TUPM
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Tuesday Poster Session: TUPM
03 Jun 2025, 16:00 -
18:00
Progress of polarized sources at BNL
The Optically Pumped Polarized Ion Source (OPPIS) has been providing polarized H- ions to the injector chain of the Relativistic Heavy Ion Collider (RHIC) since 2000. The OPPIS has undergone several upgrades. The latest upgrade, completed in 2022, included several improvements. Optimizing the Rb and Na cells has mitigated vapor dispersion in the beamline, resulting in a significant reduction of Rb and Na consumption and enhanced source stability. Modifications substantial increase in the lifetime of source.The upgrades confirmed reliable operation, with a mean current of 350 µA and an average polarization of 80% effectively provided at the end of the 200 MeV linac. We are also developing a high-intensity 3He++ polarized ion source for the future Electron-Ion Collider (EIC). This source will utilize a new technique based on the polarization of accumulated high-purity 3He gas in a high magnetic field through metastability-exchange optical pumping. The existing Electron Beam Ion Source (EBIS) will then ionize the polarized gas using its electron beam. We have developed an infrared laser system for both pumping and measurement within the high-field environment of the EBIS.
TUPM003
Return of experience in the commissioning of the new CLS LINAC injector
1144
After more than 40 years of services the 2856~MHz linac injector of The Canadian Light Source (CLS) has been retired to leave space for a new 3000.24~MHz linac injector, the frequency of which is a multiple of the 500.04~MHz CESR-B type superconductive radio frequency cavity. The new CLS linac injector has been designed and built by RI Research Instruments GmbH. The design is based on their robust S-band technology RF structures that already serve other laboratories in the USA, Australia, Taiwan, Switzerland and Sweden. In order to save money and space the CLS has replaced its six long Accelerating RF structures (3.4~m long) delivering 250~MeV electron beam by three 5~m long accelerating structures that will deliver the same beam energy. In order to do so, one RF structure is powered by one modulator-klystron and the last two RF structures received their RF power from a second modulator-klystron that passes through a SLED system. The SLED system multiplies the power by a factor 5 to 6 and is then equally split to power each structure. We are reporting on the progress of the commissioning of this new injector.
Paper: TUPM003
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM003
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM004
Simulations and experimental commissioning results of the AWAKE Run 2 photoinjector
1148
AWAKE (Advanced Wakefield Experiment) is the world’s first proton-driven plasma wake field acceleration experiment and has demonstrated the acceleration of electrons to several GeV’s in its first Run. The goal of Run2 is acceleration of a witness bunch whilst preserving beam quality and experiment scalability. AWAKE drives high gradient plasma wake fields using a proton beam, then a secondary electron beam is accelerated which is externally injected from a dedicated injector which consists of an S-band Rf-gun and an X-band bunching and acceleration system. This S band RF-Photoinjector for the AWAKE Run 2 experiment at CERN is currently being commissioned. The obtained experimental results are presented and compared to simulations in this paper. Overall, the commissioning demonstrates successful matching of beam parameters with the design values, supported by ASTRA simulations. This lays the groundwork for low emittance electron beam injection into the AWAKE plasma and opens possibilities for future high-gradient acceleration experiments.
Paper: TUPM004
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM004
About: Received: 19 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 06 Jun 2025
TUPM005
Recommissioning of the University of Hawai‘i LINAC and Free Electron Laser
1152
The electron beam linear accelerator (linac) at the free-electron-laser (FEL) laboratory of the University of Hawai‘i at Mānoa, originally developed by Prof. John Madey, has undergone recommissioning. The S-band linac delivers 45 MeV electron beams with 170 mA pulse current and 4–8 $\mu$s pulse duration to drive an infrared FEL oscillator. Recent efforts include restoration of the microwave thermionic gun with a new LaB$_6$ cathode, upgraded vacuum and RF systems, and development of a Python-based beam dynamics model to recover operational magnet settings and optimize beam transport. These upgrades address key technical challenges to restart the accelerator and pave the way for future FEL experiments, including coherent pulse shaping and inverse Compton scattering x-ray generation.
Paper: TUPM005
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM005
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Front end developments of the ESS Linac
The ion source at the European Spallation Source (ESS) since its comissioning in 2019 continues to support the beam commissioning phases of the Linac. In order enable comprehensive characterisation and benchmarking of the ion source's performance, as well as to facilitate future upgrades, a dedicated test stand has been constructed and is nearing completion. This test stand features an ion source identical to the one installed in the operational machine, allowing for detailed performance evaluation independent of the operational machine. The Low-Energy Beam Transport (LEBT) section of the Linac includes the microwave-discharge ion source, solenoid magnets, beam diagnostics, and an iris for beam current regulation, for which a new iris design was developed. This paper presents the design considerations, thermo-mechanical simulations, and preliminary testing results from the ESS Ion Source Test Stand. These efforts aim to enhance the understanding of the ion source's operational behavior, guide future improvements and upgrades, and ensure the continual optimization of the ESS Linac’s long-term performance
TUPM007
Field emission and unwanted beam propagation simulations in the SRF gun at SEALab
1156
The ideal beam coming from an RF photoemission electron gun is composed only of electrons that are produced by the incidence of the drive laser in the photocathode. The timing of the drive laser with respect to the RF fields in the gun is carefully chosen to tailor the beam properties. There are, however, sources of unwanted electrons that degrade the performance of RF photoemission guns. Field emission in superconducting radio-frequency (SRF) guns contributes to unwanted electron generation, known as dark current. This work presents simulations based on the Fowler–Nordheim (FN) model~\cite{FN} to study field emission in the SEALab SRF gun cavity. By analyzing 2D field maps and using ASTRA simulations~\cite{Astra}, emission hotspots are identified, and particle trajectories are evaluated. While most field-emitted electrons are lost within the cavity, a small but significant portion escapes, contributing up to 25\% of the emitted power. The analysis offers key insights into mitigating performance-limiting effects in SRF guns.
Paper: TUPM007
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM007
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM008
Six-dimensional phase space reconstruction with multimodal CNN
1159
The information on phase space in all six dimensions is required for various accelerator experiments. We developed an algorithm based on Convolutional Neural Network (CNN) that can be used instead of the traditional back projection techniques because it is less computationally intensive and has a simple architecture. Our method has shown consistency with the simulation, and we plan to validate it on data taken at the KEK–Superconducting Test Facility (STF).
Paper: TUPM008
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM008
About: Received: 29 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Towards lossless beam transmission in the first LHe-free Nb₃Sn SRF e-linac
Superconducting radio-frequency (SRF) electron linear accelerators (e-linacs) provide significant advantages over conventional room-temperature accelerators, especially in their capacity to accelerate high-intensity continuous-wave (CW) beams. Recently, the first liquid helium-free (LHe-free) Nb₃Sn SRF cavity was successfully operated at the Institute of Modern Physics of the Chinese Academy of Sciences (IMP, CAS), achieving 5 MeV, 200 mA CW beam acceleration and demonstrating the feasibility of miniaturized SRF e-linacs. However, the lack of time structure in the injected beam and its velocity mismatch with the cavity's optimal beta value lead to approximately 50% beam loss within the SRF cavity, presenting a critical challenge for long-term operation. This paper presents an upgrade design of the existing e-linac, ensuring 100% transmission in the SRF cavity while maintaining a compact configuration. Detailed beam dynamics design and multi-particle simulation results are discussed.
TUPM010
First THz light generated in high energy section of FLUTE
1163
FLUTE is a compact and flexible linac-based accelerator test facility at the Karlsruhe Institute of Technology (KIT) in Germany. It serves as a platform for a variety of accelerator studies and to generate intense short THz pulses for various photon science experiments. Later, FLUTE will be also used as an injector of sub-100 fs bunches into the VLA-cSR (Very Large Acceptance compact Storage Ring), which is part of the cSTART (compact STorage Ring for Accelerator Research and Technology) project currently in the technical design phase at KIT. Recently, FLUTE's high energy section has been installed and commissioned. This includes the linac, bringing FLUTE beyond 5 MeV to full energy, the bunch compressor, and two corresponding diagnostics sections. A metal foil in the last diagnostics section has been used to generate a first THz signal with high energy electron bunches.
Paper: TUPM010
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM010
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Design of a compact electron linac for the X-ray based intraoperative radiotherapy
In order to fill the gap of X-ray intraoperative radiotherapy technology in China, an X-band standing wave electron linear accelerator with operating frequency of 9.3 GHz was designed for X-ray intraoperative radiotherapy equipment. Using electromagnetic simulation software and beam dynamics simulation software, the outlet energy of the accelerator is 50 keV , and the electron capture efficiency is 37.5 %. The first cavity is 10 mm long for the optimization of the electron beam energy spectrum, and the second cavity is 12 mm long for the electron beam acceleration. The microwave power is distributed to the two cavities respectively through the power divider and the coupler. There is no energy exchange between the two cavities.
TUPM012
Stable generation of high-quality beam by 3-GeV low-emittance linear accelerator in NanoTerasu
1166
The construction of a low-emittance 3-GeV linear accelerator as an injector system of a new high-brilliance synchrotron radiation facility “NanoTerasu” was completed in January 2023. After beam commissioning of the accelerator complex for several months, the synchrotron radiation for user experiment was provided in April 2024 as planned [*]. The 3-GeV compact linear accelerator consists of 40-MeV injector system and C-band accelerator. The electron beam with a bunch charge of more than 0.5 nC and normalized emittance of less than 2 mm mrad is generated from an electron RF gun system with a gridded thermionic cathode at a “transparent” grid condition [**]. In the 40-MeV injector system, the bunched beam with a bunch length of 5 ps and normalized emittance of less than 10 mm mrad is generated. In usual operation, the bunched beam is accelerated up to 3 GeV and injected stably into the storage ring. In this presentation, we report on the establishment of beam adjustment by tuning RF amplitude and phase. We also report on the beam performance obtained, including beam stability, and comparing the design beam envelope and measured beam optics in the linear accelerator.
