TUPS
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Tuesday Poster Session: TUPS
03 Jun 2025, 16:00 -
18:00
Effects of the transverse plasma gradient in the plasma wakefield accelerator
We present basic analytical studies on the effects of the local transverse plasma density fluctuations. We show that in two acceleration schemes (blow-out regime and hollow plasma channel) transverse plasma density gradient results in a transverse wakefield. This, in turn, may lead to significant limitations in the machine's performance. We consider the classical round driver in the transverse coordinates and show, that in the blow-out regime transverse plasma inhomogeneity results in the dipole wake that may deflect the driver and result in housing instability. We show that in the case of a hollow plasma channel, transverse plasma gradient shifts the electromagnetic center of the plasma channel. As a remedy, we propose to consider flat driver injection and show, that a flat driver in the blow-out regime can be robust to the perturbation in transverse plasma density.
Femtosecond laser-induced plasma filaments for beam-driven plasma wakefield acceleration
Plasma-based acceleration technology can revolutionize particle accelerators, enabling the realization of compact systems capable of driving different user-oriented applications. We propose developing a laser-based, high repetition rate (HRR), highly stable and tunable plasma filament stage for beam-driven plasma wakefield acceleration (PWFA) systems. The plasma filament, generated by a low-energy self-guided femtosecond laser pulse, is studied experimentally and theoretically in a low-pressure N2 gas environment. Precise control of the plasma filament is crucial for plasma-based accelerators, and different techniques have been implemented to measure its density, temperature and dimensions. The measurements show the stable generation of a ≈4cm long channel with a ≈300μm diameter. The plasma density and temperature are ne≈1016cm−3 and Te≈1.3eV with a decay time of ≈8ns. Compared to other plasma stages in PWFA configurations, the proposed one allows for inherently synchronized stages at HRR. The hundreds-µm transverse structure size extends the stage lifetime, and the highly tunable parameters allow us to explore different scenarios. This technology can provide GeV-level electrons at HRR in a compact space, maintaining the high quality and brilliance of the LINAC-generated beams. This development aligns perfectly within the goals of the EuPRAXIA European project.
TUPS003
Beamline to inject laser plasma accelerated electrons to a quasi-isochronous compact storage ring
1389
Laser plasma accelerators (LPAs) can produce high-energy electron bunches from short distances. Successfully coupling these sources with dedicated compact storage rings tuned to quasi-isochronous conditions would demonstrate the capture and storage of ultra-short electron bunches in a circular accelerator. Electron bunches generated from LPAs can have a correlated distribution in longitudinal phase space: a chirp, as well as comparably large angular divergence and energy spread. We, therefore, design a flexible beamline that can transport ultrashort bunches with large angular and energy spread to a ring. We have used the accelerator design programs OPA and MAD8 to build up optical model of a beamline. The line is composed of focusing and dispersion matching sections. A set of small angle bending magnets counteracts the dispersion created by injection septum of the storage ring and provides quasi-isochronous bunch transfer with a flexible value of longitudinal dispersion (R56).
Paper: TUPS003
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS003
About: Received: 24 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
Transverse stability of multiple trailing bunches in filament-regime plasma wakefield acceleration
Plasma wakefield acceleration in the filament regime can provide wakefields suitable for high-gradient, high-quality positron acceleration while maintaining stability. However, the energy that can be extracted by the positrons is limited. Recent works have proposed accelerating a supplementary electron recovery bunch along with the positron bunch to extract more energy from the wake and improve the overall transfer efficiency during acceleration. However, it is unclear if such energy recovery schemes are stable when subject to misalignment. In this work, we employ quasi-static particle-in-cell simulations to study the transverse stability of configurations involving three bunches.
TUPS005
Developing expectations for AWAKE with simulations
1393
The AWAKE experiment at CERN makes use of a self-modulated proton bunch to excite wakefields and accelerate a witness electron bunch. Run 2c of the experiment will demonstrate stabilization of the wakefield amplitude and control of the witness bunch emittance during injection and acceleration. In this work, we present an overview of the ongoing simulation efforts to support the project as it moves towards controlled acceleration and first particle-physics applications.
Paper: TUPS005
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS005
About: Received: 28 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 06 Jun 2025
TUPS006
Proton-driven plasma wakefield acceleration for high-energy lepton beams
1396
Future colliders with discovery potential for particle physics rely on increasing the parton centre of mass (pCM) energy, with the recent P5 report calling for a 10 TeV pCM collider. However, the development of such schemes using conventional accelerator technology would result in ever-larger facilities. High-gradient plasma wakefields driven by proton beams allow the transfer of energy to a witness bunch over a short length scale, and so offer a potential method to transform high-energy proton beams into high-energy lepton beams while requiring relatively little additional civil engineering. The application of this concept to a Higgs factory driven by 400 GeV protons was recently proposed*. In the present work, we discuss the ongoing efforts to address the challenges to realising such a scheme**, and possible upgrade paths to particle physics applications beyond a Higgs factory.
Paper: TUPS006
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS006
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Modeling and evaluation of plasma channel systems 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.
TUPS009
Advancing plasma accelerator science: Insights from the EuPRAXIA Doctoral Network
1400
The EuPRAXIA Doctoral Network (EuPRAXIA-DN) trains the next generation of scientists in plasma-based accelerator technologies, addressing challenges in laser-plasma interactions, advanced beam diagnostics, and novel applications. This contribution highlights progress made in three critical areas: ) real‑time characterization of capillary discharge plasmas to stabilize laser‑wakefield accelera-tion, (ii) femtosecond‑precision X‑band low‑level RF (LLRF) control for the compact EuPRAX-IA@SPARC_LAB injector, and (iii) active‑plasma‑lens (APL)–based beam transport enabling extreme‑ultraviolet free‑electron‑laser (EUV‑FEL) operation within four me-ters of undulator. The innovative training elements with-in the network, such as the EuPRAXIA School on Plasma Accelerators held in Rome in April 2024 and upcoming EuPRAXIA Camps, are also discussed. It is shown how these foster knowledge exchange and skill development for the network's Fellows and the wider plasma accelera-tor community.
Paper: TUPS009
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS009
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS010
Electron beam scattering in rubidium vapour at AWAKE
1404
The Advanced Wakefield Experiment (AWAKE) at CERN uses bunches from the CERN SPS to develop proton-driven plasma wakefield acceleration. AWAKE Run 2c (starting in 2029) plans for external on-axis injection of a 150 MeV electron witness bunch. The goal is to demonstrate emittance control of multi-GeV accelerated electron beams. Prior to injection, the electron witness bunch may have to traverse rubidium vapour. Since the beam must have the correct beam size and emittance at injection, it is important to quantify the effect of scattering. For this, first-principle estimates and the results from Geant4 simulations are compared with measurements of a ~20 MeV electron beam scattering in 5.5 m of rubidium vapour, showing good agreement. Building on this agreement, Geant4 simulations using the estimated AWAKE Run 2c parameters are performed. These predict that scattering will not increase the electron beam size or emittance
Paper: TUPS010
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS010
About: Received: 31 Mar 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 06 Jun 2025
TUPS011
Transverse tolerances in the plasma-wakefield acceleration blow-out regime
1408
We report on recent progress in transverse instabilities and transverse tolerances for plasma-wakefield accelerators in the blow-out regime. In this regime, the transverse fields provide both strong focusing and strong deflection via transverse wakefields. The deflection effect of the wakefields on the main beam leads to limitations on the acceleration efficiency, if not mitigated. Based on comprehensive particle-in-cell simulations we summarize recent findings of the instability--efficiency relation for the blow-out regime. Ion motion and energy spread may mitigate the instability; with linac start-to-end simulations, using the recently developed ABEL framework, we demonstrate that the instability and emittance growth may be sufficiently mitigated for the colliding beams in the HALHF concept. Independent of wakefield effects, the strong focusing fields lead to very tight tolerances for the drive-beam jitter. We quantify these tolerances, using examples from HALHF start-to-end simulations. We show that the tolerances are greatly loosened by applying external magnetic fields to guide the drive-beam propagation in the plasma.
Paper: TUPS011
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS011
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS012
ABEL: The adaptable beginning-to-end linac simulation framework
1412
We introduce ABEL, the Adaptable Beginning-to-End Linac simulation framework developed for agile design studies of plasma-based accelerators and colliders. ABEL’s modular architecture allows users to simulate particle acceleration across various beamline components*. The framework supports specialised codes such as HiPACE++, Wake-T, ELEGANT, GUINEA-PIG and CLICopti, which facilitate precise modelling of complex machine components. Key features include simplified models for addressing transverse instabilities, radiation reactions, and ion motion, alongside comprehensive diagnostics and optimisation capabilities. Our simulation studies focus on the HALHF plasma linac, examining tolerances for drive beam jitter, including effects of self-correction mechanisms. Simulation results demonstrate ABEL's ability to model emittance growth under transverse instability and ion motion, highlighting the framework’s adaptability in balancing simulation fidelity with computational efficiency. The findings point towards ABEL’s potential for advancing compact accelerator designs and contribute to the broader goals of enhancing control and precision in plasma-based acceleration.
Paper: TUPS012
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS012
About: Received: 27 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPS013
Ion-motion simulations of a plasma-wakefield experiment at FLASHForward
1416
In plasma-based acceleration, an ultra-relativistic particle bunch—or an intense laser beam—is used to expel electrons from its propagation path, forming a wake that is devoid of electrons. The ions, being significantly more massive, are often assumed to be stationary. However, both theory and simulations suggest that any sufficiently dense electron bunch can trigger ion motion, and its effect must be taken into account. We simulate beam-driven plasma wakefields to identify key features—such as longitudinally dependent emittance growth—that could be observed in an experiment using plasma and beam parameters from the FLASHForward facility at DESY.
Paper: TUPS013
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS013
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Accelerating wakefield that reduces the energy spread of the witness due to beam loading
Acceleration by the wakefield in the plasma can provide compact sources of relativistic electron bunches of high brightness. Free electron lasers and particle colliders, for using plasma wakefield accelerators, require high efficiency and bunches with low energy spread. The best way to achieve low energy spread is using profiled bunches which form plateau on the wakefield. However, in experimental setups it is easier to use gaussian-kind bunches. Our numerical investigations show that thus form of bunches can assure plateau on the central part of the bunch, higher accelerating field on the tail of the bunch and lower accelerating field on its head. This field distribution leads to decreasing of the energy spread of bunches.
Hose instability suppression by bunch anharmonic oscillations in weakly non-linear regime in wakefield accelerator
Acceleration by plasma wakefield accelerators enables compact sources of high-brightness relativistic electron bunches. Applications like free electron lasers and particle colliders require high efficiency and low energy spread, achievable in the blowout regime, where the radial wake force is linear and independent of the longitudinal coordinate over much of the wakefield bubble. However, this regime introduces hose instability due to harmonic oscillations of electrons in the bunch. Studies show that anharmonic oscillations, caused by inhomogeneous focusing force along the wakefield bubble, suppress this instability. In the weakly nonlinear regime, where some plasma electrons remain in the bubble, their inhomogeneous density widens the stability region. Radial inhomogeneity in the residual plasma electron distribution further leads to anharmonicity of oscillations, stabilizing the bunch. We evaluated the oscillation period and found that the large radial and longitudinal gradients of the focusing force in the driver and witness bunch regions satisfy stochastic stabilization conditions. This enhances the stability of both bunches.
Suppression of bunch destruction under resonant excitation of the wakefield
Acceleration by the wakefield in the plasma can provide compact sources of relativistic electron beams of high brightness. Free electron lasers and particle colliders, using plasma wakefield accelerators, require high quality bunches with predictable profile. Previous studies showed that the resonant sequence of electron bunches appears to be unstable due to the destruction of the bunches. In this paper we discuss the mechanism of this destruction due to the focusing field phase shift which appears during this time evolution. We numerically and analytically showed the possible way of suppressing this instability, shifting all bunches on some distance.
