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.

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.

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.

Recently, KEK PF has started developing a superconducting multipole wiggler (SC-MPW) for an application in next-generation light source ring. The SC-MPW is expected to be a key insertion device for the light utilization of a wide wavelength region by aiming at high-brightness and high-energy X-ray production while keeping the stored beam energy as low as 2.5 GeV. In addition, the short period length of multipole wiggler not only lowers the light spread and increases the effective photon flux, but also reduces the beam orbit amplitude, which leads to suppressing the emittance growth in a low emittance ring. In our application, the magnetic field more than 2.5 T is required on the central beam orbit even in a short period length less than 80 mm with a wide gap more than 30 mm that secures the beam orbit region. As we need to investigate the candidate of Nb3Sn wires and to study the coil-fabrication techniques which meet a use as multipole wiggler, PF has completed the first prototype-coil unit consisting of three poles and successfully conducted excitation tests at the low current. The detailed fabrication of test-coil unit and the prospects for high-current testing will be reported.

The Institute for Nuclear Physics of the University of Mainz operates the accelerator complex MAMI. Outstanding qualities are the continuous beam with an excellent beam quality, a very low energy spread, as well as its extremely high reliability. All kinds of channeling experiments require such a high quality beam with a low divergence. Positrons, however, are more preferable because they have a significant longer de-channeling length. The aim the project is the preparation of high-quality positron beam using the features of the MAMI accelerator. Positrons will be created by pair conversion of bremsstrahlung, produced by a focused 855 MeV electron beam of MAMI in a 10 um thick tungsten converter target, and energy selected by an outside open electron beam-line bending magnet. A sector magnet bends back the beam. Magnetic focusing elements in between are designed to prepare in a well shielded chamber about 6 m away from the converter target a low divergence positron beam. The features of the positron beam line such as the positron rate, the beam spot size and the divergence of the positron beam will be discussed. First channeling experiments with Silicon crystals will be presented.

This study investigates the influence of insertion devices (IDs) on the optical properties of the Solaris electron storage ring through a combination of experimental measurements and simulations. The effects of various ID settings were analyzed using tune measurements and the Linear Optics from Closed Orbits (LOCO) method. These results were compared with simulations performed using the Python Accelerator Toolbox (pyAT). Furthermore, a Long Short-Term Memory (LSTM) neural network was developed and tested for forecasting corrector magnet currents associated with the IDs. Diagnostics included monitoring the electron beam in the storage ring and photons delivered to beamlines. Additionally, the performance of both slow and fast orbit correction systems in response to ID-induced perturbations was assessed. This work provides insights into ID impact on beam dynamics and highlights the potential of machine learning for predictive control in accelerator systems.

Since the completion of Taiwan Photon Source (TPS) commissioning in 2015, we have developed and constructed nine APPLE-II undulators of various designs to provide users with soft X-ray sources, particularly for circularly polarized light. To optimize the use of straight-section space, the lengths of the APPLE undulators range from 4.4 to 0.8 meters to accommodate installation constraints. Additionally, an APPLE undulator capable of tapering up to 2 mrad has been developed to meet the spectral demands of broad bandwidth. In pursuit of EPU designs suitable for operation in low-emittance accelerators, we have initiated studies on closed-gap EPUs and constructed as well as experimentally validated a novel insertion device, known as the THU, capable of delivering strong circularly polarized magnetic fields. Moreover, we are also developing a closed-gap type undulator combining electromagnets with permanent magnet structures to generate time-varying magnetic fields, enabling rapid switching of circularly polarized light.

Accurately simulating the thermal and mechanical effects of undulator power density distribution in high heat load components requires precise power implementation in finite element analysis (FEA) models. This study presents a novel methodology utilizing intermediate programming to efficiently map complex undulator power density distributions onto FEA models. The approach enables the placement of power density values (e.g., W/mm²) on each element surface while simultaneously calculating the grazing angles based on the insertion device's power source geometry. By automating these processes, the methodology significantly reduces the time and effort required for engineers to implement detailed power distributions in FEA simulations. This advancement not only ensures higher accuracy in modeling but also streamlines the workflow, allowing for faster evaluation and optimization of high heat load components in synchrotron radiation facilities. The proposed framework offers a practical solution for integrating advanced undulator power profiles into engineering analyses, enhancing both efficiency and reliability.

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.

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.

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.

Irradiation-induced damage to undulators has become a critical problem in the operation of synchrotron radiation facilities and free-electron laser facilities. During the commissioning and light output phases of the Shanghai Soft X-ray Free Electron Laser facility, the performance of the radiation deteriorated. The main reason for this problem is the impact of high-energy particles on the undulator magnets, which compromised the quality of the magnetic field. This paper examines the radiation damage sustained by the undulators and their refurbishment process.