SRF
MOO7M01
Commissioning of the RF System for High Energy Photon Source
52
The High Energy Photon Source (HEPS), recently commissioned in Beijing, is a 6 GeV diffraction-limited storage-ring light source. A double-frequency RF system was adopted, comprising five 166.6 MHz superconducting RF (SRF) cavities acting as the fundamental and two 499.8 MHz SRF cavities serving as the third harmonic for bunch lengthening. A β=1 quarter-wave SRF cavity was developed in-house to achieve the low RF frequency and high power within a compact longitudinal space, while also enabling heavy damping of higher order modes. Solid-state amplifiers provide a total installed RF power of 2.4 MW to drive the cavities in both the booster and the storage ring. A digital low-level RF system was also developed in-house and is current in stable operation. A beam current of 100 mA was successfully achieved using the nominal SRF setup. The design, construction, and commissioning results of the HEPS RF system are presented.
Paper: MOO7M01
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOO7M01
About: Received: 16 Apr 2026 — Revised: 28 Apr 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP6700
Comprehensive integration and innovation on the 1.5 GHz SRF harmonic cavity control system at NSRRC
624
This paper presents a self-developed, comprehensive electronic control system for the Superconducting Radio-Frequency passive Harmonic Cavity (SRF HC) at the Taiwan Photon Source (TPS) in Hsinchu, Taiwan. The system integrates the Break Out Box (BOB) interfaces for the cavity, Valve Box (VB), cooling water signals, and interlock systems. Additionally, it includes an intuitive correction module and updates for the discontinued or unmaintainable dial gauge module, ensuring that the system operates safely and transparently with clear status display.
Paper: MOP6700
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP6700
About: Received: 08 May 2026 — Revised: 16 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7024
Vertical testing of the Waveguide-HOM-Damped 1.5 GHz 4-Cell prototype cavities for the VSR-Demo project
691
The VSR Demo project aims for the validation of a cavity design suitable for the application in electron storage rings, characterized by currents of several hundreds of mA and a dense wakefield spectrum caused by inhomogeneous fill patterns. The cavities are equipped with five waveguides plus a coaxial fundamental power coupler, forming two groups of three radial extensions at either cavity end. Recently two prototypes were manufactured and are in the process of vertical testing at HZB’s Large Vertical Test Stand. First tests completed with Prototype 1, covering all modes of the fundamental passband and different temperature levels, did not match the Q(E)-performance expectations, but indicate a yet unknown loss mechanism in the cavity’s periphery, i.e. waveguide endgroups, beam pipe extensions, blind flanges or the coupling feedthrough. Further insights are expected from the ongoing testing program with modified coupling and with Prototype 2.
Paper: MOP7024
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7024
About: Received: 08 May 2026 — Revised: 16 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7025
Mid-T-Baking of SRF cavities driven by RF power
694
Mid-T (ca. 220 to 350°C) heat treatment is known to improve the dissipation of superconducting Nb cavities by dissolving the surface oxide and diffusing oxygen into the near-surface bulk. HZB explores the use of RF power coupled into the cavity as a technique to perform the heat treatment directly in the cryostat, thereby also avoiding venting and re-oxidation following the treatment. Such an RF-driven heating may be an attractive option for in-situ processing of an operation-ready accelerator module. We have demonstrated effective RF heating both with a TESLA-9-cell and a 1.5 GHz single-cell cavity reaching temperatures of 207°C (TESLA cavity) and 260°C (VSR single cell). Whilst the TESLA-cavity was driven via the fundamental power coupler using various modes of the fundamental passband, the single cell was heated using a higher-order mode at 4.263 GHz. The later was selected because of both its strong coupling and acceptable homogeneity of RF power dissipation. Experiments took place in two cryostats, HZB’s HoBiCaT and the Large Vertical Test Stand (LVTS), operated under elevated temperatures. In this paper, details of the experimental setup and process, heating performance and, in case of the single cell, a subsequent cold test are reported.
Paper: MOP7025
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7025
About: Received: 15 Apr 2026 — Revised: 28 Apr 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
MOP7034
Status of the High Q-High G R&D activities on SRF cavities at INFN LASA
706
INFN LASA started an R&D activity dedicated to the development of knowledge needed to understand how to improve SRF cavity performances to reach High Q and High G values to accomplish the sustainability and cost reduction requests, as needed for the future large particle accelerators. This R&D activity, funded by INFN, is also enriched by synergies with other LASA activities as PIP-II low beta cavity production, the participation to ILC Technology Network, and by the LASA experience in SRF cavity industrialization developed during the large-scale production of the Eu-XFEL and the ESS SRF cavities. First results obtained on 1.3 GHz single and multi-cell cavities, and the status of the upgraded LASA infrastructures for Vertical Test are presented and discussed.
