photon
MOPB028
Maximizing the hard-X-ray performance of SwissFEL by systematic re-alignment and recalibration of the Aramis undulator line
122
Aramis, the hard-X-ray undulator line at the free-electron laser SwissFEL at the Paul Scherrer Institute, has been in user operation at full beam energy since the end of 2018. After steady improvements of the performance until 2022, it proved difficult to maintain the achieved performance level in recent years. Now, after a systematic re-alignment and recalibration of the undulator line and a subsequent optimization of all relevant machine parameters, we have reached a new record photon pulse energy of 1 mJ at 12 keV photon energy. This contribution describes the steps taken and lessons learned to achieve and maintain this high level of performance.
Paper: MOPB028
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPB028
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
MOPB042
Conclusions from the UK XFEL conceptual design and options analysis study
157
UK XFEL is a multi-stage project to pursue ‘next-generation’ XFEL capabilities, either through developing a new facility in the UK or by investing at existing machines. The project’s Science Case envisages a step-change increase in the number of simultaneous experiments, with transform-limited (‘laser-like’) x-rays across a wide range of pulse durations and photon energies (up to ~20 keV) being delivered together with an array of synchronised sources, at high repetition rate to approximately ten FELs (evenly spaced pulses at approximately 100 kHz per experiment, with flexibility). A subset of applications require increased pulse energy and higher photon energies at low repetition rate or in short bursts. The project is now in the final year of its three-year conceptual design and options analysis phase, in which it has produced a conceptual design to efficiently meet these requirements, as well as conducting an analysis of the costs, socio-economic factors, and sustainability of the different investment options. The conclusions of this study are expected to be of general interest to the community.
Paper: MOPB042
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPB042
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPB061
Experimental study on soft X-ray generation via Inverse Compton Scattering at CERN
190
This study explores the feasibility of using Compton Backscattering (CBS) as a compact source for generating photons in the extreme ultraviolet (EUV) to soft X-ray range, with potential applications in biological imaging and modern lithography. A CBS experiment was conducted at the AWAKE Run 2c test injector (ARTI), where electron bunches, accelerated up to 6 MeV by a high-gradient, brazing-free S-band photogun were collided with 1030 nm infrared pulses from the PHAROS femtosecond laser. The electron and laser beamlines were optimised for maximum CBS photon flux.
Paper: MOPB061
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPB061
About: Received: 15 Apr 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPB118
Sub 100 keV hard X-ray inverse compton sattering experiment at BNL ATF
261
Recent progress on the experiments of Inverse Compton Scattering (ICS) at Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) is introduced. Nominal e-beam parameters utilized are electron beam energy of 70 MeV, charge per pulse of 0.5 nC with normalized emittance of 2 mm mrad. Use of long wavelength TW CO2 laser, and short wavelength Nd: YAG or Ti: Sapphire lasers allows us to explore unique nonlinear dynamics of Compton scattering such as Bi-Harmonic interaction and emission of Orbital Angular Momentum of X-ray. Currently, up to 90 keV hard X-ray yield from counter collision of Nd: YAG laser and 70 MeV electron beam is in a range of 1E6 photons per single pulse. Planning to increase electron beam energy to achieve establishment of sub 100 keV ICS to provide sufficient photon flux density, in the range of 1E10 per pulse, owing to the long wavelength multi TW CO2 laser and tighter electron beam focus is underway.
Paper: MOPB118
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPB118
About: Received: 28 May 2025 — Revised: 08 Oct 2025 — Accepted: 08 Oct 2025 — Issue date: 05 Nov 2025
MOPM046
Generation of GeV-range photons via Inverse compton scattering at the FCC-ee
425
This study explores the feasibility of generating high-energy photons, reaching up to 150 GeV, at the FCC-ee booster through inverse Compton scattering. The proposed scheme utilizes a laser within a Fabry-Perot cavity, enabling high repetition rates while minimizing recoil effects during individual collisions. This approach supports the potential use of the FCC-ee booster as a high-energy light source. The photon spectrum and energy distribution are analyzed, with simulation results presented for electron-laser interactions within the Fabry-Perot cavity.