TUPS017
Study on Ion Bunch Generation Using a Laser Plasma RF Ion Source
1420
The development of high-intensity, high-quality ion sources is essential for advanced applications such as particle beam therapy and nuclear physics experiments. The aim of this study is to integrate the Laser Plasma RF Ion Source (LaPRIS), currently under development, into the cyclotron at the Research Centre for Nuclear Physics (RCNP) in order to accelerate ion bunches with high precision and intensity for advanced applications. LaPRIS can generate laser-plasma in an RF field at the laser focus spot and produce bunches at arbitrary timings. Previous research* has achieved a proton beam with a peak current of 1.2 mA and a bunch width of 5 ns. This allows the charge per bunch to be increased by a factor of 100 compared to conventional systems. This makes it possible to track the beam behavior for each bunch, which has potential applications in high-intensity cyclotron research. The injection into the cyclotron must be matched to the acceptance, so the emittance of the beam bunches is measured under different laser characteristics and target conditions to investigate the beam properties.
Paper: TUPS017
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS017
About: Received: 02 Jun 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS018
Synthesis of efficient ordered sodium potassium antimonide photocathodes via molecular beam epitaxy
1424
Alkali antimonide photocathodes exhibit high efficacy as photoemissive materials in electron sources. This proceeding explores the fabrication of thin, ordered films of sodium potassium antimonide via molecular-beam epitaxy (MBE) at the PHotocathode Epitaxy Beam Experiments (PHOEBE) laboratory at Cornell University. Utilizing a sequential deposition technique, the photocathodes are characterized in terms of both quantum efficiency (QE) and crystal structure with the goal of reducing the chemical and physical roughness. A spectral response from 400 to 700 nm demonstrates oscillations resulting from optical interference within the (SiN) substrate. Reflection high-energy electron diffraction (RHEED) patterns confirmed the successful growth of ordered crystal structures for the first time in a sodium potassium antimonide photocathode. Additionally, we investigated the photocathodes' sensitivity to oxidation, revealing their relative robustness compared to CsSb or KSb photocathodes. Notably, the incorporation of higher partial pressures of oxygen during growth improved QE and extended the operational lifetime of the photocathodes.
Paper: TUPS018
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS018
About: Received: 29 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS019
Beam dynamics optimization in high-brightness Photo Injector with various photocathode laser pulse shapes
1428
At PITZ, a comprehensive study is conducted to analyze the factors influencing emittance growth in the European XFEL (EuXFEL) continuous wave (CW) setup. Emittance growth due to space charge effects can be mitigated using advanced photocathode laser pulse shapes. To optimize beam quality, multiobjective optimization studies using ASTRA are performed, focusing not only on minimizing emittance but also on maximizing beam brightness for various laser temporal profiles and dura-tions. The optimization is initially carried out for the CW injector section planned for EuXFEL. The optimized cases are then further tracked through start-to-end (S2E) simulations to evaluate their behavior in the compression stages of EuXFEL. A comparative analysis of gaussian, flattop, ellipsoidal, and inverted parabolic laser profiles is presented, assessing their efficiency not only in terms of emittance but also in 4D and 6D brightness. Finally, the results of the optimized photoinjector setup and the beam properties after the final bunch compression will be presented.
Paper: TUPS019
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS019
About: Received: 06 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS020
Hands on training with ASTRA at ISBA'24
1432
As part of the program of the seventh International School on Beam Dynamics and Accelerators (ISBA'24), we carried out hands-on training with the accelerator simulation code ASTRA. A selection of students used the intensive two-hour daily course to go from learning the basics of ASTRA to designing and optimizing their own accelerators. Here we report the details of training, the student projects and their presentations to their instructors and peers, and plans for future hands-on training programs.
Paper: TUPS020
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS020
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 06 Jun 2025
TUPS021
Activation of GaAs with a Cs-Te thin film
1435
GaAs cathodes with thin-film Negative Electron Affinity (NEA) surfaces affixed have been used to generate spin-polarized electron beams for decades, but still suffer from short lifetimes. Heterojunction NEA surfaces have shown promise in improving cathode lifetimes, but further optimization of cathode activation and surface deposition is possible. Here we report the results of cathode activation with evaporative deposition of a CsTe surface performed at Hiroshima University.
Paper: TUPS021
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS021
About: Received: 28 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
Plasma generation in capillary discharges simulated with COMSOL for charged particle acceleration
This study develops a gas-filled plasma-discharge capillary system for laser wakefield acceleration (LWFA). Using an external high-voltage source for pre-ionization enhances plasma formation, operational stability, and laser propagation over extended Rayleigh lengths, enabling high-energy electron beams. The uniform plasma environment improves beam charge, consistency, and energy spread, allowing efficient generation of 250 MeV very-high-energy electron (VHEE) pencil beams in a compact system. Designed at the upcoming I-LUCE facility in Catania, Italy, the setup supports VHEE and FLASH radiotherapy (FLASH-RT) research. COMSOL Multiphysics simulations of plasma density variations validate the model's accuracy and its potential for optimizing plasma-based LWFA systems.
Wafer-compatible photocathode plug design for high gradient RF photoinjector
Single crystal alkali antimonide photocathodes have been shown to produce brighter beams than their polycrystalline counterparts. These single crystal semiconductors require a lattice matched substrate to be grown, but current INFN plugs lack the capability for this growth. To relieve this issue, we modified the INFN plug to hold a disk 1cm in diameter. This allows for studies of a wide range of advanced photocathodes and geometries on arbitrary substrates in high gradient photoinjectors. We show the modified design, analysis of the local field at the cathode and cavity detuning, and demonstrate the principle with a 1cm Yttrium disk.
Revolution in generation of polarized electron beams: the world's first RF electron gun with GaAs photocathode
Polarized electron beams play critical role in fundamental physics research by providing additional observables and opening new channels of discoveries. T GaAs crystals illuminated by circular polarized IR lasers remain the best choice for generating polarized electrons. All current polarized sources are an electrostatic electron guns providing necessary extreme (XUV) vacuum conditions for survival of GaAs photo-emissivity. But they are limited in accelerating voltage and its gradient limiting both the quality and quantity of available beams. These are the reasons why accelerator community was and is attempting to extend this technology to the radio-frequency electron guns, which are capable of accelerating beams significantly higher accelerating gradients and total accelerating voltage. Unfortunately, all previous attempts of operating GaAs photocathodes in RF guns were unsuccessful. In this paper, we report on successful operation of GaAs photocathode in superconducting RF gun and describe all details of the gun, evolution of the GaAs quantum efficiency, and parameters generated electron beam.
TUPS026
Magnetic cycle optimisation in the CERN PS booster
1438
The PS Booster is the first synchrotron in the CERN proton accelerator complex, which delivers both high-brightness and high-intensity beams. Injection to the Booster is at a kinetic energy of 160 MeV, therefore space charge is a main limiting factors for beam quality. Maximising the longitudinal emittance and adding a second, and sometimes third, RF harmonic are measures to decrease the line density and so reduce the effect of space charge. Nonetheless, beam loss and transverse emittance growth are still unavoidable at low energy. Recent studies have been focused on the possibility of adapting the magnetic cycle to further reduce the impact of space charge. With a faster ramp, the time spent in a high space charge regime is reduced but the available RF voltage limits the bucket area. Alternatively, with a slower acceleration the RF bucket area and longitudinal emittance can be increased, which will reduce the magnitude of the space charge detuning, but more time will be spent at low energy. This contribution explores the effects of different magnetic cycles on the beam and the possibility of further optimising the booster acceleration.
Paper: TUPS026
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS026
About: Received: 19 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS027
RF power margin for operation with fixed-target in the CERN SPS
1442
The CERN Super Proton Synchrotron (SPS) Radio Frequency (RF) system was upgraded as part of the Large Hadron Collider Injector Upgrade (LIU) project, and now comprises six 200 MHz travelling wave structures, each fed by a separate RF power amplifier. While the upgrade was targeting the peak power for capture and acceleration of the beams for the High Luminosity LHC, it also brought an increase in the available average power for fixed-target beams. The additional power introduced margins which were first probed and exploited in 2024, when the SPS RF system had to be operated at majorly reduced power, during failures that blocked a single power amplifier or accelerating structure. Specific examples from the 2024 run are given, together with the mitigation measures. This contribution summarizes the efforts and results, highlighting in particular the improvements needed for the control of the RF voltage for easier switching to the degraded mode of operation and back, as well as the impact of the impedance of an undriven cavity.
Paper: TUPS027
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS027
About: Received: 27 May 2025 — Revised: 01 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS028
Achievement of LIU longitudinal parameters at the CERN SPS
1446
To prepare the Super Proton Synchrotron (SPS) as an injector for the High Luminosity Large Hadron Collider (HL-LHC), its Radiofrequency (RF) system was majorly upgraded. The 200 MHz travelling wave structures were rearranged, adding two solid-state power amplifiers and a new Low-Level RF (LLRF) system. The increase in RF power and reduction of the beam coupling impedance at the fundamental frequency were designed for capture and acceleration of four trains of 72 bunches spaced by 25 ns at an intensity of 2.3e11 protons per bunch with bunch lengths of 1.65 ns ±10% at SPS extraction. These beam parameters have first been demonstrated in 2024 after careful optimisation of all the main longitudinal settings: voltage program at fundamental and higher harmonics, interplay of one turn-delay feedback, feedforward and longitudinal damper, as well as controlled emittance blow-up. This contribution details the achieved beam parameters and the conditions that allowed them, along with the encountered limitations.
Paper: TUPS028
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS028
About: Received: 26 May 2025 — Revised: 01 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS029
Present status of RF system upgrade in the J-PARC MR
1450
J-PARC MR delivers 30 GeV proton beams to the neutrino facility and the hadron experimental facility, and an upgrade plan is underway to increase beam power by shortening the MR cycle time and increasing the number of particles per bunch. As a result, the beam power for neutrino experiments has achieved its original design value of 750 kW in 2023 and reached 800 kW in 2024. The target beam power of this upgrade plan is 1.3 MW for the Hyper-Kamiokande experiment.The current RF system consists of 9 fundamental cavities and 2 second harmonic cavities for a total of 11 RF systems, but it is necessary to add two more fundamental cavities to further shorten the MR cycle time. Preparations are underway to begin operation of the 10th RF system in 2025 and the 11th in 2027. In addition, as the number of particles increases, further beam loading compensation will be required, so we are also working on upgrading the RF source. We present the progress of the MR RF system upgrade.
Paper: TUPS029
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS029
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS030
Update of the tune ripple canceller system for slow extraction operation in the J-PARC MR
1454
In the slow extraction operation of the J-PARC Main Ring (MR), ensuring the uniformity of the extracted beam's time structure (“spill structure”) is crucial. One primary factor distorting the spill structure is the random fluctuation of the horizontal tune caused by current ripples in the main magnet power supplies. To address this issue, a system called the "tune ripple canceller" has been developed. This system calculates correction values for the horizontal betatron tune based on current ripples and controls the spill structure using fast-responding quadrupole magnets. In 2021, proof-of-principle beam experiments demonstrated its effectiveness in improving the spill structure. Subsequently, as part of the MR's power upgrade plan, the main magnet power supply system was upgraded by 2022. During this upgrade, the current measurement system was reconfigured, and the power spectrum of the current ripples was altered. As a result, it is now urgent to update the hardware and software of the tune ripple canceller system to align with these changes. This paper highlights updates, addresses challenges, and explores strategies to further enhance spill structure control in the MR.