Paper: MOP7034
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7034
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
MOP7035
R&D activities in view of PIP-II LB650 cavity production
710
A joint LASA–Fermilab activity is in progress to study the impact of key surface processing steps on the performance of LB650 superconducting cavities in view of future series production. Among the several cavity preparation steps, electropolishing (EP) and mid-temperature heat treatment are considered the most critical and require specific optimization for the LB650 geometry. Single-cell and 5-cell cavities are used as test prototypes to investigate the effects of EP and mid-temperature bake at 350 °C. Vertical RF tests are performed at Fermilab after EP and after the mid-T bake under identical conditions. The ongoing program aims to provide insight into the evolution of Q₀ and accelerating gradient along the processing sequence. Preliminary observations and results are here presented.
Paper: MOP7035
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7035
About: Received: 12 May 2026 — Revised: 22 May 2026 — Issue date: 22 May 2026
MOP7036
SRF cavity detuning characterization by continuous wavelet transform: a time-frequency analysis
714
Sustainability is a key issue for both current and future particle accelerators. Superconducting RF cavities with high loaded quality factors play an important role in not only lowering the energy demands of particle accelerators but also the initial investment in RF amplifiers. But the narrow bandwidth associated with this high loaded quality, makes the need to minimize cavity detuning critical to maintain stable and efficient operation. In this context, characterization of microphonics detuning is essential, as it is a major error source, for implementation of effective mitigation schemes to reduce peak and rms RF power requirements. Here we analyze SRF cavity detuning using the Continuous Wavelet Transform (CWT). Unlike conventional Fourier-based approaches, the CWT enables localized time-frequency decomposition, making it well-suited for identifying transient features that influence cavity behavior. Applying the CWT to measured detuning signals from a TESLA cavity at HoBiCaT testing facility at Helmholtz-Zentrum Berlin allows us to identify dominant detuning frequencies and track their evolution over time. The resulting time-frequency maps offer a more comprehensive understanding of the underlying mechanical environment and can support the development of more robust detuning mitigation and compensation strategies for SRF systems.
Paper: MOP7036
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7036
About: Received: 15 Apr 2026 — Revised: 14 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
MOP7043
The detail design of a twin-axial type FE-FRT for SASE
732
A Twin-axial type Ferro-Electric Fast Reactive Tuner (FE-FRT) is under development for the SASE, aiming to provide a fast and efficient microphonics suppression. The tuner consists of two magnetically coupled cylindrical resonators operating out of phase. In high-frequency FE-FRT, the temperature rise may limit the tuning range. The twin-axial configuration doubles the tuning range for the same temperature rise in the ferroelectric wafers. A key innovation of this work is the use of CST eigenmodes to rapidly optimize the figure of merit (FoM) of the FRT tuner, with some approximations, by sweeping the parameter space, including the FE wafer dimensions and cavity geometry. The thermal analysis has also been performed to assess the temperature rise during operation.
Paper: MOP7043
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7043
About: Received: 18 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
MOP7048
Uncertainty analysis of time constant measurements in SRF cavity testing
736
At the start of superconducting radiofrequency cavity testing, cavity time constant measurements are taken and from these measurements the field probe external quality factor is calculated. This value is then used for the calculation of quality factor and accelerating gradient for the remainder of the testing process. In previous analyses the uncertainty of the time constant measurement has been given as 3%, but this is dependent on the measurement equipment and method used to estimate the time constant from the measured cavity decay curve. This paper presents an analysis of the uncertainty of the measurement equipment used in the Superconducting Radiofrequency Laboratory at STFC’s Daresbury Laboratory and a comparison of the different methods that can be used to estimate the time constant from a decay curve.