Paper: MOPM046
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM046
About: Received: 23 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPM068
FCC-ee radiation environment and shielding
482
The secondary radiation fields generated by synchrotron photons pose a significant challenge for equipment in high energy electron and positron storage rings like the Future Circular Collider (FCC-ee) at CERN. The annual ionizing dose can reach MGy-levels in the FCC-ee tunnel and requires the design of a dedicated radiation shielding enclosing the photon stoppers in dipoles. In this paper, we present a first optimization of the shielding design, taking into account different aspects such as shielding efficiency, engineering and integration constraints, raw material costs, and radiological considerations. We demonstrate that the proposed shielding solution can decrease the dose in the tunnel by about two orders of magnitude, which considerably reduces the need of expensive radiation-hard equipment. In addition, we explore the option of housing accelerator electronics in a dedicated bunker near lattice quadrupoles, which can possibly allow for custom-off-the-shelf-based radiation tolerant electronics systems. We quantify the expected radiation levels in this bunker, which are driven by photo-neutron production by the high-energy component of the synchrotron spectrum.
Paper: MOPM068
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM068
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPS035
Space charge limit for light sources
682
With the adoption of multi-bend achromat lattices and the aim for diffraction limit, the state-of-the-art light sources are approaching a point where their emittance becomes so small that the effects of space charge can no longer be ignored. Space charge produces a significant betatron tune spread that affects many aspects of beam dynamics: single particle dynamics to collective beam stability. But most importantly, space charge imposes a fundamental limit to the ultimate beam brightness that can be achieved in a synchrotron light source. We demonstrate that the only way to increase the beam brightness and therefore the photon brilliance further is to opt for a higher beam energy.
Paper: MOPS035
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS035
About: Received: 06 May 2025 — Revised: 29 May 2025 — Accepted: 29 May 2025 — Issue date: 05 Nov 2025
MOPS056
Single electron storage at UVSOR-Ⅲ electron storage ring
745
We have started single electron storage experiments since 2021 at the UVSOR-Ⅲ storage ring with the aim of conducting fundamental research on electromagnetic radiation. At BL1U, which is a beamline dedicated to light source developments, we extracted undulator light in the UV wavelength range into the air and observed its intensity by a photomultiplier tube, as decreasing the electron beam intensity using a beam scraper. When the beam intensity became sufficiently small, we observed step-function-like intensity changes with a good SN ratio, each of which corresponded to a loss of one electron. Based on this technique, we confirmed the single electron storage. After establishing the technique, we conducted some experimental studies on undulator radiation from single electron. We will present the latest results at the conference.
Paper: MOPS056
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS056
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPS060
Undulators for BESSY III
748
Helmholtz Zentrum Berlin is engaged in the conceptual design of the BESSY III facility. The BESSY III storage ring will be a fourth generation synchrotron light source with an emittance of about 100 pm rad and an energy of 2.5 GeV. It will be equipped with advanced undulators to provide users with tailor-made light. So far cryogenic permanent magnet undulators, hybrid planar undulators and a variety of APPLE II undulators - conventional (in-air) and in-vacuum are planned to meet user requirements in terms of spectral range, flux and polarisation. In this paper we give an overview of the planned undulators, discuss some of the design aspects and present their expected performance.
Paper: MOPS060
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS060
About: Received: 25 May 2025 — Revised: 01 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
TUPB035
High-power testing of TPS heterogeneous one-to-four power combining
1047
The Taiwan Photon Source (TPS) is a third-generation synchrotron light source located in Taiwan. Currently, it operates with two RF stations, each capable of delivering 300 kW of RF power. As the number of beamlines at TPS increases, more insertion devices will be installed, necessitating additional RF power. Presently, each RF station provides approximately 250 kW of power. To maintain operational margin, increasing the RF power available per station is a critical task. To address this, we have implemented a heterogeneous power combination method, where the power from solid-state power amplifiers is combined to raise the available RF power per station to 375 kW. This report describes the power combination methodology employed at one of the RF stations, high-power testing results, and the outcomes of long-term operation under combined power conditions. Future plans for power combination are also discussed in this paper.
