Undulators are widely employed on accelerator-based light sources. The length of these devices is usually constrained by the length of the straight sections, and this will become even more critical for Diffraction Limited Storage Rings based on existing Synchrotrons, where the number of magnets required to store the electron beam is huge. Thus, to reach high brightness and flux, the total number of periods of undulators must remain large and the magnetic period values will be reduced. Cryogenic Permanent Magnets Undulators (CPMU) are a solution to keep a high peak field value while decreasing the magnetic period. Planar CPMUs have become widely adopted in Synchrotrons worldwide and some laboratories are developing equivalent devices providing also elliptical polarizations. A review of low period CPMU installed on accelerator-based light sources will be presented and sustainability of these sources will also be discussed.

Over the past decade, the Magnet Section at the Paul Scherrer Institute (PSI) has developed extensive expertise in superconducting magnet design, construction, and testing, forming the foundation for SMILE (Superconducting Magnets to Improve Large Research Facilities Efficiency) - a proposed R&D initiative that brings together PSI experts and international partners. SMILE’s primary goal is to enhance magnet performance while significantly reducing energy consumption and CO₂ emissions across PSI’s large research facilities. This presentation outlines the future roadmap for advancing High Temperature Superconductor (HTS) technology at PSI’s High Intensity Proton Accelerator (HIPA) complex. A key focus is the development of cryocooler-based HTS magnets for both DC and ramping applications, addressing the unique challenges of operating conduction-cooled HTS tapes in dynamic field environments. Additionally, a critical research area focuses on understanding and mitigating radiation-induced degradation in HTS materials, essential for magnets operating near high-intensity targets. This combined focus on performance enhancement, energy efficiency, and radiation resilience aims not only to reduce PSI’s power consumption and environmental footprint, but with meaningful contributions impacting the research related to the industrial use of the HTS magnets.

The EIC Hadron Storage Ring (HSR) reuses the RHIC yellow ring with substantial reconfiguration. A major challenge is mitigating beam-induced heating of cryogenic components caused by the shorter hadron bunches and an average beam current three times that of RHIC. In addition, large transverse beam offsets at injection due to helical magnet itself generate asymmetric resistive-wall losses in the cryogenic BPM region. To limit these losses, the HSR helical magnet assembly uses a new copper-plated stainless-steel beam pipe with an amorphous-carbon coating. This paper presents heating and thermal analysis of the EIC HSR cryogenic helical magnet and BPM assembly. Thermal simulations show narrow thermal margin for the helical magnet unit, and adequate margin for the BPM assembly.

The SPIRAL2 superconducting LINAC at GANIL operates 26 quarter-wave resonator cavities whose online diagnostics currently rely on physics-based models limited to single operating points. This paper presents two complementary AI-based diagnostic tools: (i) neural-network heat-load virtual observers that estimate the cavity thermal dissipation — a proxy for the intrinsic quality factor Q0 — from cryogenic process signals, with prediction errors predominantly in [−2, +1] W@4.2 K for loads up to 20 W@4.2 K; and (ii) a machine-learning pipeline meant to detecting anomalies in LLRF data, predicting alarms before they fire, and classifying fault subtypes within the cavity-quench category ($F_1$ = 92%). This paper presents a state of progress on these two applications.

PERLE, under construction at IJCLab, is a multi-turn Energy Recovery Linac designed for high intensity electron beams of 10 MW peak power (20 mA, 250 MeV). Simulations of its SRF cryomodule * predict more than 100 W of higher-order-mode (HOM) power per cavity induced by the short bunches, indicating that Beam Line Absorbers (BLAs) at 40 K may be required between cavities to dissipate the HOM power and protect the 2 K stage. However, the lack of complete properties of dielectric materials for candidate absorbers limits accurate BLA design. To address this, we are conducting dedicated studies of BLA materials at IJCLab. We measured the broadband dielectric properties of Kyocera SC1000 samples from BNL ** at room temperature using a setup at CLIC (CERN) and cross-validated the results with independent measurements from JLab***. In parallel, we designed and simulated two cryogenic coaxial test stands, one operating up to 18 GHz and another extending coverage to 40 GHz. These warm measurements provide baseline data for upcoming cryogenic studies and validated input for the design of BLAs in next-generation accelerators such as the EIC at BNL, FCC-ee at CERN, and in particular PERLE at IJCLab.