Paper: MOP7048
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7048
About: Received: 11 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
MOP7054
LIPAc RF system: on the versatile use of photomultipliers
749
Modern photomultipliers (PMs) are affordable, highly sensitive, easy to operate, compact, and sufficiently robust for demanding accelerator environments. In systems such as the Linear IFMIF Prototype Accelerator (LIPAc) in Rokkasho, Japan, whose radiofrequency (RF) subsystem delivers over 2 MW of RF power distributed among all the accelerating cavities, these characteristics make PMs particularly effective for monitoring components prone to multipacting and micro-discharge. The light produced by these phenomena is detected even at very low levels, enabling detailed investigation and fast triggering of interlocks to prevent damage. At LIPAc, the superconducting RF (SRF) accelerator currently being commissioned is fully equipped with PMs. PMs have also been successfully used in a temporary test bench* and in lightweight setups to assess the attenuation of aging optical fibers. Finally, prospects for upgrading the existing RF quadrupole (RFQ) arc detector will be presented.
Paper: MOP7054
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7054
About: Received: 12 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
MOP7173
Optimized plasma electrolytic polishing for Cu 1.3 GHz SRF cavities
1068
The performance of Superconducting Radio Frequency (SRF) cavities is critically dependent on surface quality. While Electropolishing (EP) has traditionally been the standard for achieving low-roughness surfaces on Niobium (Nb) and Copper (Cu) substrates, it relies on hazardous and corrosive acids. Since 2019, Legnaro National Laboratories (LNL) has developed an eco-friendly alternative: Plasma Electrolytic Polishing (PEP). Utilizing only diluted salt solutions, PEP offers significant advantages over EP, including superior removal rates ($2\text{-}8~\mu\text{m/min}$ for Nb and $3\text{-}30~\mu\text{m/min}$ for Cu) and surface roughness ($R_a$) below tens of nanometers. Furthermore, the setup has been optimized to use external cathodes, eliminating the need for complex internal cathode insertion in elliptical cavities. Following the establishment of patented recipes in 2022, PEP was successfully applied to Cu $6~\text{GHz}$ elliptical cavities, QPRs, and 3D-printed devices. A major milestone was achieved in August 2024 with the successful scaling of the process to a $1.3~\text{GHz}$ Cu elliptical cavity. In collaboration with CERN and KEK, the RF performance of PEP was validated on a hydroformed seamless cavity (coated with Nb thin film), demonstrating compatibility and slight performance improvements over standard EP. Further RF validation of PEP on differently produced Cu 1.3 GHz cavities will be presented.
Paper: MOP7173
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7173
About: Received: 13 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
MOP7182
Metal Additive Manufacturing for Accelerator Technologies (MAAT project at INFN)
1096
The MAAT (Metal Additive Manufacturing for Accel-erator Technologies) project is a three-year INFN re-search programme launched in 2026, aimed at establish-ing Additive Manufacturing (AM) as a validated produc-tion route for high-performance accelerator components. MAAT brings together three INFN units: Legnaro (LNL), Padova (PD), and Milano LASA, combining complemen-tary expertise in superconducting RF, materials science, and advanced manufacturing. This paper reports on the activities and preliminary results during the first year of the project, covering: 1. the Design for Additive Manufacturing (DfAM) of 6 GHz cavities produced by Laser Powder Bed Fusion (LPBF). 2. the preliminary tests of the Wire Laser Additive Manufacturing (WLAM) combined with CNC ma-chining for the fabrication of a 1.3 GHz RF cavity prototype in CuCrZr.
Paper: MOP7182
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7182
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
MOP7301
Representation of mechanical modes spectrum
1123
The static and dynamic Lorentz force detuning (LFD) derive from the sum of many mechanical modes and their interplay with EM radiation pressure. The LFD may give rise to instabilities in which the EM resonance frequency moves away from the “set point” value. The usual analytic theory for the oscillatory instability, and its threshold, are for a single, isolated mechanical mode; not a sum. We want a mathematical representation of the LFD spectrum that is compatible with an “isolated resonance” style of stability analysis, but nevertheless captures the phase-advance properties of a sum of many modes.
Paper: MOP7301
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7301
About: Received: 10 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7303
RF design progress of the 197 MHz crab cavity for EIC
1131
The interaction region (IR) crab cavity system is a special RF system designed to compensate for the luminosity loss caused by the 25 mrad crossing angle at the interaction point (IP) of the Electron-Ion collider (EIC). The configuration includes six crab cavities in the Hadron (proton or ion) Storage Ring (HSR) - four operating at 197 MHz and two at 394 MHz - installed on each side of the IP, along with one 394 MHz crab cavity on each side of the IP in the Electron Storage Ring (ESR). This paper presents the recent progress in the RF design of the 197 MHz crab cavity, addressing the geometrical constraints, required crabbing voltages, multipole components, and the Higher Order Mode (HOM) power and impedance thresholds.