Paper: TUPB035
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPB035
About: Received: 08 May 2025 — Revised: 13 Oct 2025 — Accepted: 13 Oct 2025 — Issue date: 05 Nov 2025
TUPB059
Analysis of low-frequency disturbances (0.3 Hz) in TPS and TLS beam orbit feedback systems
1102
The stability of electron beams in storage rings is vital for precise synchrotron radiation experiments. However, external vibrations, such as earthquakes, ocean waves, and human activities, often disrupt beam stability. This study analyzed low-frequency(~0.3Hz) disturbances in the beam orbit systems of the Taiwan Photon Source (TPS) and Taiwan Light Source (TLS). Using Fast Fourier Transform (FFT) and Dynamic Time Warping (DTW), we identified a strong correlation between these disturbances and ocean wave frequencies, with a similarity score of 0.12. Our findings confirm ocean waves as a major disturbance source and emphasize the need for advanced orbit control and vibration compensation to enhance beam stability.
Paper: TUPB059
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPB059
About: Received: 26 May 2025 — Revised: 01 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
TUPM060
Specification of insertion devices for ORION project at SIRIUS
1288
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-IPAC2025-TUPM060
About: Received: 29 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
TUPM061
Spectrum-based alignment of SIRIUS undulators
1292
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-IPAC2025-TUPM061
About: Received: 22 Apr 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 05 Nov 2025
TUPM062
Status of S-PRESSO, A superconducting undulator for the European XFEL
1296
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-IPAC2025-TUPM062
About: Received: 01 Apr 2025 — Revised: 31 May 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
TUPM064
Cryogenic APPLE undulator development at Helmholtz-Zentrum Berlin
1300
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-IPAC2025-TUPM064
About: Received: 28 May 2025 — Revised: 13 Oct 2025 — Accepted: 13 Oct 2025 — Issue date: 05 Nov 2025
TUPM066
Universal mode of operation of the APPLE II undulators at the MAX IV 1.5 GeV ring
1307
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-IPAC2025-TUPM066
About: Received: 13 May 2025 — Revised: 31 May 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
TUPM067
EPU coupling correction by Bayesian optimization in TPS
1311
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-IPAC2025-TUPM067
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
TUPM068
First magnetic experience with APPLE X knot undulators for SLS 2.0
1315
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-IPAC2025-TUPM068
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 05 Nov 2025
TUPS094
Diagnosing an In-Vacuum Undulator in the ALS storage ring
1598
The Advanced Light Source (ALS) has an in-vacuum undulator named “LEDA”. It was installed in 2019 and provides high-brightness, high-energy photons for the ALS macromolecular crystallography beamline, Gemini. The undulator is a hybrid design with a minimum gap of 4.3 mm, a magnetic period of 15 mm, and a photon energy range of 5–19 keV. When the device was commissioned in the ALS storage ring, it had a negligible impact on ring operations. Recently, there has been a measured degradation in storage ring performance correlated with the Leda gap. Prior to conducting an invasive magnetic measurement, we performed a suite of beam-based measurements to characterize Leda. Herein, we detail these measurements and share them with the accelerator community, who may find them useful when encountering similar challenges.
Paper: TUPS094
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPS094
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
WEPB023
Transitional solution of solid-state power amplifier at NSRRC
1777
The Taiwan Photon Source (TPS) of the National Synchrotron Radiation Research Center (NSRRC) in Taiwan has integrated Solid-State Power Amplifiers (SSPAs) into routine operations since 2023, supporting a stored beam current of 500 mA. In response to the phasing out of Ampleon's BLF578 and the growing demand for improved energy efficiency, a new SSPA was developed based on the existing module configuration, utilizing the BLF978P as an interim solution. This approach serves as a bridge while the development of the next-generation SSPA, employing GaN transistors, is still underway. Both SSPA configurations, with and without circulators, were explored during development. This paper presents the performance of the prototypes and the implementation details.
