undulator
MOXP1
The operational challenges: Achieving 500 mA high beam current at Taiwan Photon Source
1
The Taiwan Photon Source (TPS) has been in routine operation at 500 mA since the last season of 2021, utilizing two superconducting cavities, bunch by bunch feedback system, and fast orbit feedback system, along with many technical efforts. The operation of TPS maintains its high reliability and availability. The mean time between failures is more than 190 hours with an availability greater than 98.9% in 2023. With newly developed cryogenic permanent magnet undulators, IVUs, and EPUs, balancing the needs of both soft X-ray and hard X-ray users. Many challenges have been encountered in the journey to achieving a beam current of 500 mA, primarily due to the short bunch length of 16 ps and impedance issues in vacuum chambers at TPS storage ring. Ongoing efforts to improve the performance and the detailed journey to achieving 500 mA top-up operation will be presented.
Paper: MOXP1
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOXP1
About: Received: 23 May 2025 — Revised: 29 May 2025 — Accepted: 31 May 2025 — Issue date: 10 Jul 2025
MOPB007
Echo-enabled harmonic generation at the DELTA storage ring
87
Echo-enabled harmonic generation (EEHG) has been proposed as a seeding method for free-electron lasers but can also be employed to generate ultrashort radiation pulses at electron storage rings. With a twofold laser-electron interaction in two undulators ("modulators"), each followed by a magnetic chicane, an electron phase space structure with high harmonic content is produced, which gives rise to coherent emission of radiation at short wavelengths. The duration of the coherently emitted pulses in a third undulator ("radiator") is given by the laser pulse durations. Thus, EEHG pulses can be three orders of magnitude shorter but still more intense than conventional synchrotron light pulses. The worldwide first storage ring implementation of EEHG was undertaken at the 1.5-GeV synchrotron light source DELTA at TU Dortmund University by reconfiguring an electromagnetic undulator. With a total length of only 4.75 m, the setup is very compact and fits in a single straight section. The paper presents technical aspects of the EEHG implementation as well as first results.
Paper: MOPB007
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB007
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
MOPB015
Tapering enhanced superradiance - tapering rate optimization using analytical magnetic field maps
98
THz sources are typically very limited in power, making high-power sources scarce. One of the most promising THz sources are the Free Electron Lasers (FELs), which can generate high-power THz radiation using an undulator structure. Undulator radiation is an incoherent synchrotron spontaneous emission whose energy is proportional to the number of particles in the beam (𝑁). By longitudinally bunching the charged particle beam, a coherent spontaneous emission is generated and referred to as a super-radiant emission. Unlike spontaneous emission, super-radiant energy yield is proportional to N^2. However, like typical FELs, the energy conversion efficiency is rather low. Here, we demonstrate a novel THz source structure based on a radiative interaction scheme of super-radiance – Tapered Enhanced Super-radiance (TES), which employs a tapered (amplitude) undulator in the zero-slippage condition. This method yields a significantly more powerful and efficient THz radiation source. An optimization algorithm was developed to obtain a tapering rate that yields the most efficient energy conversion from the electron beam to the radiation field.
Paper: MOPB015
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB015
About: Received: 02 Jun 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
MOPB021
Commissioning of the soft X-ray variable polarization afterburner at the European XFEL
106
Following the successful commissioning of the soft X-ray planar undulator system (SASE3), the European XFEL user community expressed a strong demand to extend the radiation properties and provide the possibility to obtain variable polarization modes. It was therefore decided to build a helical afterburner behind the SASE3 system in collaboration with Paul Scherrer Institute (PSI). The final installation of the undulators in the tunnel took place at the beginning of 2024. Since then, a series of measures have been taken to commission four APPLE-X undulators, which form the base for the helical afterburner. The main objective is to maximally suppress the linear polarization of planar undulators in order to obtain the purest radiation from helical undulators. The methods and results of the optimization to achieve a maximum contrast between the pulse intensity generated by planar and helical undulators as well as the operating experience are presented.
