB2. We present our ongoing efforts towards the development of MgB2-coated SRF cavities. Thick MgB2 films, up to 5 um in thickness, were deposited onto 1.3 GHz Tesla-type copper RF cavities...
Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven nuclear transmutation system (ADS) as a future nuclear system to efficiently reduce high-level radioactive waste generated at nuclear power plants. As the first step toward the full-scale CW proton linac for the JAEA-ADS, we are currently prototyping a low-beta (around 0.2) single-spoke cavity. Because there is no...
FRIB has developed a high Q 0.53HWRs within a DOE R&D program titled Development of Transformative Preparation Methods to Push up High Q&G Performance of FRIB Spare HWR Cryomodule Cavities. In this study, we found that flux trapping produces 80 % of the residual surface resistance (Rres). The main contribution is that from thermoelectric current produced by Seebeck effect (Dynamical magnetic...
Experimental evidence of parasitic radiation originating from cavity field emission or beam losses and interacting with cryomodule diagnostics has been collected.
We focus on the case of spurious triggering of power coupler interlock system which is based on the light detection of arcs and its transmission in optical fibers. Scenario of radiation interaction are modeled using Geant4, aiming...
The Mainz Energy-Recovering Superconducting Accelerator is currently under construction at the Institute for Nuclear Physics on the campus of the Johannes Gutenberg University Mainz. A future upgrade is planned for the multi-turn Energy Recovery (ER) mode, increasing the beam current from 1 mA to 10 mA in continuous wave at 1.3 GHz. Simulations have calculated an increased power deposition of...
The fabrication of Superconducting Radio Frequency (SRF) cavities traditionally relies on forming and welding high-purity metal sheets, resulting in a local surface discontinuity that degrades the final SRF performance. In this work, we propose and explore a novel hybrid approach combining Wire Laser Additive Manufacturing (WLAM), with in situ CNC machining for the fabrication of mono-cell 1.3...
Recent advances in understanding the subsurface microstructure and microchemistry of niobium (Nb) have led to significant improvements in the quality factor (Q0) of superconducting radiofrequency (SRF) cavities. Beyond traditional surface treatments, emerging evidence highlights the critical role of the bulk microstructure, particularly in influencing the trapping and expulsion of residual...
Measuring cavity quality factors in a cryomodule requires calorimetric techniques because of the heavy input overcoupling. This involves using physical parameters of the cryogenic system such as mass flow, bath pressure, helium liquid level to estimate dynamic heat load of SRF cavities, often calibrated with heaters. The main challenges of these techniques are reducing sources of variation and...
Medium temperature (mid-T) baking of niobium superconducting radio-frequency cavities at 300–350 °C in a vacuum furnace is known to enhance the quality factor (Q₀). However, despite this improvement, cavities treated with this process often prematurely quench at relatively low accelerating fields. This limitation is suspected to arise from the formation of surface contaminants, such as niobium...
Superconducting–Insulating–Superconducting (SIS) multilayers offer a promising approach to surpass the accelerating gradients and quality factors of standard bulk-Nb SRF cavities†. Plasma-enhanced atomic layer deposition (PEALD) stands out as a key technique for the next-generation thin-film-based SRF cavities, providing conformal coatings on highly structured, three-dimensional substrates...
During the preparation for the installation of the LCLS-II HE cryomodules, one previously qualified cryomodule experienced an uncontrolled vacuum event. The cavity string vacuum unexpectedly increased to 2 × 10^ (-3) Torr. Simulation showed the vacuum incident may have introduced 0.1 μm sized particulates into the cavity RF volume. Careful analysis of the particulates' path and migration...
At FREIA, Uppsala (Sweden), an investigation of the Magnetic Field (MF) evolution during cool-down / warm-up cycles of 352 MHz single spoke cavities for the MINERVA proton linac (Phase I of the MYRRHA project) has been carried out: bulk-Nb SRF cavities equipped each with a dedicated MINERVA cavity magnetic shield (MGS) made of CRYOPHY® material have been measured during their testing in the...
Minimizing residual magnetic fields during SRF cavity cooldown is essential for reducing surface resistance and improving the quality factor. At LASA-INFN, we implemented an active compensation system using Helmholtz-like coils in vertical test cryostats. The setup is optimized to reduce the average magnetic flux through the cavity surface by accounting for the spatial inhomogeneity of the...
During last few years, an extensive efforts for obtaining Q0 vs Eacc characteristic of SRF cavities at very low accelerating gradients have been conducted in several laboratories around the world. In the Accelerator Module Test Facility (AMTF) at DESY, several attempts of such measurements were performed, mainly focused on the comparison between the widely used decay measurements technique and...
