MC7 – Accelerator Technology and Sustainability
A finite element study of stress reduction techniques in REBCO HTS conductor on a round cable (CORC) cable
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ReBCO high-temperature superconducting (HTS) tape is critical for achieving the high magnetic fields needed in next-generation particle accelerators. Enhancing the mechanical performance of ReBCO tape increases its critical current by reducing internal stress, especially in the superconducting layer. A finite element study examined how copper layer properties affect stress in ReBCO conductor on a round core (CORC) cables. The cable was modeled as a doubly supported beam under uniform compressive stresses."cable was modeled as a doubly supported beam under uniform load to simulate bending. A staged modeling approach—from a single tape to a six-layer stack—enabled validation and efficient parameter studies. Increasing the yield strength and Young’s modulus of the copper layers reduced peak stress in the ReBCO layer. These results support development of improved tape stacks for high-field accelerator magnets
SUP075
Co-sputter deposition of Nb₃Sn layer into SRF cavity using Nb-Sn composite target
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Nb₃Sn, with its superior superconducting critical temperature (Tc ~18.3 K) and superheating field (Hsh ~400 mT), is considered a promising material for superconducting radiofrequency (SRF) cavities, offering enhanced cryogenic performance compared to bulk niobium cavities. A Nb₃Sn coating technique has been developed for Nb SRF cavities using co-sputtering of Nb-Sn composite target in a DC cylindrical magnetron sputtering system. The composite target configuration and discharge conditions for co-sputtering were optimized to deposit Nb-Sn films on flat Nb substrates, followed by annealing to form Nb₃Sn. Multiple strategies have been explored to improve the surface homogeneity of the Nb₃Sn coating, including optimizing a two-step annealing process, annealing in Sn vapor, and a light Sn recoating process. A 1.5 µm Nb-Sn co-sputtered film was deposited on the interior of a 2.6 GHz Nb SRF cavity and annealed at 600 °C for 6 h, followed by 950 °C for 1 h. Cryogenic RF testing of the annealed cavity demonstrated a Tc of 17.8 K, confirming the formation of Nb₃Sn. Then, the annealed cavity underwent a light Sn recoating treatment and attained a quality factor (Q0) of 8.5E+08 at 2.0 K.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP015
About: Received: 06 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
SUP076
Design of a shipping fixture for a compact cryomodule hermetic assembly
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In support of the development of a conduction-cooled 915MHz superconducting radio frequency (SRF) cryomodule, this study highlights the design of a shipping fixture for transporting the hermetic assembly 4500 km from Jefferson Lab to General Atomics in San Diego, California. The hermetic assembly consists of a 2-cell 915 MHz SRF cavity, a coaxial fundamental power coupler and warm-to-cold transition beam tubes. The two-part shipping assembly consists of an inner frame, providing direct mounting of the components, and an outer frame mounted to the ground transport vehicle. The inner frame is then connected to the outer frame by way of wire-rope isolators. Accelerometer data from ground transportation of previous projects at Jefferson Lab provides the baseline for the expected frequency and magnitude of vibrational and shock events during transit. Modal analyses were carried out in ANSYS on the inner frame assembly and critical components to identify an appropriate wire-rope isolator configuration such that peak loads are mitigated and the incurred frequencies do not correspond with the fundamental modes of the structures.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP022
About: Received: 07 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
SUP077
Design study of an RF-Kicker module for bunch cleaning at the ATLAS Positive-Ion Injector.
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Positive-Ion Injector at ATLAS accelerator facility can accelerate heavy ions and has three key subsystems -- an electron cyclotron resonance (ECR) ion source, a 12-MHz multi-stage beam bunching system, and a 12-MV superconducting linac accelerator. The first stage of the bunching system is a multi-harmonic buncher that operates at 12.125 MHz and creates a bunch train with a period of 82.5 ns at ~70% bunching efficiency. The remaining unbunched beam must be removed to avoid the production of undesirable ‘satellite’ bunches, which can quench the superconducting solenoids downstream during operation. In this paper, we present the design of a resonant sine-wave RF-structure that effectively removes the bunch ‘tails’ using a vertically deflecting kick. We also discuss the effects of the RF-Kicker on the beam quality, which was estimated by TRACK3D simulations.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP023
About: Received: 08 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
External controller for the SRFK thyratron heaters
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The following work will detail the development and implementation of a system which will measure the voltage and current from two points on a high-voltage switch called a thyratron and automatically manipulate two variable transformers controlling these values. Each of the extraction kickers at LANSCE (SRFK71 & SRFK81) uses a thyratron to trigger their respective pulses. The thyratrons have separate heaters for the cathode and reservoir, and each needs to maintain specific voltage and current levels for the thyratron to work properly. Currently, the method of measuring and adjusting these values requires locking out the system, opening the tank, and measuring the voltage and current of each heater, then adjusting two variable transformers by hand to reach the desired values. This controller consists of four analog-to-digital converters which will relay these measurements out of the modulator as digital signals through fiber optic transceivers. An Arduino will be programmed to interpret the digital signals and display the values on an LCD. It will also return signals to DC motors controlling the variable transformers if the values lie beyond the desired range.
Integral Field Probe for Mapping of Curved Magnets
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The Single Stretched Wire (SSW) method allows highly precise integral field measurements by recording voltage across a tensioned wire mounted to 2-axis linear stages at either end of the magnet aperture. However, traditional SSW probes are not well suited for curved accelerator magnets, which are essential for steering charged particles along arced trajectories in storage rings or beamlines. The tension required to eliminate sag demands a purely straight path, making them incompatible with non-linear magnet geometries. To address this limitation for curved magnets, a modified approach was developed using a segmented, 3D-printed support structure that incorporates a pre-shaped “anti-sag” curve. Under its own weight and that of the wire bundle, the structure deforms to lie flat while conforming to the curvature of the magnet in the horizontal plane. The optimal geometry of the probe was derived using an iterative process combining FEA simulations in Ansys Mechanical with testing of various carbon fiber-reinforced filaments. The printed and assembled probe was successfully used to measure the SDD-055 magnet at Fermilab, yielding promising results.
SUP080
One-to-one mapping between the electromagnetic modes of Cylindrical and Coaxial Half-wave cavities
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Design of radio frequency (RF) couplers and diagnostics require a good understanding of the electromagnetic mode patterns of RF cavities. This study investigates the adiabatic transformation of transverse magnetic (TM) modes in a cylindrical cavity into transverse electromagnetic (TEM) modes of a coaxial cavity by gradually introducing an inner conductor. Using CST Studio Suite, we simulate the eigenmode evolution as the geometry transforms from a pure cylindrical to a coaxial configuration. We track the behavior of TM010 through TM014 modes to observe the continuous evolution into the corresponding TEM0 through TEM4 modes of the coaxial cavity. The process is governed by the evolution of the electric field orientation as the geometry shifts, enabling the axial TM fields to reorient into the radial electric field configuration of TEM modes. Field patterns, eigen-frequencies, and mode indentities are analyzed throughtout the transition. The results provide simulation-based evidence that TM to TEM conversion occurs without generation of newer eigenmodes, offering a valuable insight into the design of transition regions in superconducting RF (SRF) systems and provides a foundation for experimental validation.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP062
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
SUP081
Study of uncorrelated resonance crossing in a controlled environment
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This paper deals with estimating spin depolarization in planned very high energy electron-positron storage rings like the FCC-ee. The paper covers three aspects of the work: 1) the putative so-called uncorrelated resonance crossing due to noise in the spin-rotation phase advance caused by photon emission in synchrotron radiation. This is expected to suppress the depolarization caused by synchrotron sideband resonances, 2) a study of the performance of our code on multiple high performance systems, and 3) the novel exploitation of a high order Magnus expansion applied to spin transport. The study uses Monte-Carlo spin-orbit tracking for a simple model of spin motion, the so-called single resonance model, augmented by the effects of radiation. The results presented here represent the first steps of a planned detailed large-scale exploration.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP067
About: Received: 08 Aug 2025 — Revised: 09 Aug 2025 — Accepted: 10 Aug 2025 — Issue date: 28 Aug 2025
SUP082
Sputter coating of Nb₃Sn into SRF cavity using stoichiometric target
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Nb₃Sn has emerged as a leading alternative material due to its higher superconducting critical temperature (Tc) and superheating field (Hsh), promising a viable solution to the intrinsic performance limit currently faced by Nb superconducting radiofrequency (SRF) cavities. We sputter-coated Nb₃Sn inside Nb SRF cavity using a stoichiometric Nb₃Sn tube target in a DC cylindrical magnetron sputter coater. The target was fabricated by growing an estimated >20 μm thick Nb₃Sn layer on a Nb tube via Sn vapor diffusion using Jefferson Lab’s coating system. Approximately 150 nm thick Nb-Sn films were sputter-deposited onto flat Nb samples at positions representing the beam tubes and equator of a 2.6 GHz Nb cavity. Post-deposition annealing at 950 °C for 3 h resulted in the formation of Nb₃Sn. Microstructural analysis of the annealed films was carried out to investigate the morphology and structure of the Nb₃Sn films. Later, a 2.6 GHz Nb SRF cavity was coated with a ~1.2 μm thick sputtered Nb-Sn film using a stoichiometric Nb₃Sn target, followed by annealing. Cryogenic RF testing of the annealed cavity demonstrated a Tc of 17.8 K, indicating the formation of Nb₃Sn. After a light Sn recoating treatment, the cavity achieved a quality factor (Q0) of 6.7E+08 at lower field at 2.0 K.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP082
