photon
MOP1035
Radiation and power deposition studies for the FCC-ee halo collimation system
128
The betatron and momentum collimation system of the the Future Circular Collider (FCC-ee) is essential to isolate losses away from the experiments and other machine elements, thus reducing the radiation background in the experiments, and avoiding damage to the machine in case of accidental beam losses. The primary and secondary collimators of the collimation hierarchy, employed to scatter halo particles from the beam and remove them, respectively, will be accommodated in one of the technical insertions of the collider ring (Point F). In this paper, FLUKA simulations are presented for the collimation straight section, addressing both normal operation and accidental scenarios. The power deposition is determined for all elements in the section following beam impacts on the collimator jaws, including other collimators as well as dipole and quadrupole magnets. In particular, the fraction of the stored beam which can be safely absorbed by the collimators is estimated. Finally, the paper discusses the radiation levels in the Point F tunnel resulting from beam losses on the collimation system, and the resulting radiation hardness requirements for machine equipment and infrastructure.
Paper: MOP1035
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP1035
About: Received: 12 May 2026 — Revised: 15 May 2026 — Issue date: 22 May 2026
MOP6636
Oscilloscope-based TCSPC longitudinal beam diagnostics at HLS-II
523
Abstract: The longitudinal density distribution of electron bunch-es is a critical parameter for evaluating the performance of storage rings. To meet the requirements for real-time, cost-effective, and flexible longitudinal diagnostics for the Hefei Advanced Light Facility (HALF), we have devel-oped a Time-Correlated Single Photon Counting (TCSPC) measurement system based on a general-purpose high-speed oscilloscope at the Hefei Light Source II (HLS-II). Unlike traditional setups relying on dedicated TCSPC modules, this system utilizes an oscilloscope to directly acquire single-photon pulses from a Photomultiplier Tube (PMT). Experiments conducted at the HLS-II beamline successfully recovered the bunch fill pattern and recon-structed the photon arrival time distribution. To address the measurement errors caused by amplitude fluctuations, a post-processing algorithm incorporating Software Con-stant Fraction Discrimination (CFD) and time folding was developed. This approach effectively suppressed the time walk effect and enabled high-resolution reconstruction of the bunch profile. The results demonstrate that this oscil-loscope-based scheme possesses excellent online monitor-ing capabilities, providing a cost-effective technical solu-tion for HALF and similar facilities.
Paper: MOP6636
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP6636
About: Received: 12 May 2026 — Revised: 16 May 2026 — Accepted: 18 May 2026 — Issue date: 22 May 2026
MOP6667
Implementation of fast beam-based alignment at the Taiwan Photon Source
571
A fast beam-based alignment (BBA) method has been implemented at the Taiwan Photon Source to significantly enhance the efficiency of aligning beam position monitors with quadrupole magnet centers. By utilizing sinusoidal excitation of correctors and employing synchronous detection algorithms, alignment offsets are efficiently extracted across the entire storage ring. Experimental results demonstrate that the total measurement time is reduced from 8 hours to under 40 minutes, while maintaining precision comparable to conventional BBA methods. The primary sources of measurement uncertainty are attributed to betatron tune and orbit variations induced by magnetic hysteresis and ocean-induced ground motion. This approach provides a robust and time-efficient solution for routine orbit characterization in modern synchrotron light sources.
Paper: MOP6667
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP6667
About: Received: 15 Apr 2026 — Revised: 01 May 2026 — Accepted: 15 May 2026 — Issue date: 22 May 2026
MOP6673
A sliding mode control approach for photon beam stability at the Siam Photon Source
582
This paper presents the enhancement of photon beam position stability at the Siam Photon Source (SPS) through a real-time feedback control system based on a Sliding Mode Control (SMC) algorithm. The proposed system employs Photon Beam Position Monitor (pBPM) measurements within a global orbit feedback loop to minimize beam position fluctuations. The SMC-based Fault-Tolerant Control (FTC) algorithm enhances system robustness by effectively compensating for disturbances, and actuator faults, thereby maintaining stable beam conditions under various operational scenarios. Experimental results demonstrate that the integration of SMC significantly reduces photon orbit deviations and improves synchrotron radiation quality. By strengthening reliability and adaptability, the developed control system ensures precise beam positioning, making the SPS more dependable for scientific and industrial applications that demand high beam stability.
Paper: MOP6673
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP6673
About: Received: 06 May 2026 — Revised: 15 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7124
Overview of superconducting undulator development at the European XFEL
916
This contribution describes the recent progress of the European XFEL superconducting undulators (SCUs) program. This includes: an industrially-produced NbTi-based SCU afterburner foreseen for one of the two hard X-ray lines; a prototype SCU module (S-PRESSO) in production by Bilfinger; two magnetic measurement test stands to perform quality assurance; and further development of SCU technology to reach even larger magnetic fields, by leveraging recent developments in High Temperature Superconducting (HTS) tapes for future upgrades.