Accurate calibration of NMR probes is essential for high-quality magnetic-field measurements. Within the PNRR IRIS project, the Magnetic Measurement Facility (MMF) at LNF-INFN has implemented a new dedicated calibration system designed and manufactured by CAYLAR. The setup includes a 2.23 T dipole magnet with a 35 mm gap, a 1ppm four-quadrant power supply for low-field operation, and three NMR probes with associated electronics, covering the 200 G to 2.2 T range. The probes are mounted on a dedicated holder positioned in a highly uniform field region, ensuring that all sensors experience the same magnetic environment. Achieving excellent homogeneity over a large volume and wide field range was a key challenge; this was addressed through a genetic-algorithm-optimized magnet design complemented by active shimming coils. This contribution presents the system’s design, construction, and factory acceptance tests, along with the first calibration results obtained at MMF. Future improvements include thermostating the probe holder, potentially using cryogenic liquids, to extend the temperature range for calibrations, an important capability for probes used in superconducting magnets.

In order to achieve optimal performance in terms of transmission and separation for the S3 spectrometer, the project chose to design superconducting magnets integrating 11 magnetic functions in a single cryostat. There are seven of these magnets, called Superconducting Multipole Triplets, in the spectrometer. The compactness of these magnets makes them remarkable and unique, but has led to significant commissioning difficulties. As the design was very close to the acceptable operating limits, we experienced several breakages and leaks, as well as limitations in terms of nominal current. In this presentation, we will show the important work we carried out to repair the main conductor, improve the robustness of the current leads and feedthrough, and repair the various leaks.

All third generation synchrotron radiation sources are currently planning upgrades toward diffraction-limited storage rings with brightness close to the theoretical limit and higher hard-x-ray production. In these new photon sources superconducting bending (superbending) magnets may play an important role to extend the useful photon energy range. The radiation produced by superbending magnet is an order of magnitude higher in photon brightness and flux than that produced by a normal conducting bending magnet, making it a superior source of hard x-rays. As an example, in the framework of the Elettra 2.0 Project, a new superbending magnet is under development with an innovative compact design integrated with quadrupole side magnets. The 6T superbending magnet will replace a normal conducting 1.4T magnet. The magnetic design is combined with novel cryogenic solutions that combine the benefits of a liquid-helium cooled inner magnet with a liquid-helium-free upper cooling stage. A novel C-shaped design will allow to slip in and slip out the magnet from its position on the storage ring vacuum chamber. The NbTi Superconducting magnet will work at 3.5K conduction cooled, thanks a system of heat exchanger connected to a subcooled Helium bath.

A single-aperture, two-layer Canted-Cosine-Theta (CCT) sextupole magnet using high-temperature superconducting (HTS) ReBCO tape has been developed for the short straight sections (SSS) of FCC through the FCCee-HTS4 project. The magnet was designed, manufactured and tested under cryogenic conditions. Two HTS tapes from two manufacturers have been qualified for this specific application. Design and manufacturing details and cryogenic temperature measurements are presented. This demonstrator represents the first HTS CCT magnet ever constructed.

Efficient use of gaseous and liquid helium, a non-renewable resource essential for accelerator-based experiments, is a key priority at ALBA Synchrotron Light Source. This work presents the operational status of ALBA’s helium liquefaction plant and the liquid-helium production achieved in recent years, based on recovery from its use in the BOREAS, LOREA, CLAESS and MSPD beamlines. The helium liquefaction plant’s operating mode is discussed, with emphasis on its main limitation: the system can only process recovered gas with an average helium purity of 99.5%. To overcome this constraint, the plant was upgraded during 2025–2026 with the installation of a gas purifier capable of treating gas helium with purities as low as 90%. The first operational results and performance of the helium liquefaction plant with the integrated purifier are presented.