Paper: MOP7303
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7303
About: Received: 14 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
MOP8301
Development and fabrication of a CW copper injector For SRF industrial cryomodules
1138
Compact SRF industrial linacs can deliver beam powers exceeding 500 kW within the 10 MeV regulatory limit that is difficult to achieve with normal-conducting linacs in a constrained footprint. Although SRF technology was historically too costly and complex for widespread industrial deployment, the advent of conduction cooling has enabled compact, stand-alone SRF systems suitable for both industrial and research applications. However, the limited cooling capacity imposes stringent requirements on beam parameters, including essentially zero beam loss on the SRF cavity walls. This, in turn, demands precise control of the injected beam energy and, critically, high-quality bunching with negligible inter-bunch particles. In collaboration with Fermilab, we developed a CW normal-conducting RF injector featuring a gridded RF gun integrated with the first cell of a copper booster cavity to meet these requirements. This paper presents the complete development of the booster cavity, covering beam dynamics optimization, RF and thermomechanical design, engineering implementation, fabrication, and bench measurement.
Paper: MOP8301
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP8301
About: Received: 13 May 2026 — Revised: 15 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUP3069
Multi-objective Bayesian optimisation (MOBO) for high-quality photoinjector optimisation
1650
Optimising SRF photoinjectors is a challenging task due to the high-dimensional, nonlinearly coupled parameters and competing objectives such as transverse emittance and bunch length. Conventional methods such as manual tuning or MOGA require thousands of evaluations and are impractical for routine operation or computationally expensive simulations. This work presents a multi-objective Bayesian optimisation (MOBO) approach that uses Gaussian-process surrogate models and tunable, uncertainty-aware acquisition functions to identify Pareto-optimal solutions in an order of magnitude fewer evaluations. When applied to the 1.4-cell SRF photoinjector at SEALab, and the 1.6-cell SRF gun and 20m injector beamline for EuXFEL, this optimisation outperforms MOGA in solution-efficiency and provides interpretable sensitivity information for injector tuning. These results demonstrate the potential of MOBO as an efficient, machine-ready strategy for SRF photoinjector optimisation.
Paper: TUP3069
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP3069
About: Received: 12 May 2026 — Revised: 20 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7312
Progress Towards RF Conditioning of Low-Loss Couplers for a Conduction-Cooled Cryomodule
1723
This work presents current progress on the conditioning of two new 25 kW couplers optimized for use in a compact, conduction-cooled SRF cryomodule. A connecting waveguide, previously used for conditioning the 805 MHz SNS couplers, was altered for use at 915 MHz. The necessary modifications were determined via RF modeling, while thermal analysis results identified additional cooling requirements during RF conditioning and provided insight about potential higher-power operation. Initial low-power conditioning will be performed with a 2.5 kW solid-state amplifier, with plans to use an industrial magnetron for RF conditioning at 25 kW in the near future.
Paper: TUP7312
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7312
About: Received: 13 May 2026 — Revised: 15 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUP7326
Investigation of RF surface resistance in Sub-GHz superconducting elliptical cavities processed with various nitrogen-doping surface treatments
1756
Superconducting radio-frequency (SRF) cavity surface treatment with nitrogen-doping (N-doping) was a breakthrough in cavity processing which was found capable of increasing the cavity quality factor (Q0) by more than a factor of 2 compared to standard electropolish (EP) surface treatments, as well as achieving a highly desirable anti-Q slope behavior, an increase of Q0 with increasing accelerating field, in 1.3 GHz superconducting niobium cavities. N-doping has been extensively studied in 1.3 GHz cavities; however, a similarly significant increase in performance had not yet been observed in sub-GHz cavities. In this study, field-dependent BCS and residual resistances were measured in 644 MHz cavities for the FRIB energy upgrade with various surface treatments. The frequency dependence of the Q-slope was investigated by measuring BCS and residual resistances in the fundamental mode (FM) and 1.45 GHz higher-order mode (HOM) in the same cavity. We will report effects of various N-doping surface treatments on the FM and HOM performance, including achievements of Q0 as high as 4.9x10^10 at 17.5 MV/m in this class of SRF cavities.