Paper: MOP7124
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7124
About: Received: 11 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7139
Comparative conceptual designs of liquid lead absorbers for the FCC-ee beamstrahlung dump
959
At CERN’s Future Circular Collider (FCC-ee), the beamstrahlung photon beams produced at each interaction point carry several hundred kilowatts of power, requiring a reliable and thermally efficient absorber. Building upon an initial slope-based liquid-lead concept, this work investigates two improved configurations: 1) a double-slope geometry, designed to mitigate photon backscattering observed in earlier designs; and 2) an inclined slope section with an accumulation pool at the back, intended to maximize photon absorption, reduce system size, and ensure thermal and flow stability. Both concepts operate under an inert argon atmosphere and target an effective absorption thickness of 10–20 cm, with a liquid-lead mass flow rate of approximately 300 kg/s. Monte Carlo simulations are employed to compute photon energy deposition, while multiphase computational fluid dynamics (CFD) analyses characterize the coupled thermal and hydrodynamic behavior. The results compare the performance of the two configurations and identify key parameters for further optimization of the FCC-ee liquid-lead photon dump system.
Paper: MOP7139
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7139
About: Received: 12 May 2026 — Revised: 18 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
MOP7186
CAD integration for the PETRA IV project
1106
The PETRA IV project at DESY in Hamburg aims for a new, 4th generation light source with first light in 2032. It comprises the installation of a completely new, 2.3km long 6GeV electron storage ring and a new injection chain, installation and refurbishment of 31 photon beam lines with 60 end stations, and the construction and refurbishment of 49 buildings including a new 600m long underground experimental hall. The project will reuse existing tunnels and halls of the PETRA III light source, and targets a dark time without beam of only 30 months, which is a challenging task that requires thorough planning. To meet this challenge, a comprehensive CAD model has been set up that integrates the data of all participants: construction, photon science, accelerator, campus and logistics. The model comprises representations of all systems and subsystems in different abstraction levels. A strict structure aligned with the project’s WBS and PBS, extensive use of interfaces, and a focus on review and change management processes ensure that the model is complete, consistent and correct and will remain so throughout the entire life cycle of the project.
Paper: MOP7186
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7186
About: Received: 13 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
TUP2002
Operational aspects of crab cavities at the Elettra 2.0 storage ring light source
1276
We investigate the upgrade of the Elettra 2.0 diffraction-limited storage ring light source with radiofrequency transverse deflecting cavities generating picosecond-long X-ray pulses of moderate intensity and high repetition rate. Based on a preliminary RF design, operational aspects, challenges and solutions to make the crab cavity scheme simultaneous to the standard operation of the facility, are presented and discussed, also in view of the users’ community wish list.
Paper: TUP2002
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2002
About: Received: 21 Apr 2026 — Revised: 19 May 2026 — Accepted: 19 May 2026 — Issue date: 22 May 2026
TUP2602
Progress of physics studies and beam commissioning of the High Energy Photon Source
1367
The High Energy Photon Source (HEPS) is a 35-pm, 1360-m storage ring light source being built in the suburb of Beijing, China. The HEPS construction started in 2019, with the main civil construction finished at the end of 2021. In the past two years, the beam commissioning of the HEPS storage ring had been started and bascially finished. In this paper, we will briefly introduce commissioning of the HEPS storage ring, and relavent physics studies.
Paper: TUP2602
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2602
About: Received: 11 May 2026 — Revised: 18 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
TUP2612
Preliminary lattice design to the 1 pico-meter level emittance for the Southern Advanced Photon Source
1382
The pursuit of diffraction-limited storage rings has driven emittance targets into the picometer regime. This paper presents a novel Single Hybrid Multi-Bend Achromat (SH-MBA) lattice design for the Southern Advanced Photon Source (SAPS), targeting an emittance at the 1 pm level. The compact SH‑16BA design, operating at 3.5 GeV with 36 periods and a 945 m circumference, employs high‑gradient quadrupoles, reverse bends, and longitudinal gradient bends. While collective effects such as Intra‑Beam Scattering allow the equilibrium emittance to reach the diffraction limit for hard X‑rays, the most critical challenge lies in nonlinear dynamics optimization. The required sextupole strengths are extremely high, generating nonlinear driving terms three orders of magnitude larger than in typical 4th‑generation sources and restricting the dynamic aperture to about 1 mm. This work demonstrates that achieving a reliable 1 pm-level design will require novel methods to suppress these severe nonlinearities.
Paper: TUP2612
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2612
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP2672
Design of a 10-MHz high-energy-resolution light source
1472
High energy resolution is essential for advanced spectroscopic studies of quantum materials, especially for resolving low-energy electronic features in angle-resolved photoemission spectroscopy (ARPES). However, existing light sources for ARPES still face difficulties in simultaneously providing narrow bandwidth and high photon flux. We are developing a 10-MHz coherent light source based on angular-dispersion-induced microbunching (ADM), aiming to generate narrow-band radiation with sub-meV-level energy resolution. Start-to-end simulations from the injector to the radiator have been performed to evaluate the beam dynamics and radiation performance. The simulation results show that the proposed source can provide sub-meV-level energy resolution and a photon flux above $10^{12}$ photons/s over a broad photon-energy range.
Paper: TUP2672
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2672
About: Received: 13 May 2026 — Revised: 19 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
TUP2688
A novel method for measuring the energy spectrum of an inverse Compton scattering source based on nuclear resonance fluorescence
1509
We proposed a novel method of using nuclear resonance fluorescence (NRF) as a probe for spectrum measurements. By utilizing the continuous tunability of an ICS source, NRF photons can be excited at different points across the spectrum. The shape of the energy spectrum can then be effectively scanned and reconstructed by recording the relative NRF yields at different energy points. The feasibility of the proposed method was validated by Geant4 simulations of measuring NRF photon emission from 56Fe irradiated by an ICS source. The simulation results showed high precision for quasi-monochromatic gamma ray spectrum measurements, with a normalized root mean square error (NRMSE) of less than 5%. To maintain a sufficient signal-to-noise ratio (SNR) during the measurement, the energy resolution of detectors is suggested to be less than 1% of the energy being measured. Given an energy tuning precision of Delta E, the minimum measurable width of the energy spectrum, in terms of standard deviation, can reach 0.85 Delta E.