About: Received: 07 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
SUP083
The Pulsed Ion Reflex Klystron: A New Accelerator for High Efficiency Voltage Conversion
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Beam Alpha developed a kilowatt-scale fusion microreactor that directly converts nuclear energy to electrical energy without intermediate heat steps. This device has an output of 1.6 million volts DC. A converter is needed to transform this potential energy into useful electrical power. To achieve this the "Pulsed Ion Reflex Klystron" has been developed. The PIRK aims to achieve high conversion efficiencies by directing negatively charged ions through a re-entrant resonant cavity hundreds of times to gradually transfer energy from the moving particles to said cavity. Ions will be released into a 6-meter linear accelerator with roughly 1000 precisely spaced electrodes forming a quasi-parabolic potential. This potential is symmetric about the midpoint of the tube causing ions to oscillate with a frequency of approximately 1 MHz independent of energy. Perturbations to this parabolic potential are designed to provide radial electrostatic beam focusing. An algorithm is devised to produce optimal voltage curves to maximize both longitudinal bunching and radial confinement, and these curves are examined against practically realizable potentials. Energy is coupled out of the resonant cavity using a loop antenna connected to a silicon carbide rectifying diode. This converts the RF in the cavity to a 400V intermediate DC bus that can easily be inverted to wall power.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP086
About: Received: 10 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
SUP085
Unlocking SRF Performance: How Nitrogen and Oxygen Shape Cavity Performance
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Nitrogen and oxygen-based surface treatments have revolutionized the performance of superconducting radiofrequency (SRF) cavities, enabling them to reach higher gradients and lower losses. However, the exact mechanisms by which these treatments improve cavity performance remain largely unknown. This work provides new insights into the role of nitrogen and oxygen in SRF cavity performance by using time-of-flight secondary ion mass spectrometry (TOF-SIMS) to precisely quantify the concentrations and depth profiles of these impurities within niobium cutouts. We correlate these impurity profiles with detailed cavity performance measurements, including surface resistance and quality factor, and compare our findings with predictions from BCS theory. The results demonstrate that while both nitrogen and oxygen enhance performance, ten times more oxygen is required to achieve the same reduction in BCS resistance as interstitial nitrogen. We present a potential model in which the observed variation arises from nitrogen's greater effectiveness in trapping hydrogen, thus reducing the formation of niobium hydrides and enhancing superconducting gap.
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-THYN01
About: Received: 13 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
High-Power Targetry R&D road map for HEP
Designing a reliable target is already a challenge for MW-class facilities today and has led several major accelerator facilities to operate at lower power due to target concerns. With present plans to increase beam power for next-generation accelerator facilities in the next decade, timely R&D in support of robust high-power targets is critical to secure the full physics benefits of ambitious accelerator power upgrades. The next generation of high-power targets and beam-intercepting devices (beam dumps, absorbers, collimators…) will have more complex geometries, novel materials, and new concepts that allow for use of improved high-heat-flux cooling methods. Advanced numerical simulations need to be developed to support design of reliable high-power beam targets. In parallel, development of radiation-hardened beam instrumentation is needed. Irradiation methods for high-power targets must be further developed, and new irradiation facilities are needed since only a few facilities worldwide offer beams suitable for target testing. A comprehensive R&D program must be implemented to address the many complex challenges faced by multi-MW beam intercepting devices.
Traveling Wave excitation results in SRF Cavity With a Feedback Waveguide at 2K.
Conventional SRF cavities are used in standing wave regime and are limited by surface fields to ~50 MV/m. In order to overcome this limit, Superconducting Traveling Wave (SCTW) cavity was proposed as it allows to achieve ~1.5 times higher accelerating gradient operating at lower phase advance per cell, thus improving transit time factor. However, power recirculation through a feedback waveguide is required to maintain cavity efficiency. Funded by the U.S. Department of Energy's SBIR program, Euclid Techalbs, in collaboration with Fermilab, demonstrated in the past the surface processing capability of a single-cell prototype with a feedback waveguide. Subsequently, a 3-cell prototype was designed and fabricated to demonstrate a traveling wave regime in SRF cavity with a feedback waveguide at cryogenic temperatures and the highest gradients. Previously, we have demonstrated the feasibility of traveling wave excitation and control at 2K in the cavity with highly loaded QL=1e6, which is typical for high current machines. Here we present our recent results of traveling wave control with a more challenging smaller bandwidth.
Tuning-Free High-Gradient RF Structures: From SwissFEL to FCC-ee – A Scalable Technology for Future Accelerators
At the Paul Scherrer Institute (PSI), a novel, industrially scalable, and tuning-free manufacturing process for normal-conducting high-gradient C-band accelerating structures has been developed and successfully implemented for the Swiss Free-Electron Laser (SwissFEL). This approach, which eliminates RF post-production tuning, achieves excellent field flatness and phase accuracy through ultra-precision machining and brazing techniques. Over 100 accelerating structures were produced and installed without tuning, operating reliably with breakdown rates below 1e-9 bpp/m. Following SwissFEL’s commissioning and successful operation, PSI extended this process to other frequency bands, including S-band and X-band, for applications in collaborations with CERN, ELETTRA, and DESY. These efforts include the construction of X-band accelerating structures for CLIC, high-gradient S-band structures for the FERMI FEL upgrade, and the development of ultra-precise transverse deflecting structures (TDS) with variable polarization for advanced beam diagnostics. Building on this expertise, PSI is now leading a multi-institutional effort to develop the lepton injector for the FCC-ee, with plans for mass production of over 400 tuning-free RF structures. This contribution presents the evolution, deployment, and future prospects of tuning-free RF structure technology, underscoring its pivotal role in the next generation of accelerator infrastructures.
TUCD03
Operation and R&D of liquid lithium charge stripper at FRIB
327
Charge stripping is an essential technique for the efficient acceleration of heavy ions. The Facility for Rare Isotope Beams (FRIB) utilizes the Liquid Lithium Charge Stripper (LLCS) to produce the world’s most powerful heavy ion beams, so far demonstrated up to 20 kW with 200 MeV/u energy. In the FRIB driver linac, electrons are stripped by a thin film jet of liquid lithium flowing at 50 m/s. The LLCS has been in operation with FRIB’s linac since 2022 and will support the future ramp-up of the beam power to 400 kW. Our operation experiences have revealed that the performance of the LLCS will be further improved by increasing the film thickness twice and enhancing the uniformity and stability of the film. In this presentation, we report on the operational experiences with the current LLCS and various R&D activities for its future upgrade.
Paper: TUCD03
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-TUCD03
About: Received: 08 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
WEXN01
Accelerator workforce development
625
Accelerator science has been hugely influential on research, contributing to physics Nobel Prize-winning research every three years. The DOE Office of Science invests in accelerator science to sustain America’s excellence and constructs and operates large-scale scientific user facilities to be vital tools of discovery. Developing the next breakthroughs in accelerator science, and designing, building, and operating user facilities, requires a large, highly skilled workforce of accelerator scientists, engineers, and technical (AS&E) staff. Some portions of the AS&E workforce are best planned with a long-term, national perspective in mind. A roundtable meeting was called with participants comprising 9 DOE National Laboratories and the Office of Science Nuclear Physics User Facility FRIB. An approximate census of the current accelerator workforce at those institutions was assembled along with an approximate workforce projection with a 10-year horizon. Critical and endangered skillsets were identified and best practices for workforce development were shared. In recognition of the wider ecosystem, plans were discussed to expand the roundtable participants to universities and critical members of the accelerator industry in the next year.
Paper: WEXN01
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEXN01
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Aug 2025
Focusing of Relativistic Electron Beams With Permanent Magnetic Solenoids
Achieving strong focusing of MeV electron beams is a critical requirement for advanced beam applications such as compact laboratory X-ray sources, dielectric laser accelerators, and ultrafast electron diffraction (UED). To address these and similar relativistic electron focusing requirements, a compact radially magnetized permanent magnetic solenoid (PMS) has been designed, fabricated, and tested. The solenoid provides a compact and inexpensive solution for delivering high axial magnetic fields (1 Tesla) to focus MeV electron beams. Field characterization of the solenoid demonstrates excellent agreement with analytical models, validating the PMS design. The electron beam test employs a high-brightness photoinjector to study the focusing properties of the PMS. The results show a significant reduction in beam size with small spherical aberrations. Using the measured results, two application cases are evaluated: angular magnification in UED setups and strong focusing for Compton scattering or other microfocus uses.