Paper: TUP7326
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7326
About: Received: 13 May 2026 — Revised: 16 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
TUP7340
Understanding the connections between grain growth and flux expulsion in low RRR niobium SRF cavities
1760
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 of this study is to observe the grain growth behavior of low RRR niobium coupons subjected to high temperature annealing to identify the mechanism for improving flux expulsion in low RRR cavities. We anneal the low RRR material up to 1200 C to understand the limits of flux expulsion performance. We observe that low RRR material experiences less grain growth than high RRR when annealed at the same temperature. We search for the limitations to grain growth in low RRR material and develop a diagnostic based on grain structure to determine the appropriate recipe for good flux expulsion. The results of this study have the potential to unlock a new understanding on SRF materials and enable the next generation of high Q/high gradient surface treatments.
Paper: TUP7340
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7340
About: Received: 22 May 2026 — Revised: 22 May 2026 — Issue date: 22 May 2026
TUP7636
Performance and production status of the high-Q cryomodules for the SHINE project
1860
The SHINE Linac was optimized to accelerate the beam to 8 GeV with 54 high-Q cryomodules (CMs), benefiting from the higher performance of the cavities and CMs. Currently, the mass production of SHINE cavities and CMs is ongoing. Up to now, around 350 high-Q cavities with mid-T baking or N-doping recipes have been fabricated and tested. Most of them have been assembled in CMs. More than 30 CMs have been tested. In this paper, we report the performance of high-Q CMs and lessons learned during the production.
Paper: TUP7636
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7636
About: Received: 15 May 2026 — Revised: 16 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUP7638
RF design of a waveguide Hom-damping 1.3 GHz superconducting cavity prototype
1864
Superconducting radio-frequency (SRF) cavities represent a key technology for modern particle accelerators. In high-current energy recovery linac (ERL) facilities, suppressing higher-order modes (HOMs) is critical to ensure beam stability and minimize additional cryogenic heat loads. This work introduces a waveguide-based scheme to extract and damp harmful HOMs excited by intense beams. A systematic RF design and optimization procedure for this waveguide damping method is presented. By implementing the damping scheme into a single-cell cavity geometry, consistent HOM suppression is achieved while maintaining good properties for the fundamental accelerating mode. The single-cell waveguide HOM-damping cavity, adopting the TESLA shape with an enlarged beam pipe, is currently under fabrication and will be tested in cryogenic experiments.
Paper: TUP7638
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7638
About: Received: 14 May 2026 — Revised: 20 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7641
Ground-state and RF-frequency scaling for superconducting quantum systems
1871
A fixed-volume comparison of three-dimensional hard-wall quantum confinement is extended to a volume-dependent frequency model for superconducting quantum systems. The equivalent quantum frequency is obtained from the lowest Dirichlet eigenvalue and compared with radio-frequency (RF) scales used in supercon-ducting radio-frequency (SRF) cavities. The calculation separates the Schrödinger confinement scale from the electromagnetic wavelength scale: the quantum frequency follows an inverse two-thirds volume law, whereas a dimensional RF half-wave scale based on L = V¹ᐟ³ follows an inverse one-third volume law. Equating the two frequencies maps MHz-to-GHz SRF operation to submicron-to-micron local confinement lengths, supporting applications to superconducting islands, surface defects, qua-siparticle traps, and cavity-integrated quantum devices.cavity systems.
Paper: TUP7641
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7641
About: Received: 07 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7642
Entropy generation analysis of heat loads in an SSR2 superconducting cryomodule
1874
The SSR2 superconducting cryomodule is analyzed in terms of static and dynamic heat loads and the associated entropy rates at the 2 K stage. The reference cryomodule contains six superconducting single-spoke resonator cavities. Static heat loads arise from conduction through cryomodule supports, couplers, cables, and beam-pipe interfaces, and from radiation through the insulation vacuum. Dynamic heat load is produced by radio-frequency surface dissipation. At 2 K, static and dynamic heat loads of 20 W and 80 W correspond to entropy rates of 10 W/K and 40 W/K, respectively, for a total cold-stage entropy rate of 50 W/K. The dynamic contribution ac-counts for 80% of the total entropy rate and scales inversely with the intrinsic quality factor Q₀. A coefficient-of-performance analysis shows that 100 W at 2 K requires at least 14.9 kW in the Carnot limit and about 100 kW for a representative real COP of 0.001. The results show that reducing radio-frequency loss, increasing Q₀, minimizing static heat leakage, and improving refrigerator performance directly reduce entropy generation and improve cryomodule efficiency.