Paper: TUP2688
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2688
About: Received: 13 Apr 2026 — Revised: 17 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
TUP2707
Study on polarization control of planar undulator system based on magnetic field modulation
1535
The fast polarization switching of undulator radiation has attracted more and more attention in recent years. Recently, a new method has been proposed for fast polarization switching up to kilohertz of undulator radiation by using magnetic field modulation generated from low-current electromagnetic coils. Through fast switching the power of coils, the radiation spectra of two undulators can be rapidly shifted into and out of the bandpass of a monochromator, enabling fast polarization switching for the user beamline. In this paper, we have studied the performance of the scheme using planar undulators. The performance of related parameters, such as photon flux, polarization degree, and spot distribution, will be reported.
Paper: TUP2707
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2707
About: Received: 18 May 2026 — Revised: 21 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
TUP2708
The essence factor to deteriorate the circular polarization radiation performance in APPLE-KNOT undulator
1539
The APPLE-KNOT undulator forms composite magnetic fields by superimposing APPLE and KNOT fields with different period lengths. In this configuration, in which the APPLE field serves as the dominant component to approximate the target photon energy, while the KNOT field acts as an additional component to transversely deflect the electron beam off-axis. Although variable polarization modes can be realized with a low on-axis heat load, previous studies have observed a sharp reduction in flux and significant degradation of the polarization degree in the circular polarization (CP) mode. This paper discusses this phenomenon in detail from a theoretical perspective. The analysis reveals that the presence of an additional field with a longer period is the essence factor that inherently suppresses the radiation performance of CP mode. Theoretical findings are highly consistent with simulation results, demonstrating that selecting the KNOT field as the dominant component can effectively improve CP characteristics without significantly compromising the linear polarization performance.
Paper: TUP2708
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2708
About: Received: 15 Apr 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7358
Reconfiguration options for reusing a permanent magnet undulator as a low-field wiggler source
1778
The Canadian Light Source (CLS) currently operates a 1.9 T superconducting wiggler (SCW) that has been in service since 2005. As the risk of failure and maintenance requirements for this aging device increase, and funding for a permanent replacement remains pending, an interim solution is needed to ensure continued beamline operation. Reconfiguring a decommissioned permanent magnet undulator offers a cost-effective alternative that could minimize downtime. Several approaches to modifying the magnetic layout to enhance wiggler performance are under consideration, with the goal of reusing existing mechanical supports, permanent magnets, and vacuum chambers. Proposed modifications include reducing the gap and halving the magnetic period to achieve the desired field characteristics.
Paper: TUP7358
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7358
About: Received: 08 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7364
Building a MOPA laser for H- beam shaping
1784
We present the design and initial amplification stages of a seeded Master Oscillator Power Amplifier (MOPA) laser for H- beam shaping applications. Customizable modulation of the input (seed) laser pulse shape will be shown to optimize the amplified laser pulse shape output at the nanosecond level, allowing for high speed ‘notching’ or ‘trimming’ of photo-ionized H- bunch shapes. By matching the laser pulse train shape to the inverse of the desired H- bunch shape, the design of our laser system will be theoretically applied to the selective longitudinal neutralization of low energy (1 MeV) H- beams. Theoretically needed pulse energies for high percentage photo-ionizations above 99.9% will be presented and challenges for reaching the required laser pulse energies and repetition rates will be discussed. Finally, we will examine the potential for using these custom laser pulse trains to trim residual tails the H- beam through complex laser pulse shape and multiple laser – bunch interactions in a specially designed high reflectively laser cavity, reducing the total power required to reach high neutralization efficiency.
Paper: TUP7364
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7364
About: Received: 13 May 2026 — Revised: 21 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7655
Validation of an Improved Quadrupole Design for the 3 GeV SPS-II Storage Ring.
1895
Achieving high beam stability in the 3 GeV SPS-II storage ring critically depends on the precision of its quadrupole magnets.This work presents a crucial phase of the magnet prototype development, which is central to fostering domestic high-technology manufacturing with Thai industry partners.Field measurements on the initial quadrupole design featuring removable poles revealed a critical engineering issue of significant multipole errors caused by mechanical pole rotation. This error was traced to the stresses and assembly error that occurred during pole removal and re-assembly for coil installation.To solve this specific problem, an improved quadrupole design was employed.The new symmetrical geometry eliminates the pole-removal step, thus intrinsically preventing the assembly error and significantly increasing structural stability and field quality. Coupled mechanical-magnetic analysis using ANSYS Workbench and Opera-3D confirms this approach. The simulations demonstrate that the improved design provides the required mechanical stability to minimize multipole field errors. The data presented validates this successful design change. The strict production tolerances were defined, and it is demonstrated precisely how the new design resolves the pole rotation issue. The presentation will feature a direct comparison of magnetic field measurements from both the initial and the improved prototypes, definitively verifying the enhanced performance necessary for SPS-II commissioning.