WEAN02
Status of permanent magnet radiation resiliency studies at CEBAF
630
An ongoing investigation for the future of Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF) lies in upgrading its maximum nominal energy using Fixed-Field Alternating-gradient (FFA) technology for its recirculating arcs, using permanent magnets for the FFA arcs. A common concern among the community is the degradation of these permanent magnets during operation due to the radiation environment in which they will be present. This work, funded by a Laboratory Directed R&D grant, aims to measure the permanent magnet degradation in the CEBAF tunnel enclosure, and extrapolate to the energies expected from the upgrade. We present the latest results of this study, as well as plans moving forward.
Paper: WEAN02
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEAN02
About: Received: 07 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEAN03
PMQ radiation resistance testing at NSLS-II
634
A new lattice for the NSLS-II upgrade is likely to use high strength (> 100 T/m) permanent magnet quadrupoles (PMQs). An ID beam exiting through these quadrupoles will place highly intense x-rays very close (~ 1mm) to the permanent-magnet material. In these tests the PMQs will be placed in the IFE (Instrumentation Front End) front end to assess any degradation of their field strengths and field quality due to long term exposure to an ID beam. The IFE beamline was recently commissioned at NSLS-II and is dedicated to testing the mechanical properties of accelerator materials and components. The description of the source and experimental setup will be given.
Paper: WEAN03
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEAN03
About: Received: 01 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
A finite element study of stress reduction techniques in REBCO HTS conductor on a round cable (CORC) cable
ReBCO high-temperature superconducting (HTS) tape is critical for achieving the high magnetic fields needed in next-generation particle accelerators. Enhancing the mechanical performance of ReBCO tape increases its critical current by reducing internal stress, especially in the superconducting layer. A finite element study examined how copper layer properties affect stress in ReBCO conductor on a round core (CORC) cables. The cable was modeled as a doubly supported beam under uniform compressive stresses."cable was modeled as a doubly supported beam under uniform load to simulate bending. A staged modeling approach—from a single tape to a six-layer stack—enabled validation and efficient parameter studies. Increasing the yield strength and Young’s modulus of the copper layers reduced peak stress in the ReBCO layer. These results support development of improved tape stacks for high-field accelerator magnets
NEG coating and thermal coating spray of vacuum chamber
As the fourth-generation synchrotron radiation light source, vacuum chambers with small apertures were employed for high energy photon source (HEPS), making the performance of Non-evaporable getter (NEG) coating is very crucial for its vacuum system. After years of development, the highly stability of the NEG coating has been achieved. Massive production facilities of NEG coated vacuum chambers have been developed for HEPS in Huairou, Beijing, which based on the NEG coating prototypes. The facilities can achieve simultaneous coating of 16~20 vacuum chambers of HEPS including irregular shaped vacuum chambers. The pumping performance of the NEG coated vacuum chambers has been measured by test facilities. After heated at 200°C for 24 hours, the highest pumping speed of H2 is about 0.65 l/scm2, and the highest capacity of CO is about 1.89×10-5 mbar·L/cm2. The lifetime is more than 20 cycles of air exposure and re-activation. Multilayer thermal coating spray have been studying and preliminary test shows that the heating temperature could reach 300 ℃, and after more than 12 times reheating, the spraying layer also shows a good adhesion. The baking is the most crucial procedure in achieving ultra-high vacuum. Due to NEG coating reactivation and degassing, to meet the ultra-high vacuum requirement of achieving a dynamic vacuum level of ~10-10 mbar. Multilayer thermal coating will be coated outside of the vacuum chamber which composited by ceramic and conductivity layer, the heating temperature could reach 300℃.
A new route to improve the material quality of Nb3Sn SRF cavities with Zr inclusion
Superconducting radio frequency (SRF) cavities based on Nb$_3$Sn superconductor can exceed the performance of conventional Niobium SRF cavities and would open many new industrial applications for small scale accelerators. The material quality-especially the surface non-homogeneity and microstructural defects, is the crucial challenge to realize the full potential of Nb$_3$Sn SRF cavities. In this work, we present our recently developed route for effectively reducing the intrinsic defects in magnetron sputter coated Nb$_3$Sn SRF cavities and eventually improve the overall RF performance. In our study, we introduced a small variable fraction of Zr in Nb$_3$Sn host matrix using co-sputtering process. Post-annealing, the elemental Zr forms ZrO$_2$ precipitates of average dimensions ranging from 20-100 nm. We noted that the density of the surface and bulk voids as well as their average sizes are dramatically reduced on increasing the Zr content in Nb3Sn. We also observed that increasing Zr concentration up to an optimal level can substantially improve both superconducting transition temperature and upper critical magnetic field. Additionally, increasing the Zr concentration is also noticed to prevent the oxygen diffusion and resulting to a thinner formation of primary surface oxides. These results indicate that inclusion of Zr in Nb$_3$Sn sputtered coating will be a promising method to improve the material quality and might help to reduce the overall RF power dissipation.
An Integrated Approach to Understanding Electric Breakdown
Our approach to the physics of vacuum arcs, which limits many technologies, has been to model rf breakdown in vacuum in four stages (trigger, ionization, evolution and damage), then generalize the model, filling in details with data from other fields, such as accelerator design, power transmission grid limits, large tokamaks, sample failures in atom probe tomography and thin film sputter coating systems. The immediate goal is to understand surface damage and the probability of future breakdown events. We have found that thermal contraction of the cold surface and surface tension flattening can explain clusters of crack junctions giving field enhancements on the order of 200 on otherwise inactive cold surfaces. We also find a combination of surface tension and Maxwell stress during arc evolution can produce an unstable liquid surface at high electric fields that explains the time structure of the arc and many aspects of surface damage seen in breakdown data. We describe the mechanisms, existing data and experiments which should be useful for refining models and producing a self consistent, widely applicable model of gradient limits.
WEP005
A compact top-off injection with cascaded nonlinear Kickers for diffraction limited storage rings
690
To address the intrinsic dynamic aperture (DA) limitations of fourth-generation diffraction-limited synchrotron light source, we investigate a novel injection scheme utilizing multiple nonlinear kickers (NLKs) with optimized hardware design and phase advances in the storage ring (SR). Positioning the NLKs near the injection point reduces beam perturbation, while their on-axis zero field and gradient enable transparent injection—suppressing orbit and beam-shape oscillations during top-off operations. Particle-tracking simulations were performed using Accelerator Toolbox (AT), alongside the development of automated tools for converting magnetic field maps into AT-compatible kick maps, inserting NLKs at arbitrary lattice locations, conducting tracking, and optimizing NLK configurations. A key challenge is to shift the off-axis magnetic field peak closer to the beam orbit. Our novel NLK design achieves a peak within 5 mm of the axis—a significant improvement over the conventional greater than 7 mm range. Simulations accounting for realistic alignment and magnetic field errors indicate that a relaxed 5 mm DA and injection efficiency > 90% could be feasible for the NSLS-II upgrade lattice.
Paper: WEP005
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP005
About: Received: 07 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
WEP006
Application of low-cost sensors and deep autoencoders for monitoring water pumps in particle accelerators
694
In particle accelerator facilities, cooling-water pumps play a critical role in removing substantial amounts (in megawatts) of waste heat from numerous high-power accelerator components (e.g., magnets, radio frequency structures, power supplies) and beamline components*. Despite their role in daily operations, inspecting hundreds of water pumps is labor-intensive and performed only occasionally. Their unexpected failures can potentially lead to degradation of beam quality, hardware damage, and costly unplanned downtime**. This study introduces an innovative method for real-time monitoring of water pump vibrations to identify anomalies that signal potential mechanical failures. Our approach integrates (i) low-cost vibration sensors, which will consistently sample pump vibration data and transmit it to a (ii) Deep Autoencoder*** model for detecting anomalies. The autoencoder model recognizes each pump's normal pump vibration patterns and identifies subtle deviations. This monitoring framework can facilitate proactive maintenance by enabling early detection of anomalies, enhancing pump reliability, lowering maintenance expenses, and minimizing costly downtimes.
Paper: WEP006
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP006
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP007
A simulation of the Fermilab Main Injector dual power amplifier cavities
698
The Fermilab Main Injector accelerating cavities have sparking issues when they are run at voltages higher than those required by the PIP-II project. This is a problem Fermilab is working on as planning begins for the next upgrade to the accelerator complex. One of the methods being used to address the issue is the development of a CST Microwave Studio simulation to accurately model the PIP-II dual power amplifier cavities and identify which part(s) of the cavity is causing sparking to develop. The model will also be used to determine if changes to the cavity geometry may allow the cavity to be used at higher voltages before sparking occurs.
