WEP
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Wednesday Poster Session
13 Aug 2025, 16:00 -
18:00
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 Nb₃Sn 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 Nb₃Sn SRF cavities. In this work, we present our recently developed route for effectively reducing the intrinsic defects in magnetron sputter coated Nb₃Sn SRF cavities and eventually improve the overall RF performance. In our study, we introduced a small variable fraction of Zr in Nb₃Sn host matrix using co-sputtering process. Post-annealing, the elemental Zr forms ZrO₂ 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 Nb₃Sn 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 Jan 2026
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 Jan 2026
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 Jan 2026
WEP008
A W-band corrugated waveguide for high-efficiency high-gradient wakefield acceleration
701
Compact RF structures in the sub-terahertz regime are promising for structure wakefield acceleration due to their ability in achieving high gradients in a reduced footprint. We report on the design, fabrication, and testing of a metallic corrugated waveguide operating at 110 GHz, tailored to the 42 MeV electron beam parameters at the Argonne Wakefield Accelerator (AWA). The experiment utilized the emittance exchange (EEX) beamline at AWA for longitudinal bunch shaping in two configurations: (1) a single short drive bunch to study high decelerating gradients, and (2) a two-bunch scheme featuring a triangularly shaped drive bunch followed by a long witness bunch to probe the wakefield and achieve a high transformer ratio. We will present the experimental design and results, which show good agreement with simulation predictions.
Paper: WEP008
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP008
About: Received: 07 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Jan 2026
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
Nb₃Sn 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 Nb₃Sn 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 Jan 2026
Collider-quality electron bunches from an all-optical plasma photoinjector
In recent years, plasma accelerators have advanced significantly toward producing beams suitable for colliders, aiming to replace conventional MV/m RF fields with GV/m fields of nonlinear plasma waves. Realizing a plasma-based collider requires electron bunches with high charge (hundreds of pC), low normalized emittance (~100 nm), and energy spread below 1%. Minimizing energy spread during acceleration involves flattening the accelerating field, which is achievable with a trapezoidal charge distribution. We present a plasma photoinjector concept that enables collider-quality electron bunch generation using two-color ionization injection. The spatiotemporal control over the ionizing laser creates a moving ionization front inside a nonlinear plasma wave, generating an electron bunch with a current profile that flattens the accelerating field. Particle-in-cell (PIC) simulations of the ionization stage show the formation of an electron bunch with 220 pC charge and low emittance (ϵ_x = 171 nm-rad, ϵ_y = 76 nm-rad). Quasistatic PIC simulations of the acceleration stage show that this bunch is efficiently accelerated to 20 GeV over 2-meters with an energy spread below 1% and emittances of ϵ_x = 177 nm-rad and ϵ_y = 82 nm-rad. This high-quality electron bunch meets Snowmass collider requirements and establishes the feasibility of plasma photoinjectors for future collider applications.
WEP013
Compact electron buncher with tunable permanent magnet focusing
709
We present a compact electron buncher that uses a permanent magnet setup for beam focusing. The buncher modulates the input direct-current beam into 5.7-GHz bunch train. The buncher consists of two radiofrequency (RF) cavities. Immediately downstream of each RF cavity, there is an electrostatic potential depression (EPD) section. An EPD section in an electrically insulated beam pipe biased with a negative high voltage. The EPD method remarkably shortens the buncher structure by rapidly forming the bunch train. Each of the RF cavities and the EPD sections uses an individual set of rectangular permanent magnets, arranged in a circular array, which provide a solenoid-like focusing field. The polarity of the magnets is configured to form an alternating on-axis magnetic field orientation for minimizing the total weight. Coarse adjustment of the magnetic field is achieved by adding or removing permanent magnet rectangles. For fine adjustments, the rectangles are moved evenly in the radial direction. We show simulation results of the buncher performance and the tunable magnetic focusing. Initial experimental results are also reported.
Paper: WEP013
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP013
About: Received: 09 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
WEP016
Demonstration of a sheet electron beam production from a UNCD field emitter array
719
Ultra nanocrystalline diamond (UNCD) is a promising material for field emitters because of its mechanical and chemical stability, high thermal conductivity, and low electrical resistivity. We proposed to demonstrate fabrication of a special shape field emitter array to produce a sheet electron beam for high frequency vacuum tubes. At Los Alamos, we established a Field Emitter Array Test Stand (FEATS) where we can apply voltages up to 40 kV to test field emitter arrays in a vacuum level of 10^-7 Torr or lower. At this test stand, we can take beam images, measure beam current and study beam divergence. We fabricated diamond cathodes in form of arrays of 1 by 81 pyramids and used them to demonstrate production of a sheet electron beam. This talk will present details of the emission tests and analyses of the produced sheet beam.