Paper: TUP7655
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7655
About: Received: 13 May 2026 — Revised: 21 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7656
Influence of current excitation profiles on screening-current effects in REBCO bending magnets for the Hefei advanced light facility
1898
ReBCO coated conductors are promising for compact high-field bending magnets and are being considered for use in the Hefei Advanced Light Facility (HALF) to enhance the photon energy from bending-magnet radiation. However, screening-current effects induced during excitation remain an important issue for such magnets. In this work, these effects are investigated in the proposed bending magnet using the H-formulation. Several current excitation profiles with different ramping and holding stages are compared. The results show that the charging history strongly affects screening-current relaxation and the induced-field distribution. Under the present conditions, final holding at the operating current is more effective than a slow final ramp or distributed intermediate holding, providing guidance for optimizing charging schemes for future ReBCO bending magnets.
Paper: TUP7656
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7656
About: Received: 11 May 2026 — Revised: 16 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
TUP7660
Strain gauge implementation for a Nb_3 Sn superconducting multipole wiggler developed in KEK Photon Factory.
1905
KEK Photon Factory is developing a Nb_3 Sn superconducting multipole wiggler (SC-MPW) for a next generation light source ring. The test coil unit has three round Nb_3 Sn coils and works as a three-pole wiggler. Nb_3 Sn superconductivity is strain sensitive, and training of resin impregnated Nb_3 Sn magnets could be limited by wire motion or cracks of the resin. Thus, it is important to monitor strain variation during cooling and excitation processes. Following the Unit 1 [1], we conducted an excitation test of the Unit 2 at the current density of 378 A/mm². In this test, one of the purposes is to validate a new strain measurement system that was first introduced into the Unit 2. Multiple strain gauges were attached to the magnet for monitoring strain variation. The strain measurement points were determined by ANSYS-FEM simulation. We also compared the simulation results with the measured values to assess our FEM model. In the future, we plan to conduct excitation tests at the target current density of 1000 A/mm², In the test, the strain-monitoring system will be implemented to the quench detection. We will report on the test results of the Unit 2 and progress of the next excitation test. [1] C. Mitsuda, et al.: Proc. IPACʼ25, Taipei, Taiwan Aug.(2025) p.1851-1854
Paper: TUP7660
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7660
About: Received: 13 May 2026 — Revised: 21 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7669
Development of a GaN-FET-based fast corrector magnet power supply for the TPS
1923
A modular GaN-FET-based fast corrector magnet power supply has been developed for the Taiwan Pho-ton Source (TPS). The high switching speed of GaN devices enables a significant increase in the output current bandwidth, which improves the response of the fast orbit feedback (FOFB) system and enhances the overall beam stability and photon beam quality of TPS. In the existing FOFB system, the operating current of the corrector magnet power supply is within ±5 A. The developed power supply provides a maximum output current of ±5 A and achieves improved current resolu-tion by optimizing the internal turn ratio of the DC current transformer (DCCT). A digital control architec-ture is implemented, integrating an ADC interface, interlock protection, and a PI controller, and is fully compatible with the TPS control system. With a switch-ing frequency of 250 kHz, the proposed power supply achieves a current control bandwidth of approximately 9 kHz, providing a significant improvement over the existing system.
Paper: TUP7669
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7669
About: Received: 15 Apr 2026 — Revised: 15 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUP7681
Advances in large-scale non-evaporable getter coating techniques for the Hefei Advanced Light Facility
1940
The Hefei Advanced Light Facility (HALF), currently under construction, is a fourth-generation synchrotron radiation source operating in the low-energy region (2.2 GeV) and based on diffraction-limited storage ring technology. The storage ring employs a modified hybrid 6BA lattice with a beam emittance of 86.3 pm·rad and consists of 20 achromat cells with a total circumference of approximately 480 meters. To meet the ultra-high vacuum environment of the storage ring, non-evaporable getter (NEG) films are applied to the inner surfaces of the vacuum chambers to provide distributed pumping capability and to reduce surface outgassing and photon-stimulated desorption. Large-scale NEG coating of the HALF storage ring vacuum chambers has been officially initiated. This paper presents an overview of the HALF storage ring vacuum system and provides a systematic description of the large-scale NEG coating system, including the equipment configuration and control system. In addition, a storage system for coated vacuum chambers is described to ensure film quality prior to installation, which provides technical support for subsequent assembly and commissioning.
Paper: TUP7681
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7681
About: Received: 15 Apr 2026 — Revised: 16 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
TUP7689
Design of photon absorbers for the SPring-8-II vacuum system
1952
SPring-8-II, the forthcoming fourth-generation light source upgrade of SPring-8, aims to achieve X-ray brilliance approximately two orders of magnitude higher than that of the current facility by reducing the electron beam emittance to 100 pm·rad or less. To accommodate the narrow-bore five-bend lattice, the vacuum system features discrete photon absorbers with dedicated pumps along with compact thin-walled stainless steel chambers*. Two types of photon absorbers have been designed to withstand a total power of up to 2.25 kW and a peak power density of up to 224 W/mm², respectively. The absorber design incorporates a grazing incidence angle on the irradiation surface to reduce power density, a shielding structure designed to confine scattered radiation, and a flange integrated without brazing or welding to eliminate the risk of vacuum leaks. Copper-chromium-zirconium (CuCrZr) was chosen as the material for its superior thermal conductivity and high yield strength. Finite-element analysis using ANSYS was employed to optimize the cooling-channel layout and to ensure compliance with maximum allowable temperature and stress limits.