Paper: TUP7642
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7642
About: Received: 07 May 2026 — Revised: 11 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUP7731
Enhanced superconducting properties of Nb films via a high-power impulse magnetron re-sputtering/sputtering approach for Nb–Cu 1.3 GHz RF cavities
2025
Conformal deposition of high-performance superconducting films on complex cavity geometries, particularly ensuring robust film-substrate adhesion, remains a fundamental challenge. We address this by introducing a novel high-power impulse magnetron re-sputtering and sputtering (HiPIMRS) system designed for uniform niobium (Nb) film deposition on the interior surfaces of 1.3 GHz copper cavities. A key innovation is an in-situ copper substrate re-sputtering step prior to Nb deposition, which eliminates interfacial oxides and degradation, ensuring atomic-scale interfacial integrity. Through in-situ re-sputtering prior to deposition, we achieve oxide-free Nb/Cu interfaces with atomic-scale integrity. Crucially, electrical transport measurements demonstrate a significant enhancement in the superconducting transition temperature from 8.5 K to 9.3 K for HiPIMRS films, along with smooth surfaces (Rₐ < 20 nm) and a preferred (110) orientation. This work establishes HiPIMRS as a viable pathway for next-generation superconducting radiofrequency (SRF) cavity production, with its interfacial engineering protocols offering significant advancements in film conformity and superconducting properties.
Paper: TUP7731
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7731
About: Received: 01 Apr 2026 — Revised: 15 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUV7301
The First Beam Produced by A Conduction Cooled SRF Photogun
2112
We are excited to report on the first beam produced by the world’s first conduction cooled SRF photogun. Over the past five years, Euclid, working in collaboration with Fermilab and Argonne National Laboratory, has been developing a continuous-wave (CW), 1.5-cell, MeV-scale, conduction-cooled SRF photogun operating at 1.3 GHz. The primary objective of this effort is to demonstrate ultra-stable electron beams for UEM/UED applications, enabled by the exceptional shot-to-shot stability achievable with SRF technology compared to room-temperature RF photoguns. Although SRF systems were historically too costly for industrial deployment, two recent advancements: Nb₃Sn coatings and conduction cooling, have dramatically reduced system complexity and operating costs. This SRF photogun can deliver true CW operation while dissipating only ~2 W of RF power, eliminating the need for a high-power RF system and significantly reducing facility footprint. This SRF photogun is also featured with a raised Nb3Sn backwall serving as the photocathode, removing the need for an external cathode insert. In this paper, we present the first beam results from this system along with its cooldown performance, Q-slope behavior, synchronization characteristics, and initial beam parameters.
Paper: TUV7301
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUV7301
About: Received: 12 May 2026 — Revised: 17 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
WEP1016
UPDATE ON THE ITN COORDINATED EFFORT FOR ILC TECHNOLOGY DEVELOPMENT IN EUROPE
2231
The ITN-EU consortium, coordinated by CERN with the support of CEA-Saclay and INFN-LASA, is advancing Europe’s contribution to the International Linear Collider (ILC) through the development and validation of high-performance superconducting radiofrequency (SRF) cavities. Activities focus on establishing an optimized production chain, from single-cell R&D to the industrialization of 9-cell cavities. Material procurement and quality control have been completed, and prototype single cells are fabricated and they will be used to assess advanced surface treatment strategies. EU partners are also preparing technical specifications and harmonizing production with Japanese High Pressure Gas Safety requirements. Europe will provide two fully prepared 9-cell cavities for installation in an ILC-type cryomodule assembled and tested at KEK, demonstrating Europe’s integrated and strategic role in the global SRF program.
Paper: WEP1016
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP1016
About: Received: 14 May 2026 — Revised: 18 May 2026 — Accepted: 18 May 2026 — Issue date: 22 May 2026
WEP4619
Surface treatment of the prototype spoke cavity for the JAEA-ADS linac
2509
Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven nuclear transmutation system (ADS). As a first step toward the practical design of the JAEA-ADS linac, we have been prototyping a low-beta (~0.2) single-spoke cavity. Fabrication of the prototype spoke cavity was finally completed in FY2024. We are currently working on surface preparation for a high-field cavity testing at liquid helium temperature. In FY2025, we performed chemical polishing on the inner surface of the fabricated cavity, and subsequently proceeded to vacuum heat treatment. Although a uniform removal of the surface layer could not be achieved as initially anticipated, there were no defects observed on the inner surface. Hydrogen content of the chemically polished cavity was reduced through the furnace baking at J-PARC.