Paper: TUPM012
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM012
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
Exploring the feasibility of a few pico-Coulomb, nanometer-emittance operation at Argonne Wakefield Accelerator Facility
We present an injector simulation study to explore the feasibility of a few pico-Coulombs with nanometer-emittance operation at the Argonne Wakefield Accelerator (AWA) facility. The accelerator community have utilized or explored pico-Coulomb or even lower charges to achieve a nanometer level emittance for various applications such as ultrafast electron diffraction, attosecond pulse generation, and nanometer scale longitudinal bunch train generation. Combining such nanometer-emittance bunches with an emittance exchange beamline at the AWA facility would enable research opportunities utilizing attosecond bunches or nanometer-scale longitudinal bunch trains. While the primary focus of this study is demonstrating feasibility, we also provide preliminary simulations related to nanometer-scale longitudinal bunch train.
TUPM014
Deflecting cavity-based multifunctional longitudinal manipulator for CSR-mitigated bunch compression
1169
A deflecting cavity is an interesting tool providing a coupling between transverse and longitudinal planes. Several methods employing deflecting cavities have been proposed to shape current profiles or adjust longitudinal chirp. Even, a method using deflecting cavities was recently proposed for imparting arbitrary correlation on the longitudinal phase space. In this work, we introduce an integrated deflecting cavity-based beam manipulator capable of simultaneously controlling three longitudinal properties: chirp, linearity, and current profile. This relatively compact system can provide a linearized longitudinal chirp for bunch compression without requiring linac phase control and harmonic linearizers. Also, it generates a current profile that flattens the CSR wake, thereby minimizing emittance growth caused by CSR. The presentation includes the working principle of the system and simulation results.
Paper: TUPM014
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM014
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM015
Design study for a transverse deflecting cavity based de-chirper
1173
A collaboration is underway to experimentally demonstrate a novel approach using deflecting cavities to control a particle beam’s longitudinal chirp. While a series of deflecting cavities produces negative chirp, the de-chirping process requires additional modification on the beamline. It has been known that inserting negative drift sections between TDCs enables de-chirping. While the original idea of negative drift requires a series of five quadrupole magnets, the experimental conditions cannot provide enough quadrupoles and space for them. Additionally, it is confirmed that a negative drift using three quadrupoles introduces a significant increase in beam size and emittance in one of the transverse planes. Thus, we propose a new method to enable de-chirping by inserting a series of three quadrupoles. Here, we form a negative identity transport instead of the negative drift. Simulations have been performed to explore this new opportunity. We present the result of this design study.
Paper: TUPM015
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM015
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPM016
Linac gun driver for the Swiss Light Source 2.0
1176
The Paul Scherrer Institute has developed advanced Linac gun driver electronics designed for use in Linear Accelerators, particularly for modern Synchrotron Light Sources. A prototype of this innovative gun driver was successfully evaluated during the final three months of user operations at the Swiss Light Source (SLS). The finalized design is now installed and will be integrated into the upgraded SLS 2.0, which is scheduled to undergo commissioning in 2025. The new gun driver is engineered to achieve extremely short electron bunch lengths, a key requirement for SLS 2.0 top-up operations. It delivers single pulses with the following specifications: 80 ps fall-time, 120 ps FWHM, and a -300 V peak amplitude, with a jitter of less than 5 ps. These enhanced performance parameters will facilitate a future redesign of the SLS Linac, making it more compact while further improving its functionality. This presentation will outline the implementation of the new gun driver and showcase the results obtained during its evaluation.
Paper: TUPM016
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM016
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
Design and simulation of sub-harmonic bunchers for beam bunching efficiency in PLS-II linac
Pohang Light Source-II (PLS-II) is a third-generation synchrotron light source operated by the Pohang Accelerator Laboratory (PAL) since 2012. This study was conducted as a preliminary investigation for upgrading the linac to improve the beam operation efficiency of PLS-II. In this system, beam bunching is initially performed using a pre-buncher operating at the same frequency. To achieve more efficient beam bunching, we considered sub-harmonic buncher (SHB). Two cavities with frequencies of 1 GHz and 500 MHz were designed and beam dynamics simulations were performed, taking into account the available installation space. By comparing the bunch length of beam and other beam parameters for each cavity, we confirmed that the SHB could improve injection efficiency compared to the pre-buncher.
TUPM018
A study of improving stability and reliability in PAL-XFEL modulator system
1179
In the PAL-XFEL system, an X-ray free electron laser facility, 51 modulator power supplies in total have been operated with thyratron tubes as the high voltage pulse switch devices in order to drive an X-band linearize and 50 S-band klystrons for a beam energy of 10 GeV. PAL-XFEL requires beam energy stability of less than 0.02% and very tight control of the klystron RF phase jitter. The modulator output pulse amplitude stability is directly related to the RF phase jitter. There are several factors to satisfy stability and reliability for the PAL-XFEL modulator. The largest sources of pulse-to-pulse instability are a current charging power supply (CCPS) for PFN charging, thyratron switch parts, and a klystron focusing magnet power supply. This paper describes how to deal with the failures of these devices and the debugging results.
Paper: TUPM018
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM018
About: Received: 04 Apr 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM020
An upgraded multiprobe surface analysis tool for photocathode research and development
1182
STFC Daresbury laboratory has developed a suite of analysis equipment for characterisation of photocathode materials. This includes the TESS spectrometer for measuring the mean transverse energy* and a multiprobe surface analysis system for measuring the chemical and physical properties of samples**. Recently, the multiprobe system has been upgraded to include a monochromated X-ray source which in conjunction with the high-resolution analyser should produce improved ability to resolve the chemical state of surface constituent atomic species. This could be particularly useful in the analysis of telluride and antimonide cathodes where incomplete reaction of the constituent species could significantly influence performance. The atomic force microscope has also been recommissioned giving access to surface topological information in the same vacuum environment. Finally, a new sample deposition chamber has been added which will allow additional deposition sources to be attached thus broadening the range of photocathode research that can be carried out.
Paper: TUPM020
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM020
About: Received: 23 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM021
An update of progress on the design of the diffraction line for the relativistic ultrafast electron diffraction and imaging facility at Daresbury Laboratory
1185
The Relativistic Ultrafast Electron Diffraction and Imaging (RUEDI) facility is an approved project to provide ultrafast capability to UK researchers. The current design involves two separate beamlines for diffraction and imaging but with shared infrastructure including laser pump sources. This presentation describes recent progress in the design of the diffraction line. The diffraction line has a 2.4 cell S-band RF gun to produce 4 MeV electron bunches. Bunch compression to the sub-10 fs range is carried out with a triple bend achromat design that also suppresses arrival time jitter*. Interchangeable sample chambers are planned to allow wide ranging experiments from both solid samples at room and cryogenic temperatures and liquid and gas targets. Post sample optics are provided to image the diffraction pattern on to a high-resolution single electron sensitive detector. Temporal diagnostics including an RF TDC and THz deflector are included along with a spectrometer at the end of this line to measure beam energy.
Paper: TUPM021
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM021
About: Received: 23 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM025
Conceptual design of a compact synchrotron for proton-and-helium therapy facility
1189
In recent years, proton and heavy-ion therapy has become increasingly widespread in clinical applications, and has emerged as one of the important means for cancer treatment. The commonly used particle types for this therapy are protons and carbon ions. However, further research into the biological effect has found that helium ions have both high biological effectiveness and small penumbra characteristics, which enable more precise locate of the tumor while also effectively killing tumor cells. And the highest energy of the helium ions used in therapy is 235MeV/u. Therefore, the equipment size and cost required for helium ions therapy will be significantly less than that for carbon ions therapy. To this end, this paper proposes a design for a helium-ion therapy synchrotron that also possesses the capability for proton therapy. The design employs eight ultra-high field dipole magnets to achieve a compact envelope function. Additionally, the design incorporates both multi-turn painting injection and mismatched injection methods in two directions, significantly minimizing the use of bump magnets. This results in a highly compact accelerator structure.
Paper: TUPM025
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM025
About: Received: 03 Apr 2025 — Revised: 30 May 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM026
Advanced beam tuning and beam measurements techniques in the CLEAR facility
1193
The CLEAR (CERN Linear Electron Accelerator for Research) facility delivers to a wide user community a 200 MeV electron beam with highly flexible parameters. Running conditions range from single-bunch to multi-bunch operation, with bunch charges from 10 pC to 1 nC, bunch durations from 100 fs to tens of ps, and includes tunable momentum (30 MeV/c to 220 MeV/c). Such a variety of beam conditions poses a challenge to the beam instrumentation and to the beam measurements and tuning techniques, even more so given that quite often a rapid switch from one set of conditions to a very different one is required. In this paper we present several examples of the techniques developed in CLEAR for this purpose and discuss their advantages and limitations. Examples include emittance measurements and phase space reconstruction procedures by quadrupole scans and beam based alignment methods.
Paper: TUPM026
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM026
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM027
The future of the CLEAR facility: consolidation, ongoing upgrades and its evolution towards future electron facilities at CERN
1197
The CERN Linear Accelerator for Research (CLEAR) is a versatile 200 MeV electron linac followed by an experimental beam-line, operated at CERN as a user facility. Its user community includes research groups working on beam instrumentation R&D, advanced acceleration techniques and irradiation studies, including medical applications. A recent internal review has confirmed the excellence of its scientific output and its strategic interest for the laboratory, extending the facility operation until at least 2030. In this paper we discuss the consolidation actions needed for continued operation together with the ongoing hardware improvements and their impact on the future experimental program. These upgrades include a new front-end for the laser system allowing for a highly flexible time structure, better stability and higher repetition rates, plus the implementation of a second beam line whose optics has been designed to match user requirements and will provide additional testing capability. Finally, we discuss the potential role of CLEAR in the path towards future high-energy electron facilities at CERN.
Paper: TUPM027
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM027
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
An automated Bead-pull method used in the HALF testing
Bead-pull method is a commonly used approach to test and tune the structures of accelerator. Traditionally, this method has been time-consuming. An automated paltform has been developed in this paper, which significantly reduces the time required for the bead pull method and enhances its accuracy. This method has been implemented in the testing of the Hefei Advanced Light Facility (HALF) and has proven to meet the testing requirements of HALF.