Paper: MOPB021
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB021
About: Received: 26 May 2025 — Revised: 01 Jun 2025 — Accepted: 01 Jun 2025 — Issue date: 10 Jul 2025
MOPB022
Design of beam transport system integrating active plasma lens for laser-plasma-driven EUV free-electron lasers
110
Laser-plasma accelerators (LPAs) produce high-quality electron beams with the GeV-level of the energy, the high peak currents and low emittance, making them ideal for compact novel free-electron lasers (FELs). However, the large angular divergence and energy spread of these beams pose challenges for efficient beam transport and overall FEL performance. This study explores the use of an active plasma lens (APL) as a capture block to improve the transport of LPA-generated beams into an undulator. Initial beam parameters were based on published results from LWFA studies. In this report, we present the results of the modeling conducted to design an efficient LPA-based electron beamline and optimize the FEL regime for the extreme ultraviolet (EUV) range. Our goal is to achieve saturation of the photon beam power within a single unit. The results show that the APL enables efficient beam transport and facilitates the generation of high-brightness coherent X-rays. This work underscores the potential of APLs in developing compact FELs and advancing LPA beams. This technology is essential for creating a new generation of FELs at ELI-ERIC in the Czech Republic and within the EuPRAXIA project.
Paper: MOPB022
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB022
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 10 Jul 2025
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-IPAC25-MOPB028
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 10 Jul 2025
MOPB030
Averaged FEL algorithm to simulate an arbitrary FEL polarization
126
FEL simulation codes are essential tools for simulating various FEL scenarios. Among the algorithms, the orbit-averaged algorithm is the most widely used due to its speed and low computational cost. The averaged algorithm simplifies physics model, so present codes such as GENESIS and SIMPLEX have limitations to model accurate features like FEL polarization and variations in electron beam current. Such details are possible when using an unaveraged algorithm (like PUFFIN). In this presentation we introduce an approach based on the averaged algorithm to simulate arbitrary FEL polarization and non-fixed electron beam current. Our method involves initializing all particles at the beginning of the simulation and performing particle calculations at each simulation step to account for the non-fixed electron beam. Additionally, arbitrary FEL polarization is calculated by modifying the FEL equations using the elliptical undulator formula and the GENESIS algorithm. Finally some demonstration will be shown comparing the performance of PAL-XFEL and results from other simulation codes to highlight the capabilities of this approach.
Paper: MOPB030
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB030
About: Received: 29 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
MOPB034
Numerical simulation of on-axis helical undulator radiation using SCILAB-Xcos model
134
Abstract—A SCILAB Xcos model, developed using SCILAB software version 6.1.1, was implemented to simulate the on-axis radiation intensity of a helical undulator, (undulator parameter= 1, undulator wavelength 5cm, number of periods= 10, device length 0.6 m) with an electron beam (1, 2, & 3 GeV) and beam current as Ib = 3–6 × 10⁻⁶ Ampere. A numerical approach is utilized to perform the undulator radiation intensity calculations. The computed results were validated by comparing the on-axis undulator radiation intensity with those obtained from SPECTRA, an open-source synchrotron radiation (SR) calculation software.
Paper: MOPB034
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB034
About: Received: 13 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
MOPB035
Towards gamma-ray free-electron lasers
138
The free-electron laser (FEL), powered by an accelerator and equipped with an undulator, produces intense coherent radiation at ever-shorter wavelengths. Whilst the hard x-ray regime represents the current state of the art, the gamma-ray regime remains the next objective. Gamma-ray lasers, deemed one of the most profound and intriguing challenges in physics by the 2003 Nobel Laureate, hold the key to unlocking the largely unexplored nuclear domain. This article introduces a novel scheme that harnesses FEL harmonics, offering a pathway for existing x-ray FELs to operate as gamma-ray lasers.
Paper: MOPB035
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB035
About: Received: 15 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 10 Jul 2025
MOPB038
Bayesian optimization for generating attosecond X-ray FEL pulses
146
Ångström and attosecond represent fundamental spatiotemporal scales for studying electron dynamics in various materials. Recently, high-power attosecond hard X-ray pulses have been successfully demonstrated at the European XFEL using the self-chirping operation mode. However, the current process heavily depends on manual tuning by experienced operators, which is time-intensive and less scalable. In this work, we report recent advancements in automating and optimizing the generation of high-power attosecond X-ray pulses using Bayesian optimization techniques. By leveraging machine-learning-based approach, we aim to enhance pulse energy, spectral quality, and operational efficiency, paving the way for more accessible and reproducible attosecond X-ray experiments.