Paper: TUPS030
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS030
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS031
Electrostatic deflector Nuclotron modernization for EDM experiment
1458
Considered the current Nuclotron structure for precision EDM-experiments as an independent synchrotron storage ring equipped with electrostatic deflectors. In this regard, the design must ensure the preservation and precise regulation of spin dynamics stability. Moreover, the initial purpose of the structure as a booster of polarized beams in the collider has been preserved.
Paper: TUPS031
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS031
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS032
Wien filter method for the "Quasi-frozen" spin lattice
1462
To study the electric dipole moment of light nuclei, it is necessary to maintain the direction of the spin along the particle's motion along the ring. The first obvious solution to this problem is to use elements with an electric field that rotates the spin in the direction opposite to the spin rotation in a magnetic field. The most successful solution in this case is the Wien filter, which ensures spin rotation while maintaining the co-direction of the spin and momentum. In this case, the ring structure consists of arcs with bending magnets and straight sections on which Wien filters with crossed electric and magnetic fields are installed. The paper considers various versions of a magneto-optical structure that implements the "Quasi-frozen" spin method for studying the electric dipole moment of deuterons and protons. This approach can be used in developing an upgraded Nuclotron structure.
Paper: TUPS032
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS032
About: Received: 25 Apr 2025 — Revised: 03 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS033
Quasi-frozen spin concept to search for the electric dipole moment of the proton and deuteron
1465
One of the possible proofs of CP violation beyond the Standard Model may be the discovery of permanent Electric Dipole Moments (EDM) of elementary particles. To search for the EDM of charged particles, the Frozen Spin (FS) concept was first proposed at BNL. The implementation of the latter involves the creation of a special storage ring in which the spin vector is preserved along the momentum and precesses due to the EDM only. In a magnetic storage ring initially not dedicated to measure the EDM, it is also possible to study the EDM by inserting electrostatic or E+B elements that compensate for the spin rotation in the bending magnets in a so-called Quasi-Frozen Spin (QFS) mode. Magneto-optical structures fulfilling the QFS condition can be used in application to study the proton and deuteron EDM and for axion search at the NICA accelerator complex. The main features of the implementation of the QFS concept are discussed, the method of measuring the EDM in the frequency domain, as well as the main spin dynamics properties of the lattice are covered.
Paper: TUPS033
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS033
About: Received: 07 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
TUPS035
TURBO – Enabling fast energy switching for hadron therapy with constant magnetic fields
1469
The energy layer switching time is a limiting factor for hadron therapy, precluding fast beam delivery and reducing treatment efficacy. For rapid energy switching the beam delivery system must be achromatic with zero dispersion over a large energy range. At the University of Melbourne, the TURBO project will utilise Fixed Field Accelerator techniques to demonstrate transport of a ±42% momentum spread beam around a 30° bend, with constant magnetic fields to eliminate the energy switching bottleneck. This will be demonstrated with an electrostatic Pelletron accelerator. A fast-switching energy degrader with thin diamond films has been designed to quickly change proton beam energies in the range 0.5-3.0MeV, covering the full clinical range when scaled up. A new design technique using nonlinear magnetic fields for energy-dependent focusing has been developed to minimise delivered beam variations. A novel method has been found to produce nonlinear permanent magnet arrays without custom magnets, enabling fast prototyping and reuse of magnets. With these innovations, the TURBO project will demonstrate rapid energy switching for hadron therapy to enable improvements in patient outcomes.
Paper: TUPS035
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS035
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS036
Design and EM simulations of 750 MHz IH-DTL tank for carbon ion in medical applications
1473
This paper presents the design of 750 MHz IH-DTL (Interdigital H-mode Drift Tube Linac) tank, specifically developed to be part of a carbon ion injector for medical treatment applications. These sections provide a highly efficient solution for ion acceleration in the 5 to 10 MeV per nucleon energy range, offering a high shunt impedance. The study includes simulations of electromagnetic fields using CST Software, and beam dynamics simulations through a KONUS-type configuration
Paper: TUPS036
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS036
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS037
Simulation of RF components for the ICONE pilot: RFQ, rebuncher, DTL cavities and amplifiers
1477
CEA is committed to delivering a study for a warm linac in the frame of the ICONE project. It aims at accelerating an 80-mA beam of protons up to 25 MeV, with a 6% duty cycle. The LINAC consists of: a proton source with low-energy beam transport line, an RFQ, a medium-energy beam transport line, and a warm DTL. All these components must be tuned at 352.2 MHz, to reach the required output energy. This document presents the RF studies made by CEA and INFN on the main RF components, including the RFQ, the rebunchers, IH- and Alvarez DTL cavities and the RF amplifiers.
Paper: TUPS037
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS037
About: Received: 20 May 2025 — Revised: 01 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS038
Low energy beam transport line design for the Sarajevo ion accelerator
1481
The University of Sarajevo Physics Department, in collaboration with CERN’s Accelerator Beam Physics group, proposes a compact linear accelerator design for applied physics research spanning from beam dynamics studies to material surface analysis. The Sarajevo Ion Accelerator (SARAI) consists of an electron cyclotron resonance ion source, a low energy beam transport line (LEBT) and a radiofrequency quadrupole (RFQ). The ion source can produce an array of ions extracted with 30 kV. This study presents an iterative parameter optimization method that suggests two LEBT optics: one for beam diagnostics and another for compact beam matching to the RFQ acceptance. The RFQ discussed here is a 750 MHz, 2.5 MeV/u RFQ, used for medical applications. SARAI RFQ aims at 0.5 - 2 MeV/u. A novel RFQ technology allows a significant reduction in footprint. This paper further discusses plans for source commissioning and potential research applications.
Paper: TUPS038
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS038
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS039
Current status of beam commissioning at the Frankfurt Neutron Source
1485
The Frankfurt Neutron Source FRANZ will be a compact accelerator driven neutron source utilizing the 7Li(p,n)7Be reaction with a 2 MeV proton beam. The 700 keV RFQ has been sucessfully commissioned with a 10 mA proton beam. Conditioning of the subsequent IH-type cavity has been performed up to 10 kW. We also report on RFQ emittance measurements performed with a slit grid emittance device. In addition, a fast faraday cup (FFC) was used for bunch shape measurements behind the RFQ.
Paper: TUPS039
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS039
About: Received: 26 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS040
Current status of the MYRRHA project at IAP Frankfurt
1489
As part of the MYRRHA project, which is being implemented in Mol, Belgium, two of the planned 17 normal-conducting CH cavities have been built and tested at several kilowatts of RF power. Since the cooling concept for the stems was revised after their construction, concerns arose that the two existing cavities might have suffered a degradation in performance during high-power testing due to the outdated cooling system. Consequently, it was decided to subject cavity CH02 to renewed LLRF measurements at IAP Frankfurt to ensure that its performance has not deteriorated. The cavity is then scheduled for high-power testing at the newly established high-power station at IAP. This will not only serve to commission the test stand but also recondition the cavity This paper summarizes the recent LLRF measurements performed on CH02 and reports on the current status of preparations for the upcoming conditioning.
Paper: TUPS040
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS040
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS041
PEEK-Polymer as a vacuum-window in high power rf-couplers
1492
PEEK is an advanced polymer known for its exceptional mechanical strength, thermal stability, and radiation resistance, making it a promising candidate for applications in extreme environments. This study explores the viability of PEEK as a vacuum window material in high-power radio frequency (RF) couplers. Traditionally, materials such as ceramics are employed for this purpose; however, they are costly to manufacture and impose limitations during the design process. PEEK offers additional advantages, including the possibility of additive manufacturing, which enables the integration of cooling channels for efficient thermal management. The research evaluates PEEK's electrical, thermal, and mechanical properties under conditions typical of high-power RF couplers, such as vacuum stability, RF-induced heating, and electromagnetic transparency. At the Institute for Applied Physics (IAP), PEEK is tested as a vacuum window material in high-power experiments up to 35 kW. Following these tests, the material is analyzed to assess its performance and suitability for RF applications.
Paper: TUPS041
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS041
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
Progress in Linac Beam Commissioning for High-Intensity Operations for J-PARC Power Upgrades
The Japan Proton Accelerator Research Complex (J-PARC) has achieved stable 1 MW operation test on its neutron target and is advancing toward higher power levels of 1.5 MW to support high-power MR operations and a second target station. This progression presents challenges, including increased intra-beam stripping (IBSt) of H⁻ ions, chop leakage from higher beam currents and emittance, low-energy beam loss due to halo formation, frontend fluctuations affecting beam transmission, and RF phase and amplitude fluctuations. To address these issues, a redesigned lattice mitigates IBSt, a new MEBT1 improves chopping and collimation, and machine learning-based compensation schemes manage frontend and RF fluctuations. Additionally, longitudinal and transverse matching schemes enhance beam quality, validated through benchmarked longitudinal measurements. Results from studies at 50 mA and 60 mA beam currents demonstrate significant progress in overcoming these challenges.
Development of normal conducting heavy ion linac in China
Research on heavy ion linac was began more than ten years ago initially to improve the HIRFL operation at IMP. In China, the first continuous wave (CW) heavy ion linac, SSC Linac, working at 53.667 MHz was designed and constructed as the SSC injector. The ion particles can be accelerated to 1.48 MeV/u with the designed A/q≤5.17. At present stage, this CW linac has been put into operation and the Uranium has been accelerated to 1.48 MeV/u successfully in the end of 2023. To meet the rising requirements of the applications, a compact 162.5 MHz heavy ion linac operating in pulse mode was developed with A/q≤3. The “KONUS” beam dynamics was adopted in the IH-DTL design and the heavy ions can be accelerated to 4 MeV/u in 9m length. The 108.48 MHz SESRI linac was another pulse machine which was built at Harbin. Both of the heavy ions and proton beam can be accelerated by this linac to 2 MeV/u and 5.6 MeV, respectively. In this paper, the status of these three heavy ion linacs and their beam commissioning results were presented.
TUPS045
A standalone radio frequency quadrupole accelerator for swift heavy ions
1495
The radio frequency quadrupole (RFQ) is known for bunching, focusing and acceleration of ion beam and more importantly, it does not require transverse focusing element like quadrupole magnets between accelerating cells compared to drift tube linacs. By pushing the limits of handling surface electric field between RFQ vanes, it is possible to make a standalone 352 MHz RFQ reaching 1.8 MeV/u energy gain for swift heavy ions upto mass to charge ratio (A/q) ≤ 4. Special RFQ vane material of cryo Cu* is considered by which surface electric fields can be pushed around 50 MV/m** and the whole RFQ is designed within a length of 5m which is substantially less than any RFQ + DTL combination of equivalent energy gain accelerator for heavy ions. Such systems are highly promising for compact medical LINACS and as well as standalone facilities for nuclear physics experiments. The adiabatic bunching and focusing inherently stabilize the beam dynamics at proper RFQ power and cavity tuning. We present the beam optics design using PARMTEQ code and RFQ cavity design along with thermal analysis using CST MWS. The error analysis is provided to support the design in terms of practical feasibility.
Paper: TUPS045
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS045
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 06 Jun 2025
TUPS046
Study on the time changes of the proton beam passing current from the ion source to the RFQ at J-PARC LINAC
1498
Currently, in the J-PARC linac, beam commissioning between the ion source and RFQ mainly involves adjusting the extraction voltage of the ion source and the two solenoid magnets in the Low Energy Beam Transport line (LEBT) installed between the ion source and the RFQ. These parameters are determined to maximize the measured beam current at the current monitor (SCT) downstream of the RFQ. Previously, the SCT used as a reference had measured the beam current by cutting out a part of the macro bunch. However, to further improve the beam quality, we adjusted LEBT parameters using the newly measured method, which is an integrated whole macro bunch signal. The optimum value obtained by the new method differed from the previous. Therefore, to investigate the cause, we saved all the beam current waveforms of the SCT for reference and compared the ion sources and LEBT parameters of each. As a result, the current of the beam that passed through the RFQ changed over time within the macro bunch for certain ion source and LEBT parameter settings. In this presentation, we will introduce the above study results and discuss the cause of the temporal changes in beam current.