TUPM029
Development of photo injector employing Yb fiber laser for stimulus super-radiant THz FEL
1201
THz wave is wonderful prove for materials. Additionally new nonlinear phenomena are expected in spintronic devices if the peak electromagnetic field is greatly higher than 10 MV/cm (3.3 T/cm). Although coherent transition radiation from short bunches is intense, it is very difficult to exceed 10 MV/cm. However we found a possibility of which oscillator FEL reaches ~100 MV/cm employing a pre-bunched configuration.* On a test accelerator (t-ACTS), we are going to introduce a photo-cathode to increase the bunch charge and synchronize with round-trip frequency of an FEL optical resonator. Currently t-ACTS supplies a bunch-charge of 5 pC, whereas the goal is to increase it more than 50 pC for the pre-bunched FEL. Since the intensity of coherent radiation is basically proportional to the square of the charge per bunch, increase of the bunch charge is much effective. The laser system includes a Yb fiber laser oscillator (wavelength: 1047 nm), a multi-pass amplifier, and a fourth harmonic generation (262 nm). A target synchronization accuracy is within 1 deg at 2856 MHz. The assembly of the oscillator has almost completed, and a work for synchronization with RF is on the way.
Paper: TUPM029
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM029
About: Received: 24 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM030
Analysis of laser-electron-radiation interaction in laser modulators for three SSMB scenarios
1204
Recent studies explored a novel storage ring light source using steady-state microbunching (SSMB). Existing investigations predominantly focused on single-particle and pure-optics phenomena. Many SSMB schemes employ laser modulators, comprising an undulator and copropagating laser beam, to manipulate electron longitudinal bunch length. Electron bunch traversing the undulator emits coherent undulator radiation near the resonant wavelength. Laser beams may form a closed path to become a laser enhancement cavity. We developed a model* analyzing laser-electron-radiation interactions in laser modulator cavities, considering mirror-induced losses, externally injected laser power compensation, and coherent undulator radiation dynamics on multiple turns. Our approach integrates beamline transfer matrices with a low-gain FEL oscillator model, enabling quick estimation of the dynamic effects. In this work we examine three SSMB scenarios, amplifier, frequency-beating, and harmonic, accounting for laser-electron-radiation interactions. Under preliminary design parameters, our analysis suggests feasibility for the three scenarios. A potential self-seeding SSMB scheme is also investigated.
Paper: TUPM030
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM030
About: Received: 23 May 2025 — Revised: 29 May 2025 — Accepted: 01 Jun 2025 — Issue date: 06 Jun 2025
TUPM031
Courant-Snyder formalism for modeling, optimizing and simulating broadband THz radiation transport
1208
In order to exploit the scientific potential of user-oriented accelerator facilities, it is necessary to provide adequate pump sources to enable pump-probe science. The EuXFEL R&D project, STERN, aims to equip X-ray users with an accelerator-based THz source matching the high repetition rate of the XFEL. The proposed THz radiation generation methods involve Cherenkov wakefield structures and diffraction radiation, aiming to produce a spectrum from 300 GHz to 30 THz. To enable experimental characterization, both broadband and narrowband pulses must be transported through a single beamline to a radiation-shielded laboratory. A major challenge has been the simulation, optimization and design of the STERN beamline. The OCELOT accelerator lattice optimizer is adapted for optical transport with mirrors substituting traditional focusing magnets. The performance is corroborated using a THz transport code that considers beam clipping and diffraction. The optimized beamline achieves efficient transport over 10 meters, maintaining over 75% source-to-end efficiency across the frequency range. This development marks a significant step forward in THz beamline design for advanced applications.
Paper: TUPM031
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM031
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM032
Cherenkov waveguide design for THz production at the EuXFEL
1212
The EuXFEL R&D project, STERN, aims to provide X-ray users with an accelerator-based THz source synchronized with the X-ray repetition rate. The main proposed THz generation method consists of electron beam wakefield excitation in Cherenkov waveguides. This work focuses on the design of a copper block that holds an array of waveguides to cover the radiation spectrum spanning from 300 GHz to 30 THz. These will include a variety of lengths and dielectric layer thicknesses to vary the spectral contents of the excited TM modes. Additionally, driving the wakefield generation process with an off-axis electron beam causes the excitation of HE modes, which are of great interest to the user community and add to the spectral content of the THz pulse. To further increase pulse energy, the implementation of radiation incouplers is analyzed, demonstrating the potential for capturing the electron beams self-field completely. Such wakefield structures offer a novel option for delivering versatile THz sources tailored to next-generation pump-probe experiments.
Paper: TUPM032
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM032
About: Received: 27 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Improvement of NSRRC superradiant THz FEL
National Synchrotron Radiation Research Center (NSRRC) has been advancing its capabilities in producing intense terahertz (THz) radiation from a superradiant free-electron laser (FEL). This system utilizes a photoinjector operating in its velocity bunching mode to achieve ultra-short electron bunches. However, the highest THz frequency from the facility is determined by the shortest achievable bunch duration. Currently, the highest THz frequency is limited to 1.4 THz, corresponding to the shortest attainable bunch duration of 240 fsec from the photoinjector. To enable higher THz frequency operation, the NSRRC team is investigating the implementation of a dogleg beamline for enhanced bunch compression. We studied the possibility to generate a 25 MeV electron beam compressed to a 100 fsec bunch duration. Using the PUFFIN code, we have calculated the superradiant THz undulator radiation achievable with these compressed bunches. The results demonstrate the potential to produce intense 3 THz radiation, marking a substantial enhancement in the frequency range and intensity of the THz FEL output.
Design study of a THz SASE FEL at NSRRC
NSRRC has developed a superradiant terahertz (THz) free-electron laser (FEL) that utilizes a photoinjector operating in its velocity bunching mode. This system currently achieves a maximum THz frequency of 1.4 THz, constrained by the shortest electron bunch duration of 240 fsec attainable with the photoinjector. To extend the operation THz range to higher frequencies, we are exploring the potential of implementing a self-amplified spontaneous emission (SASE) FEL in the 3-30 THz regime. This approach is considered to be promising to overcome current frequency limitations and enable access to a broader spectrum of high-intensity THz radiation. In such setup, a dogleg bunch compressor will be installed after the photoinjector, and followed by a dielectric-lined waveguide dechirper to remove residual energy chirp left after bunch compression. The proposed THz SASE FEL is currently under simulation study and will be reported. This effort represents an exciting step forward in broadening the scope and applications of THz science and technology at NSRRC.
TUPM035
Performance of terahertz-wave beamlines at Nihon University's laboratory LEBRA
1216
National Institute of Advanced Industrial Science and Technology (AIST) has collaborated with Nihon University to study generation of high-intensity terahertz waves using coherent radiations at the Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University. In a straight section for parametric X-ray (PXR) generation, developments of various types of coherent radiation sources and a study of superimposed coherent radiation using a ring-type resonator have been conducted. Coherent edge radiation (CER) generated in the downstream bending magnet is transported to an experimental room using the PXR beamline and is used for spectroscopic measurements and imaging experiments in an acrylic box filled with dry air. In a straight section for an infrared free-electron laser (FEL), CER generated by a downstream bending magnet during FEL oscillations is extracted from an FEL resonator by a toroidal mirror with a hole.* The extracted CER is reflected by a sapphire substrate coated with Indium-tin oxide and transported to the room using an FEL beamline. In this presentation, the status of the two THz beamlines at Nihon University's laboratory LEBRA will be described.
Paper: TUPM035
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM035
About: Received: 26 May 2025 — Revised: 31 May 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPM036
Feasibility study of a THz beamline design for the THz user facility at NSRRC
1220
Feasibility design of THz beamlines for the use of the superradiant THz free electron laser driven by the NSRRC high brightness photo-injector has been studied. The Accelerator Test Area (ATA) building, where the photo-injector installed, will be transformed into a THz user facility that meets radiation safety regulations. Narrow-band intense superradiant THz radiations with pulse energy as high as 20 μJ and tunable central frequency from 0.6 to 1.4 THz, generated by injecting an ultrashort electron beam into a U100 planar undulator, can be a useful tool for nonlinear and time-resolved pump-probe experiments. There will be two stages for user experiments. Phase I will be opened for users with the experimental station installed right after the THz sources in the accelerator tunnel. Another THz beamline, which is currently being designed to maintain the quality of THz radiations after propagation over longer distances, will be built for user experiments in Phase II. This report briefly describes the beamline design and the operation of user experiments in Phase I.
Paper: TUPM036
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM036
About: Received: 27 May 2025 — Revised: 29 May 2025 — Accepted: 01 Jun 2025 — Issue date: 06 Jun 2025
Epitaxial growth of sodium potassium antimonide photocathodes
Multi-alkali antimonide photocathodes are selected as candidates for electron sources that can continuously generate electron beams with high average current, high bunch charge, and low emittance. Such electron sources are essential for the current electron cooling scheme in Electron Ion Collider (EIC) to cool the hadron beams and maintain beam luminosity. In BNL, epitaxial growth of multi-alkali antimonide photocathodes on lattice-matched substrates are investigated to achieve improved photocathode properties and performances. In this work, epitaxial growth of Na-K-Sb is reported and characterized by reflection high energy electron diffraction (RHEED). Spectral response of the epitaxial Na-K-Sb photocathodes along with lifetime tests are conducted and reported.
TUPM040
Molecular beam epitaxial growth of Sodium Antimonide photocathodes
1223
Cornell University has been working on developing techniques to grow single crystal photocathodes for electron sources using the Molecular Beam Epitaxy (MBE) technique. As a result, the first single crystal Cs3Sb photocathode was produced, which has shown high quantum efficiency and is expected to have a low Mean Transverse Energy (MTE). Now, other alkali materials are being explored. In this work, we report the epitaxial growth of Na-Sb photocathodes at the PHOtocathode Epitaxy Beam Experiments (PHOEBE) laboratory at Cornell University, employing a sequence of shuttered growth steps to form distinct unit cells. The photocathodes were characterized by Quantum Efficiency (QE) measurements and Reflection High-Energy Electron Diffraction (RHEED) patterns collected during growth. The RHEED streaky pattern shows angle dependence, confirming their single crystal structure. Notably, these Na-Sb photocathodes exhibited a QE exceeding 1% at 400 nm, which is much higher than previous reports on this compound. The possible reasons for this discrepancy are discussed.
Paper: TUPM040
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM040
About: Received: 29 May 2025 — Revised: 03 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPM043
Surface cleaning and chemical process analysis of high quantum efficiency magnesium photocathode
1226
Magnesium (Mg) has been demonstrated to be a safe, stable, and reliable photocathode for both normal-conducting and superconducting RF guns. Pure magnesium, with its low work function of 3.6 eV, exhibits significant quantum efficiency (QE) improvement — by up to two orders of magnitude — following appropriate surface cleaning procedures. This study investigates the chemical processes occurring on the material's surface in its as-received state and after thermal and plasma cleaning. These findings provide critical insights into the mechanisms underlying QE enhancement on this metallic photocathode.