Paper: WEP016
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP016
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Jan 2026
WEP017
Design and cold test of a novel waveguide power splitter for distributed power coupling in short-pulse acceleration
722
RF breakdown is the major limitation to achieving higher accelerating gradients. Recent experimental evidence shows that this limitation can be mitigated by reducing the RF pulse length to a few nanoseconds. One key challenge in designing an accelerator operating in the short-pulse regime is achieving the required short filling time. In this work, we designed a novel waveguide power splitter to independently feed an array of accelerating cells. A prototype X-band waveguide array for a one-to-four power splitter has been developed to drive standing-wave cavities operating in the short-pulse regime. The power is designed to be equally split and fed into four cavities, with the desired phase advance per cavity. A 3D-printed prototype has been used for low-power microwave measurements ("cold" tests). The results, including measurements with a vector network analyzer and time-domain measurements, show good agreement with simulations. Ongoing work includes designing a multi-cell accelerator based on this concept for two-beam acceleration with few-nanosecond RF pulses.
Paper: WEP017
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP017
About: Received: 07 Aug 2025 — Revised: 11 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Jan 2026
Design guidelines and longitudinal dynamics for plasma-based, extreme compression
High-brightness, ultra-high peak current electron beams are of great interest for a range of applications, including high-energy colliders, strong field quantum electrodynamics, and laboratory astrophysics. However, the task of compressing electron beams to attosecond pulse durations and mega-amp peak currents while maintaining beam quality continues to pose a significant challenge. We explore, with start-to-end simulations, the feasibility of using plasma-based compression to generate ultra-short, high-peak current electron beams. By taking advantage of the large longitudinal electric fields present in a plasma wakefield, we demonstrate that large chirps can be imparted onto an electron beam, allowing it to be compressed to ultrashort durations in a magnetic chicane. We investigate the viability and limitations of this technique, and establish how the compressed beam properties depend on both accelerator and plasma parameters. Using these relationships, we find the optimal beam and plasma conditions for different applications, looking towards demonstrating plasma-based compression at the FACET-II facility at SLAC National Accelerator Laboratory.
Design of a high-power X-band load with circular waveguide TE01 mode input
RF loads are critical components in any high-power rf system. There are two types of commonly used rf loads in multi-megawatt systems: water loads and dry loads. Water loads have a ceramic window separating vacuum from the water. Use of water loads in large scale rf systems is risky because of the possibility of water leaking into vacuum. At SLAC multi-megawatt dry loads were developed and used in S-band and X-Band applications. For example, a compact X-band load based on a tapered WR90 and circularly polarized TE11 mode has been in use for decades. To increase high power performance of a load beyond the state-of-the art, we designed an 11.424 GHz load fed by the TE01 circular waveguide mode. The load is of disk-loaded-waveguide type, built out of a set of cells. The cells are made of magnetic stainless-steel with bulk conductivity is 160000 S/m. The passband of the load is about 180 MHz. The load utilizes axially symmetric TE mode which has minimal surface electric fields. We show the design of the load and results of X-band resonant measurements of the load’s cells. The measurements allow us to determine conductivity of the 430 stainless steels after multiple brazing cycles.
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 Jan 2026
WEP021
Design of an optical amplifier for amplified OSC in IOTA facility at Fermilab
729
Optical stochastic cooling (OSC) is a cutting-edge beam cooling technology to reduce, control the 3 dimensional spread and the motion of particle beams. It has recently been successfully, experimentally, demonstrated in Fermilab's IOTA storage ring, marking a major step forward in beam cooling. OSC has the potential to significantly improve both the performance and flexibility as a beam cooling system. One promising way to boost OSC performance is by adding a high-gain optical amplifier. However, this amplifier must be carefully designed to meet the specific constraints of the OSC system. A major challenge lies in the limited optical delay, which is just 6 mm for the case of IOTA, set by the beam bypass, restricts us to use a short-length gain medium. This, along with IOTA’s high repetition rate and the relatively long duration of the optical pulses, limits the peak power available for the pump laser without damaging the crystal, which is crucial for achieving strong nonlinear gain. Additionally, it's essential to preserve the phase coherence of the undulator radiation during amplification, which further complicates the amplifier design. This report details a specialized amplifier setup that addresses these challenges, includes simulations of the integrated system, and summarizes the latest experimental progress and results.
Paper: WEP021
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP021
About: Received: 12 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
WEP024
Design study of novel deuteron cyclotron auto-resonance accelerator
741
A novel deuteron cyclotron auto-resonance accelerator (dCARA) is described here. It is predicted to produce a 40-MeV, 125 mA CW deuteron beam, with notable features including continuous acceleration without bunching for good beam stability, high efficiency, wide beam aperture, and an exceptionally short length of 1.6 meters. Such an accelerated beam can be used to produce the intense neutron flux via breakup of deuterons on a low-Z target. It is estimated that 5-10 small dCARA-based modules could provide the same level of transmutation as one acceleration driven system (ADS) employing a GeV-level 25-MW linac. Other applications of dCARA include medical isotope production system, or fusion prototypic neutron source for testing inner-wall materials for a future fusion power reactor.