Paper: TUP7689
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7689
About: Received: 13 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
TUP7690
Beam lifetime evaluation based on simulation of a vacuum pressure distribution for the SPring-8-II commissioning strategy through vacuum conditioning
1956
SPring-8-II, a major upgrade of the third generation light source SPring-8, aims to achieve low emittance below 100 pm·rad and to reduce the power consumption of the light source machine. High magnetic field magnets for SPring-8-II naturally result in narrow bore diameters and are densely distributed. As a result, vacuum chambers along the entire storage ring are designed with narrow apertures, leading to low conductance, and space for vacuum equipment such as photon absorbers and vacuum pumps is limited. To meet these requirements, we employ small-diameter stainless steel chambers and discrete compact photon absorbers*. Non-Evaporable Getter (NEG) pumps are placed near photon absorbers to effectively evacuate photon stimulated desorption (PSD) gas. We simulated a pressure distribution within a SPring-8-II unit cell as a function of beam dose considering the degradation of a pumping speed of the NEG pump due to gas absorption. On the basis of these results, we evaluated the beam lifetime and formulated a commissioning strategy for increasing a stored current through systematic vacuum conditioning.
Paper: TUP7690
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7690
About: Received: 13 May 2026 — Revised: 16 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7695
Development and Validation of Aluminum Vacuum Chamber Prototypes for the SPS-II Storage Ring
1967
The development of the Siam Photon Source II (SPS-II), a fourth-generation light source, represents a significant leap in Thailand’s synchrotron infrastructure. A primary objective of the project is the establishment of domestic technical expertise and industrial capability for producing high-precision vacuum components. This paper details the manufacturing and geometric validation of two critical aluminum alloy prototypes: a straight-section chamber and a bending chamber. Key technological advancements include the optimization of domestic aluminum extrusion processes to achieve ultra-high vacuum (UHV) surface requirements and the implementation of oil-less, ethanol-cooled CNC machining to eliminate hydrocarbon contamination while maintaining high precision. A comprehensive metrology framework, utilizing laser trackers and high-resolution profiling, was employed to characterize manufacturing-induced distortions. Results confirm that the integrated fabrication workflow, which combines specialized internal fixturing and multi-pass TIG welding, successfully maintains the stringent geometric tolerances required for the storage ring. This work validates the technical readiness of Thailand’s industrial sector for the full-scale production of the SPS-II vacuum system.
Paper: TUP7695
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7695
About: Received: 15 Apr 2026 — Revised: 19 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
TUP7704
Improvement and optimization of a permanent-magnet phase shifter
1978
A permanent-magnet (PM) phase shifter for phase matching between tandem elliptically polarizing undulators (EPUs) at the Taiwan Photon Source (TPS) has been developed, and its initial version has already been installed in the storage ring. Current efforts focus on improving the device by enhancing the mechanical precision of the gap-adjustment system, maintaining magnetic-field quality, and minimizing beam-orbit perturbations within the limited installation space. Magnet sorting and shimming techniques were used to refine the magnetic performance of the first version. At small operating gaps, strong magnetic forces introduce substantial mechanical loading and can affect the field directionality. To overcome this limitation, an upgraded design incorporating a spring-assisted mechanism is under development. This work presents the optimization approach and the resulting improvements achieved through the integration of the spring system, demonstrating enhanced structural stability and improved reproducibility under high-force operating conditions.
Paper: TUP7704
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7704
About: Received: 13 May 2026 — Revised: 16 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
TUP8016
Development of VHEE Scattering Systems for FLASH Radiotherapy
2064
Very High Energy Electrons (VHEE) are an emerging radiotherapy modality offering magnetic steering and focusing for conformal treatments, with potential for compact, cost-efficient clinical systems. VHEE beams may also enable Ultra-High Dose Rate (UHDR) delivery for the FLASH effect, which can selectively spare healthy tissue while maintaining tumour toxicity. A key challenge is achieving transversely uniform VHEE dose at UHDR, as current magnets cannot scan large tumour volumes within FLASH timescales (~0.1 s). Conventional dual-scattering systems—using a pre-scatterer for magnification and a Gaussian scatterer for flattening—are unsuitable at VHEE energies, generating substantial photon contamination unless the beamline is greatly extended. This work replaces the pre-scatterer with a quadrupole lattice that magnetically enlarges the beam while reducing Bremsstrahlung. RF-Track and TOPAS simulations show that an optimised quadrupole-scatterer design produces a 75 mm uniform field and reduces photon yield by 94.5% compared with dual-scattering. BDSIM confirms the modelling. Experimental validation at CLEAR at CERN is in preparation, and an optimiser is being developed to design quad-scatterer systems for generic VHEE machines using existing quadrupoles. These results suggest that magnetic beam magnification upstream of a Gaussian scatterer is a promising route to FLASH-compatible VHEE therapy with reduced secondary radiation and improved dose conformity.