Large-scale helium refrigeration cryogenic systems are a key element, essential to the safe and reliable operation of particle accelerators using superconducting devices such as radio-frequency cavities or magnets. The long-term success of the LHC operation with an outstanding physics production to date paves the way towards the High-Luminosity LHC (HL-LHC) upgrade to be operated until the early 2040s, after which it could be followed by the Future Circular Collider (FCC). Such large-scale projects, requiring a significant amount of cryogenic cooling capacity to be installed, pose the question of the cost estimation methodology to be employed, as the cryogenic system represents a non-negligible fraction of the total capital, operation & maintenance cost of the facility. Capitalizing on the experience of the LHC project, then on its recent HL-LHC upgrade, the existing CERN methodology was updated with the latest available industrial indexation, thus allowing the cost of the FCC cryogenic system to be assessed. This paper reports on the approach used to estimate the cost of the FCC cryogenics, refining the method adopted at the time of the LHC project. It considers the evolution of material and labour costs over the past two decades, studies the updated economics of 4.5 K and 1.8 K helium refrigeration, and presents the strong impact of the cryogenic distribution system. It also identifies and proposes ways for improving the capital, operation & maintenance expenditure.

The HL-LHC project is currently in the fabrication and assembly phase for numerous components and systems, in particular the new beam-screen assemblies to be installed inside the upgraded final-focusing superconducting magnets operating at 1.9 K. These complex beam screens integrate tungsten absorbers and exist in two variants: the Q1 and Q2 types, with absorber thicknesses of 16 mm and 6 mm, respectively. In total, 24 assemblies will be installed. Their successful implementation requires complex design work, non-standard and demanding manufacturing processes, and stringent quality assurance. Fabrication has proven to be very challenging in terms of welding and assembly and requires close follow-up and dedicated qualification processes throughout the manufacturing phase. To maintain a high standard of manufacturing, a Quality Management approach derived from industrial standards and based on ISO 9001 principles, has been implemented. This paper presents how the quality-management framework is deployed throughout the project phases and how it ensures traceability, smooth process execution, and compliance with the required workflows and technical specifications.

Undulators are widely used in synchrotron storage rings and free-electron laser facilities. With the advent of low-temperature superconductors (LTS), a new generation of superconducting undulators (SCUs) emerged, including the recent new THz LTS undulator for FLUTE. At KIT, state-of-the-art magnetic and cryogenic measurement capabilities — provided by the Magnet and Cryogenics Facilities (MCF) and the Accelerator Technology Platform (ATP) — form a foundation for the development and characterization of these systems. Building on this experience, KIT is now advancing magnets and undulators based on high-temperature superconductors (HTS), aiming for compact, sustainable, energy- and resource-efficient solutions. These activities are driven by in-house research and providing the full value chain of HTS technology from tape development via structuring to prototypes and tests in real-world environments at KIT. In this contribution, we provide an overview of our current developments and the supporting experimental infrastructure.

Since 2018, the BESSY II storage ring has operated a cryogenic permanent magnet undulator (CPMU), which was developed and constructed in-house. With a period of 17 mm, CPMU17 was the first in-vacuum undulator to be installed at BESSY II. Another CPMU (CPMU20) and the world’s first in-vacuum APPLE II undulator (IVUE32) are currently under construction and will be installed at BESSY II within the next few years. To meet the needs of its diverse and ever-evolving user community, BESSY II has pioneered innovative operating modes, such as low-alpha and TRIBS, in addition to the hybrid mode. These special operating modes are based on phase space manipulation, which is enabled by the accelerator lattice's great flexibility and tight tolerances for the insertion devices. Accordingly, there are also tight tolerances on in-vacuum IDs. This paper discusses some of the main challenges, as well as the key developments and strategies, involved in meeting tolerance requirements.