Paper: WEP024
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP024
About: Received: 08 Aug 2025 — Revised: 15 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Jan 2026
Developing a hybrid accelerating structure based on short-pulse Structure Wakefield Acceleration
Structure Wakefield Acceleration (SWFA) powered by -short RF pulses (~10 ns) generated by Two-Beam Acceleration (TBA) at the Argonne Wakefield Accelerator (AWA) has demonstrated effective suppression of RF breakdowns and achieved gradients exceeding 400 MV/m at X-band (11.7 GHz) frequencies. To fully exploit the benefits of this short RF pulse operation, an accelerating structure must simultaneously achieve two goals: high group velocity (Vg) to ensure rapid RF filling (need for high efficiency), and simultaneously maintain high shunt impedance (R) (need for high accelerating gradient). Conventional accelerating structures involve inherent tradeoffs between these parameters, limiting their effectiveness in the short-pulse regime. To this end, we developed a hybrid structure composed of two co-optimized sub-structures fed by one coupler at the middle: one backward wave (BW) filling and one forward wave (FW) filling sub-sections.This design not only preserves the short-pulse advantage, it also simplifies the setup (one input coupler for two structures) and enhances the beam’s energy gain by doubling the acceleration length without requiring extended RF pulse duration. In this work, we present the detailed RF design with preliminary beam dynamics simulations demonstrating efficient energy gain within a compact acceleration length.
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 Jan 2026
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.
WEP029
Developments in LUME-ACE3P including S-parameter optimization for S3P
748
We present here the introduction of optimization to LUME-ACE3P (LUME: Lightsource Unified Modeling Environment; ACE3P: Advanced Computational Electromagnetics 3D Parallel). LUME-ACE3P is a Python wrapper that streamlines workflows for ACE3P, a suite of finite element solvers for electromagnetic fields in complex geometries. LUME-ACE3P offers parameter sweep capabilities, which was previously the only means to perform optimization with this code. In the integration of LUME-ACE3P with the optimization package Xopt, we facilitate efficient and easy to use optimization for accelerator component design. We present the LUME-ACE3P-Xopt workflow with an example problem.
Paper: WEP029
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP029
About: Received: 07 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
Experimental generation of petawatt peak power, extreme electron beams for advanced accelerator applications
In this contribution we report on the experimental generation of high energy (10 GeV), ultra-short (fs-duration), ultra-high current (∼ 0.1 MA), petawatt peak power electron beams at the FACET-II National User Facility at SLAC National Accelerator Laboratory. These extreme beams enable the exploration of a new frontier of high intensity beam-light and beam-matter interactions broadly relevant across fields ranging from high-field plasma wakefield acceleration to laboratory astrophysics and strong field quantum electrodynamics. We demonstrate our ability to generate and control the properties of these electron beams by means of a laser-electron beam shaping technique. This experimental demonstration opens the door to on-the-fly customization of extreme beam current profiles for desired experiments and is poised to benefit a broad swathe of cross-cutting applications of relativistic electron beams including optimization of advanced accelerator applications.
Experimental progress of PWFA in a laser-ionized plasma source FACET-II
To compete with conventional accelerators, collider and light source applications based on plasma wakefield acceleration need to be able to handle 10s of Joules of energy transfer between the drive beam, plasma, and witness beam at repetition rates exceeding 100 Hz. Scaling up to these parameters is challenging due to the large amount of heat deposited in the plasma source. To begin approaching this regime, we developed a laser ionized plasma source using a pair of diffractive optics to produce a meter-scale Bessel focus with a tailored axial intensity profile. Using this source, we demonstrate multi-Joule energy transfer in the plasma accelerator at SLAC’s FACET-II facility with strong deceleration of the drive bunch and acceleration of a witness bunch.
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.
Fast and efficient modeling of structure-based wakefield accelerators
Structure-based wakefield accelerators (SWFA) have been identified as a candidate technology for future applications ranging from free electron lasers to colliders. However, achieving the desired beam energy and quality requires meter-scale structures with tight tolerances, placing constraints on structure and beam characteristics to minimize emittance growth and combat transverse instabilities. High fidelity and self-consistent simulations over these lengths necessitate enormous computational resources, making parametric studies of novel structures or instability-mitigation schemes unfeasible with standard practices. We present a technique for decomposing high dimensional wakefield systems into a set of lower dimensional components, capable of accurately reconstructing the structure response in a fraction of the time. We discuss the approach and implementation of this technique using Green’s Functions for common structure geometries. We demonstrate the potential for significant reduction in computation times and memory footprint using such representations. Finally, we discuss the application of machine learning in generating these representations for novel structure geometries.
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 Jan 2026
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 Jan 2026
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 Jan 2026
WEP042
Heavy ion implantation analysis in graphite for the FRIB charge selector
769
An advanced charge selector is currently under development at the Facility for Rare Isotope Beams (FRIB) to intercept unwanted charge states of stripped heavy ion beams. Rotating graphite wheels are employed to absorb beams with a power up to 5 kW and a size as small as an rms width of 0.7 mm × 1.25 mm. The implantation of beam ions and accumulated radiation damage affect the material properties, potentially leading to its structural failure. Determining the foreign ion accumulation behavior is one critical aspect for predicting the operational lifetime of the graphite wheels. In this study, ion implantation distribution was first characterized using SRIM simulations, then coupled with Monte Carlo analysis to account for wheel geometry and rotational dynamics. The evolution of the ion concentration profiles was subsequently determined considering the diffusion effects. The analysis reveals that strategic beam positioning optimization, combined with diffusion effects, substantially reduces peak ion concentrations and implantation rates, providing essential data for graphite wheel lifetime assessment.