Paper: TUPM043
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM043
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Cathode insertion and transfer system for the LCLS-II-HE SRF Gun
A new QWR SRF electron gun has been designed as a low-emissivity light injector for LCLS-II-HE, and a prototype is currently being developed in collaboration between SLAC, FRIB, HZDR, and ANL. The new gun will use an HZDR-type cathode, which includes a cathode load-lock (cathode stalk) developed by FRIB and a complex cathode exchange system designed by HZDR. A dedicated alignment process allows the cathode to be precisely aligned to the axis of cathode stalk without touching the cathode plug itself, ensuring particle-free exchange. At the same time, a chamber system has been built to transfer one cathode from the clean room to the electron gun under a request clean environment.
TUPM045
Latest dark current studies of RF photocathode gun of Delhi Light Source
1229
The Delhi Light source is a pre-bunched Free Electron Laser facility to generate coherent THz radiation. The electron beam is generated from a normal conducting 2.6 cell RF photocathode (PC) gun operated at 2860 MHz. The RF gun is powered by a high power RF source for a duration of 4 µs at 10 Hz repetition rate. The dark current during the operation of the RF gun has been found to be substantially high with increasing forward powers (above 3 MW) even after prolonged RF conditioning. Dark current measurements has been done with an in-house developed faraday cup with an objective to understand the possible primary dark current source from locations at the PC that witnesses high accelerating fields. The measurements include the study of solenoid field variation to understand the dark current energies and effect of its steering to understand the possible dark current locations. Simulations to make inference from the measurements has been done assuming different radial position of dark current emitters at the PC surface. The details of the measurements, simulation results and the inference drawn are discussed in the paper.
Paper: TUPM045
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM045
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM046
Study on deposition method for improving quantum efficiency and lifetime of NEA-GaAs photocathode using cesium, antimony and oxygen
1233
Negative Electron Affinity (NEA) activated GaAs photocathodes are the only one capable of generating spin-polarized electron beam larger than 90%. However, the NEA layer currently made from mainstream cesium (Cs) and oxygen (O) is chemically unstable, the NEA-GaAs photocathode has a rapid quantum efficiency degradation over time or electron beam. As a result, it requires an operating vacuum pressure of below 10-9 Pa and has a short lifetime. Recently, a new NEA layer using heterojunctions with semiconductor thin films of alkali metals and antimony (Sb) or tellurium has been proposed. Recent works have shown that the deposition of the NEA layer was realized using cesium, antimony and oxygen. In this work, we attempted to introduce Sb at two different timing. One is introduction from the beginning, and the other one is introduction after Cs and oxygen deposition. We systematically investigate the deposition temperature and antimony thickness to find the optimal conditions for improving quantum efficiency and lifetime. We will report the latest results.
Paper: TUPM046
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM046
About: Received: 20 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
A new deposition method for potassium cesium antimonide photocathodes about increasing the potassium content towards theoretical stoichiometry
As accelerators and electron microscopes become more advancement, high-performance photocathodes are required. In particular, CsK$_2$Sb photocathode is of interest because of its low emittance, excitability in visible light, and high quantum efficiency (QE). Two challenges with CsK$_2$Sb photocathodes are (1) the lack of a universal deposition recipe to achieve crystal stoichiometries and (2) their high susceptibility, which restricts their operation pressure to ultrahigh vacuum and leads to a short lifetime and low extraction charge. To resolve these issues, it is essential to understand the elemental compositions of deposited photocathodes and to correlate them to active pressures and lifetimes. Here, we report depth profiles for potassium cesium antimonide photocathodes, investigated using synchrotron radiation x-ray photoelectron spectroscopy, and their active pressures.
TUPM048
Development of electronic orbit stability monitoring and analysis system in the Taiwan Photon Source
1236
The Taiwan Photon Source (TPS) storage ring features 172 strategically deployed Beam Position Monitors (BPMs) forming a high-precision electron orbit monitor-ing network. This paper presents an automated monitoring system that periodically extracts BPM data from the data-base and calculates standard deviations to quantify beam stability through statistical methods. The system employs a hierarchical filtering algorithm to identify BPMs with the highest standard deviations and generates analytical visualizations while tracking temporal trajectories of sig-nificantly varying BPMs. During the resolution of BPM electrode anomalous jumps, we developed and integrated a Q-value-based anomaly diagnostic method that effective-ly differentiates between BPM electrode anomalies and actual orbit variations. The system incorporates the LINE Bot API for real-time notification capabilities, establish-ing a comprehensive data acquisition-analysis-alert work-flow. Through its multi-level monitoring architecture, the system has successfully identified and resolved several critical issues affecting beam stability, including electrode abnormalities in BPM183 and BPM126, significantly enhancing source stability and providing users with more reliable beam quality assurance.
Paper: TUPM048
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM048
About: Received: 21 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM049
Studying photoemissive properties of stable Cs-Sb compound thin-film photocathodes using a combination of Monte Carlo simulations and Density Functional Theory
1240
Cs-Sb compound thin-film photocathodes are an excellent candidate to produce bright electron beams for use in various accelerator applications. Despite the virtues of these photocathodes being known, the mechanics that govern their photoemission are not well-understood. Crystalline and other material properties affect the mean transverse energy (MTE) and quantum efficiency (QE) and, thus, the overall brightness. Electrons photoemitted from these thin-film crystals experience an unexpected energy loss similar to that found in bulk crystals despite their being a significantly shorter transport phase. Deeply understanding the relationship between the crystalline properties and the emitted electron beam’s brightness, as well as this drop in energy, is vital to generating ultra-bright electron beams for advanced accelerator applications. The purpose of this work is to use the Monte Carlo method to simulate photoemission from semiconducting films with electronic band structure parameters supplied by Density Functional Theory (DFT) calculations. This method is used to study all steps of photoemission and to identify the key parameters necessary for optimizing photocathode performance.
Paper: TUPM049
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM049
About: Received: 29 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Low-temperature and strained-lattice effects on Monte Carlo modeling of spin-polarized photoemission from GaAs
The degree of spin-polarization of electrons photoemitted from unstrained, room-temperature GaAs is usually significantly less than the theoretical maximum of 50%. However, it has been experimentally observed that the degree of electron spin polarization can be increased and even exceed the theoretical maximum when the sample is cooled to low temperatures and in strained-lattice samples. The previously developed Monte Carlo approach to spin-polarized photoemission from unstrained, room temperature NEA GaAs provides excellent agreement with experimental data in a wide range of doping densities and photoexcitation energies. This work aims to extend the model’s capabilities by incorporating both low-temperature and strained-lattice effects into the band structure and investigating their impact on spin and momentum relaxation mechanisms. Modeling of both low-temperature and strained NEA GaAs with the use of parameters obtained via Density Functional Theory (DFT) calculations will provide a foundation for modeling photoemission from novel spin-polarized materials and complex layered structures and aid in the discovery of new cathode materials.
LCLS-II photo-injector operational challenges and developments
LCLS-II has turned into users operations since 2023 and has gradually ramped the beam rate to 16kHz to date. LCLS-II photoinjector has demonstrated low emittance beam operating at high rate. During operation, we also experienced challenges such as charge production and FEL intensity dependence to the beam rate, beam split, and emittance growth due to unexpected nonlinear field. These problems are addressed through systematic studies. Recently, the over-inserted Cs2Te photocathode has been developed and installed in the LCLS-II gun for significant dark current reduction and emittance improvement. This paper is to discuss LCLS-II photoinjector's ultra-low emittance operational challenges and developments with tens of kHz beam rate as well as the first measurements of the dark current and emittance with the over-inserted photocathodes.
Simulation study of nanostructured plasmonic copper photocathodes
We present an electromagnetic characterization and beam dynamics study of nanostructured plasmonic copper photocathodes for electron gun applications. The study concentrates on photocathodes operated at ultraviolet and infrared wavelengths. Various types of nanopatterns are explored in order to understand how different geometrical parameters affect light reflectance. Optimized nanostructure geometries show significant plasmonic field enhancement, leading to improved photon absorption and increased quantum efficiency at the target laser wavelength. The results of electromagnetic simulation are used to obtain quantum efficiency spatial distribution on the structured cathode surface. The resulting distribution is used for optically induced emission simulation. Beam dynamics simulation results of the photoemitted electron bunch in the vicinity of the nanostructured cathode are presented, analyzed, and compared to those of a flat photocathode.
TUPM053
Design of a resonant slow extraction from the planned DESY IV booster synchrotron
1243
The planned upgrade of the synchrotron light source at DESY, Hamburg will include an upgrade of the booster synchrotron. We discuss the considerations for the design of a slow resonant extraction from this future machine. The implementation of a bent crystal as a potential septum shadower and/or as a septumless option is considered.
Paper: TUPM053
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM053
About: Received: 26 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM054
Progress towards kick and cancel injection for Diamond-II
1247
With the aim of maintaining transparent and efficient injection during top-up, a kick-and-cancel injection scheme has been developed for Diamond-II. In this, stripline kickers are used with 3 ns pulses to deflect individual bunches, with the stored bunch receiving two kicks separated by 180 degrees phase advance to leave it on-axis and the injected bunch timed to arrive at the second kick. In this paper we present progress with the hardware design and recent prototyping results, alongside updates to the simulations.
Paper: TUPM054
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM054
About: Received: 19 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM056
Beam control and characterization of the new SLS 2.0 booster-to-ring transfer line
1251
Off-axis top-up injection into 4th generation storage ring light sources is complicated due to the transverse acceptance, which is typically in the order of a few millimeters. Therefore, the characteristics and control of the incoming beam from the transfer line plays an important role in achieving successful injection. SLS 2.0, the storage ring upgrade of the Swiss Light Source, is among the facilities where precise knowledge and control of the injected beam is important, particularly due to the usage of emittance exchange in the booster synchrotron. Here we highlight the most important design aspects of the new SLS 2.0 booster-to-ring transfer line, including the nondispersive section for beam characterization and the double-corrector configuration allowing injection position and angle control. Furthermore, we present the first experience with quadrupole scans and stabilization of the injected beam.