Paper: MOPB038
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB038
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 10 Jul 2025
MOPB066
Compensation of an elliptically polarizing undulator in the HLS-II storage ring
201
The insertion devices (IDs) can severely affect the beam dynamics of a storage ring. Recently, a new elliptically polarizing undulator(EPU) is installed in the Hefei Light Source II (HLS-II) storage ring. The effects of this EPU can be modeled using the kick map method. In this paper, we present the kick map of the EPU with vertical mode and how it affects the beam dynamics. Since the HLS-II storage ring is compact, only four quadrupoles in the same straight section can be used to compensated the ID effect. The compensation result is also reported in this paper.
Paper: MOPB066
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB066
About: Received: 21 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 10 Jul 2025
MOPB106
Optimizing Cherenkov waveguide seeding for THz SASE FELs towards stable, few-cycle pulses
250
The PITZ facility at DESY in Zeuthen has demonstrated the first operational high peak and average power THz self-amplified spontaneous emission (SASE) free electron laser (FEL). The current setup displays the onset of saturation at a central frequency of 3THz using a 3.5m long LCLS-I undulator. However, the THz user community has expressed the need for carrier-envelope phase (CEP) stability and the availability of few-cycle THz pulses to complement the currently demonstrated long pulses. In this work, simulations are conducted to evaluate and optimize FEL performance by incorporating a Cherenkov waveguide to seed the process. The waveguide parameter space is scanned to vary energy modulation depth and frequency, after which the performance is estimated using the space charge tracking algorithm, ASTRA, and the FEL simulation code, Genesis1.3. The optimized parameters allow saturation to be reached much earlier, while also significantly increasing the shot-to-shot stability. Down the line, the implementation of such a scheme would facilitate generation of few-cycle, CEP-stable THz pulses to be used in user experiments.
Paper: MOPB106
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB106
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
MOPB108
Coherent undulator radiation with account of the beam energy spread
254
When a microbunched beam is sent to a resonantly tuned undulator it radiates coherent radiation with the intensity propotional to the bunching squared of the beam. According to *, the radiated energy increases with the undulator length. This conclusion, however, is only valid if one ignores the energy spread of the beam (and also the beam angular spread). The finite energy spread smears the microbunching, ultimately suppressing coherent radiation beyond a certain distance. In this work, we calculate the radiation of a microbunced beam with an energy spread and find the maximum energy that it can radiate coherently.
Paper: MOPB108
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPB108
About: Received: 22 May 2025 — Revised: 30 May 2025 — Accepted: 03 Jun 2025 — Issue date: 10 Jul 2025
MOPM099
Accelerator and Compton gamma-ray source research program at Duke University
548
The accelerator and Compton gamma-ray source research program at Duke Free-Electron Laser Laboratory (DFELL), TUNL, is focused on the development of the storage ring-based free-electron laser (FEL) and a state-of-the-art Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS) driven by the storage ring FEL. With a maximum total flux of about 3.5E10 gamma/s and a spectral flux of more than 1,000 gamma/s/eV around 10 MeV, the HIGS is the world's highest-flux Compton gamma-ray source. Operated in the energy range from 1 to 120 MeV, the HIGS is a premier Compton gamma-ray facility in the world for a variety of nuclear physics research programs, both fundamental and applied. In this work, we will describe our recent FEL development to enable the production of gamma rays in the higher energy range from 100 and 120 MeV. We will also provide a summary of our recent activities in accelerator and FEL physics research and Compton gamma-ray source development.
Paper: MOPM099
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPM099
About: Received: 05 Jun 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
MOPS055
Magnet assembly of IVUE32 in-vacuum-APPLE II at BESSY II
741
At HZB / BESSY II the first in-vacuum APPLE II undu-lator is under construction. The design includes three magnet arrays for each of the four magnet rows for an efficient force compensation. The support and drive sys-tem has been delivered. Currently the magnets for the 10-period prototype are fabricated by Vacuumschmelze. Within the project IVUE32 a new soldering technique based on reactive foils has been developed in collabora-tion with Vacuumschmelze. The magnet structure of the IVUE32 undulator will employ the soldering technique aiming for enhanced assembly simplicity. Two new ex-perimental setups for the characterization of soldered subassemblies have been built for obtaining stress-strain curves and for lifetime (fatigue) tests. These instruments will be presented and measurements will be discussed.