Paper: WEP042
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP042
About: Received: 10 Aug 2025 — Revised: 13 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026
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.
WEP047
Investigating Dirac semimetal cadmium arsenide as a potential low-MTE photocathode
773
We report on the quantum efficiency (QE) and mean transverse energy (MTE) of photoemitted electrons from cadmium arsenide (Cd₃As₂), a three-dimensional Dirac semimetal (3D DSM) of interest for photocathode applications due to its unique electronic band structure, characterized by a 3D linear dispersion relation at the Fermi energy. Samples were synthesized at the National Renewable Energy Laboratory (NREL) and transferred under ultra-high vacuum to Arizona State University (ASU) for measurement using a photoemission electron microscope (PEEM). The maximum QE was measured to be 3.37 × 10⁻⁴ at 230 nm, and the minimum MTE was 55.8 meV at 250 nm. These findings represent the first reported QE and MTE measurements of Cd₃As₂ and are an important step in evaluating the viability of 3D DSMs as low-MTE photocathodes. Such photocathodes, constrained to lower MTEs by the electronic band structure, may prove effective in advancing beam brightness in next-generation instruments and techniques.
Paper: WEP047
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP047
About: Received: 01 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 10 Aug 2025 — Issue date: 28 Jan 2026
Investigation of transverse instability in efficient plasma-based accelerators
Plasma-based accelerators offer a promising route to compact high-energy particle sources. However, recent theoretical work* has suggested that accelerating a low-energy-spread electron beam may not be feasible at high efficiency because of the excitation of transverse beam break up (BBU) instability. This instability, which leads to a growing spatio-temporal oscillations of the beam centroid, is a consequence of a significant misalignment or loss of symmetry between the beam and the accelerating structure (ion cavity) and arises because of the coupling between the accelerating beam electrons and the plasma sheath electrons surrounding the ion cavity. The instability deteriorates the electron beam parameters (notably, the beam emittance) and hinders the usefulness of the plasma-based accelerators for some potential applications like, particle colliders. Here, using particle-in-cell simulations and analytical modelling, we evaluate the centroid evolution of a partially misaligned trailing electron bunch coupled with a plasma accelerator and provide novel solutions for its suppression. We also present preparation status of an experiment designed to characterize the transverse instability on a well-defined externally injected electron beam from a conventional linac in a CO2 pulse driven LWFA at Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL).
WEP049
Progress report on two-bunch excitation of wakefield in dielectric structures
777
Wakefield accelerators have the potential to achieve accelerating fields in the GV/m range, offering a promising path to more compact and cost-effective acceleration compared to conventional methods. Structure-based wakefield accelerator (SWFA) technology provides a viable approach to implementing beam-driven wakefield acceleration. An experiment at the Argonne Wakefield Accelerator (AWA) will utilize dielectric-lined structures to explore multi-beam excitation of wakefields for wakefield-pulse shortening and mapping of the transverse wakefield topology. These structures were commercially sourced and require a thin metallic film deposited on their outer surface. The first part of this paper summarizes the preparation of these structures. In parallel, a two-bunch beam configuration is required to support the experimental investigation, where one bunch excites the wakefield and the second serves as a loading or probe bunch. The experimental generation and testing of this two-bunch scheme at AWA are presented in this work.
Paper: WEP049
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP049
About: Received: 15 Aug 2025 — Revised: 18 Aug 2025 — Accepted: 19 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
Laser-ionized plasma sources for plasma wakefield accelerators: Alignment technique, tolerance, and applications
Plasma wakefield accelerators (PWFA) are promising candidates for next-generation colliders due to their ability to sustain extremely high acceleration gradients. Laser-ionized plasma sources offer key advantages for PWFA, including precise control over the transverse and longitudinal plasma density profiles for emittance preservation, tunable plasma column widths suited for positron acceleration, and resilience to heat deposition. A critical experimental challenge, however, is the precise alignment of the plasma source to the electron beam and maintaining that alignment over time. We report on a novel alignment technique developed at the Facility for Advanced Accelerator Experimental Tests II (FACET-II), enabling high-precision alignment of a 1-meter-long laser-ionized plasma source to a 10 GeV, 1.6 nC electron beam with a transverse accuracy better than 10 µm, limited primarily by laser pointing jitter. We present our methodology, discuss the alignment tolerances between the drive beam and the laser-ionized plasma, and explore future opportunities for using narrow plasma columns for positron acceleration.
Latest progress on Plasma Wakefield Acceleration at FACET-II
Plasma Wakefield Acceleration (PWFA) can provide 10’s of GeV/m acceleration gradients, providing a novel path towards efficient and compact future colliders and high brightness free electron lasers. At the Facility for Advanced Accelerator Experimental Tests II (FACET-II) at SLAC, we are undertaking experiments in PWFA using a 10 GeV electron beam configured as a drive and witness pair. We will share our progress towards the ultimate goal of doubling the energy of the 10 GeV witness bunch by PWFA, with high efficiency and while preserving beam quality. Our latest results demonstrate multi-GeV acceleration of the witness bunch, with energy gains exceeding 5 GeV and sub-percent energy spread, using a 40 cm long lithium vapor plasma source. Additionally, we have achieved near-complete charge capture of the witness bunch and are actively working to minimize emittance growth through careful control of the transverse properties of the bunches.