Paper: WEP007
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP007
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Baking of the vacuum chamber and Activation of the inside NEG coating film in the storage ring arc zone of HEPS
Due to the spatial constraints of the small-aperture magnets in the storage ring arc zone of the High Energy Photon Source (HEPS), where the magnetic pole gap is 26 mm and the vacuum chamber outer diameter is 24 mm, it is necessary to bake the vacuum chamber within a unilateral clearance of only 1 mm for the vacuum chamber degassing and NEG-coated film activation. This work introduces the online baking and activation scheme for the vacuum chamber in the storage ring arc zone of HEPS, including the design of the vacuum chamber heating method and the baking-activation procedures. Additionally, it records the changes in vacuum pressure and the variation in partial pressures of residual gases during the baking-activation process. After the baking-activation of the entire 48 arc zones were completed, the static vacuum pressure measured at the two gauge sites of the standard arc zones were, on average, 1×10−8 Pa and 5×10−8 Pa respectively across the whole ring. Compared with the simulation results after sufficient beam dose sweeping, the measured vacuum pressure is still nearly one order of magnitude higher.
Centrifugal Barrel Polishing of a 650 MHz Single-Cell Niobium SRF Cavity
This work reports the first application of centrifugal barrel polishing (CBP) to a 650 MHz single-cell niobium superconducting radio frequency cavity. The CBP was performed using a newly installed large tumbler designed to accommodate four large-sized 650 MHz multi-cell cavities. The CBP process was applied to reset the cavity’s internal rough surface prior to electropolishing (EP). The study presents results on the surface condition and SRF performance following the CBP and subsequent standard cavity surface processing.
WEP011
Analysis of vapor diffusion Nb3Sn coating at Fermilab: Minimizing impurities using TOF-SIMS
705
Nb$_3$Sn demonstrates steady advancements nowadays offering reduced power cost in superconducting radio-frequency cavities due to its high critical temperature, quality factor, and achieved accelerating gradient. However, theoretical estimates of its radio-frequency parameters have not been achieved due to several potentially limiting mechanisms: tin spots, patchy regions, defects, thermal impedance, and impurities. While some of these limitations have been intensively studied, impurity analysis in Nb$_3$Sn coatings have received less attention. We report an investigation of impurities in several vapor-diffused Nb$_3$Sn coated samples using time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and show allowable impurity levels in view of superconducting cavity performance. Challenges and lessons learned in maintaining clean Nb$_3$Sn coatings are also discussed.
Paper: WEP011
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP011
About: Received: 06 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP014
Consideration of HTS rapid-cycling magnet for staged muon acceleration
712
The HTS conductor hysteresis dominates magnet cable power loss but is independent of the magnetic field ramping rate. This makes the HTS conductor suitable to power the rapid-cycling accelerator magnet. We present a possible application of the HTS rapid-cycling magnet as outlined in [1,2] for the staged muon acceleration including the front-end Recirculating Linear Accelerator and the followed-up Rapid Cycling Synchrotrons delivering the muon beams to the Muon Collider. [1] H. Piekarz, S. Otten, A. Kario, H. ten Kate, “Rapid-cycling HTS magnet for muon acceleration”, US MC Inaugural Meeting, FERMILAB-POSTER-24-0219-AD, August 7-9, 2024 [2] H. Piekarz, B. Claypool, S. Hays, M. Kufer, V. Shiltsev, “Record High Ramping Rates in HTS Based Supercond. Accelerator Magnet”, MT 27, IEEE Trans. on Applied Superccond, 32 (2022) 6, 4100404
Paper: WEP014
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP014
About: Received: 05 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
WEP015
Co-sputter deposition of Nb₃Sn layer into SRF cavity using Nb-Sn composite target
715
Nb₃Sn, with its superior superconducting critical temperature (Tc ~18.3 K) and superheating field (Hsh ~400 mT), is considered a promising material for superconducting radiofrequency (SRF) cavities, offering enhanced cryogenic performance compared to bulk niobium cavities. A Nb₃Sn coating technique has been developed for Nb SRF cavities using co-sputtering of Nb-Sn composite target in a DC cylindrical magnetron sputtering system. The composite target configuration and discharge conditions for co-sputtering were optimized to deposit Nb-Sn films on flat Nb substrates, followed by annealing to form Nb₃Sn. Multiple strategies have been explored to improve the surface homogeneity of the Nb₃Sn coating, including optimizing a two-step annealing process, annealing in Sn vapor, and a light Sn recoating process. A 1.5 µm Nb-Sn co-sputtered film was deposited on the interior of a 2.6 GHz Nb SRF cavity and annealed at 600 °C for 6 h, followed by 950 °C for 1 h. Cryogenic RF testing of the annealed cavity demonstrated a Tc of 17.8 K, confirming the formation of Nb₃Sn. Then, the annealed cavity underwent a light recoating treatment and attained a quality factor (Q0) of 8.5E+08 at 2.0 K.
Paper: WEP015
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP015
About: Received: 06 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
WEP020
Design of a low-power proof-of-concept multi-stage amplifier test stand to model and implement outphasing control for the LANSCE 805 MHz solid-state high-power RF amplifier
725
Los Alamos Neutron Science Center (LANSCE) has a project to investigate the feasibility for a replacement radio-frequency (RF) amplifier that is not reliant on vacuum electron tubes, has a similar footprint, and equivalent RF functionality. Gallium Nitride (GaN) on Silicon Carbide (SiC) high electron mobility transistors (HEMT) will be used in combined configuration. To maintain existing operational capabilities with these GaN amplifiers, the low-level control system needs to be modified for maximum transistor lifetime. The HEMT operates in a saturated condition, with a constant amplitude drive signal to avoid the high-power dissipation of linear operation with reduced drive. This leaves the phase of the RF inputs as a control mechanism, utilizing outphasing for amplitude modulation of the multistage amplifier. The GaN amplifiers also require a bias sequencing/protection board that is being designed and tested separately. To test and verify the control system, a low power test rack using commercial wideband RF components was built. This model system includes drive control, four 10 W amplifier stages, a final combination chassis, and accelerator timing system. The information from this test rack will be used to learn how to efficiently control a multistage high-power GaN amplifier to fit the requirements of the LANSCE linear accelerator.
Paper: WEP020
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP020
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP022
Design of a shipping fixture for a compact cryomodule hermetic assembly
733
In support of the development of a conduction-cooled 915MHz superconducting radio frequency (SRF) cryomodule, this study highlights the design of a shipping fixture for transporting the hermetic assembly 4500 km from Jefferson Lab to General Atomics in San Diego, California. The hermetic assembly consists of a 2-cell 915 MHz SRF cavity, a coaxial fundamental power coupler and warm-to-cold transition beam tubes. The two-part shipping assembly consists of an inner frame, providing direct mounting of the components, and an outer frame mounted to the ground transport vehicle. The inner frame is then connected to the outer frame by way of wire-rope isolators. Accelerometer data from ground transportation of previous projects at Jefferson Lab provides the baseline for the expected frequency and magnitude of vibrational and shock events during transit. Modal analyses were carried out in ANSYS on the inner frame assembly and critical components to identify an appropriate wire-rope isolator configuration such that peak loads are mitigated and the incurred frequencies do not correspond with the fundamental modes of the structures.
Paper: WEP022
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP022
About: Received: 07 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
WEP023
Design study of an RF-Kicker module for bunch cleaning at the ATLAS Positive-Ion Injector
737
Positive-Ion Injector at ATLAS accelerator facility can accelerate heavy ions and has three key subsystems -- an electron cyclotron resonance (ECR) ion source, a 12-MHz multi-stage beam bunching system, and a 12-MV superconducting linac accelerator. The first stage of the bunching system is a multi-harmonic buncher that operates at 12.125 MHz and creates a bunch train with a period of 82.5 ns at ~70% bunching efficiency. The remaining unbunched beam must be removed to avoid the production of undesirable ‘satellite’ bunches, which can quench the superconducting solenoids downstream during operation. In this paper, we present the design of a resonant sine-wave RF-structure that effectively removes the bunch ‘tails’ using a vertically deflecting kick. We also discuss the effects of the RF-Kicker on the beam quality, which was estimated by TRACK3D simulations.
Paper: WEP023
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP023
About: Received: 08 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
Development and fabrication of CW copper injector for SRF industrial cryomodules
Compact SRF industrial linacs can provide unique parameters of the beam (>1 MW and >1-10 MeV) hardly achievable by normal conducting linacs within limited space. SRF technology was prohibitively expensive until the development of conduction cooling which opened the way for compact stand alone SRF systems suitable for industrial and research applications. Limited cooling capacity puts strict requirements on the beam parameters with zero losses of the beam on the SRF cavity walls. This implies strict requirements on the beam energy to be accepted by the cryomodule and most importantly the beam bunching with zero particles in between. We designed a CW normal conducting RF injector which consists of a gridded RF gun integrated with a first cell of a copper booster cavity to satisfy these requirements. Here we present a finalized as well as the fabrication status of the injector.