Paper: MOPS055
DOI: reference for this paper: 10.18429/JACoW-IPAC25-MOPS055
About: Received: 19 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 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-IPAC25-MOPS056
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 10 Jul 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-IPAC25-MOPS060
About: Received: 25 May 2025 — Revised: 01 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 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-IPAC25-TUPM060
About: Received: 29 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 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-IPAC25-TUPM061
About: Received: 22 Apr 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 10 Jul 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-IPAC25-TUPM062
About: Received: 01 Apr 2025 — Revised: 31 May 2025 — Accepted: 04 Jun 2025 — Issue date: 10 Jul 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-IPAC25-TUPM066
About: Received: 13 May 2025 — Revised: 31 May 2025 — Accepted: 03 Jun 2025 — Issue date: 10 Jul 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-IPAC25-TUPM067
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 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-IPAC25-TUPM068
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 10 Jul 2025
TUPM070
Progress of SUNDAE2 magnetic measurement setup for superconducting undulators at European XFEL
1319
At European XFEL up to six superconducting undulators with 18 mm period and 1.83 T magnetic field are planned to enlarge the hard X-ray photon range above 30 keV. Currently, S-PRESSO, a prototype with 2x 2m long undulator sections plus phase shifter in a 5m long cryostat is being produced. The SUNDAE2 (Superconducting UNDulAtor Experiment 2) magnetic field test facility aims to perform in-vacuum magnetic field measurements of superconducting undulators (SCUs). This work provides an update on the progress of SUNDAE2, which employs Hall probe, moving wire, and pulsed wire techniques for precise magnetic field characterization to meet the specifications for the FEL operation.
Paper: TUPM070
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM070
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
TUPM071
Finalizing the multiphysics design of a high heat-load superconducting undulator
1322
RadiaBeam is developing and manufacturing a 15mm period, high temperature superconductor undulator using Magnesium Diboride (MgB2) wire at 10K-15K temperature range. This temperature range can be achieved by cryocooler, a simpler and less expensive cryogenic solution compared to a liquid helium approach. After optimizing the thermal-mechanical design, the operating temperature is finalized at 7K. We examine the current density, critical field, tensile stress, tensile strain, and temperature of MgB2 wire in multiphysics approach and determine the operating field to be 1.13T with safety margin. A quench-protected power system is developed for training the SCU to the operating point in controlled ramp rate. The SCU will be characterized by in-vacuum pulse wire measurement system.
Paper: TUPM071
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM071
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 31 May 2025 — Issue date: 10 Jul 2025
TUPM072
Two in-vacuum undulators developed for the Sirius
1326
The Shanghai Synchrotron Radiation Facility (SSRF) project team developed two in-vacuum undulators (IVUs) with a period length of 18.5 mm and a gap of 4 mm for the SIRIUS. This paper introduces the design and magnetic field measurements. The results indicate that with a gap range of 4-20 mm, the phase error is less than 3°, the quadrupole field is less than 37 Gs, the sextupole field is less than 83 Gs/cm, and the octupole field is less than 84 Gs/cm².
Paper: TUPM072
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM072
About: Received: 27 May 2025 — Revised: 31 May 2025 — Accepted: 14 Jun 2025 — Issue date: 10 Jul 2025
TUPM095
Coherent high-harmonic generation with laser-plasma beams
1379
Active energy compression scheme enables generating laser-plasma accelerator electron beams with a small relative slice energy spread, of the order of 10 ppm. When modulated by a laser pulse, such beams can produce coherent radiation at very high, about 100-th harmonics of the modulation laser wavelength, which are hard to access by conventional techniques. The scheme has a potential of providing additional capabilities for future plasma-based facilities by generating stable, tunable, narrow-band radiation.