WEP055
Light-induced enhancement of quantum efficiency in III-nitride photocathodes
786
High quantum efficiency (QE) semiconductor photocathodes are essential for generating high average beam current and brightness. One class of semiconductor photocathodes considered for use in photoinjectors for unpolarized and polarized electron beams are III-nitride heterostructures. These materials can exhibit negative electron affinity at the surface, utilizing intrinsic polarization fields to engineer the band structure without the need for additional surface treatments. In this study, we investigate the effects of light exposure on the surface of III-nitride photocathodes and the resulting changes in QE and photoemission, using photoemission electron microscopy (PEEM) for characterization. We demonstrate that exposing a GaN photocathode to a 240 nm wavelength laser at 870 µW for 15 minutes increases the QE by two orders of magnitude, with a maximum QE of 2.34 × 10⁻⁴ observed. Although III-nitride photocathodes are known for their robustness, our findings indicate that laser exposure can significantly alter their QE. Our observations reveal the need for a detailed investigation of photo-induced effects on QE in III-Nitride photocathodes.
Paper: WEP055
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP055
About: Received: 08 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
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 Jan 2026
Modeling of plasma channels for laser plasma accelerators
Structured plasma channels are an essential technology for driving high-gradient, plasma-based acceleration and control of electron and positron beams for advanced concepts accelerators. Laser and gas technologies can permit the generation of long plasma columns known as hydrodynamic, optically-field-ionized (HOFI) channels, which feature low on-axis densities and steep walls. By carefully selecting the background gas and laser properties, one can generate narrow, tunable plasma channels for guiding high intensity laser pulses. We present on the development of 1D and 2D simulations of HOFI channels using the FLASH code, a publicly available radiation hydrodynamics code. We explore sensitivities of the channel evolution to laser profile, intensity, and background gas conditions. We examine experimental measurements of plasma channels and their comparison to model predictions. Lastly, we discuss ongoing work to couple these tools to community PIC models to capture variations in initial conditions and channel influence on wakefield accelerator applications.
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 Jan 2026
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 400 mA to more permanent 500 mA 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 Jan 2026
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 Jan 2026
Overview of the FACET-II facility at SLAC
FACET-II is a National User Facility offering unique capabilities for the advancement of accelerator science. Utilizing high-energy electron beams, it enables state-of-the-art research in advanced acceleration methods, ultra-high-brightness beam generation, and novel radiation sources. Here, we provide an overview of the FACET-II facility and highlight its experimental infrastructure, which is accessible to the scientific community through a competitive user program.
WEP064
Passive plasma lens experiments at FACET-II
808
The beam-driven, passive plasma lens can provide axisymmetric focusing with strengths orders of magnitude greater than conventional quadrupole magnets, while remaining ultra-compact. These characteristics make it attractive for beam matching into a plasma wakefield accelerator and for controlling beam divergence downstream of plasma stages. Optimal performance can be achieved in the underdense regime, resulting in a linear focusing force and emittance preservation of the focused beam. We report progress on experimental results from SLAC’s FACET-II facility, where we utilized a fs Ti:Sapphire laser pulse to ionize hydrogen gas from a supersonic gas jet to focus several hundred pCs of charge of a 10 GeV electron beam.
Paper: WEP064
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP064
About: Received: 11 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
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 Jan 2026
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.
WEP069
Preliminary computational study on minimizing longitudinal emittance in photoinjector
824
Recently, we proposed a novel photoinjector that incorporates an emittance exchange (EEX) beamline. Previous studies demonstrated promising 4D emittance performance of an EEX-based injector, but the beam’s longitudinal emittance at the linac exit still limits the final transverse emittance downstream of the EEX stage. We performed a comprehensive scan of injector parameters—including gun phase, laser spot size and pulse length, and solenoid strengths—to (1) estimate the minimum achievable longitudinal emittance, (2) identify sources of emittance growth, and (3) explore mitigation strategies. Here, we present the status of this study. Simulations were carried out using General Particle Tracer (GPT) including space-charge effects.
Paper: WEP069
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP069
About: Received: 08 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026
WEP070
Progress of polarized ion sources at BNL
828
The OPPIS has undergone multiple upgrades since 2000, with the most recent completed in 2022. Improvements to the Rb and Na cells have reduced vapor dispersion in the beamline, significantly lowering consumption and improving source stability. Plasmatron modifications extended component lifetimes. These upgrades enabled reliable Run-24 operation, with a mean current of 350 μA, 300 μs pulse width, and ~80% polarization delivered at the 200 MeV linac exit. Development is also underway for a high-intensity (2×10¹¹ ions/pulse) polarized ³He⁺⁺ source for the future EIC. The approach uses metastability-exchange optical pumping of high-purity ³He gas in a strong magnetic field, followed by ionization in EBIS. In tests with an “open” cell, 80–85% polarization has been achieved. The final gas cell configuration is now being tested with a 5 T EBIS solenoid magnet.