WEP027
Development of combined function Dipole-Quadrupole PMQs magnets for NSLS-II upgrade
744
This paper focuses on the R&D performed for the development of permanent magnets-based dipoles-quadrupoles combined function magnets (PMQs) for the future NSLSII upgrade “complex bend” lattice (CB). This new lattice uses PMQs that provide both bending (dipole) and strong focusing (quadrupole) magnetic field on the electron beam. The permanent magnet (PM) technology is suitable for the high magnetic field strengths (0.5 T, 130 T/m) required for such combine function magnets. PM technology leads to a compact magnet design that is essential in realizing the complex bend lattice concept, as well as a passive magnet solution which does not require electrical power supply reducing power consumption by ~ 80% (from 1.7 MW to 0.3 MW for NSLS-II). Two PMQs magnets designs are under consideration: A hybrid design that use both PM and soft iron poles, and Halbach type that is a pure PM design. Both PMQs designs present challenges in achieving the specified magnetic field quality due to their higher sensitivity to errors (mechanical tolerances and PM properties). This paper presents cost-effective designs and prototypes results for hybrid and Halbach PMQs, addressing various technical challenges while meeting the field requirements of the complex bend lattice for the NSLS-II upgrade.
Paper: WEP027
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP027
About: Received: 06 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Development of ultra high power compact X-band pulse compressor
We have developed a new SLED-type RF pulse compressor for powering ultra-high gradient X-band photoinjectors with pulse lengths shorter than 10 ns. Klystrons capable of generating these short pulses at multi-MW levels are non-existent. However, RF pulse compression is an alternative technique used to increase klystron output peak power at the cost of pulse length. Over the years, we have developed numerous pulse compression systems, including super-compact SLEDs for X-band transverse deflectors at SLAC’s LCLS and LCLS-II. Our new compact pulse compressor uses spherical cavities with axially-symmetric TE modes which have no electric field on the cavity surface. This allows our new SLED to potentially achieve higher peak RF power compared to the LCLS-II SLEDs. We present the design of this SLED composed of two spherical cavities and a waveguide hybrid with TE01 circular waveguide ports. During high power test this SLED produced peak RF power up to 317 MW.
WEP030
Efficient continuous-wave normal conducting accelerator for industrial applications
751
A normal conducting, high power, high efficiency copper linear accelerator prototype is being developed for industrial applications. The system will be powered by low-cost high-efficiency magnetron RF sources and will use a gridded thermionic cathode electron gun. Leveraging the significant accelerator expertise at JLab and industry partners, these technologies will be combined to deliver high-power (>100 kW) electron beams with energies of 1 MeV or higher that are cost-effective to produce and operate. The design is modular such that energy and power can be increased by adding additional sections as required. The status of the design, prototype fabrication and plans for a beam demonstration at JLab are described.
Paper: WEP030
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP030
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Elimination of Training in Nb3Sn and NbTi Superconducting Magnets
By using TELENE® resin as superconducting magnet impregnation material, training and magnet retraining after a thermal cycle were nearly eliminated in Nb3Sn undulators. This allows reducing operation margins in light sources, and increasing the on-axis magnetic field, thereby expanding energy range and brightness intensity. TELENE is Co-60 gamma radiation resistant up to 7-8 MGy, and therefore already applicable to impregnate planar, helical and universal devices operating in lower radiation environments than high energy colliders. Radiation resistance further increases in TELENE when mixed with high-Cp and/or high-thermal conductivity powders. We herein show that when combined with the ductility and toughness properties of TELENE, these resins display superior training performance with respect to CTD-101K in a variety of Nb3Sn magnet models. In addition, TELENE was proven to eliminate training also in NbTi accelerator magnets. Therefore, TELENE can be used in the Magnetic Resonance Imaging (MRI) industry to solve the NbTi solenoids training problem. The transfer of technology in using TELENE resin to the MRI industry will have transformative societal impact on global health.
WEP032
High power 805 MHz solid state amplifiers using GaN on SiC HEMT for LANSCE CCL
755
The Los Alamos Neutron Science Center uses a coupled-cavity linac (CCL) to accelerate H- ions from 100 to 800 MeV. It is powered by forty-four 1.25 MW 805 MHz klystrons of older design. Continued supplies of identical klystrons for the linac operation beyond 2050 are uncertain. We have embarked on a feasibility study for a replacement RF amplifier without vacuum electron tubes, that fits in the space of one klystron. Commercial silicon LDMOS transistors have reduced power above 600 MHz and are limited by the maximum drain to source breakdown voltage. We selected high voltage Gallium Nitride (GaN) on Silicon Carbide (SiC) high electron mobility transistors (HEMT) to reduce the number of active devices and the complexity of power combing smaller amplifiers. They are able to operate at higher channel temperature and voltage ratings compared to silicon transistors. We have tested devices with 3.6 kW of saturated power at 100 volts, and are planning for 5 kW HEMTs for the final design. Outphasing modulation schemes allow higher efficiency and lower thermal dissipation than class AB linear amplifiers. Power supplies and combining technology are also under study for this system.
Paper: WEP032
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP032
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Aug 2025
External controller for the SRFK thyratron heaters
The following work will detail the development and implementation of a system which will measure the voltage and current from two points on a high-voltage switch called a thyratron and automatically manipulate two variable transformers controlling these values. Each of the extraction kickers at LANSCE (SRFK71 & SRFK81) uses a thyratron to trigger their respective pulses. The thyratrons have separate heaters for the cathode and reservoir, and each needs to maintain specific voltage and current levels for the thyratron to work properly. Currently, the method of measuring and adjusting these values requires locking out the system, opening the tank, and measuring the voltage and current of each heater, then adjusting two variable transformers by hand to reach the desired values. This controller consists of four analog-to-digital converters which will relay these measurements out of the modulator as digital signals through fiber optic transceivers. An Arduino will be programmed to interpret the digital signals and display the values on an LCD. It will also return signals to DC motors controlling the variable transformers if the values lie beyond the desired range.
WEP037
Final design and first use of in-situ measuring apparatus for measurement of permanent magnet resiliency in CEBAF’s radiation environment
759
In this work we outline the final design and initial measurement lessons for the holders and measuring apparatus of the permanent magnet resiliency experiment which is a part of the FFA@CEBAF proposed upgrade. The experiment will expose permanent magnets to the radiation environment of CEBAF. Due to safety regulations we need to measure the magnets in the tunnel without bringing them out, so we designed a mobile measuring system as well as a series of protocols to allow us to speedily measure these samples even under adverse conditions. We also designed our system to be capable of taking measurements even with component failures.
Paper: WEP037
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP037
About: Received: 06 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 11 Aug 2025 — Issue date: 28 Aug 2025
WEP038
First results from a Nb3Sn-coated 1.5-cell 650 MHz SRF cavity for cryogen-free industrial accelerators
762
Fermilab is advancing the development of a compact, high-power electron beam accelerator using superconducting radio frequency (SRF) technology as a non-radioactive alternative to traditional radiological sources. The current design targets continuous-wave (CW) operation at 1.6 MeV and 20 kW. To ensure suitability for industrial environments, the system is being designed for cryogen-free operation, driving the adoption of a novel Nb₃Sn-coated 1.5-cell SRF cavity operating at 650 MHz. This contribution reports on the fabrication, surface preparation, and Nb₃Sn coating process of the cavity, as well as first results from vertical test stand (VTS) measurements performed in a liquid helium bath. These initial tests mark a key milestone toward demonstrating the viability of conduction-cooled Nb₃Sn SRF cavities for industrial-scale deployment.
Paper: WEP038
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP038
About: Received: 06 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Fitness For Service Assessment of a Corroded Heat Exchanger
Fermilab’s Main Injector Accelerator has used shell & tube heat exchangers to cool various beamline components since its construction in the late 1990s. Many of the heat exchangers still around today are original to the machine. Untreated pond water has been used to exchange heat with the Low Conductivity Water. Throughout the lifetime of Fermilab’s heat exchangers, they have undergone significant material degradation in the carbon steel end channels due to corrosion. Wall thickness measurements (per API 510) of each heat exchanger were used to generate a 3D model of the corroded surfaces. In order to continue their safe and reliable operation, ASME FFS-1/API 579 (Fitness-For-Service) was implemented to address their integrity. The assessments consisted of finite element analysis techniques outlined in ASME Section VIII Div. 2 (design by analysis methods for pressure vessels), in accordance with the requirements of ASME FFS-1 Part 4: General Metal Loss, Part 5: Local Metal Loss, and Part 9: Crack Like Flaws. The assessments concluded that each heat exchanger is coined “Fit For Service”. The Fitness-For-Service standard offers a unique opportunity to facilities and institutions within the DOE National Lab complex to properly and safely assess the integrity of aging equipment necessary to conduct science and research. This poster demonstrates the assessment process and techniques used to determine the heat exchangers are fit for service.