Paper: TUPM095
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPM095
About: Received: 06 May 2025 — Revised: 29 May 2025 — Accepted: 01 Jun 2025 — Issue date: 10 Jul 2025
TUPS089
Helical undulators assembled from magnetized ring sectors
1588
Undulators assembled from quasi-helices consisting of readily available magnetized ring rare-earth sectors are proposed. "Radially" magnetized sectors create a stronger field on the axis than longitudinally magnetized ones. The field value weakly depends on the number of sectors per undulator period. An experimentally studied prototype Halbach-type helical undulator of "radially" and longitudinally magnetized quasi-helices consisting of ring NdFeB sectors with a period of 2 cm and a comparatively large inner diameter of 8 mm provides a field of about 0.6 T on the axis. By reducing the inner diameter to 5 mm, it is possible to obtain a field twice as large. When assembling such an undulator, it is convenient, while maintaining the positions of all ring sectors, to use a division of the undulator not into quasi-helices, but into cylindrical sectors shifted along the axis and rotated relative to each other. Permanent undulators from ring sectors can provide a higher velocity of transverse electron oscillations than planar ones, and therefore seem promising for increasing the efficiency of FELs in various frequency ranges.
Paper: TUPS089
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS089
About: Received: 14 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
TUPS092
Wakefield studies of the taper section of the elliptical in-vacuum undulator - IVUE32
1591
The elliptical in-vacuum undulator (IVU) IVUE32 is being developed at Helmholtz-Zentrum Berlin (HZB). The APPLE-II design allows for not only gap changes but also longitudinal shift movements, putting additional design challenges on the tapers at the entrance and exit of the undulator. The chosen design philosophy separates the gap and shift movement compensation into two assemblies respectively. This approach allows for a solid foil taper as gap movement compensation, which is proven in previously commissioned planar IVUs e.g. CPMU17 at HZB. The shift movement compensation, which requires a slit foil, can be kept parallel. The proximity of this complex structure to the electron beam makes the device susceptible to wakefield effects which can influence beam stability. Investigating and understanding these effects is vital for accelerator operation. The taper design will be presented alongside wakefield simulations and model measurements.
Paper: TUPS092
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS092
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
TUPS093
Permanent hybrid helical micro-undulators for FELs and inverse FELs
1595
High-field micro-undulators are one of the key elements in most compact Terahertz and X-ray FEL projects. In our works, helical undulators of several helices, each made of a single piece of rare-earth magnet, are proposed for this purpose. We demonstrated previously the possibility of high-precision manufacturing helices with centimeter periods using the Wire Electric Discharge Machining. In this paper, we will discuss an experimental prototype micro-undulator of two oppositely longitudinally magnetized NdFeB helices with a period of 6 mm and an inner hole diameter of 1 mm, creating a transverse field close to 1 T. The magnitude of the field and/or the inner diameter of the helices can be significantly increased by using hybrid systems with two longitudinally pre-magnetized rare-earth and two pre-unmagnetized steel helices. We are currently developing methods for manufacturing, assembling and measuring the parameters of such systems with periods of 6 and 3 mm and a field of 1 T and will demonstrate the corresponding results in the presentation.
Paper: TUPS093
DOI: reference for this paper: 10.18429/JACoW-IPAC25-TUPS093
About: Received: 14 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 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-IPAC25-TUPS094
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
WEPB028
Kicker magnets for fast-switching elliptical polarized undulators beamline of the TPS
1796
The variation of polarized light is a critical characteristic of synchrotron radiation sources. To accommodate diverse user needs and enable helicity switching, a soft X-ray beamline has been designed to alternate the helicity of polarized undulator radiation. This is achieved by switching between two undulators, configured to provide right and left circularly polarized radiation, respectively. To separate and select these two circularly polarized photon beams, six kicker magnets are installed in the straight section. This paper details the design considerations, fabrication processes, and field measurement results of these kicker magnets, emphasizing their role in achieving seamless helicity switching and supporting the beamline’s functionality for cohabitation of multiple users.
Paper: WEPB028
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPB028
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 10 Jul 2025
WEPB047
Insertion devices for the ultralow emittance storage ring ALBA II
1839
The ALBA synchrotron light source is undergoing a transformative upgrade to become a state-of-the-art fourth-generation facility, known as ALBA II. This upgrade will reduce the electron beam emittance to approximately 200 pm·rad, achieving a twentyfold improvement over the current performance. A key goal of the project is to maintain the existing source points for the insertion device beamlines; in fact, most of the currently installed devices will be kept after the upgrade. Nevertheless, selected insertion devices will be replaced to fully exploit the enhanced capabilities of the upgraded electron beam. Additionally, two available straight sections will be utilized to support the development of ultra-long beamlines exceeding 250 meters, enabling advanced nano-probing and coherence-based experimental techniques. This paper outlines the strategic plans for the new insertion devices, detailing the design criteria and the constraints guiding their development.