Paper: TUPM056
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM056
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM057
Commissioning of the SLS 2.0 machine protection system
1255
The Swiss Light Source (SLS) at the Paul Scherrer Institute (PSI) was Switzerland’s first and only 3rd-generation light source. For the SLS 2.0* upgrade the old 2.4 GeV, 12-fold 3-bend achromat lattice with 5 nm horizontal emittance was decommissioned in September 2023 after 22 years of successful user operation. The new 2.7 GeV storage ring has a 12-fold 7-bend achromat lattice achieving 150 pm horizontal emittance. Injectors remain mostly unchanged: the 100 MeV linac feeds the 3 Hz booster synchrotron with extraction at 9 nm horizontal emittance and now 2.7 GeV to match the storage ring’s increased energy. Technical details and an overview of the SLS 2.0 commissioning are presented in separate contributions to this conference. This contribution focuses on the machine protection system challenges for the SLS 2.0**. These required the implementation of a sophisticated system including a fast beam dump kicker, dedicated beam dump, fast beam dump controller and a machine interlock system monitoring over 6000 signals. We discuss challenges encountered and lessons learned while commissioning this advanced machine protection system in parallel to commissioning of the new accelerator.
Paper: TUPM057
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM057
About: Received: 30 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM058
Simulation and optimization of nonlinear kicker injection for PAL-EUV storage ring
1259
The PAL-EUV storage ring has been designed to provide extreme ultra violet (EUV) beams, and is currently under commissioning. With a circumference of 36 m and an electron beam energy of 400 MeV, injection from the booster to the ring is achieved using a nonlinear kicker. Successful injection requires precise tuning of the kicker’s timing delay and maximum strength to match the injected beam’s conditions. This paper investigates the optimization method for these parameters and presents the results obtained through simulation.
Paper: TUPM058
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM058
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM059
SPS-II beam injection using a non-linear kicker
1262
SPS-II is the fourth generation electron storage ring in Thailand. The medium-sized ring constructed with a Double- Triple Bend Achromat (DTBA) cell provides low emittance and high capacity for the beamlines. To complement the compact storage ring with DTBA cell, a Non-Linear Kicker (NLK) was chosen for beam injection. This approach not only simplifies the injection system by reducing the number of required kickers but also enhances the overall reliability and efficiency of the injection process. This paper discusses the injection dynamics and optimization strategies associated with implementing the NLK in the SPS-II storage ring. Through comprehensive simulations and analyses, we demonstrate the NLK’s efficacy in achieving high injection efficiency.
Paper: TUPM059
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM059
About: Received: 26 May 2025 — Revised: 29 May 2025 — Accepted: 29 May 2025 — Issue date: 06 Jun 2025
TUPM060
Specification of insertion devices for ORION project at SIRIUS
1265
The pioneering ORION project will integrate a biosafety level 4 (BSL-4) laboratory with the SIRIUS synchrotron light source. The project includes three beamlines: TIMBÓ, HIBISCO, and SIBIPIRUNA, optimized for X-ray microscopy on biological materials. This study focused on evaluating Insertion Devices (IDs) for the TIMBÓ and HIBISCO beamlines, which demand high photon flux in the ranges of 3–20 keV and 16-40 keV, respectively. Achieving high photon energies with undulators in a 3 GeV synchrotron poses significant challenges. To address this, radiation emission calculations were performed for three ID types: in-air (IAU), in-vacuum (IVU), and cryogenically cooled permanent magnet (CPMU) undulators. With a numerical method based on SPECTRA* software, CPMUs were identified as optimal: a 2 m CPMU with a 14.6 mm period was identified for TIMBÓ, while HIBISCO ideal option is a 2 m CPMU with a 13.6 mm period. As a comparison of the types found for HIBISCO at 40 keV, CPMUs demonstrated approximately a 2.7x flux gain compared to IVUs, and IVUs about 3.8x the flux of IAUs. Further evaluations will consider also the impact on the electron beam dynamics and fabrication feasibility.
Paper: TUPM060
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM060
About: Received: 29 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM061
Spectrum-based alignment of SIRIUS undulators
1269
Recently, two SIRIUS beamlines, EMA and PAINEIRA, received their definitive insertion devices (IDs). Both IDs are in-vacuum devices (IVUs), the first of this kind at SIRIUS. Due to the proximity of the IVU cassettes to the electron beam, the spectrum emitted by these devices is highly sensitive to misalignments of the ID magnetic center. Such misalignments can result in photon flux losses, spectral shifts toward lower energies, and broadening of the resonance. This work presents the application of O. Chubar’s* spectrum-based alignment method to one of the new SIRIUS IVUs, aiming to optimize its performance at the beamline.
Paper: TUPM061
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM061
About: Received: 22 Apr 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
TUPM062
Status of S-PRESSO, A superconducting undulator for the European XFEL
1273
Up to six superconducting undulator modules are foreseen to be installed downstream with respect to the permanent magnet undulators of SASE2, one of the two hard X-ray lines at European XFEL. Aim is to provide users with photon energies above 30 keV. The superconducting undulator pre-series module (S-PRESSO) is currently under production.Before installation in the tunnel, the magnetic structures are characterized in the vertical He bath cryostat SUNDAE1 (Superconducting UNDulAtor Experiment), and in the horizontal test stand to perform quality assurance of the SCU coils installed in the final cryostat SUNDAE2. This contribution describes the status of the project.
Paper: TUPM062
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM062
About: Received: 01 Apr 2025 — Revised: 31 May 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPM064
Cryogenic APPLE undulator development at Helmholtz-Zentrum Berlin
1277
In order to achieve polarization control at tender photon energies at a medium energy light source, a cryogenic in-vacuum APPLE device is being developed at Helmholtz Zentrum Berlin. The project builds on the innovative design of the in-vacuum APPLE II IVUE32 also in development at HZB. The state of the magnet and mechanical design is presented, in addition to the expected spectral performance of the device upon installation in the BESSY II storage ring.
Paper: TUPM064
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM064
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM065
Nb3Sn superconducting multipole wiggler as a vertically polarized hard X-ray source
1281
Vertically polarized superconducting wigglers enable unique hard X-ray experiments based on horizontal optical setups. However, their implementation in modern low-emittance storage rings has been limited due to significant emittance growth. We present a vertically polarized superconducting multipole wiggler designed to reduce the impact on beam emittance. By limiting the magnetic field to 2-3 T and shortening the period length using Nb3Sn wires with higher critical current density compared to conventional NbTi, the beam orbit amplitude and the resultant emittance growth are reduced. As a case study for the future light source project at KEK, PF-HLS (Photon Factory Hybrid Light Source), we discuss a design based on vertical circular winding coils with a sub-100 millimeter period length and a sub-100 micrometer orbit amplitude, as well as its influence on beam emittance.
Paper: TUPM065
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM065
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM066
Universal mode of operation of the APPLE II undulators at the MAX IV 1.5 GeV ring
1284
At the MAX IV 1.5 GeV ring, two APPLE II undulators with period lengths of 84 mm (Bloch) and 95.2 mm (FinEstBeams) cover minimum photon energies of 7 eV and 4 eV, respectively. Operating below 80 eV, the polarization state is distorted significantly by the beamlines' optical elements. A combination of helical and linear inclined modes during undulator operation - the so-called universal mode - can compensate for the distortions. In this paper, we describe how we compensate for the effect of the undulators on the beam orbits and ring optics when operating in universal mode. Additionally, some of the achieved commissioning results at both beamlines will be shown.
Paper: TUPM066
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM066
About: Received: 13 May 2025 — Revised: 31 May 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM067
EPU coupling correction by Bayesian optimization in TPS
1288
APPLE-II type elliptically polarized undulators (EPUs) are critical for producing elliptically polarized light in modern synchrotron light sources. However, residual skew quadrupole components from manufacturing imperfections can couple horizontal betatron motion and dispersion to the vertical plane, changing beam size and degraded beam quality. This paper introduces a Bayesian optimization-based approach to correct these coupling effects for EPU66 at the Taiwan Photon Source (TPS). By constructing a two-dimensional coupling feed-forward table as a function of EPU gap and phase. Experimental implementation and verification with the closest-tune approach demonstrate the efficacy of this method. This article details the optimization process, mathematical framework, and experimental results, establishing a practical strategy for EPU coupling correction in TPS.
Paper: TUPM067
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM067
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM068
First magnetic experience with APPLE X knot undulators for SLS 2.0
1292
The next generation of synchrotrons will have undulators with shorter periods, stronger magnetic fields, and thus higher radiation power. Consequently, concepts for reducing on-axis heat load will become more relevant. One possible idea is to introduce so-called APPLE “knot” undulators that shift the main energy peak off-axis. Thanks to almost on-axis injection, APPLE X undulators with a round vacuum chamber can be used for the upgraded SLS 2.0 at the Paul Scherrer Institute (PSI). This contribution presents an adaptation of the APPLE “knot” concept tailored to the needs of SLS 2.0 in the form of two-meter-long APPLE X undulators with a 36 mm period length and a gap of 11.5 mm. Our design faces the challenge of dealing with up to 16 different magnetization angles introduced by combining and merging NdFeB magnets into four arrays with peak fields around 1 T. Consequently, the magnetic design and the first measurement results are discussed with an outlook on magnet optimization.
Paper: TUPM068
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM068
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 06 Jun 2025
New compact modular in-vacuum undulators for SLS 2.0
A new design for in-vacuum undulators has been developed for the upgraded SLS 2.0 at the Paul Scherrer Institute (PSI), combining several new, beneficial concepts: modular, compact construction, integrated keepers for automated field optimization, and magnetic force compensation. This enables a scalable and relatively lightweight realization. The basis is solid aluminum vacuum chamber modules capable of handling the forces, replacing the classic bulky support. These 50 cm-long modules are connected on girders up to the desired length. A wedge-based drive, operated selectively by a hydraulic or an electrical system, adjusts the gap. The magnetic forces are compensated in the keeper, where the magnets are adjustable via flexor elements, facilitating automated field optimization. This contribution shows the status by presenting measurements and optimization results of our new design, currently realized at PSI, employing a hydraulic drive system for a one-meter-long undulator with a period length of 15 mm. Furthermore, an outlook is given on the manufacturing of such three-meter-long undulators using NdFeB with a period length of 17 mm and 1.2 T maximum field amplitude at a 4 mm gap.