Paper: WEP070
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP070
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 13 Aug 2025 — Issue date: 28 Jan 2026
Progress of the plasma acceleration research platform at IHEP
Plasma acceleration is an innovative principle characterized by high acceleration gradients, which has attracted significant interest from major accelerator laboratories worldwide, because of its potential to increase accelerator energy and reduce size. One promising approach involves using existing conventional accelerators as external injectors for plasma-based accelerators, a topic of considerable interest within the research community. At IHEP, we propose utilizing the BEPCII Linac in conjunction with a new linac based on a photocathode RF gun to develop a new plasma acceleration research platform. This manuscript presents recent progress in the development of this platform.
Progress on commissioning of the CARIE facility at LANL
The cathodes and RF interaction at extremes (CARIE) is a project in Los Alamos National Laboratory (LANL) that aims for generating a high-brightness electron beam from a high-gradient photocathode. The commissioning of the CARIE facility started in 2022. A 50 MW C-band klystron was conditioned in 2023. A waveguide line including a high-power circulator was constructed and conditioned up to 12 MW in 2024. The facility has new control and logging systems currently being in implementation. An RF injector without a cathode plug was successfully tuned and is ready for installation. This talk will present the progress on commissioning and outlook of the project.
WEP073
Progress update on compressed ultrashort pulse injector demonstrator
832
Stable high gradient operation of a photoinjector is important for generating high brightness electron beams. The Argonne Wakefield Accelerator (AWA) facility recently commissioned an X-band photoinjector at 400 MV/m cathode field without significant breakdown rates using nanosecond RF pulses generated from a wakefield accelerator. We propose to develop an X-band photoinjector at 500 MV/m cathode field fed by ultrashort RF pulses generated by RF pulse compression technology developed at SLAC National Accelerator Laboratory, named as Compressed Ultrashort Pulse Injector Demonstrator (CUPID). The klystron based pulse compression is more stable and allows higher repetition rate. Here we provides the progress update of CUPID project, in particular on the mechanical design of the electron gun, solenoid's requirement and design constraints.
Paper: WEP073
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP073
About: Received: 07 Aug 2025 — Revised: 08 Aug 2025 — Accepted: 10 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
WEP076
R&D progress of electron cyclotron resonance accelerator
840
Several attractive features of a novel electron Cyclotron Resonance Accelerator (eCRA) include: a compact robust room-temperature single-cell RF cavity as the accelerator structure; continuous ampere-level high current output without bunching; and a self-scanning accelerated energetic e-beam, obviating need for a separate beam scanner. Hence an eCRA can be highly compact and efficient to produce high power electron beams and x-ray beams. The applications of the eCRA includes the replacement of Cs-137 based dosimeter calibration system, and the replacement of Co-60 based sterilization system. The R&D progress of eCRA is reported here. A 2 MeV eCRA Demonstrator is under construction at BNL to validate the eCRA acceleration mechanism experimentally. A 5 MeV eCRA Upgrade with high beam power is in the design phase.
Paper: WEP076
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP076
About: Received: 08 Aug 2025 — Revised: 15 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
WEP079
RF breakdown and dark current studies in short-pulse acceleration
847
Recent experimental studies at the Argonne Wakefield Accelerator (AWA) have shown that operating RF cavities with short pulses, only a few nanoseconds in duration, can raise the accelerating gradient to nearly 400 MV/m in a series of X-band structure tests. These results motivate further investigation into the breakdown physics underlying the short-pulse acceleration regime. In this work, we present analytical models and numerical simulations of dark current dynamics in X-band cavities driven by short RF pulses. These studies explore key phenomena associated with RF breakdown across various time scales, including field emission, secondary electron emission, and plasma formation, with particular focus on their dependence on RF pulse length. Building on these insights, we describe the design and experimental plan for a single-cell X-band RF cavity operating at 11.7 GHz, optimized for high-gradient operation with 6~ns long RF pulses and integrated with RF breakdown diagnostics. This work aims to deepen the understanding of RF breakdown physics in the short-pulse regime and support the development of compact linear accelerators for future applications.
Paper: WEP079
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP079
About: Received: 08 Aug 2025 — Revised: 10 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Jan 2026
Science enabled by the the FACET-II low-energy laser arm
The FACET-II 10 TW laser system enables a variety of studies ranging from plasma wakefield acceleration over laboratory astrophysics to strong-field QED. While we successfully improved the performance of the high-energy laser-arm has, the much more versatile low-energy arm has yet to keep up. We report on the currently ongoing efforts to improve the performance of the low-energy laser-arm performance. The improvements are expected to enable studies, such as ultra-low emittance electron beams from plasma accelerators, plasma lenses, and novel ultrafast beam diagnostics.