Paper: TUPS046
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS046
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS047
Assembly and testing of a QWR for the new ISIS MEBT
1501
The quarter wave resonator (QWR, a.k.a. λ/4 resonator) for the new ISIS MEBT is a bunching cavity that longitudinally compresses the H- beam into smaller bunches. It has two gaps with a distance of βλ/2 between mid-gaps, and works in π mode at the resonant frequency of 202.5 MHz, with a phase angle of -90 degrees, and a maximum voltage per gap (E0L) of 55 kV. The detailed RF and thermal design was developed, followed by the manufacturing of a prototype, all being presented elsewhere. Several mechanical issues were noticed with the RF finger strips and tuners during the assembly of the prototype cavity. The manual tuner (to account for the manufacturing tolerances and the vacuum load) was machined to the final dimension to achieve the desired resonant frequency, according to the Vector Network Analyser (VNA) measurements. The measured quality factor was found to be much lower than expected, which required a redesign of some of the RF seals. The cavity was powered and conditioned in a relatively short time up to a nominal power, but severe multipacting was observed, initially only at low power, but later also at medium power levels, which required a creative approach to be fixed without a major cavity redesign.
Paper: TUPS047
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS047
About: Received: 03 Apr 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPS048
Comprehensive studies of linear accelerators for muons in the medium velocity range
1505
The muon linac has been developed at J-PARC to accelerate muons from thermal energy (25 meV) to 212 MeV using electrostatic extraction and four different types of radio-frequency cavities: RFQ, IH-DTL, DAW-CCL, and disk-loaded structures. Although some of the technologies employed were relatively novel, most proof-of-principle demonstrations have been successfully completed through prototype testing and actual production. Based on these experiences, it has become possible to propose a shorter or more efficient schematic design derived from the current design. In this poster, the new schematic design will be presented.
Paper: TUPS048
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS048
About: Received: 26 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPS049
Low-power test of bridge coupler in disk-and-washer structure for muon acceleration
1509
A muon linear accelerator is under development at J-PARC for precise measurement of the muon anomalous magnetic moment (g-2) and electric dipole moment (EDM). A disk-and-washer (DAW) structure is employed to accelerate muons from 30% of the speed of light (kinetic energy = 4 MeV) to 70% (40 MeV) at 1296 MHz. The muon DAW consists of tanks accelerating the muons and bridge couplers that couple the tanks and focus the beam using an internal quadrupole doublet. A bridge-coupler prototype is currently being fabricated and will be tested. This paper presents the design and performance evaluation of the bridge coupler prototype.
Paper: TUPS049
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS049
About: Received: 07 Apr 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
TUPS050
Mechanical design of a spin rotator for the ISIS Super MuSR beamline
1513
The Super MuSR spin rotators (SR) are electromagnetic devices with a horizontal dipolar magnetic field to rotate the muon spin by 34o and a perpendicular electric field that operates at +/-192 kV. The electromagnetic design was already presented elsewhere. The mechanical design is now complete, and the manufacturing of components has started, both of which are discussed here. The stainless steel vessel is 598 mm in diameter, 1.8 m long and has several ports along it. Most notably the large feedthrough port with a 15 mm inner radius to reduce the electrical fields. Mirror polished electrodes are mounted on ceramic insulators, optimised to shield the triple points from the high electric fields. The insulator mechanical design, manufacture & testing will also be discussed here. A high voltage test rig has been developed in parallel to test critical aspects such as the high voltage feedthrough, insulator design, vessel manufacture and surface finish requirements, before testing and assembling the main vessel. The magnet yoke is H-shaped with traditional racetrack coils. It was designed to be assembled around the around the vacuum vessel with kinematic feet for adjustment and alignment.
Paper: TUPS050
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS050
About: Received: 06 May 2025 — Revised: 01 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 06 Jun 2025
TUPS051
Avoiding overcooled ion beams by exciting energy spread through electron cooling
1517
Ion accelerators use electron cooling to improve luminosity and beam lifetime. However, extremely low momentum spread in a cold beam weakens Landau damping, enabling the development of instabilities and potentially decreasing lifetime. To combat this, the NICA Booster electron cooling system allows to generate electron beams with oscillating energy to increase the momentum spread in ion beams. Here we describe the implementation of the energy oscillation technique and provide numerical calculations predicting the achievable momentum spread.
Paper: TUPS051
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS051
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS052
Development of FFA at Center for Accelerator and Beam Applied Science of Kyushu University
1520
Center for Accelerator and Beam Applied Science of Kyushu University has been established to promote activities in various fields such as, medical, educational and engineering fields at Kyushu University. An accelerator facility, consist of a 10 MeV proton cyclotron, 8 MeV tandem accelerator and of 150 MeV FFA, has been constructed in the center. In this paper, status of the hardware developments and results of the beam commissioning of the FFA in Kyushu University is described.
Paper: TUPS052
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS052
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS054
Optimization of a multichannel solid state plasma for laser wakefield acceleration with realistic laser parameters using a Bayesian algorithm
1523
Nanostructures based on carbon nanotube arrays are emerging as promising media for achieving ultra-high acceleration gradients in laser wakefield acceleration (LWFA). In this study, we design and optimize plasmas with hexagonal lattice structures, where the lattice parameters directly define the nanostructure's properties. Using WarpX, a state-of-the-art particle-in-cell (PIC) simulation framework, we conduct fully three-dimensional simulations to model the interaction between these advanced plasmas and laser pulses. To refine the lattice parameters, we apply Bayesian optimization through the Python library BoTorch, identifying optimal configurations for generating effective wakefields. These results are intended to guide preliminary simulations for future experiments at leading laser facilities, such as ELI and VEGA3, advancing the exploration of LWFA with nanostructured plasmas.
Paper: TUPS054
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS054
About: Received: 16 May 2025 — Revised: 31 May 2025 — Accepted: 02 Jun 2025 — Issue date: 06 Jun 2025
TUPS055
Simulations study of transverse wakefields in a dielectric wakefield acceleration scheme
1527
Novel acceleration schemes aim to address the need for higher acceleration gradients which enable to minimise the size and costs of particle accelerators. One of these novel accelerator schemes is the dielectric wakefield acceleration (DWA), where an electron bunch is accelerated by the longitudinal wakefields generated within a dielectric lined waveguide by a leading drive bunch with higher charge. The advantages of this novel acceleration method include high accelerating field strength, the simplicity of its structure and the stability of the wakefield generated which is synchronous with the electron bunch. However, the drive bunch propagation length, and hence the achievable energy gain, is limited by the effect of the transverse wakefields. These fields deflect the bunch towards the dielectric, leading to charge losses, a phenomenon commonly referred to as beam break-up (BBU) instability. This study uses simulations to investigate the transverse wakefields and their impact on the beam dynamics in a DWA scheme with drive and witness (main) bunches. The findings will be further explored experimentally at the CLARA facility in Daresbury Laboratory.
Paper: TUPS055
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS055
About: Received: 23 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS056
First beam through the superconducting linac of European Spallation Source
1531
The European Spallation Source (ESS), currently under construction in Lund, Sweden, is designed to be the brightest neutron source in the world. It will be driven by a superconducting proton linac with a design beam power of 5 MW and energy of 2 GeV. The construction and installation of the linac are completed for the initial user operation envisaged in 2026 with capability of 2 MW beam power and 800 MeV energy. Beam commissioning of the full linac up to the dump in the line of eyesight is planned in early 2025. At this stage, the main focus will be on establishing optimal transport of 800 MeV beam as well as validating the critical components such as the RF system, diagnostics devices and machine protection systems. This contribution presents the highlights from this commissioning phase that will send the beam through the superconducting linac of ESS for the first time.
Paper: TUPS056
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS056
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Key issues in the high intensity beam commissioning for the CSNS RCS
TUPS059
Novel deuteron accelerator for nuclear waste transmutation
1535
Accelerator-driven systems (ADSs) can accelerate high intensity ions to generate high flux of neutrons to transmute the long-lived species in used nuclear fuel (UNF) from nuclear reactors. A typical specification would be for a 1-2 GeV proton beam, comprising multi-MW-level power load on a spallation target. An alternative approach could be to produce the neutrons via breakup of 40-MeV deuterons on a low-Z target. For this purpose, an innovative 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. It is estimated that 5-10 smaller ADS dCARA-based modules could provide the same level of transmutation as one 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: TUPS059
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS059
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPS060
Electron cyclotron resonance accelerator for industrial radiation processing
1538
Industrial radiation processing is used on a wide variety of products, including medical devices for eradication of pathogens, food for preservation and safety, and plastics for material property modification. But millions of curies of Co-60 that are still used in some industrial sterilization facilities can pose a significant security risk in an act of radiological terrorism. Lower-cost electron beam systems with high beam-power efficiency and high reliability are needed to replace Co-60 based sterilization systems. A novel accelerator under development, electron Cyclotron Resonance Accelerator (eCRA) is described here. It is highly compact and efficient to produce high power electron beams and x-ray beams. The several attractive features of 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. Details of design and predicted performance will be described.
Paper: TUPS060
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS060
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS062
Assembly of the IFMIF SRF Linac cryomodule
1541
Complementing its contributions to the JT-60SA and ITER fusion reactors, Fusion for Energy contributes to the R&D for material characterization facilities. Under the Broader Approach agreement, Europe and Japan are developing the Linear IFMIF Prototype Accelerator (LIPAc) in Japan, a deuteron accelerator demonstrator producing neutrons by nuclear stripping reactions on a liquid lithium target, part of the International Fusion Materials Irradiation Facility (IFMIF) project. In 2024, LIPAC prepared for the installation of the SRF cryomodule, concluding its construction. As first prototype, the cryomodule assembly faced challenges at various stages. Started in March 2019, the assembly was paused during its cleanroom phase due to quality issues with the superconducting solenoids, resuming in Aug. 2022. Further issues delayed the completion of the cleanroom activities until Sept. 2024. In 2024, the cryomodule assembly progressed at a good rate. The clean room worked concluded in Sept. and by late 2024 the cold mass was ready for insertion into the vacuum vessel, with transfer to the vault planned for early 2025. In this paper, we will outline the critical steps of this assembly process.
Paper: TUPS062
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS062
About: Received: 29 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPS063
NLCTA and the X-band Test Area at SLAC
1545
The Next Linear Collider Test Accelerator (NLCTA) facility at SLAC National Accelerator Laboratory provides unique capabilities for conducting accelerator research and testing technology with accelerator applications, as well as beam time for experiments using the X-band Test Accelerator (XTA). Test areas in the facility support high power RF testing over a range of frequencies and operating temperatures, allowing for a broad range of ongoing research programs. Experiments include irradiation studies, high gradient accelerator testing, superconducting materials testing, detector testing, prototype development for medical applications like proton therapy for cancer treatment, and electron beam diagnostics using THz streaking. This variety in research topics takes advantage of the NLCTA's flexible infrastructure and wide range of in-house expertise. Facility capabilities and highlights from the active experimental program are presented here.
Paper: TUPS063
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS063
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Experimental demonstration of terahertz transport using overmoded iris-line waveguide
The need for THz pulses with 100 µJs of pulse energies at a 100 kHz (or higher) repetition rate that are well synchronized with X-ray free electron laser (XFEL) pulses is paramount to studying novel ultrafast phenomena. Efficient THz generation (3 – 20 THz), coupling, and transport over long distances has posed several challenge. In particular, THz wavelengths makes it impractical to rely on metal waveguide for long distance transport, while free space propagation is prone to strong diffraction. In addition, water absorption causes significant attenuation to THz propagation. We present a tabletop experiment to demonstrate efficient transportation of THz radiation at 3.25 THz using metallic irises. This experiment demonstrates efficient transport of THz radiation over 20 meter distances which notable behavior of slower attenuation compared to free space propagation.