Paper: WEP4619
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP4619
About: Received: 16 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
WEP5107
Coupled-bunch instabilities with a defocusing higher-harmonic RF system
2814
Coupled-bunch instabilities restrict the beam intensity in many synchrotrons. These limitations can be mitigated by adding a higher-harmonic radiofrequency (RF) system, which modifies the potential well. Of particular interest is the bunch lengthening mode (BLM), in which the higher-harmonic voltage produces a defocusing effect at the bunch centre. By decreasing the peak line density, space-charge effects are reduced in hadron synchrotrons, while Touschek scattering is mitigated in synchrotron light sources. This contribution investigates the impact of a higher-harmonic RF system in BLM on the intensity threshold, growth rate, and mode behaviour of coupled-bunch instabilities. The influence of beam parameters such as the bucket filling factor, narrowband impedance properties, and RF system configuration is highlighted. Regimes in which BLM is advantageous or disadvantageous are compared to the ones for a single-harmonic RF system. The comparisons are based on semi-analytical solutions of the Vlasov equation as well as macro-particle simulations using the BLonD code.
Paper: WEP5107
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5107
About: Received: 15 Apr 2026 — Revised: 16 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
WEP6607
Longitudinal Beam Diagnostics with a Streak Camera at Taiwan Photon Source
3334
The Taiwan Photon Source (TPS) streak camera system has been used for longitudinal beam studies since the early commissioning stage. This paper first presents a representative high-current instability observation associated with the CU15 insertion device taper and then recent measurements of bunch length and synchronous phase under operation with the superconducting RF (SRF) + passive 3rd harmonic cavity (HC), here abbreviated as SRF HC. The CU15 case shows different instability behaviors along the fill pattern in streak images. The SRF HC measurements provide bunch-by-bunch information under different fill patterns and SRF HC settings for comparison of bunch lengthening and phase shift. Under operation with the passive SRF HC, a phase drift of about 35 ps is observed along the bunch train, consistent with transient beam loading under quasi-uniform filling. These measurements show that the streak camera is useful for longitudinal diagnostics and machine studies at TPS.
Paper: WEP6607
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP6607
About: Received: 15 Apr 2026 — Revised: 15 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
THP2125
First demonstration of MeV electron diffraction using the superconducting RF photoinjector at the Helmholtz-Zentrum Dresden-Rossendorf
3679
Ultrafast electron diffraction (UED) allows for the characterization of structural and electronic dynamics in samples with sub-picosecond resolution. Utilizing a continuous wave photoinjector gives rise to MHz MeV UED, which has the benefits of better temporal resolution, higher beam coherence, higher resolution, and high repetition rates. A superconducting radiofrequency (SRF) photoinjector is part of the existing ELBE user facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), delivering electron beams in user operation since 2010. The HZDR is planning the construction of the Dresden Advanced Light Infrastructure (DALI), a source of positrons and IR and THz radiation. One of DALI's end stations will consist of the MeV UED facility, allowing to pump with IR and THz beams, and probe the samples with an electron beam, generated using an HZDR-type SRF photoinjector. In this proceeding, we present the first MeV electron diffraction results using the HZDR-type SRF photoinjector at ELBE.
Paper: THP2125
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2125
About: Received: 13 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
THP2129
Options analysis of MHz injectors for the UK XFEL project
3690
The UK XFEL conceptual design and options analysis (CDOA) process has recently been completed. The UK XFEL design uses a superconducting linac operating with up to a 1 MHz repetition rate electron beam and demands beyond state of the art electron beam quality. This leads to strict requirements on the injector. The requirement for MHz repetition rates restricts the electron source technology to a number of operations: DC guns, VHF guns, L-band SRF guns, VHF SRF guns and DC-SRF guns. Two of these injector technologies were investigated in detail: a VHF gun and a high field L-band RF gun. In this proceeding the simulated beam dynamics performance and the technical readiness of the options will be compared and a number of conclusions will be drawn for the UK XFEL project.
Paper: THP2129
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2129
About: Received: 13 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
THP2131
Production and Initial Testing of a Nanostructured Copper Photocathode in an S-Band RF Gun
3698
A copper photocathode based on bulk Cu(100) substrate with a 50 𝜇m-diameter nanostructured region was fabricated and integrated into an S-band radio-frequency gun. We report the procedure for production and preparation of high- quality copper cathodes with nanostructured area compatible with state-of-the-art S-band RF gun. Experimental results indicate absence of increased dark current up to 70 MV/m at the cathode.