Simulating dielectric wakefield acceleration of positrons from a solid target converter
Positrons and electrons can be generated by impinging a relativistic electron beam onto a solid converter, sometimes referred to as a non-neutral fireball beam. Depending on the scenario, a substantial fraction of the incoming driver bunch may still have sufficient quality to drive high gradient (~GV/m) accelerating wakefields in a dielectric structure. Here we consider the design of a dielectric loaded waveguide, positron converter, and electron driver bunch structure to realize capture and GV/m dielectric wakefield acceleration of positrons at SLAC FACET-II.
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 Jan 2026
WEP083
Status of the experimental demonstration of GW power generation from THz-TBA
855
We present the current status of preparations for the experimental demonstration of GW power generation from THz-TBA. The presentation will cover the status of structure fabrication, RF power extraction and absolute power measurement, and THz drive beam preparation. Currently, 0.4 THz structures are being fabricated using two improved methods over previous fabrication techniques. RF power extraction will be achieved using an on-axis elliptical horn antenna and off-axis parabolic mirrors. The RF power will be detected with a bolometer and calibrated based on the total beam energy loss measured by a spectrometer. In recent machine studies, we successfully generated a high-charge bunch train (1 nC/bunch) compatible with 0.4 THz structure.
Paper: WEP083
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP083
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026
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 1.25 MW 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 Jan 2026
WEP085
Start-to-end simulations of a compact, linac-based positron source
862
Slow positrons are increasingly important to the study of material surfaces. For these kinds of studies, the positrons must have low emittance and relatively high brightness. Unfortunately, fast positron sources like radioactive capsules or linac driven sources have broad energy and angular spread, which make them difficult to capture and use. Moderators are materials that produce slow, mono-energetic positrons from a fast positron beam. Since their efficiencies are typically less than 10^-3 slow e+ per fast e+, research into how to maximize efficiency is of great interest. Previous work has shown that using a linac, one can decelerate the fast positron beam in order to greatly increase moderation efficiency. We present here start-to-end simulations using G4beamline to model a 100~MeV electron beam incident upon a Tungsten target, focused by an adiabatic matching device, and decelerated by a 1.3~GHz, 5-cell pillbox cavity. We show that by decelerating the positrons after their creation we can increase the number of positrons under 500~keV by 15 times, translating to a 16.3 times improvement in moderation efficiency, and therefore leading to a brighter positron source.
Paper: WEP085
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP085
About: Received: 08 Aug 2025 — Revised: 08 Aug 2025 — Accepted: 10 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
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.
THz detection and investigation of vacuum-compatible optical components
Detecting terahertz (THz) radiation in ultra-high vacuum (UHV) environments presents notable challenges due to the limited availability of commercially compatible components. In preparation for upcoming THz measurements at the Argonne Wakefield Accelerator (AWA) facility, we investigated two critical aspects: (1) the THz transmission characteristics of fused silica windows, and (2) the suitability of commercial off-axis parabolic mirrors (OAPs) for use in UHV conditions. While fused silica is widely used in optical systems, its performance in the THz regime is rarely documented. We present transmission measurements and assess its viability for THz diagnostics. Additionally, we address the incompatibility of anodized, off-the-shelf OAPs with UHV by developing and testing both mechanical and chemical de-anodization techniques. These methods aim to maintain surface integrity and optical quality. This work provides practical guidelines and compatibility benchmarks for implementing THz diagnostics in UHV environments and serves as a reference for future experiments at AWA and other accelerator facilities.
WEP091
Transverse deflecting cavity optimization for active control of electron beam energy chirp
873
The Transverse Deflecting Cavity Based Chirper (TCBC) is a novel concept of imposing and removing a significant energy chirp of an ultra-relativistic electron beam. The TCBC method requires much less footprint, compared to the conventional chirping and dechirping method involving operating a linear accelerator off-crest. When the compressed bunch is very short, the dechirping has to rely on the wakefields. We present our updated design of the L-band traverse deflecting cavity (TDC) for demonstrating the TCBC concept at the Argonne Wakefield Accelerator (AWA) facility. Our TDC design update is based on the original design provided by Tsinghua University. The TDC design update focused on ensuring improved performance under more intense electromagnetic fields, reducing the peak pulsed temperature rise. The tuners of the TDC were meanwhile reworked to allow greater adjustability of the resonant frequency and of the electromagnetic field balance among the cells. We also report the tolerance study of the TDC. Two copies of the TDC with the updated design are currently under fabrication with Dymenso, LLC.
Paper: WEP091
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP091
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 15 Aug 2025 — Issue date: 28 Jan 2026
WEP092
Ultra-violet laser transverse shaping with phase plates
876
Shaping ultraviolet (UV) laser beams is critical for optimizing photoinjector performance for applications in free-electron lasers (FELs). It has been shown that a 50% truncated Gaussian beam can achieve the lowest emittance via space charge compensation at LCLS-I. However, conventional shaping techniques to prepare this beam are limited by significant power losses or are not adapted for UV light. Here we report a high-precision transverse-shaping technique based on custom fused-silica phase plates with >99 % transmission at 253 nm. This approach enables spatial beam profile tailoring and significantly enhances beam stability at the photocathode. Using IMPACT-T simulations, we predict a 33% (from 0.67um to 0.45um) reduction in normalized emittance for a 250 pC bunch at LCLS-I. Experimental implementation at FACET-II demonstrated a 37% emittance reduction (from 5.4um to 3.4um) at 1.6 nC. These results establish phase-plate beam shaping as a high-fidelity, low-loss approach for high-brightness photoinjectors. Implementation at LCLS-II which will enable stable operation at megahertz repetition rates is underway.