Generation of THz coherent undulator radiation by velocity bunching of electron beam
We experimentally study the generation of THz coherent undulator radiation by electron beam at NTHZ facility which is located in USTC. Velocity bunching scheme in a travelling-wave accelerating structure is employed to produce the short electron bunch. An undulator which has 20 periods with a period length of 5.8cm and a maximum undulator parameter of 3.95 has been developed to produce intense coherent THz radiation.
TUPS067
Development and operational performance of multi-alkali antimonide photocathodes
1549
Multi-alkali antimonide photocathodes, particularly potassium–cesium-antimonide, have gained prominence as photoemissive materials for electron sources in high-repetition-rate FEL applications due to their properties, such as low thermal emittance and high sensitivity in the green wavelength. To explore the potential of these materials in high-gradient RF guns, a collaborative effort was undertaken between DESY PITZ and INFN-LASA to develop and study multi-alkali photocathode materials. A batch of three KCsSb photocathodes and one NaKSb(Cs) photocathode was grown on molybdenum substrates using a sequential deposition method in the new preparation system at INFN LASA. These cathodes were successfully transferred and tested in the high-gradient RF gun at PITZ. Following the tests, a post-operational optical study was conducted on all the cathodes. Based on these findings, efforts are underway to optimize the fabrication recipes for KCsSb and NaKSb(Cs) photocathodes to achieve lower field emission and longer lifetimes. This contribution summarizes the experimental results of the production, operational performance, and post-usage analysis of the current batch of cathodes.
Paper: TUPS067
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS067
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS071
Theoretical models for CsTe thin film semiconductor photocathodes at high electromagnetic fields
1553
Understanding performance and limitation of CsTe photocathodes under high field gradients in a radio-frequency gun requires adequate theoretical models for material properties, photoemission and surface morphology. We are developing a suite of models based on Density Functional Theory (DFT), moment and Monte-Carlo (MC) photoemission models, and meso-scale material surface model informed by DFT and Molecular Dynamic (MD) simulations. Our DFT calculations provide detailed structural, elastic, electronic, optical, and transport properties of CsTe for photoemission applications. Temperature, density of states, and thin film optical effects have recently been incorporated in a moment-based photoemission model, while the high field effects for electron transport and emission are being modeled in the MC model. Our meso-scale surface model addresses surface morphology under high field stress and surface heating. Machine-learning technique has also been used to enhance the DFT and MD calculations for CsTe. This poster will present an overview of these theoretical models and their results with applications to the LANL CARIE project and other relevant experiments.
Paper: TUPS071
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS071
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Advanced growth and characterization of alkali antimonide photocathodes for bright beam applications
The properties of the photoemitting electron sources are the determining factors contributing to the performance of the most advanced electron accelerator applications such as particle colliders, X-ray free electron lasers, ultra-fast electron diffraction and microscopy experiments. Therefore, low mean transverse energy (MTE), high quantum efficiency (QE) along with long operational lifetime and robustness under high electric fields and laser fluences must be demonstrated by the photocathode for these bright beam applications. Recent investigations have revealed that the epitaxial growth of single-crystal cesium antimonides can be achieved by photocathode growth on lattice-matched substrates. In this paper, the experimental setup for highly promising alkali antimonide photocathode growth by molecular beam epitaxy on lattice-matched substrates and in-situ characterization with reflection high-energy electron diffraction (RHEED) has been presented. To adapt the L-band RF gun of Argonne Cathode Test-stand (ACT) for extensive testing of alkali antimonides in real accelerator conditions, compatible cathode plug design, and smooth transportation process have been developed and described.
Preliminary test of the MeV ultrafast electron diffraction instrument at e-labs
The injector test facility for PAL-XFEL project has been evolved into R&D facility named e-labs, where a preliminary test of MeV ultrafast electron diffraction (UED) was carried out. MeV-UED provides similar scientific opportunities as femtosecond time-resolved XRD experiments at XFEL facilities, and would be a useful tool to overcome a limited beam time problem of XFEL. MeV-UED is a pump-probe experiments required high stability to see a small difference in femtosecond time scale. In e-labs, experimental tests for routine operation and improving S/N ration has been studied
TUPS074
Packaged photocathodes for X-ray free electron lasers
1557
Alkali photocathodes are vital for generating high-performance electron beams in accelerator technologies, but their production remains challenging. Current in-house fabrication methods are complex, costly, and unreliable, limiting the potential of these materials for bright electron sources. Our innovative approach seeks to commodify photocathodes, offering a ready-to-use product for accelerator facilities and scientific institutions. We use a proprietary sputtering process with in-house-manufactured bulk targets, ensuring consistent quality and streamlined production. Unlike traditional vacuum suitcases, which are heavy and require active power, our photocathodes are stored in portable, palm-sized vacuum canisters that maintain vacuum without power. This design preserves their integrity during transport and handling, addressing their extreme sensitivity to air and moisture, which demands ultra-high vacuum protection. By delivering pre-fabricated, protected photocathodes, we eliminate the need for facilities to invest in specialized equipment, enabling broader adoption and reducing downtime. Our work paves the way for accessible, affordable, and readily available photocathodes.
Paper: TUPS074
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS074
About: Received: 31 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Laser-based cleaning of phocoathode at SXFEL
The Shanghai soft X-ray Free-Electron Laser user facility has open to users since 2023. The electron beam is generated by Cu photocathode, integrated in an S-band electron gun. As the photocathode quantum efficiency drops to less than 10<sup>-5</sup>, photocathode cleaning technology based on drive laser is used to improve the performance of the photocathode.
Recent advances in superconducting undulators at the Advanced Photon Source
The Advanced Photon Source (APS) continues developing novel SCUs, several of which have operated for a decade, delivering high-brightness, hard X-ray beams for scientific research. As part of the APS Upgrade, eight new NbTi SCUs were planned. While cryogenic and support systems were in place, challenges in scaling magnet lengths and reducing periods led to magnet failures and fabrication delays. The APS SCU team launched an R&D program to refine designs and materials, with two SCUs expected to be installed by late 2025 and six more to follow. Before the APS Upgrade, a novel Nb₃Sn SCU deployed and operated successfully for three months, validating its predicted performance. Building on this, the APS SCU team is developing a 14 mm period Nb₃Sn SCU with cryogen-free, conduction-cooled magnets and a thin-wall vacuum chamber, enhancing the field and simplifying cryogenics. Looking further ahead, the team is exploring implementation of high temperature superconductors for lower period undulators (~10 mm) to achieve unprecedented field strengths. This presentation will provide an overview of the APS SCU program, the challenges addressed, and ongoing efforts to advance SCU technology.
Force-neutral adjustable phase undulator array for compact FELs and multiline FEL facilities
The Force-Neutral Adjustable Phase Undulator (FNAPU) is set to revolutionize future free-electron laser (FEL) undulator designs. This innovative technology is gaining rapid traction as its compact and lightweight design offers a cost-effective solution for X-ray production. The FNAPU can be efficiently scaled to lengths of 5 meters and beyond and meet the requirements for light production with specific polarizations. Their multiplexing capability is especially beneficial for covering a wide photon energy range and enabling multiple X-ray beams, making them ideal for diverse scientific and industrial applications such as FELs for extreme ultraviolet (EUV) lithography in semiconductor fabrication and X-ray FELs that require small-period undulators.
Status of the 1st Article NbTi SCU for the Advanced Photon Source Upgrade
The 1st article NbTi SCU consists of two 1.5 m-long superconducting undulators (SCU) installed in a single cryostat that will occupy an entire straight section in the upgraded storage ring at the Advanced Photon Source. Installation is planned during the winter shutdown of 2025/2026. The initial design of the magnets proved to be difficult to successfully implement and a new design was pursued to resolve the issues that were identified. Manufacturing of the updated magnet design is scheduled to be completed in early 2025 after which the magnets will be tested in a vertical bath cryostat followed by installation into the production cryostat. A description of the magnet design modifications along with test results from the bath cryostat will be provided.
TUPS089
Helical undulators assembled from magnetized ring sectors
1559
Undulators assembled from quasi-helices consisting of readily available magnetized ring rare-earth sectors are proposed. "Radially" magnetized sectors create a stronger field on the axis than longitudinally magnetized ones. The field value weakly depends on the number of sectors per undulator period. An experimentally studied prototype Halbach-type helical undulator of "radially" and longitudinally magnetized quasi-helices consisting of ring NdFeB sectors with a period of 2 cm and a comparatively large inner diameter of 8 mm provides a field of about 0.6 T on the axis. By reducing the inner diameter to 5 mm, it is possible to obtain a field twice as large. When assembling such an undulator, it is convenient, while maintaining the positions of all ring sectors, to use a division of the undulator not into quasi-helices, but into cylindrical sectors shifted along the axis and rotated relative to each other. Permanent undulators from ring sectors can provide a higher velocity of transverse electron oscillations than planar ones, and therefore seem promising for increasing the efficiency of FELs in various frequency ranges.
Paper: TUPS089
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS089
About: Received: 14 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS092
Wakefield studies of the taper section of the elliptical in-vacuum undulator - IVUE32
1562
The elliptical in-vacuum undulator (IVU) IVUE32 is being developed at Helmholtz-Zentrum Berlin (HZB). The APPLE-II design allows for not only gap changes but also longitudinal shift movements, putting additional design challenges on the tapers at the entrance and exit of the undulator. The chosen design philosophy separates the gap and shift movement compensation into two assemblies respectively. This approach allows for a solid foil taper as gap movement compensation, which is proven in previously commissioned planar IVUs e.g. CPMU17 at HZB. The shift movement compensation, which requires a slit foil, can be kept parallel. The proximity of this complex structure to the electron beam makes the device susceptible to wakefield effects which can influence beam stability. Investigating and understanding these effects is vital for accelerator operation. The taper design will be presented alongside wakefield simulations and model measurements.
Paper: TUPS092
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS092
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS093
Permanent hybrid helical micro-undulators for FELs and inverse FELs
1566
High-field micro-undulators are one of the key elements in most compact Terahertz and X-ray FEL projects. In our works, helical undulators of several helices, each made of a single piece of rare-earth magnet, are proposed for this purpose. We demonstrated previously the possibility of high-precision manufacturing helices with centimeter periods using the Wire Electric Discharge Machining. In this paper, we will discuss an experimental prototype micro-undulator of two oppositely longitudinally magnetized NdFeB helices with a period of 6 mm and an inner hole diameter of 1 mm, creating a transverse field close to 1 T. The magnitude of the field and/or the inner diameter of the helices can be significantly increased by using hybrid systems with two longitudinally pre-magnetized rare-earth and two pre-unmagnetized steel helices. We are currently developing methods for manufacturing, assembling and measuring the parameters of such systems with periods of 6 and 3 mm and a field of 1 T and will demonstrate the corresponding results in the presentation.
Paper: TUPS093
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS093
About: Received: 14 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS094
Diagnosing an In-Vacuum Undulator in the ALS storage ring
1569
The Advanced Light Source (ALS) has an in-vacuum undulator named “LEDA”. It was installed in 2019 and provides high-brightness, high-energy photons for the ALS macromolecular crystallography beamline, Gemini. The undulator is a hybrid design with a minimum gap of 4.3 mm, a magnetic period of 15 mm, and a photon energy range of 5–19 keV. When the device was commissioned in the ALS storage ring, it had a negligible impact on ring operations. Recently, there has been a measured degradation in storage ring performance correlated with the Leda gap. Prior to conducting an invasive magnetic measurement, we performed a suite of beam-based measurements to characterize Leda. Herein, we detail these measurements and share them with the accelerator community, who may find them useful when encountering similar challenges.