TUPM070
Progress of SUNDAE2 magnetic measurement setup for superconducting undulators at European XFEL
1296
At European XFEL up to six superconducting undulators with 18 mm period and 1.83 T magnetic field are planned to enlarge the hard X-ray photon range above 30 keV. Currently, S-PRESSO, a prototype with 2x 2m long undulator sections plus phase shifter in a 5m long cryostat is being produced. The SUNDAE2 (Superconducting UNDulAtor Experiment 2) magnetic field test facility aims to perform in-vacuum magnetic field measurements of superconducting undulators (SCUs). This work provides an update on the progress of SUNDAE2, which employs Hall probe, moving wire, and pulsed wire techniques for precise magnetic field characterization to meet the specifications for the FEL operation.
Paper: TUPM070
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM070
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM071
Finalizing the multiphysics design of a high heat-load superconducting undulator
1299
RadiaBeam is developing and manufacturing a 15mm period, high temperature superconductor undulator using Magnesium Diboride (MgB2) wire at 10K-15K temperature range. This temperature range can be achieved by cryocooler, a simpler and less expensive cryogenic solution compared to a liquid helium approach. After optimizing the thermal-mechanical design, the operating temperature is finalized at 7K. We examine the current density, critical field, tensile stress, tensile strain, and temperature of MgB2 wire in multiphysics approach and determine the operating field to be 1.13T with safety margin. A quench-protected power system is developed for training the SCU to the operating point in controlled ramp rate. The SCU will be characterized by in-vacuum pulse wire measurement system.
Paper: TUPM071
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM071
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
Two in-vacuum undulators developed for the Sirius
The Shanghai Synchrotron Radiation Facility (SSRF) project team developed two in-vacuum undulators (IVUs) with a period length of 18.5 mm and a gap of 4 mm for the SIRIUS. This paper introduces the design and magnetic field measurements. The results indicate that with a gap range of 4-20 mm, the phase error is less than 3°, the quadrupole field is less than 37 Gs, the sextupole field is less than 83 Gs/cm, and the octupole field is less than 84 Gs/cm².
Study on radiation performance of circular polarization in traditional APPLE-KNOT undulator
The traditional APPLE-KNOT undulator forms composite magnetic fields by superimposing APPLE fields and KNOT fields with the period ratio of 2:3. The APPLE field serves as the main component to approximate the target photon energy, while the KNOT field acts as an additional component to transversely deflect the electron beam away from axis. Variable polarization states can be generated with a low on-axis heat-load in the APLLE-KNOT undulator. Compared the traditional APPLE-KNOT undulator with the APPLE II undulator, a sharp reduction on flux of circular polarization state can be observed. In this paper, this phenomenon is detailed discussed from the theoretical perspective. It indicates that a larger period length of KNOT field than APPLE field with a strong field contribution of KNOT field will greatly suppress the flux of circular polarization state, which is highly consistent with the simulation result. To keep a good performance both at the linear and circular polarization states with little on-axis heat load, the period ratio and field amplitude ratio between APPLE and KNOT fields should be comprehensively optimized.
TUPM076
Refined FLUKA simulation model of neutrino-induced effective dose from a multi-TeV muon collider
1303
Most muons injected into a muon collider decay into an electron (or positron) and a neutrino-antineutrino pair, producing a narrow disk of high-energy neutrinos emitted tangentially to the beam in the collider plane. These neutrinos reach the Earth’s surface at distances far away from the collider. Vertical diffusion of the neutrino cone, reducing integrated neutrino flux at any surface exit point, has been proposed as mitigation technique. This study presents effective dose calculations performed with the FLUKA Monte Carlo code for various geometrical models, each representing conservative radiation exposure scenarios from neutrino flux emerging from the ground at specific distances from muon decay points. These scenarios correspond to different parts of the muon collider ring: bending sections and long straight sections housing experiments. Results are provided as effective doses for annual exposure scenarios with a 100% occupancy. Two muon beam energies are considered: 1.5 TeV and 5 TeV, with a more detailed approach applied to the higher energy.
Paper: TUPM076
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM076
About: Received: 27 May 2025 — Revised: 01 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM077
New developments in the design of the muon production target area of a multi-TeV muon collider
1307
As the International Muon Collider Collaboration advances the conceptual design for a multi-TeV muon collider facility, new technical constraints continue to arise in the muon production stage, where a high-power proton beam interacts with a target. Achieving the required muon bunch intensity may necessitate increasing the primary beam power up to 4 MW. Consequently, the shielding design must address sustained radiation exposure, particularly on critical components such as superconducting solenoids, which generate strong magnetic fields essential for capturing both pions and decay muons. Additionally, the portion of the proton beam that passes through the target without undergoing inelastic interaction leads to a very high power density in the chicane area and an intense ionising dose on the insulation material of the normal-conducting chicane magnets, which are used to separate the muon component. A robust method to safely extract these spent protons is crucial. This study presents the latest results from FLUKA Monte Carlo simulations, modelling the radiation load on solenoids and the extraction channel across varying beam power and target designs.
Paper: TUPM077
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM077
About: Received: 27 May 2025 — Revised: 01 Jun 2025 — Accepted: 01 Jun 2025 — Issue date: 06 Jun 2025
TUPM078
A proposal of superconducting RF electron gun with the latest 4K superconducting technology for CW high-brightness electron beam generation
1311
A superconducting accelerator is an excellent technology that can efficiently accelerate high-current beams and is being applied to free electron lasers and next-generation linear electron-positron colliders such as ILC. Not only for the fundamental science, but also the high current electron beam plays a rather important role in industrial and medical applications. This is because the demand for high-current beams is also strong in these applications. While superconducting accelerators are becoming more widely used, there are not many examples in practical use of the superconducting RF gun, such as the ELBE RF Gun in HZDR. The entire accelerator should be superconducting for its energy efficiency and technical compatibility. To bridge this technical gap, we propose a superconducting RF gun utilizing the latest 4K superconducting technology, which can generate continuous, high-brightness beams.
Paper: TUPM078
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM078
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM079
A report from ISBA24 (The 7th international school on beam dynamics and accelerator technology) in Chiang Mai, Thailand
1315
ISBA24 (The 7th International School of Beam Dynamics and Accelerator Technology) was held in Chiang Mai, Thailand, jointly hosted by Chiang Mai University, Hub of Talents in Particle Accelerators (operated by the Thailand Center of Excellence in Physics), Synchrotron Light Research Institute (Public Organization) and Hiroshima University. ISBA is a series of international accelerator schools initiated in 2018 at Hiroshima, Japan promoted by IINAS(IINAS-NX). ISBA24 was held from November 1 to 9, 2024. The school brought together over 80 participants, including 18 professors and experts, and 64 students from ASEAN countries and beyond. All participants enjoyed intense lectures, practical exercises, student presentations, and social events such as excursions and Thai northern style banquet. An overview of ISBA24 will be presented and human resource development in accelerator science will be discussed.
Paper: TUPM079
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM079
About: Received: 28 May 2025 — Revised: 29 May 2025 — Accepted: 30 May 2025 — Issue date: 06 Jun 2025
TUPM080
A portable muon source for artificial muon muography
1319
Muography is a useful technology for non-destructive inspection of a large-scale structure. Muography with cosmic ray muons has limitations such as low rates, particularly low muon rates in the horizontal direction, and energy spreading, which require long observation times and limit its resolution. Worldwide, large structures such as bridges built during the economic development period of the 1950s-1960s have reached the end of their useful life, and the principle of preventive maintenance is being applied to save the resources, by understanding their interiors and renewing them with priority given to structures that have deteriorated. At this time, a technology of non-destructive inspection applicable to such large structures is required, and Muography using a portable artificial muons source is a promising candidate for this purpose. In this presentation, the results of the investigation of the portable artificial muon source will be presented.
Paper: TUPM080
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM080
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
Comparison of direct laser acceleration performance using radially polarized near infrared and long-wave infrared lasers
Direct laser acceleration with radially polarized lasers is an intriguing variant of laser-based particle acceleration that potentially offers GeV/cm-level gradients while avoiding the instabilities and complex beam dynamics associated with plasma-based accelerators. Currently, the performance of this method is primarily limited by the difficulty of generating high-power radially polarized beams. We propose the use of CO2-based long-wave infrared (LWIR) lasers as a driver for direct laser acceleration, as the polarization insensitivity of the gain medium allows for higher peak powers, since amplification can occur after polarization conversion. Additionally, the larger waist sizes and pulse lengths associated with a longer wavelength can improve electron beam injection efficiency. By comparing acceleration simulations using a near-infrared laser and an LWIR laser, we show that the injection efficiency is indeed improved by up to an order of magnitude using the LWIR laser. Furthermore, we show that even sub-TW LWIR lasers can provide MeV-level energy gains. Thus, radially polarized LWIR lasers show significant promise as a driver of a direct laser-driven demonstration accelerator.
Development of a novel segmented THz-driven electron source
Scaling the RF-accelerator concept to terahertz (THz) frequencies possesses several compelling advantages, including compactness, intrinsic timing between the photoemission and driving field sources, and higher field gradients associated with the shorter THz wavelength and higher breakdown threshold promising vastly smaller and cost-efficient accelerators. These benefits, however, come at the cost of smaller dimensions and tighter tolerances which are challenging to reach in practice. Experiments to test and characterize a multi-layered structure easy-to-implement electron source with tunable interaction length powered by 2 × 100 µJ of twin single-cycle THz pulses predicted to produce 100 fC electron bunches with 100 keV energy, < 1 % energy spread, 0.01 - 0.07 mm mrad transverse emittance and a bunch duration of 20 − 40 fs are currently in progress. Besides the gun structure, the performance characteristics of the THz-driven electron source, including the generation of terahertz pulses, UV beam profile, coupling efficiency of the gun structure, electron beam dynamics, etc are discussed in detail. Such THz-based accelerator prototypes are not only promising as injectors for compact THz-based LINACs but also as a source for ultrafast electron diffraction experiments
TUPM085
An upgrade to the normal conducting miniature transport line for laser plasma accelerator-driven FELs
1323
In this contribution, we present advancements in upgrading the employed normal-conducting electron beam transport line at the JETI laser facility, University of Jena. To address spectral broadening caused by the large energy spread in Laser-plasma accelerators (LPAs), a transverse gradient undulator (TGU) with an energy acceptance of ΔE/E0 = ±10% has been developed. Although efficiently transporting the electron beam from the LPA to the TGU within this acceptance range required an optimized beam transport line too. Phase-space analysis for single particles across this energy range revealed that earlier transport line designs at KIT exhibited a nonlinear dependence of beam transverse position x on energy deviation, leads to beam dynamics complication. By incorporating combined dipole-quadrupole magnets, maintaining a transport line length of 2.9 m for 300 MeV beams, a linear relationship between transverse position x and energy deviations was achieved, with minimal variation in the phase x' (less than 2.4 × 10−4). This redesigned transport line meets the TGU's dispersion requirements, enabling more precise beam alignment and transport.