Paper: WEPB023
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPB023
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 31 May 2025 — Issue date: 05 Nov 2025
WEPB038
Magnetic circuit design and consideration for HTSW using 12mm HTS tape
1822
The National Synchrotron Radiation Research Center (NSRRC) is focused on the application of 2G high-temperature superconducting tape (2G-HTS) for the insertion device in the Taiwan Photon Source (TPS) synchrotron ring. A preliminary design for a 2G-HTS wiggler (HTSW) is being developed, with considerations for sharing the SRF straight-section to make efficient use of space. The target field strength of the HTSW is 3.5 T, chosen to avoid increasing electron beam emittance. The HTSW is also designed to operate using a cryogen-free cryostat with a cryocooler to reduce liquid helium consumption. Safety margins for the current density applied to the HTS tape have been considered to prevent quenching during operation. Various parameters of the HTSW have been optimized and discussed to meet operational requirements, and a set of suitable parameters for HTSW in TPS is presented in this letter.
Paper: WEPB038
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPB038
About: Received: 16 May 2025 — Revised: 29 May 2025 — Accepted: 31 May 2025 — Issue date: 05 Nov 2025
WEPB056
Status of VPU development for PAL-XFEL
1865
PAL-XFEL is planning to install second hard X-ray undulator line (HX2) to meet the high beamtime demand from the users. The photon energy range for the second hard X-ray beam line is from 2~ to 11 keV which is lower than the first hard X-ray photon energy range (2 ~ 20 keV). The required undulator parameters are 35 mm period, max Keff=3.48 at 9.00 mm gap, ~ 3.0 m magnetic length with phase error less than 5 degrees. In addition to the existing conventional undulator design, horizontal gap vertical polarized undulator (HGVPU) concept is also being considered. HGVPU is well developed by LCLS-II team and applied in LCLS-II. In this report, we summarize the VPU design for PAL-XFEL HX2, and reports progress in the prototyping.
Paper: WEPB056
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPB056
About: Received: 29 May 2025 — Revised: 30 May 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
WEPM032
Online optimization of beam lifetime by Bayesian Optimization in TPS
2032
The beam lifetime in synchrotron light sources is critically influenced by nonlinear beam dynamics, particularly in low-emittance storage rings where the Touschek effect dominates. At the Taiwan Photon Source (TPS), a third-generation 3 GeV storage ring, optimization of harmonic sextupole magnet strengths has been conducted using Bayesian Optimization (BO) techniques to minimize beam loss monitor (BLM) readings and thereby enhance beam lifetime. This study demonstrates an integrated approach to nonlinear optics tuning using machine learning, with constraints on chromaticity correction. The experimental implementation involves tuning harmonic sextupole families. Results indicate significant improvements in lifetime while maintaining machine stability, demonstrating the potential of data-driven control in modern accelerator operations, establishing this technique as a powerful tool for synchrotron light source operation. This paper details the implementation, experimental validation, and performance analysis of BO in optimizing beam lifetime at TPS.
Paper: WEPM032
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPM032
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
WEPS025
Design, manufacturing and validation of fast-ramping alpha magnet for interleaving operation at ANL APS
2298
RadiaBeam has designed and manufactured a fast-ramping alpha magnet (FRAM) that is developed for interleaved operation at the Advanced Photon Source (APS) at Argonne National Laboratory. This interleaving operation requires the alpha magnet to stably complete a 5 s long cycle with a 100 ms ramp-up, 1s nominal field output and a 100 ms ramp-down. A laminated yoke is used to minimize eddy currents, ensure fast field response times and reduce core-loss during operation. The magnet has been measured by a Hall probe at Radiabeam and at Argonne, demonstrating 2.75 T/m maximum field gradi-ent within a 10 cm x 14 cm good field region in both DC and pulse modes.
Paper: WEPS025
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPS025
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
WEPS049
Development of stretched wire system for magnetic field measurement of magnets for Siam Photon Source II
2351
A stretched wire measurement system was developed for magnetic field measurement of magnet prototype for Siam Photon Source II. It is used for magnetic field integral measurement for characterization of multipole field errors, magnet centering and fiducialization of multipole magnets. The wire trajectory across magnet aperture can be either linear or circular. The maximum wire movement is ±100 mm in both horizontal and vertical directions with the positioning accuracy of ±2 µm. The system is built on a 3.2-m granite support which allows the maximum magnet length of 2.2 m and magnet weight of 2,500 kg to be measured. Effects of wire tension, scan region, pause time between measurements, wire movement speed, number of repeated measurements and number of data points have been studied. With the optimized measurement parameters, the repeatability of 3E-4 or better can be achieved for the normalized multipole components measured using the circular scan.