Paper: TUPS094
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS094
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Force-neutral adjustable phase undulators
Variable gap undulators require large and complex motion systems to operate, making their tunability to generate specific radiation wavelengths cumbersome, limited, and slow. RadiaBeam Technologies is engaging in a project to advance undulator manufacturing by utilizing force-neutral adjustable phase undulator (FNAPU) technology developed by Argonne National Laboratory (ANL). This innovative approach allows high precision undulators to be more compact, cost-effective to fabricate and assemble, and safe and user friendly in alignment, manipulation and operation. The innovation of FNAPU technology is based on the inclusion of a secondary array of permanent magnets, arranged to compensate the internal forces brought on by the main undulator array. The flexibility and compact design of FNAPUs allows for exotic applications (X-undulators) and multiple FNAPUs can be packed together to form an undulator matrix, covering extensive X-ray energy ranges and a broad range of applications, relevant to the needs of XFEL and SR communities, and beyond.
Extreme radiation from electron beams in ion channels and undulators
We compare radiation from relativistic electrons (γ≫1) in magnetic undulators and ion channel betatron oscillations, addressing limitations in conventional theories for high undulator parameter (K) and K/γ regimes. Differences in magnetostatic and electrostatic oscillations lead to inaccurate trajectory and radiation descriptions. By reformulating key parameters, we enable comparisons of equivalent oscillation conditions and analyze distinct spectral features via numerical simulations. A novel transverse orbit precession effect in ion channels, significant for particles with initial angular momentum, is identified and shown to impact radiation divergence and beam emittance. Theoretical predictions are validated through simulations, providing insights for experimental applications.
Progress on infrared/terahertz free-electron laser and ultrafast laser facility at Chiang Mai University
An accelerator-based mid-infrared (MIR) and terahertz (THz) free-electron laser (FEL) light source has been developed at Chiang Mai University, Thailand, along with experimental stations for high-field irradiation, spectroscopy, and ultrafast interaction studies. The 25-MeV linear accelerator system, serving as the electron beam injector, has been extended to support two newly developed MIR/THz FEL beamlines. Engineering and construction of the magnetic bunch compressors and FEL components were based by physics design and essential beam dynamic simulations. Currently, the commissioning of the accelerator system and its beamlines is underway. Integrated with femtosecond Ti-sapphire laser technology, the facility aims to be a user-accessible ultrafast IR/THz laser facility in Thailand. Offering cutting-edge tools for spectroscopy, imaging, and irradiation, it supports advanced research in material science, biotechnology, and medicine while serving as a training center for accelerator and ultrafast laser technologies. This unique facility will become a regional pioneer in the future.
Status report on modification of a 5 MeV electron photo-gun for generating vortex electrons at JINR
At the Joint Institute for Nuclear Research (JINR), we use an RF photo-gun generating electrons via UV laser-driver and accelerating them up to 5 MeV to make a source of the so-called vortex electrons with a quantized orbital angular momentum projection onto the propagation axis. Such electron beams with a low current have previously been obtained only at electron microscopes with the highest kinetic energy of 300 keV. If successful, this gun would be the first such source in the MeV energy range in the world that could further be used, for instance, as a source for the 200-MeV electron linac at JINR. We discuss the needed steps to achieve this goal and report on the results already obtained. In particular, we have modified the laser driver and obtained twisted light beams in the deep ultraviolet wavelength range with different values of the topological charge. The vorticity of the photons is expected to be transferred to electrons via photoemission. We also discuss alternative schemes with a magnetized cathode, usually employed for angular-momentum dominated beams which are classical counterparts of the vortex particles.
Design guidelines and longitudinal dynamics for plasma-based, extreme compression
High-brightness, ultra-high peak current electron beams are of significant interest to applications including high-energy colliders, strong field quantum electrodynamics, and laboratory astrophysics. Despite such interest, compressing tightly-focused electron beams to attosecond pulse durations and mega-amp peak currents while preserving beam quality remains a challenge. In this work, we examine the feasibility and challenges involved in generating such extreme beams using plasma-based compression. Using simulations, we demonstrate that the large electric field gradients in plasma wakefields enable orders of magnitude higher compression than conventional radiofrequency compressors. Scalings of various beam properties with respect to accelerator and plasma parameters are explored with limitations on achievable final beam brightness evaluated. Optimal beam and plasma conditions are investigated for different applications, with the goal of experimentally demonstrating this technique at the FACET-II facility at SLAC National Accelerator Laboratory. Insights gained from this study will help design the next-generation of high-brightness beams for new frontiers in scientific research.
RF heating and dark current at cryogenic temperature
Stable peak surface electric fields in excess of 200 MV/m are achievable at cryogenic temperatures in test cavities due to emprical reductions in RF breakdown rates. In order to fully capitalize on these effects, the complex physics at RF cavity interfaces in extreme conditions must be further understood from a basic physics perspective. Even before the onset of RF breakdown several precursor phenomena such as electron emission and RF pulse heating become relevant. To this end we present models for temperature dependent dark current and RF pulse heating focusing on temperatures between 40 and 80 K at peak fields between 100 and 200 MV/m. The models are semi-empirical and where relevant reference will be made to data collected at the CrYogenic Brightness Optimized Radio frequency Gun (CYBORG) at UCLA.
High efficiency muonium beam source
A highly efficient muonium source will enable fundamental muon and precision measurements, including sensitive symmetry-violation searches. There are no U.S. muonium sources, nor available muon beams. Muonium sources internationally are significantly oversubscribed. The intense 800 MeV PIP-II linac under construction at Fermilab is capable of providing world-class muon and muonium beams with unparalleled intensity to drive the next generation of precision muon-physics experiments at the intensity frontier. Timing is critical to initiate the prerequisite R&D necessary to prepare for the PIP-II era. This paper describes a muonium beam for experiments such as measurement of antilepton gravity and improved searches for muonium–antimuonium mixing. The low-energy µ+ and µ─ beams can also support muon spin-rotation applications to material science including critical surface studies of quantum computing devices, precision muon experiments, muon-cooling studies for a future muon collider, muon-catalyzed-fusion R&D, and unique studies of semiconductor device physics.
Standing wave dielectric disk accelerating structure design and high power test results
A Dielectric Disk Accelerator (DDA) is a metallic accelerating structure loaded with dielectric disks to increase coupling between cells and group velocity, while still maintaining a high shunt impedance. This is crucial for achieving high efficiency, high gradient acceleration in the short pulse acceleration regime. Recent research of these structures has produced traveling wave structures that are powered by very short (~9 ns), very high power (400 MW) RF pulses using two beam acceleration at the Argonne Wakefield Accelerator. In testing, these structures have withstood more than 320 MW of power and produced accelerating gradients of over 100 MV/m. A new standing wave DDA structure was fabricated and high power tested on the Nextef2 test stand at KEK. This experiment tested how the structure behaves on a more conventional, klystron power source. Simulation results of this structure show that at 50 MW of input power, the DDA produces a 457 MV/m gradient. It also has a large shunt impedance of 160 MΩm with an r/Q of 21.6 kΩm. High power testing concluded November 2024 with data processing ongoing. During testing a peak power of > 20 MW was reached and a pulse length of 200 ns.
Wakefields in an elliptical cavity and alternating-structure stability analyses
We present the analytical solution for the transverse and longitudinal wakefields in a perfectly conducting elliptical cavity following from a conformal mapping formalism. These closed-form results are corroborated by numerical calculations. Simple representations of the dipole and quadrupole modes as a function of the cavity dimensions then precipitate, permitting the analyses of the beam tail’s emittance preservation and BNS damping in an alternating structure. We then consider general forms for the dipole and quadrupole components as functions of the longitudinal coordinate and determine what perturbations to such a structure may improve stability.
TUPS110
Implementation of novel acceleration functionality in BDSIM
1572
Beam Delivery Simulation (BDSIM) is a Geant4 based accelerator tracking code which includes interactions of particles with material. BDSIM has become an important code in the accelerator community to simulate beam lines. Since laser and beam driven plasma wakefield acceleration (LWFA/PWFA) is a promising acceleration method we found it important to include related capability in BDSIM. This requires the addition of new beamline elements that are commonly used in plasma acceleration experiments. A gas volume where the LWFA/PWFA takes place and a beam mask to create a separate drive beam and a witness beam. In the former, the beam interacts with gas so ideal gas calculations are required to input the gas properties. Biasing can specifically be applied to the gas material in those elements. Simulating the interactions between the beam and a plasma is not done in BDSIM. An external software is used to compute the fields and the particles data. BDSIM can now read the output HDF5 files to reconstruct the fields inside the gas capillary or use the particle data as a bunch definition for the beginning of a beamline. Some results explaining how to make a LWFA/PWFA simulation are presented.
Paper: TUPS110
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS110
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS111
Optical and laser systems for the AWAKE run 2C experiment
1575
In the AWAKE Run 2c experiment, two electron beams are injected into two separate rubidium (Rb) vapour sources. The first electron beam initiates the self-modulation of a proton bunch in the first vapour source, while the second electron beam serves as a witness beam for plasma wakefield acceleration with low energy spread in the second vapour source. This setup requires the precise spatio-temporal delivery of four laser beams: two deep UV beams that generate the electron beams with a relative timing jitter well below 100 fs, and two near-IR beams that ionize efficiently the Rb vapour sources. The UV pulses are generated by an established Yb laser system, capable of producing 400 uJ, 0.2-10 ps pulses at 257 nm with high reliability (<0.1% RMS energy fluctuation), and enables emittance optimization via spatial beam shaping. The same system is used for both electron sources, utilizing a partial reflector to split the beam and account for differing photocathode yields. For the Rb ionizing pulses, which are directed into the vapour sources in a counter-propagating geometry, the pulses from the AWAKE Ti:Sapphire laser system are transported using a series of vacuum relay telescopes.
Paper: TUPS111
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS111
About: Received: 15 Apr 2025 — Revised: 30 May 2025 — Accepted: 01 Jun 2025 — Issue date: 06 Jun 2025
TUPS113
3D characterization of plasma density in capillary discharges for plasma-based accelerators
1579
Accurate characterization of plasma density profiles is vital for optimizing plasma-based accelerators, as density directly affects beam acceleration and quality. Plasma capillaries also serve as lenses and for beam guiding, highlighting their role in advanced accelerators. This study measures longitudinal and transverse density profiles of plasma capillaries, achieving 3D characterization using Stark broadening techniques. Two optical lines capture emitted plasma light. Parameters include gas flow rate, operating mode (pulsed/continuous), voltage, capillary type and geometry, gas type, and repetition rate, allowing evaluation of operational impacts on plasma density. Results show consistent density measurements across various positions, indicating the method's capability to capture spatial variations in plasma density. Understanding these profiles is crucial for developing and optimizing laser-driven and beam-driven plasma accelerators, as well as enhancing plasma lenses and beam guiding, enabling fine-tuning of parameters to maximize acceleration efficiency and control beam quality.
Paper: TUPS113
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS113
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS115
Optimization of the driver energy deposition in plasma wakefield acceleration simulations by varying transverse offset of sextupole magnets
1582
Plasma Wakefield Acceleration (PWFA) is a method of accelerating charged particles using a plasma. It has the potential to produce exceptionally large accelerating gradients on the order of 10’s of GeV/m. The FACET-II test facility accelerates pairs of 10 GeV electron bunches to study the PWFA process—a drive bunch to produce a wake in the plasma in a lithium-ion oven, and a witness bunch to be accelerated by PWFA. By using arrangements of sextupole magnets, it is possible to alter the chromaticity and other energy-dependent properties of the beams prior to their entry into the plasma. The purpose of this study was to determine how the transverse offsets of the sextupole magnets could be optimized to increase the amount of energy deposited into the plasma by the drive bunch as this energy deposition is critical to maximising the efficiency of PWFA. To achieve this, a simulation of the FACET-II beamline was performed with sextupole offsets as adjustable parameters in a Bayesian Optimization procedure. The results demonstrate the value of using beam simulations as guides to improve the PWFA process, thereby reducing the need to perform costly experiments at the FACET-II facility.