WEP040
Grid disturbance rejection via improved DC-Link voltage feedforward control for L-Bend power supplies in the APS upgrade
766
As part of the Advanced Photon Source Upgrade (APS-U), two high-power DC supplies for the L-Bend M1 and M2 magnets were installed. During the APS-U commissioning, a 1 Hz ripple was detected in the output currents of the M1/M2 and slow corrector supplies, leading to 1 Hz beam motion. This low-frequency harmonic originated from the booster ramping supply operating at 1 Hz, causing periodic grid voltage sags. This paper proposes an improved DC-Link voltage feedforward control for the M1/M2 supplies to reject grid disturbances, significantly attenuating the 1 Hz and other low-frequency ripples in the output currents. Combined with regulation circuit modification of the slow corrector power supplies, the 1 Hz harmonic was successfully eliminated from the beam motion.
Paper: WEP040
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP040
About: Received: 08 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
High efficiency L-band IOT design and high power testing
Recent efforts at SLAC aim at developing high-power accelerators powered by compact, high-efficiency rf sources such as klystrons and Inductive output tubes (IOT). In particular, a high-efficiency IOT is an electron-beam-driven RF source employed in the UHF band that offers high efficiency at variable output power levels. In this talk, we show the progress of developing a 1.3 GHz HEIOT in terms of design, and manufacturing.
High-Voltage Pulsed Power Generator for Beam Injection Systems
Beam injection systems in hadron colliders require kickers generating ±50 kV peak voltages into a 50 Ω impedance, with peak currents of 1000 A and sub-10 ns rise and fall times. This paper presents a novel high-voltage pulse power generator utilizing a dis-tributed pulser architecture. It combines gallium nitride (GaN) transistors in a Marx to-pology with an inductive adder, achieving nanosecond-scale switching speeds and high-power efficiency. Compared to other solutions such as based on MOSFETs or fast ioniza-tion dynistors, our development offers superior peak and average power performance, reduced system complexity, and enhanced reliability, marking a significant step forward in high-voltage pulse generation for accelerator applications.
Integral Field Probe for Mapping of Curved Magnets
The Single Stretched Wire (SSW) method allows highly precise integral field measurements by recording voltage across a tensioned wire mounted to 2-axis linear stages at either end of the magnet aperture. However, traditional SSW probes are not well suited for curved accelerator magnets, which are essential for steering charged particles along arced trajectories in storage rings or beamlines. The tension required to eliminate sag demands a purely straight path, making them incompatible with non-linear magnet geometries. To address this limitation for curved magnets, a modified approach was developed using a segmented, 3D-printed support structure that incorporates a pre-shaped “anti-sag” curve. Under its own weight and that of the wire bundle, the structure deforms to lie flat while conforming to the curvature of the magnet in the horizontal plane. The optimal geometry of the probe was derived using an iterative process combining FEA simulations in Ansys Mechanical with testing of various carbon fiber-reinforced filaments. The printed and assembled probe was successfully used to measure the SDD-055 magnet at Fermilab, yielding promising results.
WEP050
Prelimimnary introduction of the IOTA Bake System
781
The IOTA ring is vital to the advancement of accelerator sciences, and a large part of its attractiveness to accelerator physicists is its modularity and the versatility that this function provides. Up until this point, the FAST accelerator has provided electron beam for the studies in IOTA. With the soon to be commissioned IOTA Proton Injector in lieu, the requirement for better vacuum to support future proton studies in the ring have arrived. Our solution is the IOTA Bake System which has the goal of facilitating this requirement.
Paper: WEP050
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP050
About: Received: 14 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Jefferson Lab’s multi-purpose modular FPGA based controller board improves on project design cycle
Embedded control design often requires extensive engineering time. Development boards, while useful, provide minimal peripherals for complex projects. A modular Field Programmable Gate Array (FPGA) controller printed circuit board (PCB) was designed which reduces concept to implementation time dramatically. A low cost flash embedded FPGA was chosen for this board which helped reduce components and complexity. A detailed specification and design choices for the controller board will be presented. Initially this controller was designed for a linear DC-DC power converter for trim magnet system. It was further realized that with available ADC and DAC channels, many I/O ports and available MODBUS, serial communication protocol that this board can be used for other applications. Such as, Jefferson Lab’s low noise supply (LNS) (100 parts per million (ppm) 20A DC power supply) and a controller for three 15kW power supplies each with motorized polarity switches. These applications make this controller an "all-in-one" design for low cost quick turnaround projects.
WEP052
Improvements to the LANSCE CCL klystron evaluation
783
This paper describes the existing procedure for LANSCE 805 MHz klystrons testing and evaluation and realized avenues for improvement. Each of the 1.25 MW klystrons used for powering LANSCE CCL (side Coupled Cavity Linac) are tested during first installation or fol-lowing a fault in operations. Executed testing process includes high potting, pulsing, and full power RF testing. Generated testing data is used for evaluation and certifi-cation of spare units for the linac. In this paper, we hope to breakdown this expert-dependent, lengthy 1–2 month process and examine improvements which can accelerate time to evaluation. The goal of this paper is to fully cap-ture the current procedures and investigate improvements to modernize our legacy systems and processes.
Paper: WEP052
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP052
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP056
LLRF commissioning of the CEBAF C75 upgrades SAM 2024/25
789
An often-overlooked aspect of Low Level Radio Frequency (LLRF) design is commissioning of a new system. During Jlab’s Scheduled Accelerator Maintenance (SAM) in 2024, two C75 Cryomodule were installed in CEBAF with Jlab’s LLRF 3.0 system. Jlab’s team has invested effort in automating and standardizing their commissioning process. Several key components are klystron characterization, cavity characterization, and interlock verification. This poster will present the summary of LLRF preparation and commissioning efforts at Jlab.
Paper: WEP056
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP056
About: Received: 07 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP057
Low frequency ripple current attenuation for slow corrector power supplies in the APS Upgrade
792
As part of the Advanced Photon Source Upgrade (APS-U), approximately one thousand bipolar power supplies were installed to power the slow corrector magnets. During the APS-U commissioning, a 1Hz harmonic was detected in the beam motion. This harmonic originates from the 480V AC grid, caused by the booster ramping power supply operating at 1 Hz. The resulting grid disturbance introduced low-frequency ripples into both the corrector magnet power supplies and the L-Bend M1/M2 supplies, leading to the observed 1 Hz beam motion. This paper proposes two methods to mitigate these ripples in the corrector supplies: setpoint compensation using repetitive control, and regulation circuit adjustments through a simple jumper reconfiguration. The second approach was adopted and applied to all slow corrector magnet power supplies. Operational data showed that the low-frequency ripples were significantly attenuated in the corrector supplies, and in combination with fine-tuning of the L-Bend M1/M2 supplies, the 1 Hz beam motion was successfully eliminated.
Paper: WEP057
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP057
About: Received: 08 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP058
Magnetic field and force calculation of the new SCU prototypes
795
New 0.5m long SCU prototypes were designed based on lessons learned from the previous full length (1.5 m) core experiences. The original monolithic cores have all steel poles. The new cores have plastic back poles to avoid electrical shorts of superconducting wires to cores. Magnetostatic calculation was made for one period model for each of two designs under consideration. Then, magnetostatic, and mechanical analysis was also conducted for the prototype SCUs with the lengths of 29.5 and 23.5 periods. The software used for this simulation is ANSYS Maxwell and Mechanical. Both the magnetostatic and the mechanical analyses confirm the validity of the new design.
Paper: WEP058
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP058
About: Received: 04 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
WEP060
New development and testing facility for HPRF SSA system at LANSCE CCL
799
A new high-power RF test facility was developed at the Los Alamos Neutron Science Center (LANSCE) to evaluate components of a RF Solid-State Amplifier (SSA) system operating at 805 MHz and targeted for a final output power of 1.25 MW. The system is powered by a 100 V DC supply and stabilized with a 0.1 F capacitor bank to support transient power demands, capable of storing up to 1.125 kJ of energy. The SSA utilizes Gallium Nitride (GaN) on Silicon Carbide (SiC) high electron mobility transistors (HEMTs) and employs water cooling to manage thermal loads and ensure stable operation under high duty-factor pulsed conditions. Multiple HEMT amplifier modules will be power combined to achieve the full 1.25 MW output, with the aim of enhancing reliability, modularity, and maintainability in accelerator RF infrastructure. Integrated protection procedures allow for secure shutdown of RF drive and DC power in the event of overvoltage, overcurrent, or thermal excursions. This test configuration supports ongoing evaluation of solid-state amplifier performance, thermal handling, and integration with RF passive components under realistic operational conditions.
Paper: WEP060
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP060
About: Received: 10 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Aug 2025
WEP061
NSLSII RF-shielded bellows offset testing
802
The NSLSII storage ring contains over 180 RF shielded bellows over its 792 m circumference. Three of these bellows are instrumented with RTD temperature sensors on the internal components to monitor and validate expected performance. The temperature data showed an increasing internal temperature trend during successive 500mA beam operation on one of these bellows. This bellows and many other installed bellows throughout the ring, are near to or over the vertical and horizontal offset tolerance. Offsets can create an RF path between the sleeve and fingers, which raised concern there was degradation of performance resulting from the offset condition. The bellows was removed and inspected with some visual signs of discoloration and loose RTD anchor points were also observed. With the prospects of moving from 400mA to more permanent 500mA operation, a test was conducted to confirm internal temperatures were safe. Two fully instrumented bellows were remotely offset under steady beam operation while observing the internal temperatures. The bellows with offset geometry was also studied with GdfdL code. The experimental results will be presented and compared to the wake-potential calculations.