Paper: THP2131
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2131
About: Received: 12 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
THP2132
Thermal study of a 2 Kelvin copper photocathode in a CW SRF gun cavity
3702
We assess the thermal behavior of a cryogenically cooled copper photocathode integrated into a continuous-wave superconducting radio-frequency injector cavity through direct thermal contact. A coupled three-dimensional thermal-electromagnetic model incorporating both the bulk photocathode and the injector cavity is presented. For the current injector design, the laser heat load is predicted to have a negligible effect on the intrinsic quality factor of the cavity. The cryogenic stability of the copper cathode is identified as the primary operational constraint. To address the associated cooling challenges, we propose a modified cathode plug geometry.
Paper: THP2132
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2132
About: Received: 12 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
THP2133
Development of a particle-free cathode loadlock system for SRF-Gun
3705
A prototype of SRF Gun has been built and successfully tested at MSU for LCLS-II HE project. This gun uses an HZDR-type cathode and required the development and implementation of a special cathode transfer and insertion system to ensure reliable operation. The main objectives were to prevent particle contamination, achieve a transverse alignment accuracy of less than 100 µm over a transfer distance of 1.3 m under ultra-high vacuum conditions (<10⁻⁹ Torr), and ensure the safe and repeatable insertion of the cathode into the cold cavity of the SRF gun. The cathode suitcase is used to transport a single cathode but can be upgraded in the future to accommodate high quantum efficiency (QE) semiconductor cathodes. To enable robust cathode exchanges, HZDR developed and built a special manipulation mechanism and an automated alignment system. The alignment concept was implemented using a translation rod equipped with contact electrodes and driven by precision stepper motors. Commissioning and final testing were successfully carried out at MSU to validate the transfer process. No change in RF performance was observed after the cathode exchange. The results confirmed that the system meets the design specifications and enables particle-free cathode exchange for the SRF gun at varying temperatures.
Paper: THP2133
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2133
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 18 May 2026 — Issue date: 22 May 2026
THP2134
Photocathode development plan for DALI multifunctional facility
3708
DALI is an accelerator-based terahertz (THz) light source that uses multiple superconducting accelerators to drive CW electron bunches through undulators to emit ultra-intense THz pulses, including two ELBE SRF photo injects as the e- sources for high bunch charge beamline and for the UED, respectively. It requires a versatile portfolio of photocathodes to support diverse electron gun configurations and beam parameters targets. For the SRF gun commissioning, robust polycrystalline copper cathodes and magnesium cathodes will be employed, providing reliable performance and simplified handling during initial RF conditioning. Beam commissioning and routine user operation will firstly rely on the mature Cs₂Te photocathode, chosen for their proven robust, stability and realiable quantum efficiency. To enhance operational flexibility, especially in scenarios where UV laser generation presents challenges for special user appliations, we will consider to apply high-efficiency “green” photocathode optimized for visible-wavelength drive lasers. In parallel, an ultra-low-emittance photocathode in tens of micrometers will be under investigation to meet the stringent beam quality requirements of UED applications. This multi-cathode strategy ensures reliable commissioning, user-friendly operation, and state-of-the-art beam performance across all beamlines of the new accelerator facility.
Paper: THP2134
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2134
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 18 May 2026 — Issue date: 22 May 2026
THP4027
INFN LASA activities toward PIP-II
3922
INFN LASA is advancing its in-kind contribution to the PIP-II project at Fermilab, with significant progress achieved in both cavity production and testing infrastructures. The main activity is the fabrication of 38 five-cell β = 0.61 superconducting cavities for the LB650 section of the linac. Manufacturing is well advanced with mechanical production of the series cavities progressing while the two pre-series ones are being used to validate the complete industrial workflow, including surface processing and final preparation, that is mostly entrusted to industrial partners. Crucial to ensure compliance with the stringent performance requirements of PIP-II, all cavities will undergo final qualification through a vertical cold tests facility at DESY AMTF (Germany) that is being finalized and commissioned. Lastly cavities will proceed with the delivery to CEA Saclay (France) as fully validated components ready for string assembly. This contribution summarizes the status of these activities, presenting updates from the manufacturing of series cavities, results from pre-series qualification and recent upgrades to both LASA and DESY the testing infrastructures.
Paper: THP4027
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP4027
About: Received: 13 May 2026 — Revised: 19 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026