Paper: WEPS049
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPS049
About: Received: 28 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 05 Nov 2025
WEPS144
Understanding superconducting cavities through the least action principle
2454
Superconducting cavities are indispensable elements in modern particle accelerators, utilizing the ultra-low sur-face resistance of superconductors to achieve exceptionally high quality factors. In this work, we apply the least action principle to derive an equivalent RLC circuit model, offering a unified theoretical framework to describe the electromagnetic behavior of superconducting cavities. Beyond the classical model, we examine the underlying heat dissipation mechanisms and identify quantized physical quantities that influence cavity performance. Particular attention is given to the quantum aspects of the quality factor, including its manifestation in decay time measurements. By bridging classical electrodynamics and quantum dissipation, this study provides a deeper under-standing of the fundamental principles governing super-conducting cavity dynamics.
Paper: WEPS144
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPS144
About: Received: 26 May 2025 — Revised: 13 Oct 2025 — Accepted: 13 Oct 2025 — Issue date: 05 Nov 2025
THPB005
Surface characterization of vacuum chambers with synchrotron radiation exposure at a beamline
2510
Exposure of synchrotron radiation on the vacuum chambers induces high yield of photoelectrons and the consequent increase of pressure from stimulated gas desorption. Characterization of the surface quality of vacuum chambers, either after chemical cleaning or with thin film coating, by synchrotron radiation exposure at a beamline is powerful and sensitive. In this study, analysis of photo-desorption and photoelectron yield for various vacuum chambers, metallic tubes with or without NEG-coatings, at the BL19B-beamline of Taiwan Light Source (TLS) with critical photon energy of 2.14 keV will be described and compared.
Paper: THPB005
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB005
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 31 May 2025 — Issue date: 05 Nov 2025
THPB006
Improvement of PLS-II Photon Absorbers
2513
In synchrotron accelerators, managing the intense photon flux generated by bending magnets is very important for maintaining the accelerator's performance. The emitted synchrotron radiation, characterized by its high intensity and broad spectrum, imposes significant thermal and structural demands on accelerator components. Photon absorbers are essential to effectively block excess photons, ensuring stable operation and extending the lifespan of the vacuum components. In this poster, I would like to introduce the new shape and analysis results to improve the performance of the vertical-type photon absorbers operating in PLS-II.
Paper: THPB006
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB006
About: Received: 28 May 2025 — Revised: 13 Oct 2025 — Accepted: 13 Oct 2025 — Issue date: 05 Nov 2025
THPB011
Design, fabrication, and characterization of 3D-printed photonic crystals for THz filtering applications in particle accelerator
2520
The advancement of broadband terahertz (THz) sources has become increasingly important for various scientific and technological applications, including those in particle accelerators. To enable tunable and flexible THz source development, components capable of selective THz spectrum filtering are essential. In this work, we investigate the use of 3D-printed photonic crystal structures, specifically woodpile designs, for THz filtering applications. Using high-precision digital light processing (DLP) 3D printing, we successfully fabricate woodpile photonic crystals with high accuracy. The fabricated structures demonstrate effective spectral filtering capabilities within the THz range, offering promising potential for applications in advanced accelerator technology and related fields.
Paper: THPB011
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB011
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
THPB018
Conceptual design and optimization of a liquid lead circuit as beamstrahlung absorber for the CERN’s FCC
2540
Beamstrahlung radiation represents a new challenge at CERN's lepton Future Circular Collider (FCC-ee), specifically for electron-positron collisions. At each interaction point, its unprecedented beam intensities give rise to two photon beams with a power of several hundred kW each. Liquid lead, known for its high density and Z and relatively low melting point, is proposed as a beam dump material to safely dispose of this power. Achieving the necessary effective interaction thickness of 10 to 20 cm presents challenges in optimizing both mass flow rates and the geometric configuration of the lead. This study employs the Monte Carlo code FLUKA to simulate energy deposition and thermal simulations to investigate multiphase flow dynamics within an open-channel configuration. Various slope designs for a free-flowing liquid lead stream within an argon-filled vessel are explored to prevent oxidation. By optimizing the slope and shape of the lead flow, this work seeks to enhance energy absorption and thermal management, improving the effectiveness of liquid lead in high-power beam dump applications.