Paper: WEP061
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP061
About: Received: 01 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP062
One-to-one mapping between the electromagnetic modes of cylindrical and coaxial half-wave cavities
805
Design of radio frequency (RF) couplers and diagnostics require a good understanding of the electromagnetic mode patterns of RF cavities. This study investigates the adiabatic transformation of transverse magnetic (TM) modes in a cylindrical cavity into transverse electromagnetic (TEM) modes of a coaxial cavity by gradually introducing an inner conductor. Using CST Studio Suite, we simulate the eigenmode evolution as the geometry transforms from a pure cylindrical to a coaxial configuration. We track the behavior of TM010 through TM014 modes to observe the continuous evolution into the corresponding TEM0 through TEM4 modes of the coaxial cavity. The process is governed by the evolution of the electric field orientation as the geometry shifts, enabling the axial TM fields to reorient into the radial electric field configuration of TEM modes. Field patterns, eigen-frequencies, and mode indentities are analyzed throughtout the transition. The results provide simulation-based evidence that TM to TEM conversion occurs without generation of newer eigenmodes, offering a valuable insight into the design of transition regions in superconducting RF (SRF) systems and provides a foundation for experimental validation.
Paper: WEP062
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP062
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
WEP065
Performance enhancement of medium temperature baked niobium SRF cavity by surface contamination removal
812
Medium temperature baking (300- 350 °C) enhances the quality factor of niobium superconducting radio frequency cavities. However, surface contamination introduced during vacuum furnace baking limits the quench field and may also degrade the quality factor of the cavity. To investigate this effect, a 1.3 GHz single-cell Nb cavity underwent mid-T baking, followed by a chemical treatment to remove the surface contaminants. Post-treatment measurements revealed a significant improvement in both the quality factor and the quench field.
Paper: WEP065
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP065
About: Received: 10 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Aug 2025
WEP066
Plasma processing of SRF cavities at Jefferson Lab: Experiment results and simulation insight
816
Plasma processing of superconducting radio frequency (SRF) cavities has been an active research effort at Jefferson Lab (JLab) since 2019, aimed at enhancing cavity performance by removing hydrocarbon contaminants and reducing field emission. In this experiment, processing using argon-oxygen and helium-oxygen gas mixtures to find minimum ignition power at different cavity pressure was investigated. Ongoing simulations are contributing to a better understanding of the plasma surface interactions and the fundamental physics behind the process. These simulations, combined with experimental studies, guide the optimization of key parameters such as gas type, RF power, and pressure to ignite plasma using selected higher-order mode (HOM) frequencies. This paper presents experimental data from argon-oxygen and helium-oxygen gas mixture C75 and C100 cavity plasma ignition studies, as well as simulation results for the C100-type cavity based on the COMSOL model previously applied to the C75 cavity.
Paper: WEP066
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP066
About: Received: 07 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP067
Study of uncorrelated resonance crossing in a controlled environment
820
This paper deals with estimating spin depolarization in planned very high energy electron-positron storage rings like the FCC-ee. The paper covers three aspects of the work: 1) the putative so-called uncorrelated resonance crossing due to noise in the spin-rotation phase advance caused by photon emission in synchrotron radiation. This is expected to suppress the depolarization caused by synchrotron sideband resonances, 2) a study of the performance of our code on multiple high performance systems, and 3) the novel exploitation of a high order Magnus expansion applied to spin transport. The study uses Monte-Carlo spin-orbit tracking for a simple model of spin motion, the so-called single resonance model, augmented by the effects of radiation. The results presented here represent the first steps of a planned detailed large-scale exploration.
Paper: WEP067
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP067
About: Received: 08 Aug 2025 — Revised: 09 Aug 2025 — Accepted: 10 Aug 2025 — Issue date: 28 Aug 2025
Power coupler and tuner design for a 2 MeV Distributed-Drive Linac
A distributed-drive linac consists of individually powered and phased single- cell cavities. In this paper, we evaluate options for coupling RF power into the linac cavities, and present an initial design for a cavity frequency tuning mechanism.
Radiation Dose Simulations on Permanent Magnets for the CEBAF Energy Upgrade
The ongoing work related to the LDRD funded by JLab is investigating the effects of radiation on permanent magnet materials intended for use in the CEBAF energy upgrade. This effort combines experimental exposure of magnet samples to radiation rates within the accelerator with detailed simulation studies. Samples are positioned at various locations to capture a range of radiation environments, helping researchers assess how different doses influence magnetic performance over time. Simulations using BDSIM support the interpretation of measured results and extend predictions to the higher energy stages planned for CEBAF. This paper presents recent findings and outlines the progress made toward understanding the long-term behavior of these materials in high-radiation settings.
WEP075
Radio-frequency hardware considerations for a high-power solid-state amplifier
836
A feasibility study is developing a prototype solid state power amplifier to supplant or replace 805 MHz klystrons powering the coupled-cavity linac at the Los Alamos Neutron Science Center (LANSCE). We are considering the RF passive hardware used for such an amplifier. The power from individual transistor pallets that provide 5 kW each must be power-combined to the requisite 1.25 MW needed to replace a klystron. Various approaches are being considered for combining Additionally, the protection of the various components from reflected power is essential to avoiding damage to the pallets and all of the passive RF components such as combiners and connectors. The use of magic tees as both combiners and isolators is discussed, and circulators are another critical component for this design. Finally, as power is combined, another concern is the power handling of connectors, and the balance between performance and the practicality of the large number of connectors becomes crucial.
Paper: WEP075
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP075
About: Received: 08 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Recent Efforts on Rebuilding LANSCE CCL Klystrons
The Los Alamos Neutron Science Center (LANSCE) uses forty-four (44) 1.25-MW 805-MHz klystrons to power its side-Coupled Cavity (CCL) linear accelerator (LINAC). In recent years, the facility has experienced a significant klystron failure rate and dwindling hot spare inventory, producing ample beam downtime and reliability risk. This paper presents a LANSCE case study on rebuilding a klystron, a first attempt to revitalize a manufacturing technology that was vibrant for decades as LANSCE. We present data collected during the klystron’s initial testing alongside pre-failure (i.e. live) performance. Our failure analysis investigates possible causes given observed irregularities in the data collected. Rebuilding efforts to address all failure modes are presented, highlighting our troubleshooting and refurbishment process, methods, and techniques. We end our discussion by presenting post-rebuild results, lessons learned, and potential future improvements.
WEP078
RF amplifier system reconfiguration plans for new DTL and RFQ
843
The first 100 MeV of acceleration for protons and H- ions at the Los Alamos Neutron Science Center (LANSCE) is presently accomplished with a Cockroft-Walton generator (750 keV), followed by four Alvarez drift tube linac (DTL) cavities commissioned in 1970. The RF duty factor is 12 %, leading to significant thermal loading in the room temperature copper structures. Increasing obsolescence and structural reliability problems have created the need for replacements to these systems. The LANSCE Modernization Project (LAMP) developed a conceptual design for the Medium Energy Beam Transport (MEBT) and the Drift Tube Linac (DTL) using new accelerator components. This approach utilizes a Radio Frequency Quadrupole (RFQ) and six replacement DTL cavities. The current 201.25 MHz radio-frequency power amplifier system was replaced 10 years ago and has demonstrated high reliability with Diacrode tube lifetimes over 60,000 hours. We propose an RF amplifier topology that leverages this RF system to provide the required power for the LAMP conceptual design through innovative reconfiguration of the amplifiers.
Paper: WEP078
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP078
About: Received: 13 Aug 2025 — Revised: 15 Aug 2025 — Accepted: 17 Aug 2025 — Issue date: 28 Aug 2025
WEP082
Sputter coating of Nb₃Sn into SRF cavity using stoichiometric target
851
Nb₃Sn has emerged as a leading alternative material due to its higher superconducting critical temperature (Tc) and superheating field (Hsh), promising a viable solution to the intrinsic performance limit currently faced by Nb superconducting radiofrequency (SRF) cavities. We sputter-coated Nb₃Sn inside Nb SRF cavity using a stoichiometric Nb₃Sn tube target in a DC cylindrical magnetron sputter coater. The target was fabricated by growing an estimated >20 μm thick Nb₃Sn layer on a Nb tube via Sn vapor diffusion using Jefferson Lab’s coating system. Approximately 150 nm thick Nb-Sn films were sputter-deposited onto flat Nb samples at positions representing the beam tubes and equator of a 2.6 GHz Nb cavity. Post-deposition annealing at 950 °C for 3 h resulted in the formation of Nb₃Sn. Microstructural analysis of the annealed films was carried out to investigate the morphology and structure of the Nb₃Sn films. Later, a 2.6 GHz Nb SRF cavity was coated with a ~1.2 μm thick sputtered Nb-Sn film using a stoichiometric Nb₃Sn target, followed by annealing. Cryogenic RF testing of the annealed cavity demonstrated a Tc of 17.8 K, indicating the formation of Nb₃Sn. After a light Sn recoating treatment, the cavity achieved a quality factor (Q0) of 6.7E+08 at lower field at 2.0 K.