The accelerating gradient of Nb₃Sn superconducting radiofrequency (SRF) cavities is currently limited, and the underlying cause remains an open question in the field. One leading hypothesis attributes this limitation to the presence of tin-deficient regions within the Nb₃Sn coating, which can suppress the superheating field. Due to the relatively large coherence length of Nb₃Sn, defects near...
Residual magnetization of ferromagnetic coldmass components located near superconducting RF (SRF) cavities poses a significant threat to cavity performance, especially when a magnetic source, such as a focusing lens, is in close proximity. Previous work evaluated several passive mitigation techniques, including the use of local magnetic shields, and quantified both the residual fields induced...
Traveling-Wave (TW) technology can push the accelerator field gradient of niobium SRF cavity to 70 MV/m or higher beyond the fundamental limit of 50~60 MV/m in Standing-Wave regime. The success of TW resonance excitation in a proof-of-principle 3-cell SRF cavity in 2 K liquid helium encouraged to advance TW technologies necessary more for future accelerator-scale one. Fermilab has proposed a...
Niobium (Nb) has long been recognized as the primary material for superconducting radio-frequency (SRF) cavities due to its excellent superconducting properties and mechanical formability. However, improving its structural stability under cryogenic operating conditions and high electromagnetic loads remains a key challenge. In this study, we employ molecular dynamics (MD) simulations to...
STFC has built new infrastructure to enable particulate control whilst building superconducting radio frequency cavity string and beam line assemblies that can be used in high beta cryomodule applications. The new facility includes an ISO4 cleanroom, low particulate high pressure rinse, and most recently, a nitrogen purge system that can allow varying and controlled purge of nitrogen through...
The Proton Improvement Plan - II (PIP-II) project at Fermi National Accelerator Laboratory (Fermilab) is the first U.S. accelerator initiative to include major in-kind contributions (IKC) from international partners. As part of the French contribution, the French Alternative Energies and Atomic Energy Commission (CEA) will deliver ten 650 MHz low-beta (LB650) cryomodules. These cryomodules...
Positron annihilation spectroscopy (PAS) is a powerful and precise tool to study atomic-scale defects in a wide range of materials, especially superconductors. The PAS methods available at the user facility radiation source ELBE (HZDR, Germany) enable analysis of point defects and their agglomerations including within the range of micro- and mesopores. The extended defects and their complexes...
In the Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL), Continuous Wave (CW) Low-Level Radio Frequency (LLRF) systems perform critical functions including adjusting the power coupling of accelerator cavities, regulating the amplitude and phase of the RF field, and maintaining the resonance frequency and phase of the cavities. These functions are essential to ensure the electron...
High gradient CW electron guns are essential for high-repetition-rate, high-brightness electron beams, key to advanced light sources and other applications. Compared to DC guns and normal conducting VHF guns, SRF guns are considered the next-generation solution for further boosting CW gun acceleration capabilities and electron source brightness. This paper presents the initial physics design...
Picosecond-long X-ray pulses of moderate intensity and high repetition rate are highly sought after by the light source community, especially for time-resolved fine spectroscopic analysis of matter in the linear response regime. We investigate the upgrade of the Elettra 2.0 diffraction-limited storage ring light source to radiofrequency transverse deflecting superconducting cavities generating...
Three superconducting linear accelerators are under construction at the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS). 96 superconducting radio frequency (SRF) cavities housed in 17 cryomodules were fabricated, preparation and installed in the accelerator tunnel in 14 months. The cold test of the SRF cavity and cryomodule is skipped due to our excellent...
RaSTA, the Rapid Superconductor Test Apparatus, is a sample test cavity project at HZB. It shares the sample geometry and the calorimetric measurement principle with the QPR but is targeted at quicker turnaround times and a more compact footprint at higher operating frequency. RaSTA 2.0 features a niobium coated copper cavity allowing for higher RF field levels and better thermal stability....
Time-dependent Ginzburg-Landau (TDGL) numerical simulations can capture vortex nucleation and motion, as well as proximity effects, at high frequencies in superconductors.† We use TDGL to study the nucleation of RF semi-loop vortices in Niobium in the presence of surface defects when the material is subjected to an intense RF magnetic field arising from a near-field microwave frequency dipole...
High acceleration gradients Eacc and high quality factors Q0 can be achieved by heat treatments of the cavity [1]. However, the heating processes are carried out in furnaces where the cavity is forcibly exposed to air afterwards, which can lead to contamination. For moderate temperatures (T < 350 °C), this issue could be overcome by in-situ heating. A few studies on in-situ heating have...
A new superconducting (sc) continuous-wave (cw) linear accelerator (linac) is currently being built at GSI to meet the future requirements in research on superheavy elements (SHE) synthesis and material science with a particular focus on fusion studies. The HElmholtz LInear Accelerator (HELIAC) will provide ion beams in the energy range from 1.4 MeV/u to 7.3 MeV/u with a mass-to-charge ratio...