Paper: TUP8016
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP8016
About: Received: 16 Apr 2026 — Revised: 20 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
WEP5046
Beamstrahlung and Pair Production Under IP Aberrations at the FCC-ee
2676
Beamstrahlung and secondary pair production are relevant sources of backgrounds but can also be exploited as potential tuning signals at the FCC-ee. They depend on possible interaction point (IP) optics errors and on general beam–beam conditions. Using GUINEA-PIG, we simulate beamstrahlung photons, and pair production through Breit–Wheeler, Bethe–Heitler, and Landau–Lifshitz processes and analyse the spectra, emitted power, and pair count for different sets of IP aberrations, including waist shift, vertical dispersion, and transverse coupling. The resulting photon and pair energy–angle distributions are examined, where comparisons with analytical expectations allow for consistency checks. We also compare GUINEA-PIG beamstrahlung predictions with multi-turn results delivered by the newly adopted code Xsuite, for a further benchmarking of Xsuite's beam-beam simulation package. Our study sheds light on possible beamstrahlung-related signals at the FCC-ee, including electron-positron pair production, and their dependence on the quality of the IP optics tuning.beamstrahlung-related signals at the FCC-ee, including electron-positron pair production, and their dependence on the quality of the IP optics tuning.
Paper: WEP5046
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5046
About: Received: 13 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
WEP5129
Benchmarking of the PENELOPE/PENH and PHITS codes for calculation of beam quality correction factors in therapeutic proton beams
2873
This work benchmarks the PENELOPE/PENH (2021 version) and PHITS Monte Carlo codes for calculating beam quality correction factors (kQ) in therapeutic proton beams. The latest PENH extension to PENELOPE enables proton transport simulation, including an approximate description of nuclear reactions and neutron production. PHITS, conversely, is an established multi-particle transport code covering protons, neutrons, and electron-gamma showers. The study compares simulated absorbed doses and kQ factors by modeling three configurations: a thin reference water cavity, a plane-parallel air cavity, and a cylindrical air cavity (representing typical ionization chambers). To determine the kQ factors, simulations involve a 1.25 MeV photon reference beam (Cobalt-60) and a 150 MeV monoenergetic proton beam. The computed results are validated against equivalent simulations published in the literature and obtained using FLUKA and GEANT4/TOPAS. This comparison assesses the suitability and consistency of the PENELOPE/PENH and PHITS codes for accurate clinical proton beam dosimetry.
Paper: WEP5129
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5129
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
WEP5130
Benchmarking the PENH Monte Carlo Code Against PHITS: Assessment of Proton Depth-Dose
2877
This study provides a benchmark of the PENELOPE/PENH (2021 version) Monte Carlo code for proton transport using reference results from the established PHITS code. The comparison focuses on absorbed-dose distributions generated by a finite-spot proton pencil beam. Integrated depth-dose curves were simulated for monoenergetic beams ranging from $100 \text{ to } 250 \text{ MeV}$ incident on a water phantom. The degree of agreement between PENH and PHITS is quantitatively assessed for depth-dose behavior. The results evaluate PENH’s accuracy and establish its suitability for general proton transport applications.
Paper: WEP5130
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5130
About: Received: 13 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
WEP5138
Progress and Developments of Beam Delivery Simulation (BDSIM)
2893
Beam Delivery Simulation (BDSIM) is a Monte Carlo program (written in C++ ) that creates a 3D radiation transport model designed for the simulation of accelerators and beamline modelling. BDSIM uses Geant4 for precise particle-matter interactions combined with particle-tracking through 3D geometries of accelerators and their environments. All particle species are tracked, allowing for studies for collimation, beam losses, secondary radiation generation, and dosimetry. BDSIM allows for detailed customisation, with numerous applications in the design of high-energy physics facilities, medical beamlines, particle detection experiments, and novel acceleration experiments. Recent developments to BDSIM are presented, including; updated BDSIM deployment methods, development of regression testing, coupling between Xsuite, RF-track and bdsim, updates to the muon cooling modelling, updates to medical modelling for loading DICOM files, applications of BDSIM for FCC-ee, and general updates including optical physics examples. Information on the formation of the BDSIM collaboration community are also detailed.
Paper: WEP5138
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5138
About: Received: 13 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
WEP6089
Feasibility of Non-invasive OSR Diagnostics in the AWAKE run-2C Injection Region
3120
AWAKE is CERN's proton-driven plasma wakefield acceleration experiment, currently advancing toward Run-2c to demonstrate the higher energy acceleration of electrons while maintaining the beam quality. A second electron beam (of 150 MeV energy), produced in a newly installed electron source, will be injected and accelerated to several GeVs while aiming to keep good emittance. Diagnostics are being upgraded for this geometrically constrained injection-region to enable single-shot characterization of that beam, among which this contribution evaluates the feasibility of optical synchrotron radiation (OSR) as a non-invasive real-time mean. OSR can provide shot-by-shot transverse position and profile information without disrupting beam delivery, critical for benchmarking beam-alignment and quality check. The prompt, non-invasive nature also makes it a candidate for future virtual diagnostic implementations, where online beam profiles could inform predictive models or feedback correction schemes. For performance optimizations the expected OSR photon flux, photon statistics, projected image quality are computed with realistic imaging optics and detector quantum efficiency. Results demonstrate that sufficient OSR signal can be extracted through this compact optical chain to achieve meaningful single-shot transverse profile measurements.