Paper: WEP082
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP082
About: Received: 07 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP084
LANSCE CCL klystron high potting investigation and improvements
859
LANSCE uses 44 805MHz klystrons to power the Coupled Cavity Linac (CCL). Modulated anode tubes such as the 1.25 MW LANSCE klystrons need high volt-age testing and processing prior to full operation. This not only verifies the klystron can hold-of HV but also allows the klystron to process out some internal imperfections prior to being pulsed by the modulator for the accelerator. The LANSCE accelerator is a relatively long pulse machine, and improper processing can lead to premature degradation in the performance of the tube. This paper describes recent improvements to the 1.25MW 805MHz klystron HV check and conditioning process through the development of a new high-potting test stand. High-potting setup and techniques that were historically used are contrasted with the new implementation. Our goal is to improve LANSCE operations by accelerating the high-potting process and reducing expert time and dependence. The new test stand will optimize legacy processes by improving diagnostics, automating control and reducing inconsistencies and process invariability due to human factors. Analysis and automation efforts for this critical process are discussed along with current benefits and future work.
Paper: WEP084
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP084
About: Received: 08 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP086
The Pulsed Ion Reflex Klystron: A new accelerator for high efficiency voltage conversion
866
Beam Alpha developed a kilowatt-scale fusion microreactor that directly converts nuclear energy to electrical energy without intermediate heat steps. This device has an output of 1.6 million volts DC. A converter is needed to transform this potential energy into useful electrical power. To achieve this the "Pulsed Ion Reflex Klystron" has been developed. The PIRK aims to achieve high conversion efficiencies by directing negatively charged ions through a re-entrant resonant cavity hundreds of times to gradually transfer energy from the moving particles to said cavity. Ions will be released into a 6-meter linear accelerator with roughly 1000 precisely spaced electrodes forming a quasi-parabolic potential. This potential is symmetric about the midpoint of the tube causing ions to oscillate with a frequency of approximately 1 MHz independent of energy. Perturbations to this parabolic potential are designed to provide radial electrostatic beam focusing. An algorithm is devised to produce optimal voltage curves to maximize both longitudinal bunching and radial confinement, and these curves are examined against practically realizable potentials. Energy is coupled out of the resonant cavity using a loop antenna connected to a silicon carbide rectifying diode. This converts the RF in the cavity to a 400V intermediate DC bus that can easily be inverted to wall power.
Paper: WEP086
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP086
About: Received: 10 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP087
Thermal analysis and preliminary cooldown performance of the SCU cryostat
869
The SCU cryostat, featuring two 1.5-meter-long Nb-Ti superconducting undulators (SCUs), is currently being built for the Advanced Photon Source Upgrade. The final design, along with the thermal and mechanical models of this cryocooler-cooled, liquid helium-based cryostat, has been completed. The cryostat has been fabricated, and preliminary cool-down tests were conducted both with and without the two 1.5-meter-long Nb-Ti SCUs. This paper presents a comparison between the measured and calculated thermal performance of the cryostat.
Paper: WEP087
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP087
About: Received: 04 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Aug 2025
Thermal Performance of a 50 kW Minichannel Beam Dump at FRIB
The Facility for Rare Isotope Beams (FRIB) produces high-intensity, high-purity rare isotope beams through interactions between a primary beam and a graphite production target, currently operating at approximately 20 kW of primary beam power. To absorb unreacted primary beams downstream of the production target, an intermediate beam dump, called the minichannel beam dump (MCBD), was developed and implemented. The MCBD features a static structure tilted at 6°, which reduces the surface power density by a factor of 10. It is fabricated as a bimetallic assembly with a high-thermal-conductivity copper alloy absorber and aluminum alloy cooling channels (2 mm wide × 7 mm high) to mitigate oxidation and enhance heat removal. The system’s thermal performance was experimentally validated using a 17 keV electron beam, with measured surface temperatures agreeing with CFD simulations within 10%, confirming its reliability for higher-power operation. The current system is thermally limited by the temperatures at the absorber and wing surfaces. To enable operation at 50 kW, geometric optimization was performed by adjusting the surface angle across the entire structure to more effectively distribute heat on the copper absorber and reduce the thermal load on the aluminum wings. This work presents both thermal validation and simulation results demonstrating enhanced cooling performance with the optimized MCBD design for 50 kW beam operations at FRIB.
UED/UEM Conduction cooled Nb3Sn SRF photogun commissioning results
SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb3Sn and conduction cooling. SRF gun can provide a CW operation capability while consuming only 2W of RF power which eliminates the need of an expensive high power RF system and saves a facility footprint. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, we present commissioning results of the gun in the newly developed conduction cooled cryomodule with beamline integration. The project is funded by DOE SBIR #DE-SC0018621
WEP095
Understanding the RHIC triplet magnet vibrations in preparation for EIC
880
Throughout its operation, the RHIC triplet magnets have been subject to a mechanical vibration around 10 Hz. These mechanical vibrations were found to produce a beam orbit jitter that was detrimental to the collider luminosity. During RHIC operation, this has been effectively mitigated by the implementation of a fast feedback orbit control system. For the Electron Ion Collider (EIC) Hadron Storage Ring (HSR), the RHIC triplet package will be modified, magnets will be removed, and the cryogenic lines will be rearranged inside the cryostat. A comprehensive analysis of the RHIC triplet vibration has been undertaken to ensure that the planned triplet piping modifications would not increase the current triplet magnet vibrations and overwhelm the existing fast feedback control system. This paper aims to describe the current understanding of the root cause and kinematic of the RHIC triplet vibrations and offer mitigation options for EIC.
Paper: WEP095
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP095
About: Received: 05 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
WEP097
Ground vibration studies in the RHIC tunnel in view of EIC
884
As beam sizes get smaller at the collision point, the environment vibrations and their amplification through the accelerators supporting structures need more careful considerations. Indeed these mechanical disturbances can produce a beam orbit jitter that is detrimental to a collider operation, through loss of luminosity or increased beam-beam effects. In preparation for EIC, measurements of the ground vibration environment in the RHIC tunnel were carried out. This paper will summarize the measurement methodology and present its main results. The expected effect on the hadron and electron beam jitter will be described and we will discuss some design consideration on the new electron ring magnet supports to mitigate this effect.
Paper: WEP097
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP097
About: Received: 05 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
THYN01
How nitrogen and oxygen shape SRF cavity performance
932
Nitrogen and oxygen-based surface treatments have revolutionized the performance of superconducting radiofrequency (SRF) cavities, enabling them to reach higher gradients and lower losses. However, the exact mechanisms by which these treatments improve cavity performance remain largely unknown. This work provides new insights into the role of nitrogen and oxygen in SRF cavity performance by using time-of-flight secondary ion mass spectrometry (TOF-SIMS) to precisely quantify the concentrations and depth profiles of these impurities within niobium cutouts. We correlate these impurity profiles with detailed cavity performance measurements, including surface resistance and quality factor, and compare our findings with predictions from BCS theory. The results demonstrate that while both nitrogen and oxygen enhance performance, ten times more oxygen is required to achieve the same reduction in BCS resistance as interstitial nitrogen. We present a potential model in which the observed variation arises from nitrogen's greater effectiveness in trapping hydrogen, thus reducing the formation of niobium hydrides and enhancing superconducting gap.
Paper: THYN01
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-THYN01
About: Received: 13 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Aug 2025
Achieving 10 MV cryomodule with Nb3Sn cavities
Nb$_3$Sn SRF cavities have the potential to reduce operating and capital costs for SRF accelerators. A first-of-its-kind Nb$_3$Sn 2-cavity CEBAF-type cryomodule has been assembled and tested. The cryomodule contains two 5-cell cavities: one coated and qualified by the team at Jefferson Lab and the other by the team at Fermilab. The cryomodule, assembled and tested at Jefferson Lab, achieved 10 MV accelerating voltage. This talk highlights steps during this development, including cavity preparation and qualification, mitigations to avoid cavity performance degradation during string and cryomodule assembly, and cryomodule testing.
Accelerator Technology for the Electron Ion Collider
The Electron Ion Collider design includes sophisticated accelerator technology to produce high energy, high luminosity collisions with polarized beams. This talk overviews some of the key technologies, including a suite of different SRF cavities for accelerating and crabbing, cryogenics system, as well as high field interaction region magnets. The talk will also describe several examples where engineering decisions related to cost/performance and operational flexibility optimization needed to be made on the path for maturing the EIC design.