Paper: THPB018
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB018
About: Received: 26 May 2025 — Revised: 31 May 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
THPB023
Numerical simulation of a modified air conditioning system of the experimental hall at TPS
2552
Taiwan Photon Source (TPS) has been committed to serve users for eight years. In the first and second phases of TPS beamline project, there were 16 beamlines had been in operation. The third phase project had been launched in 2021. Facing the more persons and equip-ment in the experimental hall as well as power saving issue, we applied the computational fluid dynamic (CFD) scheme to simulate the air conditioning system to obtain better cooling efficiency. We modelled one twelfth of the TPS experimental hall and two beamlines.
Paper: THPB023
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB023
About: Received: 28 May 2025 — Revised: 30 May 2025 — Accepted: 13 Oct 2025 — Issue date: 05 Nov 2025
THPB085
Design and structural analysis of a bending chamber for EPU applications in the SPS-II storage ring
2647
Designing a vacuum chamber for the Elliptically Polarized Undulator (EPU) in the SPS-II storage ring presents challenges due to a constrained bore aperture, minimal clearance between magnet poles, and requirements for synchrotron radiation delivery. This study focuses on a vacuum chamber design that accommodates the large opening angle necessary for EPU operation. A complex transition cross-section was developed to achieve the required beam aperture while maintaining compatibility with the magnet structure. The limited clearance of 0.5 mm between the chamber and magnets necessitates precision machining and fabrication. Structural reinforcements were added to the thin sections of the chamber to ensure mechanical stability, and a specialized welding approach was implemented to minimize deformation. The chamber is fixed to supports designed to control thermal deformation during operation. Finite element analysis (FEA) evaluates the chamber’s structural performance, including stress, safety factors, and deformation, confirming the design meets the operational requirements for EPU applications in the SPS-II storage ring.
Paper: THPB085
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB085
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
THPM071
Synchronous phase measurement and study at the Taiwan Photon Source
2835
A bunch-by-bunch synchrotron phase detector system has been implemented to investigate the synchronous phase behavior of the storage ring at the Taiwan Photon Source. This detector employs I/Q demodulation to cal-culate the beam phase on a bunch-by-bunch basis. The acquired data is integrated into the accelerator control system, visualized through a graphical user interface, and made available for further analysis. Independent component analysis (ICA) is employed to identify under-lying sources. For a trapezoid-like filling pattern, transi-ent beam loading effects are clearly observed in the flat-top region, whereas significant phase variations occur along the sloped edges of the pattern. During the beam decay period, an in-phase synchrotron phase oscillation at 7 kHz is observed, which originates from the rotation frequency of the radio-frequency transmitter. During injection, three distinct modes are identified through ICA decomposition. Among them, the amplitude of the syn-chronous oscillation mode shows a strong dependence on the injected bucket address.
Paper: THPM071
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPM071
About: Received: 20 Apr 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 05 Nov 2025
THPM072
The online emittance monitor at Taiwan Photon Source
2839
This study summarizes the X-ray pinhole camera results from two recently constructed diagnostic beamlines. We provide updated emittance and energy spread measurements for the TPS storage ring and implement online measurements for routine operational monitoring.
Paper: THPM072
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPM072
About: Received: 19 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
THPM073
The Issue with XBPM2 in the TPS Front End
2842
Two sets of blade-type beam position monitors (XBPMs) are installed in the Taiwan Photon Source (TPS) front-end. The upstream XBPM, referred to as XBPM1, has been calibrated and can calculate the photon beam center position. The downstream XBPM, referred to as XBPM2, encountered difficulties during calibration. It was unable to obtain an effective linear range. Adjustments to the blade spacing and alternative calibration methods were explored to address this issue. These details will be discussed in the article.