In continuous mode operation, performance of normal-conducting copper RF cavities is limited by high power dissipation around 100 kW/m, needed there for achieving a modest 2 MV/m gradient. In contrast, superconducting RF (SRF) cavities can easily exceed 15 MV/m under similar conditions due to nominal Ohmic losses, thus making them ideal for high-duty accelerators like SNS and ADSS.
We are...
As part of the Quantum Technology Initiative (QTI) at CERN, a programme to develop a novel SRF cavity for axion searches has been launched. This Axion Detector Demonstrator (QTI_ADD) is based on the heterodyne approach to axion detection, and uses a dedicated SRF cavity design with overlapping, quasi-degenerate modes to search for axion-induced photon conversion from a driven, resonant cavity...
Sideband excitations observed in superconducting radio-frequency (SRF) cavities during vertical tests are indicative of complex underlying phenomena that can impact cavity performance and their measurements. This work presents an analysis combining experimental data and numerical simulations to investigate the origins and contributions of multipactor and field emission to sideband generation....
This contribution provides an updated overview of the Mainz Energy-Recovering Accelerator (MESA), a continuous-wave superconducting electron linac currently under construction at the Institute for Nuclear Physics at Johannes Gutenberg University Mainz. Designed to deliver high-current, highly polarized beams with energy recovery, MESA aims to support a diverse experimental program. The current...
The VSR cavities, featuring protruding waveguides and HOM absorbers, are designed to be installed as part of the cold string in a spaceframe within a cryogenic vessel. Precise alignment of the cavities during installation and continuous position monitoring during operation are required to prevent damage of other cold string components such as bellows. To achieve this, strain gauges are...
The Helmholtz Linear Accelerator HELIAC is a superconducting (sc) continuous wave linear accelerator for heavy ions currently under development at GSI in Darmstadt. However, single cavity tests and the majority of cleanroom activities took and still take place at the designated facilities of the Helmholtz Institute Mainz (HIM). Each of the sc cryomodules of the HELIAC houses 3 crossbar...
Currently, 1.3 GHz Nb superconducting elliptical cavities have achieved accelerating gradients of Eacc ≈ 40 MV/m. In contrast, theoretical predictions suggest that accelerating cavities with multilayer thin-film structures on their inner surfaces might reach gradients of Eacc ≈ 100 MV/m. Such significant performance improvements would represent a major advancement not only in high-energy...
Since the second half of 2022, the design of the CSNS-II elliptical cavities was completed and their manufacturing was initiated. After nearly three years of research, we have successfully developed three prototype elliptical cavities. Vertical tests demonstrated a maximum gradient of 25.7 MV/m, significantly surpassing the operational requirement of 14 MV/m. This achievement has laid a solid...
The consistent production of high-RRR Nb cavities for superconducting radiofrequency applications is critical to advancements in accelerator performance and technology. Despite standard guidelines for material and cavity production, the properties and performance of these cavities can vary significantly. Improvements in cavity performance due to better flux expulsion are observed after heat...
The ability to accurately and consistently quantify the recrystallized (Rx) microstructure of heat-treated high-purity Nb used in superconducting radiofrequency (SRF) applications is critical for the improvement of material processing and cavity production. The production of SRF cavity half-cells by deep-drawing Nb sheets into the half-cell geometry results in different stain paths in...
A high-Q, high-gradient 1.3 GHz cryomodule containing eight 9-cell SRF cavities has been designed, manufactured, and assembled at IHEP-CAS. The eight cavities achieve an average unloaded quality factor (Q₀) of 3.8×1010 at 16 MV/m and 3.6×1010 at 18 MV/m. After horizontal testing, the cryomodule was transported approximately 1,000 km to Dalian.
To achieve such exceptional performance, the...
While the fabrication technology superconducting Niobium cavities is advanced, a wide gap exist between the theoretical threshold field $H_{sh}$ and the observed values. The reasons behind this discrepancy continue to pose intriguing questions, highlighting the need for further investigation. While material properties undoubtedly influence performance, we believe that the intricate dynamics of...
Thermal shrink of materials is always an obstacle when designing cryogenic systems. In superconducting cavity cryomodules, some adopt reference bars, which are made by Invar, to keep cavities’ position same at cryogenic temperature from room temperature. Linear expansion of Invar from 300 K to 2 K is about 0.04 %, resulting in approximately 5 mm of thermal shrink for the 12.6 m ILC cryomodule,...
The fabrication of SRF cavities from sheet materials includes deep-drawing, electron beam welding, chemical and mechanical polishing, high-temperature heat treatment, and material diffusion. The performance of these cavities is frequently constrained by magnetic flux trapping. In this presentation, we thoroughly examine how recrystallization influences flux expulsion in SRF cavities, using...