Paper: WEP6089
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP6089
About: Received: 11 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
WEP6607
Longitudinal Beam Diagnostics with a Streak Camera at Taiwan Photon Source
3334
The Taiwan Photon Source (TPS) streak camera system has been used for longitudinal beam studies since the early commissioning stage. This paper first presents a representative high-current instability observation associated with the CU15 insertion device taper and then recent measurements of bunch length and synchronous phase under operation with the superconducting RF (SRF) + passive 3rd harmonic cavity (HC), here abbreviated as SRF HC. The CU15 case shows different instability behaviors along the fill pattern in streak images. The SRF HC measurements provide bunch-by-bunch information under different fill patterns and SRF HC settings for comparison of bunch lengthening and phase shift. Under operation with the passive SRF HC, a phase drift of about 35 ps is observed along the bunch train, consistent with transient beam loading under quasi-uniform filling. These measurements show that the streak camera is useful for longitudinal diagnostics and machine studies at TPS.
Paper: WEP6607
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP6607
About: Received: 15 Apr 2026 — Revised: 15 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
THP2084
SwissFELplus: a Mid-Term Upgrade Plan for the Swiss Free-Electron Laser
3606
SwissFEL, the free-electron laser facility at the Paul Scherrer Institute (PSI) in Switzerland, is about to complete its first decade of user operation. The knowledge gained during this period, together with important developments at FEL facilities worldwide, suggests a number of key upgrades to the accelerator and undulator complex that would substantially enhance the scientific capabilities of the two existing SwissFEL beamlines. The SwissFELplus project, planned for 2029-2032, aims to implement these upgrades - including full coherence in the hard- and soft-X-ray regimes via self- and external-laser seeding, as well as preparations for a new beamline - and thereby bring SwissFEL to a new level of scientific excellence ahead of its quantitative expansion with a third beamline. The resulting improvements in beam stability and coherence will benefit applications ranging from atomic physics to biology and will enable new approaches, such as quantum optics for X-rays, with its advantages in the management of radiation damage. This contribution describes the upgrade elements and their expected impact on SwissFEL’s photon-science capabilities.
Paper: THP2084
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2084
About: Received: 13 May 2026 — Revised: 13 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
THP2106
The compton backscattering source COBRA at the S-DALINAC
3644
The COBRA source (Compton Backscattering at a Recirculating Accelerator) utilizes a 100 W Yb:YAG laser that is synchronized with the electron beam of the superconducting Darmstadt linear accelerator S-DALINAC * for head-on collisions. The backscattered photons in the X-ray energy range can be collimated into a quasi-monochromatic beam for electron beam diagnostics and as a technology demonstrator. The first collision of the electron and laser beam is planned in an upcoming beamtime with multi-turn recirculation. During operation, COBRA utilizes stabilization systems for both beams. Later, COBRA is foreseen to be operated during energy-recovery mode **, serving as a demonstrator for future Compton scattering light sources. This contribution provides an overview of the COBRA source, highlighting recent upgrades to the detector setup and developments of the laser beamline.
Paper: THP2106
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2106
About: Received: 01 Apr 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP2136
Photoemission study of nanostructured plasmonic photocathodes
3714
We present a simulation study of a nanostructured plasmonic copper photocathode for use in the new photoinjector that is presently being developed for the high-duty-cycle operation upgrade of the European XFEL. The simulations are based on a spatially resolved photoemission model using the Fowler-DuBridge formalism and including the Schottky effect induced by the accelerating field on the cathode surface. Particle-in-cell simulations are performed to evaluate the phase-space of the beam in the near-cathode region. It is shown that while quantum efficiency is improved, photoemission from the plasmonic cathode leads to a substantially increased transverse emittance and higher energy spread of the beam compared to the case of a flat copper surface. Space-charge effects remain moderate for the operating bunch charge considered in the study.
Paper: THP2136
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2136
About: Received: 13 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
THP2152
The SOLEIL II insertion devices
3753
The SOLEIL II insertion devices will be presented. They range from long period Adjustable Phase Undulator of long period, APPLE X, Dual undulators for the intermediate energy spectral range, and in vacuum undulators, cryogenic permanent magnet undulators and wigglers for hard X-rays.
Paper: THP2152
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2152
About: Received: 11 May 2026 — Revised: 18 May 2026 — Accepted: 18 May 2026 — Issue date: 22 May 2026
THP2154
Design, training and magnetic field characterization of the superconducting THz-undulator coils for FLUTE
3761
FLUTE, a short-pulse linac and short-bunch THz test facility, serves as an accelerator test setup for a variety of accelerator physics studies. In its final stage of expansion, it is foreseen to provide coherent radiation in ultra-short, very intense light pulses in the terahertz and far-infrared spectral range. A superconducting undulator (SCU) at the end of the accelerator structure offers the possibility to generate photon radiation between 4 THz and 12 THz (energies between 16.5 meV and 50 meV) with a high pulse energy. This energy range, for instance, is of interest for studies of water-soluble interactions. The final undulator design was carried out by Bilfinger Nuclear & Energy Transition GmbH (BNET) in close collaboration with the Institute for Beam Physics and Technology (IBPT) of the Karlsruhe Institute of Technology (KIT). Before assembling the final undulator device the superconducting coils were trained and magnetically characterized in CASPER II, a magnetic measurement setup which is part of the Magnet and Cryogenics Facilities (MCF) at the IBPT at KIT. In this contribution we describe the general SCU layout, presenting the results of the coil training, the local magnetic field characterization and field integral minimization of the THz-undulator coils.