Paper: TUPM085
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM085
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM086
Simulation study of beam-driven plasma wakefield experiments on CLARA
1327
The Compact Linear Accelerator for Research and Applications (CLARA) is an electron test facility capable of delivering tunable 250 MeV electron beams with up to 250 pC charge to the Full Energy Beam Exploitation (FEBE) experimental area . In this study, we investigate the feasibility of conducting beam-driven plasma wakefield acceleration (PWFA) experiments using the CLARA beam and experimental area. We present simulations of various potential experiments, considering the baseline and R&D beam parameters expected to be delivered to the FEBE experimental chambers*. Our findings highlight the potential for CLARA to support advanced PWFA research, with detailed analysis of beam dynamics and experimental configurations.
Paper: TUPM086
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM086
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM087
A high-efficiency dielectric wakefield energy booster for CLARA
1331
Structure-based wakefield acceleration, using dielectric-lined or corrugated waveguides, is a novel acceleration method currently being explored by several research groups globally. This technology facilitates the transfer of energy from a high-charge drive beam to a lower-charge main bunch with high accelerating gradients. In this study, we propose an energy booster for the Compact Linear Accelerator for Research and Applications (CLARA) at Daresbury Laboratory, utilising dielectric wakefield acceleration (DWA). Our simulation study optimises the drive beam and structure to achieve maximal energy efficiency across varying main beam energies, enabling the delivery of a main beam with adjustable charge and final energy. Additionally, we have considered the stability of both the accelerated and drive beams, selecting the geometry and layout of accelerating structures to maximise accelerated beam quality and mitigate the development of beam breakup instability in the drive beam
Paper: TUPM087
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM087
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
A compact linear accelerator coaxially integrated with a high-power microwave source
Particle accelerators have long been instrumental in advancing scientific research, medical treatments, and industrial processes. However, traditional radio-frequency accelerators are encumbered by their size, expense, and reliance on external microwave sources. In this paper, we propose a novel linear accelerator concept that integrates a high-power microwave source directly into the accelerator, which eliminates the need for external microwave drivers, resulting in a more compact, cost-effective, and simplified system. We designed an X-band backward wave oscillator driven by a hollow continuous electron beam of 50 keV, the high-power microwave generated from which is then input to a centrally positioned X-band standing-wave acceleration structure via a radial coupler. The witness beam, traversing the acceleration structure, can be accelerated from 50 keV to higher than 4 MeV through 10 acceleration cells. This scheme serves as a fundamental exploration of the possibilities of integrated accelerator designs, paving the way for further innovations in the field of more efficient, scalable and versatile accelerator systems.
TUPM089
Twin-bunch modelling in linear accelerators for plasma wakefield acceleration
1335
Twin electron bunches accelerated by high-energy linacs are attracting increasing interest especially in twin free-electron laser (FEL) pulse generation and beam-driven plasma wakefield acceleration (PWFA) studies. High-energy linacs may benefit from plasma accelerators, where a trailing bunch is accelerated in GV/m fields in a plasma wave driven by the leading bunch. This could facilitate high-energy physics, as well as greatly increase the available photon energy range of existing FELs without increasing the footprint. Here, initial analytical studies of twin-bunch generation in FLASH accelerator are carried out. With the initial beam longitudinal phase space properly tuned by temporally shaping the photocathode laser, together with optimizing linac settings, high-quality twin electron bunches with tunable delay and simultaneous bunch shaping can be generated, which is essential for energy-efficient PWFA with low energy spread.
Paper: TUPM089
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM089
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM090
An energy recovery proton linear accelerator for muon production
1339
Muons have important applications in both scientific research and industry. In order to produce muons, an effective way is to use a high-power proton beam interacting with a targeting material. After the interaction, the proton beam is disposed of for other purposes. In this paper, we propose a new type of proton accelerator, an energy recovery proton linear accelerator, so that the high-energy proton beam can be reused to give its energy back to the accelerator. This substantially saves the operational cost of the accelerator and also avoids the burden of high-power beam dumps.
Paper: TUPM090
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM090
About: Received: 20 May 2025 — Revised: 31 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
TUPM091
An optimization of the ILC E-driven positron source with the TPE algorithm
1343
The International Linear Collider (ILC) is a next-generation electron-positron collider based on the superconducting linear accelerator. Many positrons are required for the ILC because beams are not reused in linear colliders. Therefore, the ILC electron-driven (E-driven) positron source system should be designed to optimize efficient positron generation. In this study, we optimize the accelerator parameters including the booster linac RF phase and amplitude, ECS RF phase and amplitude, optics over the system, etc. by the black-box optimizer with TPE algorithm. The results of the optimization are presented.
Paper: TUPM091
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM091
About: Received: 30 May 2025 — Revised: 01 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM092
Design studies on a kHz–MHz repetition rate pulsed muon source based on electron accelerator
1346
Certain types of muon experiments, such as muon spin rotation techniques and muon lifetime measurements, require beams with repetition rates around 50 kHz for optimal statistical performance. However, existing facilities are limited to pulsed beams operating at 25-50 Hz or continuous beams, both constrained by the time structure of proton drivers. Despite ongoing efforts to optimize these proton time structures, significant limitations in flexibility persist. This work introduces an alternative approach to muon production using high-repetition-rate (kHz-MHz) electron beams generated by superconducting linacs at XFEL facilities. This method provides unique temporal characteristics, promising substantial improvements in beam precision, flexibility, and experimental efficiency. We present comprehensive particle tracking simulations for the design of a surface muon beamline and detailed Monte Carlo studies to optimize target materials and geometries. The results underscore the potential of electron-driven muon sources to complement muon-based fundamental and applied physics research while extending the capabilities of current and future XFEL facilities.
Paper: TUPM092
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM092
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM094
Simulations of transverse dynamics in a laser-plasma accelerator
1350
Laser Wakefield Accelerators (LWFA) offer a promising solution for producing high-energy electron beams in compact setups. Beyond obtaining the required energy, the beam quality (emittance, energy spread, intensity) must also be optimized for LWFA to be considered an alternative to conventional accelerators. Achieving precise control of the transverse beam dynamics is one of the key challenges. This article thoroughly studies the physics governing the evolution of emittance and Twiss parameters within the plasma stage, on the density plateau, and in the up-ramp and down-ramp connections to conventional transport lines. Analytical and numerical analysis will be conducted using a toy model made of special quadrupoles, allowing numerical calculations to be sped up to a few seconds/minutes. Matching between plasma and transport lines will be extensively studied, clearly showing the dependence on initial conditions, and recommendations for the best realistic configurations will be provided*.
Paper: TUPM094
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM094
About: Received: 03 Jun 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM095
Coherent high-harmonic generation with laser-plasma beams
1353
Active energy compression scheme enables generating laser-plasma accelerator electron beams with a small relative slice energy spread, of the order of 10 ppm. When modulated by a laser pulse, such beams can produce coherent radiation at very high, about 100-th harmonics of the modulation laser wavelength, which are hard to access by conventional techniques. The scheme has a potential of providing additional capabilities for future plasma-based facilities by generating stable, tunable, narrow-band radiation.
Paper: TUPM095
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM095
About: Received: 06 May 2025 — Revised: 29 May 2025 — Accepted: 01 Jun 2025 — Issue date: 06 Jun 2025
TUPM096
Development of an achromatic spectrometer for a laser-wakefield-accelerator experiment
1357
The large gradients of plasma-wakefield accelerators promise to shorten accelerators and reduce their financial and environmental costs. For such accelerators, a key challenge is the transport of beams with high divergence and energy spread. Achromatic optics is a potential solution that would allow staging of plasma accelerators without beam-quality degradation. For this, a nonlinear plasma lens\* is being developped within the SPARTA\*\* project. As a first application of this lens, we aim to implement an achromatic spectrometer for electron bunches produced by a laser-wakefield accelerator. We report on progress in designing such an experiment.
Paper: TUPM096
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM096
About: Received: 16 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
TUPM097
Study of electron density in capillary discharge plasma for laser plasma accelerator
1361
Laser-plasma accelerators have demonstrated the ability to accelerate high-energy electrons but require improved beam stability and repeatability for practical applications. Pre-formed plasma channels enhance the stability in Laser-Wakefield Accelerators by maintaining laser focus over longer distances, increasing energy transfer efficiency. The characteristics of such channels are highly dependent on capillary geometry, gas parameters, discharge setup, and repetition rate. This study investigates the electron density profiles in plasma from gas-filled capillary discharges. Using interferometry and Stark broadening, we measured profiles under varying conditions, achieving densities of (2-6)×10^18 cm^-3. In this presentation, we showcase the stability and uniformity of the plasma, highlighting its capability to preserve beam quality in high-energy, high-repetition-rate applications. This type of plasma source is a crucial technology for the plasma accelerator-based Free Electron Laser developed at ELI-ERIC as well as for the EuPRAXIA project. Also, we discuss the conceptual design of plasma diagnostics for providing 'real-time' information in high-repetition-rate applications.
Paper: TUPM097
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM097
About: Received: 27 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
How can electrons be accelerated by a longitudinal wake field excited in a plasma?
Abstract The possibility of charged particle acceleration by a longitudinal wake field excited in plasma by an electron bunch and a train of electron bunches is investigated. The exact solution of the stationary nonlinear self-consistent interaction of a monoenergetic relativistic bunch with cold plasma is obtained. It is shown that under certain conditions a self-acceleration of the bunch tail electrons up to high energies is possible.