Compared to normal-conducting accelerators, superconducting linacs require a dramatically larger number of parameters to be monitored, including not only RF power and beam-related signals, but also cryogenic conditions such as helium tank pressure, vacuum levels, and cavity temperatures. This increased complexity demands robust and flexible monitoring systems, especially during extended...
Burst-noise events are primary trip sources at the China Accelerator Facility for superheavy Elements (CAFE2), characterized by a rapid burst noise in the cavity pick-up signal categorizable into three distinct types: flashover, electronic quench (E-quench), and partial E-quench. Herein, we design an algorithm identifying the burst-noise event types in real time to realize a real-time...
The mission of the RIKEN Radioactive Isotope Beam Factory (RIBF) is to improve our understanding of the mechanism of synthesis of elements in the universe via experiments using intense heavy-ion beams. The RIBF accelerator complex consists of booster ring cyclotrons and three injectors of AVF cyclotron, RIKEN Linear ACcelerator (RILAC), and RILAC2. Beams of ion species ranging from hydrogen to...
PIP-II project is based on 5 types of SRF cavities. Developing the linac includes several advances in the SRF cavity processing and cryomodule design and assembly. This talk will summarize these advances, report recent results, and plans for further developments.
The Electron Ion Collider (EIC) pushes the limits of superconducting radio frequency systems to fulfil a variety of accelerator physics requirements. Thomas Jefferson National Accelerator Facility (TJNAF) and Brookhaven National Laboratory (BNL) in partnership are leading an international collaboration designing and building 46 independent superconducting cavity resonators comprised of 4...
The production of over hundreds of 1.3 GHz high-Q superconducting cavities for the Shanghai High repetition rate XFEL and extreme light facility (SHINE) has now been successfully carried out. Both high temperature nitrogen doping (N-doping) recipe and mild temperature (Mid-T) baking recipe have been adopted to achieve high-Q performance. The main challenge for SHINE mass production is to...
Large-scale 4.5 K and 2.0 K helium cryogenic systems are a foundational support system for modern superconducting accelerator facilities. These are highly energy intensive systems. Large-scale efficient helium systems presently require approx. 800 W/W of cooling at 2 Kelvin (30 mbar) and 250 W/W at 4.5K. Due to the nature of the application, these systems require very high reliability...
FCC-ee is the baseline for future lepton collider projects at CERN. To meet specific physics objectives, CERN is developing two types of accelerating cavities in collaboration with international partners. For low-energy applications, namely the Z pole, W, and H physics cases, CERN is working on 400 MHz seamless cavities with Nb-coating technology, in partnership with KEK. Prototype cavity...
The first RF Dipole crab cavity cryomodule, jointly developed by CERN and UK-STFC under the HL-LHC project, was built for proton beam tests in the SPS machine. In 2024, the cryomodule was tested in the CERN horizontal test facility prior to its installation in the SPS. During acceptance tests, two critical non-conformities related to the fundamental power couplers were identified. This paper...
In the context of the FCC study where strongly damped RF structures are required to accelerate high beam currents, a new slotted waveguide cavity called SWELL has been proposed. The design is based on an elliptical cavity shape split into four quadrants making it compatible with Niobium-on-Copper coatings. A first prototype at 1.3 GHz has been fabricated at CERN to demonstrate the feasibility...
High-gradient superconducting RF structures are of keen interest to next-generation linear colliders because they offer substantial savings in terms of reduced construction cost by shortening the machine, and reduced operating costs. The gradient of bulk niobium superconducting RF structures is fundamentally limited by the maximum surface magnetic field these structures can sustain before...
When Nb₃Sn was reintroduced to the SRF community as an alternative to pure niobium, one key motivation has been to reduce the cryogenic requirements of new and existing accelerators by shifting from 2 K to 4 K operation. Meanwhile, a variety of implementations beyond research machines are being explored. The combination of Nb₃Sn with conventional cryocoolers, enabling cryogen-free operation,...
Large experiments in fundamental physics such as the detection of dark matter axions [1] or new particle accelerators like the CERN FCC [2], can greatly benefit from the low surface impedance Zs of superconductors (SC) in high magnetic fields H. In the pursuit of high-Q SC cavities (haloscopes), the understanding and control of high frequency vortex motion, the main dissipative channel acting...
Today, apart from some isolated R&D efforts, there are no GW experiments, yet which explore a large part of the vast frequency range above the LIGO/Virgo band. It is planned to establish an experiment at DESY and FNAL to search for high-frequency GWs in the frequency range of 10 kHz to 100 MHz. The basic idea is to use superconducting radiofrequency (SRF) cavities to detect tiny harmonic...