Paper: THP2154
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2154
About: Received: 12 May 2026 — Revised: 18 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
THP2155
Upcoming insertion devices at MAX IV facility
3765
Currently, there are 17 Insertion Devices (ID) in operation at the MAX IV facility. The soft X-ray undulators are based on the 3 APPLE II undulator at the 3 GeV ring, 4 APPLE II and 1 planar undulators at the 1.5 GeV ring, and the hard X-ray IDs are based on room-temperature in-vacuum technology at the 3 GeV ring and the Short Pulse Facility. A recently funded Tomography beamline for materials science at the 3 GeV ring will utilize two sources within the same straight section: a short-period cryogenic permanent magnet undulator (CPMU) with a 14 mm period length for nano-tomography and a 3 T 3-pole wiggler for micro-tomography. Both IDs are currently in production, with installation planned for summer 2027. Further developments include a planned tender hard X-ray (2–20 keV) spectroscopy beamline and a new medical-imaging beamline covering an energy range of 15–80 keV at the 3 GeV ring. At the 1.5 GeV ring, a new APPLE II undulator providing polarization control from 50 eV photon energy is foreseen to replace an older planar undulator. In this paper, we present the parameters of these upcoming insertion devices and provide estimates of their expected performance.
Paper: THP2155
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2155
About: Received: 04 May 2026 — Revised: 18 May 2026 — Accepted: 18 May 2026 — Issue date: 22 May 2026
THP2157
Demonstration of a transverse gradient undulator in an X-ray free-electron laser
3772
Modern synchrotron light sources employ various types of undulators to generate highly coherent and well collimated X-rays. A large and homogeneous magnetic field around the beam axis is typically the preferred configuration, since it simplifies both alignment and operation. Nevertheless, a nonhomogeneous field, such as that of a transverse gradient undulator (TGU), offers attractive possibilities for advanced operating modes, for example enabling large bandwidth operation in a free electron laser. In this contribution, we present the first beam-based characterization of such a TGU for various magnetic field gradients and X-ray polarization settings, and we compare the experimental results with corresponding simulation data. The measurements were carried out at Athos, the soft x-ray beamline of SwissFEL. This line employs Apple X undulators, whose independent radial and shift motion of all four magnetic arrays makes them uniquely capable of generating the required transverse gradients.
Paper: THP2157
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2157
About: Received: 18 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
THP2158
The first APPLE X knot undulators: magnetic characterization and initial performance
3775
Concepts for reducing on-axis heat load become essential as photon flux increases in next-generation synchrotrons, especially in the soft X-ray regime. Therefore, APPLE “knot” undulators are promising insertion devices, as they divert most of the energy off-axis without compromising polarization purity. The first two APPLE X knot undulators, 2 m long and with a period of 36 mm, were designed and built at Paul Scherrer Institute (PSI) and installed into the newly upgraded Swiss Light Source (SLS2.0) electron storage ring. This contribution presents the final magnetic characterization results of the novel undulators and derives photon characteristics, including how effectively the radiation power is expected to be reduced on-axis in contrast to a regular elliptical undulator, especially in linear modes. Further, their initial performance with the beam is demonstrated, providing a glimpse of the ongoing beamline commissioning and operation.
Paper: THP2158
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2158
About: Received: 13 May 2026 — Revised: 19 May 2026 — Accepted: 19 May 2026 — Issue date: 22 May 2026
THP5362
A level set based immersed boundary method for modeling phase transition dynamics in high-energy-density beam simulations
4274
In this work, we present a numerical method for modeling phase transitions in solid–liquid–plasma systems under the high-energy-density conditions generated by beam strikes in fourth-generation storage-ring light sources. Our approach extends prior level set immersed boundary techniques by employing a signed distance function to represent multiphase interfaces and by coupling interface evolution to local velocities and latent-heat transfer laws. Compared to existing tagging methods, where each computational cell is heuristically labeled as solid, liquid, or plasma based solely on temperature thresholds, our level set formulation yields substantially higher fidelity. Tag-based methods inherently produce poorly-resolved interfaces and rely on simplified assumptions about phase transition. In contrast, the signed-distance representation provides smooth, sub-cell resolution of phase boundaries, enabling a more accurate application of interface-aware forcings and boundary conditions. Furthermore, interface advection governed by latent-heat transfer, rather than threshold-based switching, results in a more physically realistic description of phase transition dynamics. We demonstrate that this level-set-based immersed boundary framework significantly improves the accuracy and robustness of multiphase beam-impact simulations in high-energy-density environments, providing a foundation for predictive modeling in next-generation light-source facilities.
Paper: THP5362
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5362
About: Received: 12 May 2026 — Revised: 18 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
THP5636
Benchmarking impedance calculations for two types of transition structures in HALF: CST vs. ECHO3D
4346
Photon masks and tapered transitions in the Hefei Advanced Light Facility (HALF) storage ring are typical transition structures that can make non-negligible contributions to the geometric impedance. In this work, ECHO3D is used to benchmark the CST calculations for these two types of structures. The longitudinal and transverse wake potentials, the corresponding impedance spectra, and the resulting loss factor, kick factor, and effective impedance are analyzed and compared. This study provides a reference for impedance evaluation of these transition structures in HALF.
Paper: THP5636
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5636
About: Received: 15 Apr 2026 — Revised: 09 May 2026 — Accepted: 15 May 2026 — Issue date: 22 May 2026