Paper: WEPB047
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPB047
About: Received: 27 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 10 Jul 2025
WEPB048
Magnetic measurement of a decommissioned insertion device at the Canadian Light Source
1843
The Canadian Light Source has decommissioned three insertion devices in recent years, replacing each with upgraded devices. The decommissioned devices are planar undulators that have seen approximately 15 years of operation in a 2.9 GeV storage ring, two being out-of-vacuum devices with 45 mm and 185 mm periods and one being an in-vacuum 20 mm device. In this paper we present magnetic measurements of the decommissioned 185 mm device (U185) with comparisons against the original measurements from before it was put into service.
Paper: WEPB048
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPB048
About: Received: 24 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 10 Jul 2025
WEPB049
Upgrade of the insertion device measurement benches and associated software at the ESRF
1847
The European Synchrotron Radiation Facility (ESRF) has built and characterized many insertion devices and magnets over the past decades. The magnetic measurements rely on dedicated benches, based on stretched wire for integral measurements and on hall probes for local measurements. A major upgrade of these benches is being developed. It includes new features such as coordinate measurents, upgraded acquisition boards and hall probes, and a new control software based on Python, HDF5 data format and Qt. The B2E software, used for computing synchrotron radiation and for shimming undulators, was completely refactored. This paper presents the architecture of these new benches, the status of the project and the first results.
Paper: WEPB049
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPB049
About: Received: 26 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 10 Jul 2025
WEPB055
Design and development a measurement system for magnetic tuning of undulator magnets
1861
The permanent-magnet in-vacuum undulator technique is critical for the Taiwan Photon Source(TPS) at the National Synchrotron Radiation Research Center(NSRRC). Before installing the magnet arrays in the vacuum chamber, the phase error of the undulator is optimized by adjusting the magnetic field. Optimizing phase errors is a complex and time-consuming task. The conventional measurement method involves using Hall probes to measure the magnetic field and a stretched-wire(SW) to measure the integral field of the undulator. In this work, we propose a method for tune the local magnetic field by utilizing the correlation between the gap and the magnetic field. We have demonstrated that using gap sensors allows us to more effectively determine whether to tune the magnetic field of the upper or lower magnet array. Additionally, we have demonstrated for the first time the use of the pulsed wire measurement (PWM) method for magnetic sorting.
Paper: WEPB055
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPB055
About: Received: 14 May 2025 — Revised: 01 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 10 Jul 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-IPAC25-WEPB056
About: Received: 29 May 2025 — Revised: 30 May 2025 — Accepted: 02 Jun 2025 — Issue date: 10 Jul 2025
WEPB057
Field measurements of a short period helical superconducting undulator
1868
Superconducting undulators (SCUs) may be capable of generating stronger magnetic fields at shorter periods than can be achieved using permanent magnet undulators. Therefore, the range of x-ray wavelengths that an XFEL facility can generate for users could be expanded by exploiting SCU technology. Prototyping work is ongoing at STFC to build a helical superconducting undulator (HSCU) with 13 mm period and 5 mm magnetic gap designed for future XFEL facilities. As part of this work, a test cryostat has been built to cool 325 mm long prototype magnets to 4 K and to measure the field profile of the HSCU using a cryogenic Hall sensor. The magnetic field measurements are necessary to confirm the peak-to-peak field quality and trajectory wander of an electron beam through the device. These quantities must be measured to understand the impact of the HSCU on the FEL radiation output. The trajectory wander can be minimised through the use of field integral corrector coils at either end of the HSCU coil. We present here a description of the test cryostat and the results of the magnetic field measurement regime performed on the prototype HSCU coil.