Paper: WEP092
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP092
About: Received: 10 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 12 Aug 2025 — Issue date: 28 Jan 2026
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 Jan 2026
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 Jan 2026
Monte-Carlo modeling and experimental investigation of photoemission from CsTe semiconductor photocathode under high fields
Beam brightness can be enhanced with high gradient operation in photocathode guns. Such high gradient guns, such as the L-band gun at the Argonne Wakefield Accelerator (AWA) facility and the C-band high gradient gun being commissioned in the CARIE project at Los Alamos National Laboratory, are also typically equipped with semiconductor photocathodes due to their high quantum efficiency. To investigate the photoemission process in semiconductor thin-film photocathode under such conditions, we developed Monte-Carlo transport and photoemission models employing electronic, phonon, dielectric and optical properties directly from Density Functional Theory (DFT) calculation, as well as the photo excitation model based on the light interference effect in thin films. This photoemission model is further employed in photocathode gun simulation and used to investigate a recent high-gradient experiment conducted at the AWA photo injector. We will discuss the effects of the high field gradient on photoemission through a comparison of the measurement and the simulated beam dynamics.
Recent LANSCE efforts on improving H+ duoplasmatron capabilities
LANSCE uses a duoplasmatron ion source to produce H+ ion beams for the Isotope Production Facility, which uses 100 MeV proton beams to produce a variety of therapeutic and diagnostic isotopes for research purposes and also supports a variety of other experiments for materials and nuclear physics. We have recently begun work to improve the reliability, peak current, and lifetime of the ion source, while restoring existing capabilities to build new ion sources and filaments. This poster will cover these efforts, with a particular focus on the work to re-establish and improve the filament production capability and production of higher peak current beams.
WEP100
Upgraded photoinjector laser pulse train generator at the Argonne Wakefield Accelerator
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The Argonne Wakefield Accelerator (AWA) facility operates a high-charge (100s of nC) electron beam in a bunch train, with eight electron bunches at a 769 ps spacing matching the linac operating frequency of 1.3 GHz. AWA’s electron beam is optimized for producing large wakefields in resonant structures to study structure wakefield acceleration. This is achieved by maximizing total beam charge, and by correct bunch train timing to enhance the wakefield via inter-bunch coherence. The properties of the bunch train are determined by a “multisplitter” in the photoinjector laser system, in which a series of beamsplitters splits one laser source into eight - ideally equal - pulses. However, AWA’s previous system did not split pulses evenly, with up to a 2:1 ratio between pulse energies within a train. Damaging electrical breakdown events within the electron gun, driven by high single bunch charge, occurred at lower total charge in this non-uniform set-up, limiting maximum charge. Thus, a new multisplitter using polarizing beamsplitters and half-wave plates (HWPs) was implemented. Unlike the previous fixed-ratio beam-splitter design, the new system enables tuning the splitting ratio for each beamsplitter, resulting in a more uniform pulse train. Large 2” optics and uncoated HWPs are also used to increase the laser intensity damage threshold (LIDT). This paper presents the design, characterization and lessons learned in early commissioning of AWA's upgraded laser pulse train generator.
Paper: WEP100
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP100
About: Received: 08 Aug 2025 — Revised: 12 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026
WEP101
Booster cavity damper redesign for PIP-II
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A new Higher Order Mode (HOM) damper was designed and is undergoing testing for the Booster accelerator cavity at Fermilab. In anticipation of the PIP-II upgrade, it was discovered that the higher intensity of PIP-II may cause beam instability due to an excited mode at 106 MHz. This unfortunately corresponds with the cavity’s 2nd order harmonic mode, which will sweep from 86-105.7 MHz. The new damper is a modification of an existing damper that was designed to reduce an existing static HOM at 83 MHz, with the new design intending to cover the 2nd order HOM as well. The existing damper uses an inductive coupling loop to extract RF energy from the cavity which then goes through a filter in order to reflect the fundamental frequency back into the cavity while passing HOMs to a dump load. The new damper intends to replace the filter portion of the system with a wider band variant while also changing the topology from a coaxial cable loop filter to a componentized PCB-based design. Primary design challenges include bandwidth coverage, impedance matching of the various modes, long term thermal and mechanical stability, radiation hardness, and high voltage handling. Initial designs achieved the desired damping but were found to quickly succumb to destructive arcing due to the voltages present. More finalized designs intend to address this problem through circuit design modifications as well as the use of hardier components.
Paper: WEP101
DOI: reference for this paper: 10.18429/JACoW-NAPAC2025-WEP101
About: Received: 01 Aug 2025 — Revised: 14 Aug 2025 — Accepted: 14 Aug 2025 — Issue date: 28 Jan 2026