Paper: THPM073
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPM073
About: Received: 23 May 2025 — Revised: 14 Oct 2025 — Accepted: 14 Oct 2025 — Issue date: 05 Nov 2025
THPM102
High efficiency multi-objective Bayesian algorithm for APS-U nonlinear dynamics tuning
2905
The Advanced Photon Source (APS) facility has just completed an upgrade to become one of the world’s brightest storage-ring light sources. Machine learning (ML) methods have seen extensive use during commissioning. One important application was multi-objective tuning of dynamic aperture and lifetime, a complex high-dimensionality task intractable with classic optimization methods. In this work we will discuss novel Bayesian optimization (BO) algorithmic and implementation improvements that enabled this use case. Namely, pre-training and uncertainty-aware simulation priors, dynamic parameter space and acquisition function refinement, and an adaptive wall-time convergence criteria. We will also show results of optimization runs from 10 to 24 dimensions, benchmarking scaling and efficiency as compared to standard MOGA and MGGPO. Given the promising performance, work is proceeding on tighter BO integration into the control room.
Paper: THPM102
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPM102
About: Received: 29 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
THPS009
The observer-based estimation of photon beam position for improved beamline stability at SPS
2960
This paper presents the development and implementation of an observer-based estimation method to determine the photon beam position for various beamlines at the Siam Photon Source (SPS). The research, executed over multiple phases, aims to address position drift issues in photon beamlines, particularly those without installed photon Beam Position Monitoring Systems (pBPMs). The method allows real-time estimation of beam positions, which are then used as inputs for the SPS’s central control system to enhance beam stability. This observer-based approach provides a cost-effective solution by eliminating the need for additional pBPMs installation in space-constrained beamlines while maintaining an error margin of less than 10% between estimated and measured positions. This innovation is essential for enhancing the operational stability of existing beamlines and offers a scalable model for similar applications in the future.
Paper: THPS009
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS009
About: Received: 21 May 2025 — Revised: 31 May 2025 — Accepted: 14 Oct 2025 — Issue date: 05 Nov 2025
THPS010
On-line estimation approach to fault-tolerant control of orbit stability at Siam Photon Source
2964
A novel approach combining online unknown input estimation with reconfigurable control has been developed to enhance orbit stability in the Siam Photon Source (SPS) storage ring. These unknown inputs, representing disturbances or uncertainties in the dynamic system, provide valuable insights for achieving robust control. Disturbances such as noise, temperature changes, and modeling uncertainties affecting the control variables can be treated as fault signals, allowing the application of fault estimation and compensation techniques from Fault Diagnosis (FD) and Fault-Tolerant Control (FTC) theories. The initial implementation of this slow orbit feedback (SOFB) system has significantly reduced X-Y orbit fluctuations while maintaining robust control stability against temperature disturbances in the SPS storage ring. This presentation will cover the FD/FTC principles, hardware, software, commissioning results of the current SOFB system, and plans for future developments.
Paper: THPS010
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS010
About: Received: 21 May 2025 — Revised: 14 Oct 2025 — Accepted: 14 Oct 2025 — Issue date: 05 Nov 2025
THPS060
Photon stimulated desorption from cryogenic surfaces of high temperature superconductor and amorphous carbon thin films
3101
High Temperature Superconductor (HTS) and amorphous Carbon (a-C) thin films, and their combination, are being considered as possible surface coatings for the FCC-hh beam screen (BS) with the aims of reduction of the resistive wall impedance and mitigation of the electron cloud. Along with these required properties, i.e., the high electron conductivity and low secondary electron yield, the Photon Stimulated Desorption (PSD) yield is one of the most essential characteristics in the design and operation of the FCC-hh vacuum systems. For this purpose, a series of the PSD measurements is currently conducted at a dedicated beamline in the KEK Photon Factory, where similar conditions to FCC-hh in terms of the Synchrotron Radiation energies and power density are available. In order to realize a similar cryogenic condition of the BS (40-60 K), the sample container is equipped with a LN2 jacket (77 K) and installed in an insulation vacuum chamber. The conditioning behaviors of the PSD yields as a function of the photon dose are being obtained for uncoated copper and HTS, and a-C coated copper and HTS, and each sample is examined at cryogenic and room temperatures for comparative analysis.
Paper: THPS060
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS060
About: Received: 31 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025