Paper: WEPB057
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPB057
About: Received: 21 May 2025 — Revised: 06 Jun 2025 — Accepted: 06 Jun 2025 — Issue date: 10 Jul 2025
WEPM030
Beam optics simulations of achromatic section of Delhi Light Source
2024
The Delhi Light Source is an upcoming user facility for coherent THz radiation and electron beam. Electron beam of energy upto 8 MeV generated from a RF photo-cathode gun will be used for coherent THz generation from a planer undulator. The beam after passing through the undulator field will be separated from the THz and THz line by a $60^{o}$ achromatic section and delivered to electron experimental area. Simulation studies has been performed to achieve achromatic condition and acceptable beam size at the electron experimental area for the case of electron transmission through non-trivial undulator field. However for the case of open gap undulator (no THz generation), the study shows that the same design gives a limited control on the overall beam size at the electron experimental area. To overcome this the extended quadrupole correction (EQC) coils of the undulator can be used as a suitable focussing element to achieve required beam size control in addition to the achromatic condition. The paper presents the simulation studies of the achromatic section for both with and without(open gap) undulator field.
Paper: WEPM030
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPM030
About: Received: 20 May 2025 — Revised: 30 May 2025 — Accepted: 01 Jun 2025 — Issue date: 10 Jul 2025
WEPM100
Parametric optics for FUDU lattices with strongly focusing undulators
2211
In low-energy FEL beamlines, like SXFEL-SBP at the Shanghai Synchrotron Radiation Facility and FLASH1 and FLASH2 at DESY, SASE undulators with perfectly reasonable strength may dynamically affect the optics of the Focusing-Undulator-Defocusing-Undulator (FUDU) cells, pre-matched for a given fixed set of undulator parameters, so violently that a dynamical re-adjustment of the FUDU quadrupoles becomes mandatory. Here we refine and generalize a result reported at the FEL conference 2024. Our almost-analytical result allows implementation in the control system, and is valid for fairly general symplectic coupling-free perturbing matrices. In an approximative sense it includes undulators changing along the beamline and even missing undulators in given cells.
Paper: WEPM100
DOI: reference for this paper: 10.18429/JACoW-IPAC25-WEPM100
About: Received: 28 May 2025 — Revised: 29 May 2025 — Accepted: 01 Jun 2025 — Issue date: 10 Jul 2025
THPB013
The wire alignment method in a magnetic field measurement system
2526
In the magnetic field measurement system, a single-core CuZr wire is used in both the stretched-wire (SW) and pulsed wire measurement (PWM) systems. Before measuring the magnetic field of the undulators, the CuZr wire must be aligned with the center of the undulator mechanism. The SW system is then employed to locate the magnetic field center of the undulator. The traditional method involves using a theodolite and level to align the CuZr wire with the center of the undulator mechanism. However, for cryogenic permanent magnet undulators (CPMUs), superconducting magnets, or any magnets installed in a vacuum chamber, aligning the CuZr wire with the center of the mechanism using traditional methods presents challenges. In this paper, we propose a method that utilizes the wire's contact with the magnet to observe changes in resistance for positioning purposes, thereby overcoming the limitations of center alignment in chamber-surrounded undulator mechanisms.
Paper: THPB013
DOI: reference for this paper: 10.18429/JACoW-IPAC25-THPB013
About: Received: 22 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025
THPM077
Measurement of vertical and horizontal emittance via undulator high harmonics at the APS-U
2852
The transition from 3rd to 4th generation synchrotron light sources can primarily be characterized by a significant reduction in horizontal emittance. This enables a nearly uniform transverse X-ray beam profile and a brilliance that approaches the diffraction limit. A consequence of the upgrade to Diffraction Limited Storage Rings (DLSRs) is that the traditional emittance measurement techniques lack the resolution required to accurately measure emittances in the picometer-radian range. At the Advanced Photon Source Upgrade (APS-U), we explore the use of high harmonics of undulator radiation for precise emittance characterization. Previously at the Advanced Photon Source (APS), vertical emittance measurements, validated through SPECTRA simulations, were performed. This drove the desire to measure the horizontal emittance at the APS-U. Simulations performed in SPECTRA and Synchrotron Radiation Workshop (SRW) guide our experimental strategy for characterization. We present measurements of both the horizontal and vertical emittance at the APS-U, including variations across different bunch timing modes. We conclude by discussing the advantages of this approach over traditional methods.
Paper: THPM077
DOI: reference for this paper: 10.18429/JACoW-IPAC25-THPM077
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 05 Jun 2025 — Issue date: 10 Jul 2025