Paper: TUPS115
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS115
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Progress on the flat beam PWFA experiment at AWA
A wakefield experiment at the Argonne Wakefield Accelerator (AWA) facility employs flat electron beams with highly asymmetric transverse emittances to drive plasma wakefields in the underdense regime. These beams generate elliptical blowout structures, leading to asymmetric transverse focusing forces. The experiment features a compact 4-cm-long capillary discharge plasma source developed at UCLA. Analytic models of blowout ellipticity and matching conditions, validated by particle-in-cell simulations, inform the experimental design. Key engineering preparations, including vacuum-gas separation windows, beam transport systems, and diagnostics, are detailed. Initial beam runs focusing on flat beam generation and transport are also presented.
Development of the capillary discharge plasma source at UCLA
At UCLA, we’ve developed a versatile capillary discharge plasma source for plasma wakefield experiments at the MITHRA and AWA facilities. This compact device, with an adjustable length and a 3-mm aperture, is designed to transmit high-aspect-ratio beams and generate plasmas across a wide density range. Its tunable density allows us to explore the shift from linear to nonlinear plasma wakefield acceleration (PWFA) in detail. Recently, we compared the performance of thyratron and solid-state switches, using an interferometric diagnostic system to measure the resulting plasma densities and these results are presented.
Beam transport and diagnostics study for a space plasma experiment at MITHRA
The MITHRA facility being commissioned at UCLA, will be capable of producing low emittance beams with 100s pC of charge with bunch lengths in the 100s of fs range having an energy of 60 MeV. This can be used to drive plasma wakefields and the long bunch length compared to the plasma skin depth allows us to create a beam with a broadband energy spectrum. The energy spectrum resembles the electron spectrum observed in the radiation belts of Jupiter and can be used as a proxy for electron radiation exposure for flyby operations. In this paper, we discuss the beam transport, plasma source and diagnostics needed for the proposed experiment.
Analysis of energy spread and longitudinal field characteristics in flat beam PWFA
The plasma wakefield excited by highly asymmetric drivers has recently been the subject of extensive study. Unlike the case of axisymmetric drivers, the transverse focusing and longitudinal fields exhibit coordinate dependencies. There are still open questions regarding the longitudinal characterization of this blowout regime. In this work, we analyze the transverse dependence of the longitudinal field and explore the transverse distribution of the energy spread in witness beams for drivers with varying asymmetric emittances. These analytical results are compared with Particle-in-Cell (PIC) simulations to provide deeper insights into the dynamics of asymmetric wakefield interactions.
TUPS120
The SPARTA project: toward a demonstrator facility for multistage plasma acceleration
1586
Plasma acceleration is a rapidly maturing technology, but is not yet ready for large-scale applications such as linear colliders. The SPARTA project aims to develop a near-term, medium-scale plasma-accelerator facility to enable new experiments in strong-field quantum electrodynamics (SFQED)—an application that requires solving two of the most important remaining challenges in plasma acceleration: reaching high energy by using multiple accelerating stages; and achieving high beam stability. We report on progress toward the three main objectives: demonstrating a nonlinear plasma lens for achromatic beam transport between stages; developing self-stabilization and instability suppression mechanisms; and developing a conceptual design for a multistage SFQED facility.
Paper: TUPS120
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS120
About: Received: 20 May 2025 — Revised: 01 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
Design and simulation of negative hydrogen ion extraction system for the C30 cyclotron accelerator
This study focuses on the design and simulation of a negative hydrogen ion beam extraction system for the C30 cyclotron accelerator. The filament-driven arc discharge multi-cusp ion source, capable of producing H⁻ ions with 30 keV energy and 2 mA current. The ion source consists of two main components: the driver and the extraction system, with the latter playing a crucial role in ensuring the quality and efficiency of the generated ion beam. The C30 cyclotron capable of accelerating protons to 30 MeV and deuterons to 16 MeV. It is utilized in medical, industrial, and research applications, particularly in the production of isotopes. The extraction system design was carried out using the three-dimensional ion-optics simulation code IBSimu. It includes three electrodes: the plasma electrode, the puller, and the ground electrode. The puller is equipped with a water-cooling system and four permanent magnets to create a magnetic field profile for the suppression of co-extracted electrons. The optimized design of the extraction system not only minimizes beam emittance growth but also enhances the overall performance of the accelerator.
Optimization of eletron beam brightness in the photoinjector of the European XFEL
Photoinjector performance is a key to accessing to the sub-angstrom operation regime of the European XFEL. Optimization of the photoinjector determines the lowest possible emittance along the long accelerator beamline, thus strongly influencing the lasing performance at a given electron beam energy and undulator settings of the user facility. In this paper, an injector optimization approach is established based on a semi-analytical model. It aims at achieving the maximum achievable brightness of the extracted electron beams from the photocathode, taking into account multiple cathode laser properties and gun operation parameters. The semi-analytical predictions are compared with conventional simulation results for an extended parameter range of the European XFEL injector. The obtained results will be presented and discussed.
Design of a C band cryogenic copper photocathode RF gun
Ultra-High brightness electron sources are enabling technologies for frontier applications of electron accelerators, such as FEL, UED, and UEM. Due to the higher cathode acceleration gradients and lower initial thermal emittance at cryogenic temperatures, cryogenic copper radio-frequency electron guns have the potential to achieve higher brightness. In this paper, a 2.5-cell C-band cryogenic copper RF gun operating at 77 K has been desinged, which requires the accelerating gradient on the cathode to exceed 180 MV/m. The cavity geometry is automatically optimized in CST to reduce the modified Poynting vector and pulsed heating temperature. A mode converter coupler is applied to maintain the symmetry of the electromagnetic field, which can reduce emittance growth caused by multipole modes. The fabrication of this electron gun has already been started and high-power conditioning is expected to begin in August 2025.
Compact CW 1-15 MeV 10-100 kW electron accelerators
Our understanding underscores a global demand for affordable, efficient, and compact/mobile electron beam solutions across various sectors, including:1.Replacement of Co60 sources: Co60 radiation sources must be replaced with safer and more efficient alternatives. 2.Isotope production and medical accelerator treatment: Accelerators utilized in isotope production and medical treatments necessitate reliable and cost-effective solutions.3.Medical sterilization via electron beams: Utilizing electron beams for medical sterilization purposes, ensuring safety and efficacy in healthcare settings. 4. Employing electron beams for food processing applications, enhancing food safety and preservation. 5/Electron beam for water processing: Electron beams are utilized for water treatment and purification, addressing water quality concerns. The proposed solution employs a 1497 MHz frequency, enabling compactness and efficiency. The accelerator design utilizes a single linac and racetrack configuration, ensuring gradual acceleration while minimizing footprint. Future directions include integrating NB3Si-based superconducting cavities with cryocoolers for higher beam energies and scalability.
TUPS128
Simulations of ion bombardment in thermionic cathode RF guns
1590
Thermionic cathodes are well known as a robust source of electrons for a wide range of accelerator applications. In the case of Barium Oxide cathodes the low work function that allows emission at modest temperatures is achieved through a surface coating. This coating can be damaged from both ion bombardment and, in the case of RF sources, electron bombardment. Lifetime models that predict the dynamics of these coatings are based on DC electron guns. Understanding the dynamics of ion bombardment in thermionic RF electron guns and under operational conditions is paramount to understanding cathode lifetime and optimizing performance. In this paper we simulate the generation of ions through impact ionization in the APS electron gun. We then compute the energy distribution of ions deposited on the cathode and effective ionization cross section as we vary operational conditions. These simulations are compared with analytical calculations based on first principles.
Paper: TUPS128
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS128
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Design iteration of a compact photoinjector
The study of high-brightness, low-emission photocathode injectors and high-gradient electron guns is an important topic in the field of linear accelerator. Research has been carried out on cryogenic photocathode electron guns to obtain higher quality beams with shorter driven laser. However, problems such as multipole fields and dark currents have been found in the research experiments. An iterative design was carried out to address these issues and an attempt was made to use a short Gaussian shaped drive laser to generate the initial beam. This iterative design significantly reduces the length of the photocathode injector and there exists a means of beam cluster pre-compression that improves the beam quality of the accelerator.
TUPS130
Compressed ultrashort pulse injector demonstrator
1594
High brightness electron beams have a wide range of applications ranging from accelerator-based light sources to ultrafast electron diffraction and microscopy. High accelerating gradient photoinjector is an important tool to generate brighter electron beams. However, high gradient photoinjector suffers issues from material breakdown due to extremely high surface electric fields. One possible path to simultaneously achieve high gradient and suppress breakdowns is to reduce the rf pulse duration fed into the photoinjector. Such an approach was recently demonstrated at the Argonne Wakefield Accelerator (AWA) facility where they commissioned an X-band photoinjector at 400 MV/m cathode field without significant breakdown rates. SLAC National Accelerator Laboratory recently developed rf pulse compression technology optimized for short pulses up to 500MW. We propose to develop an X-band photoinjector which can utilize these ultrashort rf pulses to produce surface fields at 500 MV/m or higher at the cathode. This presentation focuses on the design of the X-band photoinjector.
Paper: TUPS130
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS130
About: Received: 24 May 2025 — Revised: 31 May 2025 — Accepted: 01 Jun 2025 — Issue date: 06 Jun 2025
An overview of research on nanostructured negative electron affinity GaAs photocathode at Jefferson Lab
Inspired by the progress of surface plasmon research and the rapid development of nanotechnology, we embarked on an endeavor aiming to improve the GaAs-based photocathode performance by patterning semiconductor wafer surfaces with pillar arrays on the scale of hundreds of nanometers. Over the past a few years, extensive research effort involving both simulation and experimental studies have been made, leading to the demonstration of some important underlying physical mechanisms such as Mie-resonance at different laser wavelengths and strong quantum efficiency enhancement over their peers with conventional flat surfaces. In this report, we present an overview of our research activities including previous work, current status, and the near future plan about an on-going effort to test newly designed nanostructured photocathodes in a high voltage electron gun.
Fast greens experiment program status at FERMI IOTA/FAST facility
In this paper we will report on the recent progress made on FAST-GREENS experiment program at IOTA/FAST facility at Fermilab. FAST-GREENS experiment will take advantage of the superconduct LINAC in IOTA/FAST facility. A 4 m-long strongly tapered helical undulator with a seeded prebuncher is used in the high gain TESSA regime to convert a significant fraction (up to 10 %) of energy from the 240 MeV electron beam from the FAST linac to coherent 515 nm radiation. We will report the progress of the preparation for this experiment, which includes the preparation work for the beamline, the preparation work for laser development and characterization work, and the design and installation of the laser transport system. We will also discuss the future timeline for the program.
TUPS134
Improvement of electron beam properties for Few-TW LWFA conducted in a sub-mm gas cell filled with a helium-nitrogen mixture
1598
Developing a laser wakefield acceleration (LWFA) scheme by focusing few-TW laser pulses into a thin, dense gas target paves the way for generating high-average-current electron beams driven by a modern high-repetition-rate laser. Our previous study demonstrated that using a sub-mm nitrogen (N₂) gas cell facilitates the routine generation of 10-MeV-scale electron beams from few-TW LWFA with ionization-induced injection*. However, excessive ionization-induced defocusing of the pump laser pulse tends to occur in an N₂ target, motivating the use of a helium (He) – nitrogen (N₂) mixture as the gas target to mitigate pump pulse defocusing in few-TW LWFA**. In this study, the effect of nitrogen doping ratio ranging from 0.5% to 5% was investigated using 40-fs, 1-TW pulses with a 0.4-mm-long gas cell. We found that a manifest peak repeatedly appears around 10 MeV in the energy spectra with the 99.5% He - 0.5% N₂ gas mixture - a result never observed with the pure N₂ cell. Using the He-N₂ mixture also leads to a noticeable increase in the charge of high-energy electrons (>5 MeV) and a reduction in the pointing fluctuation of the output beams compared to the pure N₂ target.