TUPM099
Initial characterization of a laser-driven betatron radiation source in the EuAPS project
1365
Betatron radiation is the spontaneous emission of radiation produced by the betatron oscillations of electrons in a plasma during the Laser Wakefield Acceleration (LWFA) process. A high-intensity and ultra-short laser pulse is focused on a supersonic gas jet, simultaneously creating a plasma, injecting, and accelerating electrons, which then emit this radiation. In the framework of the EuPRAXIA project, EuAPS (EuPRAXIA Advanced Photon Source) will be the first user-oriented radiation source based on betatron radiation developed at LNF-INFN Frascati in collaboration with CNR and the University of Rome Tor Vergata. This radiation source has a wide range of applications, including materials science, medical and biological research. The user facility aims to deliver 1-10 keV photons using a compact laser-driven plasma accelerator operating in a self-injection mechanism, which occurs in highly nonlinear laser-plasma interaction. In this contribution, we present the expected parameters of the source and the result of several dedicated experimental campaigns conducted within the EuAPS project to provide the preliminary characterization of the x-rays betatron radiation source.
Paper: TUPM099
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM099
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 06 Jun 2025
TUPM101
RF and synchronization system for VEGA project
1369
The Variable Energy Gamma (VEGA) system is under implementation in Bucharest-Magurele (Romania) as one of the major components in the project of Extreme Light Infrastructure Nuclear Physics (ELI-NP). Photon beams will be resulting from the Inverse Compton Scattering of laser photons off relativistic electrons. VEGA is dedicated for photonuclear research both in applied and fundamental physics and will be open for worldwide users. The RF and synch system has to ensure stable, synchronized and coherent operation of all RF pulsed devices. It plays a crucial role in the overall performance of the particle accelerator and ultimately the beam quality. This paper presents the LLRF and synch system for the VEGA electron linac. It is based on commercial S-band Libera products from Instrumentation Technologies (Slovenia). Experience with its operation, tests results of key performance parameters and the current operational status together with plans for future upgrade are presented. Likewise the HLRF system for the RF photocathode gun and the TW cavities, based on klystrons followed by SLEDs and hybrid power dividers, is described here. Also the phase tuning of the RF cavities is discussed.
Paper: TUPM101
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM101
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
The APS linac refurbishment program at Argonne
The linac refurbishment program is an initiative to modernize the linear accelerator (linac) at the Advanced Photon Source (APS) for the APS Upgrade (APS-U). This program addresses critical operational challenges, including obsolete components and the need for higher beam energies. Key projects involve upgrading RF stations to 50 MW capacity using modern klystrons , solid-state modulators, and digital low level rf controls, enabling the linac to achieve higher energy. New thermionic RF guns are being developed and installed to replace aging guns, enhancing beam stability and reliability. Magnet power supplies are being overhauled with modern units that offer faster response times and improved control, and the timing system is being upgraded for better precision and flexibility. Collectively, these efforts ensure that the linac will meet the stringent performance and reliability requirements of the APS-U, supporting advanced scientific research with improved operational stability.
Performances of a dual-axis radiographic diagnostic for hydrotest
Since 2023, the hydrotest Epure facility, located at Valduc, Burgundy, operates as a dual-axis radiographic system for French and British nuclear deterrence programs. Each of the two axes is a single pulse electron linear induction accelerator rated nominally at 20MeV, 2kA and driving an X-ray conversion target. The first one is in use since 2013 at Valduc, and the other since 2023. Both share many traits and design features. We tested each one under a range of operating parameters, mainly current for the one and energy for the other. We assessed performances in terms of X-ray output, beam stability and reliability and evaluated coherence between different diagnostics, including between X-ray detectors and electrical monitors, and between electrical monitors.
Study of the microbunching instability in the THz FEL at PITZ
The PITZ accelerator comprises a radiofrequency photogun and an RF booster cavity, capable of generating electron beams with bunch charges of several nC and momenta of up to ~24 MeV/c. To achieve higher beam currents which is a key parameter for the single-pass high-gain THz FEL, a four-dipole chicane is installed upstream of the undulator. Given the low beam energy and high bunch charge, amplification of microbunching instability (MBI) could be expected in the photo injector. Since the modulation induced by MBI typically occurs in the micrometer wavelength range—comparable to the THz wavelength—the impact of MBI on the THz source at PITZ will be analyzed and discussed in this paper.
TUPM107
Preliminary studies for a high gradient 6GeV injector linac for EBS
1373
The ESRF mid-term plan for the upgrade of the injection complex foresees a full energy linac option. Given the space limitations of the site, compactness is a strong design constraint and high gradient technology is a potential candidate to fulfill this goal. Beam dynamics simulations have been performed for several different accelerating structures in the S-, C- and X-band frequencies to define the best candidate.
Paper: TUPM107
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM107
About: Received: 23 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 06 Jun 2025
Physics design of linear accelerator for S3FEL
Shenzhen Superconducting Soft X-Ray Free Electron Laser (S3FEL), a continuous-wave superconducting facility aimed at providing soft X-ray FEL pulses with a repetition rate of 1 MHz, is currently under construction. These FEL pulses originate from the electron beam generated in a superconducting linear accelerator (linac). This paper comprehensively describes the physics design of the linac, detailing the determination of the longitudinal working point, the optimization of the transverse lattice, and also the particle tracking simulation. Additionally, this paper presents a detailed summary of the linac beam performance.
Current status of the linac system for Korea 4GSR
The development of a 4th-generation storage ring (4GSR)-based light source has been in progress in Korea since 2021, utilizing a linear accelerator (LINAC) and a booster ring as injection systems. The LINAC generates a 200 MeV electron beam using an RF photocathode gun. Electron bunches produced by a UV laser in the RF photocathode gun are focused by a solenoid magnet positioned between the gun and the first accelerating column to ensure initial focusing. The LINAC system comprises four accelerating columns. To achieve proper beam focusing and matching to the LTB (Linac to Booster), nine quadrupole magnets are installed downstream of the second accelerating column. Energy for the RF gun and accelerating columns is supplied by two klystron-modulator systems. For stable energy delivery, klystron-modulator systems with a power capacity of 70 MW are employed, each regulated separately by dedicated LLRF-SSA (Low-Level RF and Solid-State Amplifier) feedback systems. Additional details will be provided in the presentation.
The Australian X-Band electron test accelerator
The University of Melbourne's Xband Laboratory for Accelerators and Beams (XLAB) is collaborating with CERN on the design and testing of high-gradient accelerating structures. Together with the Australian Synchrotron (ANSTO), we are developing the X-Band Electron Test Accelerator (xBeta), a compact high-gradient electron accelerator. The system will feature a photogun to generate short electron bunches of less than 10ps, producing pulsed electron beams of energy 5–30 MeV at repetition rates of 50–400 Hz. A spectrometer will be available for precise characterization of the energy spectrum and the facility will be used to explore medical and industrial applications of high-gradient accelerator technology. Applications include electron bombardment to create nitrogen-vacancy centres in diamond, mono-energetic X-rays for medical imaging offering enhanced contrast and reduced radiation doses and novel channels for medical isotope production. These features make the system a versatile platform for innovations in fundamental research, healthcare, and industry.
TUPM113
Beam results for the new super-conducting booster at Jefferson Lab
1377
The performance results of a new super-conducting booster for the CEBAF injector at Jefferson Lab, could be of interest for other similar electron injectors. A recent addition of this new booster has provided us the ability to achieve a more adiabatic acceleration and therefore an improvement to the beam dynamics and beam brightness. It has also simplified the design and operation of the section of the injector responsible for accelerating the electron beam from a few hundred keV to several MeV (typically 6.7 MeV). The addition of the new booster was part of an upgrade to the CEBAF injector to improve the beam quality for future physics experiments with high sensitivity to beam quality. The booster consists of two cavities: a 2-cell cavity followed by a 7-cell cavity. This combination allows for a wide range of input electron beam energies, from 130 keV to more than 300 keV. In fact, during the last year, the booster was successfully operated with 140,180, and 200 keV input beam energies as the electron gun was being upgraded. This paper describes the new booster, presents beam optics data results from different beam studies, commissioning, and the physics quality beam operation.
Paper: TUPM113
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM113
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 06 Jun 2025
TUPM114
An extraction scheme for future CEBAF FFA based energy upgrade
1381
Jefferson lab is considering an energy increase from current 12 GeV to 22 GeV for its CEBAF accelerator. This will be accomplished by recirculating 5-6 additional turns through two parallel CEBAF LINACs using an FFA arc at each end of the racetrack. The total recirculation turns would be 10 times, the first four turns use present conventional arcs to make the 180-degree bends from one LINAC to the other. However, the last 5-6 turns will all share a single beam line inside two FFA arcs. This reduces the footprint and the cost of the project significantly. On the other hand, having the trajectories of last 5-6 recirculating beams close to each other makes it challenging to extract beams from different passes with different energies. In this paper we will explain our present extraction system for 12 GeV, our challenges and limitations, and a possible extraction solution for the 22 GeV upgrade with the goal of extracting beam at different turns/energies to different experimental halls.
Paper: TUPM114
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM114
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
TUPM115
Simulation and developmental status for generation and detection of THz using coherent transition radiation technique in Delhi Light Source
1385
THz technology being a highly growing and potent field, finds use in a wide range of research applications. Delhi Light Source (DLS) at IUAC, New Delhi is at final stage of commissioning to produce intense and coherent THz radiation based on pre-bunched Free Electron Laser principle. As an addition to the narrowband undulator radiation, broadband Coherent Transition Radiation (CTR) will also be produced by passing femtosecond electron beam bunches through an Al foil . To generate the electron bunches with multi-micro bunch structure from the RF photo cathode gun, a state of the art femtosecond fiber laser system has been developed in collaboration with KEK, Japan. The generated electron beam bunches with energy up to 8 MeV is expected to produce CTR maximum up to few microjoule of energy. The multi-micro bunch structure increases the average CTR power. This paper reports the simulation results of the CTR showing the power, angular and frequency distribution produced from DLS facility. The schematic design and developmental status of DLS for generation and detection of THz CTR are also discussed.
Paper: TUPM115
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM115
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 06 Jun 2025
Progress on emittance exchange-based nano-modulation generation
An emittance exchange (EEX) beamline may provide a unique capability in transferring a transverse beam density modulation into longitudinal bunching. This process can be advantageous for generating coherent radiation below the micron level, through super-radiant emission in a radiating system, or by providing a large input signal for a high gain FEL. Indeed, this mechanism has been proposed to enable FEL action down to the few nm scale for a future facility now under construction at ASU. We investigate the feasibility of creating longitudinal density modulation at the Argonne Wakefield Accelerator, beginning with 800 nm bunching in a pC-level beam. We discuss plans for modulated beam creation, also addressing collective and nonlinear effects in the EEX beamline and subsequent radiation-based diagnosis via CTR or FEL processes.