Paper: TUPS134
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS134
About: Received: 27 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS135
Concrete structure and shielding in the IFMIF-DONES main building
1601
IFMIF-DONES is devoted to the irradiation of fusion materials, based on a high energy linear accelerator and a lithium-deuteron stripping reaction, creating the high intensity neutron source which simulates the damage on the 1st wall of the future fusion reactors. The core of the facility are the Accelerator, Lithium and Test Systems hosted inside IFMIF-DONES Facility, in the so-called Main Building (MB). The detailed design of this building was initiated first during the IFMIF-EVEDA activities in the framework of the Broader Approach (EU-Japan Bilateral Agreement) and pursued within EUROfusion for the development of an Early Neutron Source (WPENS). The design has evolved in which the main areas in terms of neutronics shielding are the Accelerator Vault and the Test Cell, where the nuclear reaction takes place and the materials are irradiated. Additional rooms like the Access Cell or the radwaste treatment area, are key in terms of shielding. In this work, it is presented the status of the integration into the design of the MB structure of the safety requirements from the definition of the radiation maps, neutronics studies and heavy concrete vs ordinary concrete capabilities.
Paper: TUPS135
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS135
About: Received: 27 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS136
Characterization of the energy spectrum of a 30-MeV cyclotron-based quasi-monoenergetic neutron beam using a time-of-flight spectrometer
1604
We conducted time-of-flight (TOF) measurements to characterize the spectrum of a quasi-monoenergetic neutron beam driven by a 30-MeV proton cyclotron at the National Atomic Research Institute in Taiwan*. Neutrons were produced by irradiating 30-MeV protons onto a 1-mm-thick beryllium target. The developed TOF spectrometer comprised two 2-inch EJ-309 organic scintillators positioned 200 mm from the neutron beam port to detect gamma rays emitted from the target, and a 3-inch EJ-309 scintillator placed at a flight distance of 2940 mm to measure neutrons. As the signals of gamma-ray bursts triggered TOF measurements at an RF frequency of 73.13 MHz, repetitive distributions of coincidence events between gamma-ray and neutron-related signals were observed, resulting in an effective time window of 13.67 ns for measuring neutrons in the energy range of 16.19–30 MeV. The measured neutron spectrum exhibited a peak at 26 MeV, verifying the simulated spectrum obtained from an MCNP Monte Carlo model. Additionally, we developed a fast-timing scintillator module that measured the proton bunch duration as 0.97 ns, enabling accurate estimation of the energy resolution of the neutron spectrum.
Paper: TUPS136
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS136
About: Received: 24 May 2025 — Revised: 31 May 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
The application of laser-irradiated pyroelectric crystals in neutron generators
Pyroelectric neutron generators have been one of the research hotspots in the field of neutron generation due to their advantages of compact structure and controllable intensity. A novel laser pyroelectric neutron generator was proposed by utilizing 1064nm wavelength pulsed laser irradiation on LiTaO3-Mo-TiDx for simultaneous heating and ionization. The laser irradiation on the pyroelectric crystal to generate high voltage potential, then focusing the laser to ionize TiDx to produce deuterium ions. Under the influence of an electric field, these deuterium ions bombard the surrounding titanium deuteride annular target to induce deuterium-deuterium nuclear reactions for neutron production. Experimental comparisons of crystal temperature change rates and surface temperature distributions under the action of pulsed laser and continuous laser are conducted. Finally, combined with COMSOL simulation results, the correlation between temperature changes and the maximum potential and acceleration gap electric field distribution is established. This study explores the main influencing factors of the maximum potential and electric field distribution in laser pyroelectric neutron generators.
TUPS140
Design of Pelletron accelerator using novel accelerating tube without gap insulators
1608
A novel modular electrostatic accelerating tube*, free from gap insulators, is designed that addresses the limitations of traditional metal-insulator bonded accelerating tubes**, which are costly and prone to damage from high-voltage discharges and beam impacts. This design uses ultra-high vacuum (UHV) as the insulator, with electrodes placed in series under vacuum. High voltage is coupled longitudinally to the first cylindrical electrode via a ceramic-bonded stainless steel flange, with homogeneous electric field flatness of 0.001. Electrostatic analysis using COMSOL Multiphysics and TRAVEL code confirms the field homogeneity and smooth beam acceleration, respectively. Designed for 75 kV operation, extendable to q×100keV energy gains, it leverages vacuum-compatible resistors for inter-electrode HV coupling. Field flatness is extendable to few meters of length and thus enabling megavolts. Beam optics and electrical specifications for Pelletron accelerators using these tubes supports practical feasibility. The grounded cylindrical structure ensures safety and offers an economical, scalable design for small low-energy implanters, Pelletron accelerators, and mass spectrometers.
Paper: TUPS140
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS140
About: Received: 29 May 2025 — Revised: 01 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
Simulation of carbon ion beam charge exchange in a tandem accelerator
A tandem accelerator is a type of electrostatic accelerator that utilizes the high-voltage terminal twice to achieve higher ion energy. In this accelerator, a charge exchange cell is positioned between the low-energy and high-energy sections of the accelerating tube, converting the negative ion beam into a positive one. The charge exchange cell can be categorized into two types: gaseous charge exchange cells and carbon foil-based charge exchange cells. To enhance beam transfer efficiency in a tandem accelerator, the gaseous charge exchange cell is generally preferred. This paper presents a simulation of the charge exchange process for negative carbon ions using nitrogen gas. The conversion efficiency of negative carbon ions to positive ions is calculated for various nitrogen gas throughputs.
Technologies to sustain FRIB establishment and power ramp up
FRIB is the first linac to deploy a large number of half-wave-resonators (220 HWRs) and the first heavy ion linac to operate at 2 K. Such key technology has enabled FRIB to operate as the world’s highest energy continuous-wave hadron linac and highest-energy heavy ion linac delivering world’s highest uranium beam power (>10 kW) on target. The key technological experience may be shared with our society. Key technologies that have sustained FRIB facility establishment and beam power ramp up include large-scale superconducting RF, SC magnets, liquid metal charge stripping, and high power targetry. This talk provides a summary of the technological development key to FRIB’s successful project completion and power ramp up to world’s frontier of high power heavy ion facilities.
Design of a fully 3D-printed 350MHz-CH-structure
This study presents the design and fabrication of a fully 3D-printed Crossbar H-mode (CH) cavity operating at 350 MHz, optimized for continuous-wave (CW) operation. The cavity is manufactured using a 1.4404-grade stainless steel additive manufacturing process, followed by electrochemical polishing and galvanic copper plating to enhance surface conductivity and reduce power losses. The structure will be tested at the FRANZ accelerator in Frankfurt with a 2 MeV proton beam. The accelerating gradient is designed to achieve approximately 1 MV/m, limited by the available RF-power-amplifier of 2 kW. This research demonstrates the feasibility of integrating additive manufacturing with high-frequency accelerator technology for cost-effective and robust cavity production.
Investigations on H-mode drift tube linac structures in the ultra-high frequency range
This study deals with the design and performance analysis of H-mode drift-tube linac (DTL) accelerators in the ultra-high frequency (UHF; 0.3 - 3 GHz) range. Simulations of typical application scenarios were performed, including particle velocities from 0.05c to 0.25c and different drift-tube internal structures. The RF efficiency of different H modes was analyzed. In addition to the shunt impedance, the field distribution and the thermal load also play a role.
Tomographic reconstruction and comparison with emittance data in the RAON
Tomographic reconstruction of beam distribution using four wirescanners has been carried out and a comparison is made with the Allison scanner data at the RAON. Tomography technique which is valid under strong space charge effect is applied in the LEBT, MEBT and SCL sections. Also comparison is made with method to get beam parameters using wirescanner rms beam sizes
TUPS151
Preliminary study of beam dynamics for SDTL-Based 200 MeV energy upgrade of KOMAC proton linac
1611
Korea Multipurpose Accelerator Complex (KOMAC) proposes an energy upgrade of the 100 MeV proton linac. The design of the extended linac is based on a normal-conducting separated-DTL (SDTL) structure which has several advantages over other accelerating structures. The SDTL structure is the same as the DTL, however, unlike the general DTL, the quadrupole magnet is not placed inside the DT but is placed outside. This adds more flexibility to optimize the DT structure for better accelerating efficiency. In addition, since only 4 DTs are placed in the SDTL tank, a separated field gradient stabilization device is not needed, so it is known to be easier to manufacture and align than the general DTL. Our upgrade design consists of a beam matching section between the SDTL and the existing DTL, and 20 SDTL tanks each containing four drift tubes (DTs) with a doublet focusing lattice structure. Beam dynamics simulations were performed using an optimized DT structure to accelerate proton beams from 100 to 200 MeV. We report the preliminary beam dynamics study of the 200 MeV SDTL linac carried out at KOMAC.
Paper: TUPS151
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS151
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 06 Jun 2025 — Issue date: 06 Jun 2025
TUPS152
Study on 200 MeV separated drift tube linac in Korea Multi-purpose Accelerator Complex
1615
Korea Multi-purpose Accelerator Complex (KOMAC) has been preparing 200 MeV energy upgrade. As a possible upgrade choice, separated drift tube linac (SDTL) type is considered in this study. From 2D analysis, optimum cell design deriving maximized effective shunt impedance and minimized Kilpatrick number is obtained. Then, final tank parameters considering stems, slug tuners, vacuum ports are determined under resonance frequency of 350 MHz. Based on that, 3D calculation is conducted to address electromagnetic and thermo-mechanical analysis. Electromagnetic mode and field flatness are analyzed by tuning slug tuners. In addition, appropriate cooling system is designed to minimize resonance frequency and electromagnetic structure variation.
Paper: TUPS152
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS152
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPS154
S-parameters live measurement for the multiport RF components: applications to the circulator and the LIPAc RFQ cavity
1619
In general, it is not easy to measure the drifting RF properties of a device during its operation. If the scatter matrix changes depending on the temperature, the vector network analyzer provides only a static or a starting point of the thermal development. In particular, it is impossible to fully characterize the component that has more than two ports only by the online measurement. So, in the model proposed, assuming that the heat source defined as the average dissipation is given by stored power in the device and the duty cycle, preliminary measurements for several average dissipations are performed. Analytical solutions are derived by using the preliminary and online measurement for the same average dissipation based on the input-output power pickups. As study case, the method is applied to the circulators and the RFQ of the Linear IFMIF Prototype Accelerator, for the three-port and eight-port device case respectively. The model, the results of experiments, and discussions will be summarized in this report.
Paper: TUPS154
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS154
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
Multi-physics analysis of a 280 MHz superconducting radio-frequency quadrupole test cavity
Superconducting(SC) radio-frequency(RF) quadrupole (RFQ) integrates the high efficiency of SC technology with the strong focusing and stable acceleration capabilities of RFQ .It is a critical development in next-generation high-performance accelerators.In this study, we present the multi-physics analysis results of a SC RFQ test cavity operating at a frequency of 280 MHz. This test cavity is designed to be a constant voltage of 240 kV and can be used to accelerate a 10 mA proton beam. The RF design adopts a four-vane structure, which is both structurally stable and facilitates efficient liquid helium cooling. Multi-physics analysis indicates that the cavity deformation and thermal stress meet the operational requirements after the post-treatment of the electrodes.The SC RFQ holds significant potential in many areas, including medical isotopes,particle physics experiments,Boron Neutron Capture Therapy (BNCT) and Proton Therapy. Because of the low operational costs and compact structure, it provides an possibility to enable industrialization and applications of high-power accelerators.