The European Spallation Source (ESS), as one of the complex accelerators require installation and commissioning of many systems and components. One of them is the accelerator which is composed with the cryomodules uses to accelerate of the particles. Taking into account that ESS is one of the most technological advanced accelerators in the world we can expect also that accelerator is very complex and advanced part of this research infrastructure . Among other things three types of the cryomodules: spokes, medium- and high-beta are used to assembly accelerator line. In 2017 first engineers from the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Science (IFJ PAN) arrived to Lund in order to start execution of IFJ PAN contribution to this project. In total 31 cryomodules have to be tested and prepared for assembly in the tunnel as a part of the accelerator line. In this paper the current status of the tests as well as early stage of the optimization process regarding test program for cryomodules tests is showed. The main focus is done on the procedures and quality aspects, required skills and challenges occurring during the tests work; inter alia: incoming inspection, tests before installation in the bunker, preparation of the cryomodules for the test, test in the bunker, outgoing inspection. A cutting-edge RF cryomodules and systems required the special skills and the right approach to quality which is provided by engineers and technicians from IFJ PAN.

The “Super Separator Spectrometer” project S3 is under technical commissioning at the GANIL facility (Caen-France). It is a new research installation designed for fundamental physics experiments with high intensity radioactive heavy ions beams produced by the SPIRAL2 linear accelerator. This spectrometer will open new horizons for nuclear physics. The S3 spectrometer is made of 77 superconducting magnets, 12 room temperature magnets and one high-electric field dipole. This electric dipole combined with a magnetic dipole will allows a very precise energy/mass selection of ions with extremely small effective sections. This paper presents the electric dipole technology and its initial high voltage conditioning carried out on-site in 2025.

In order to achieve optimal performance in terms of transmission and separation for the S3 spectrometer, the project team decided to design superconducting magnets integrating 11 magnetic functions in a single cryostat. There are seven of these magnets, called Superconducting Multipole Triplets, in the spectrometer, and they operate at liquid helium temperature. These are unique objects with no equivalent anywhere else in the world, offering a very high degree of integration. This complexity has resulted in a significant commissioning delay and the need for a dedicated team to operate this set of magnets. This presentation will show the progress made in qualifying the various functions associated with these magnets: the qualification of cryogenic, electrical, and magnetic functions.

The electron source at the MOTHRA beamline is a novel 0.5-cell cryogenic C-band photoinjector designed to operate at gradients up to 200 MV/m. This work reports on recent developments toward implementing a load lock and modular cathode backplane that enables the insertion and testing of next-generation photocathode materials and structures under high-field, cryogenic operating conditions. The combination of a high launch field, low intrinsic emittance cathodes, and cryogenic temperatures is expected to significantly increase the achievable beam brightness. We present the current design status, experimental progress, and performance measurements of the cryogenic photoinjector with the modified backplane. In addition, we discuss beam-dynamics optimization for operating the source in an ultrafast electron diffraction (UED) configuration, where the high gradient and low intrinsic emittance offer a promising pathway to MeV-scale UED with exceptional brightness and temporal resolution.

The SSR2 superconducting cryomodule is analyzed in terms of static and dynamic heat loads and the associated entropy rates at the 2 K stage. The reference cryomodule contains six superconducting single-spoke resonator cavities. Static heat loads arise from conduction through cryomodule supports, couplers, cables, and beam-pipe interfaces, and from radiation through the insulation vacuum. Dynamic heat load is produced by radio-frequency surface dissipation. At 2 K, static and dynamic heat loads of 20 W and 80 W correspond to entropy rates of 10 W/K and 40 W/K, respectively, for a total cold-stage entropy rate of 50 W/K. The dynamic contribution ac-counts for 80% of the total entropy rate and scales inversely with the intrinsic quality factor Q₀. A coefficient-of-performance analysis shows that 100 W at 2 K requires at least 14.9 kW in the Carnot limit and about 100 kW for a representative real COP of 0.001. The results show that reducing radio-frequency loss, increasing Q₀, minimizing static heat leakage, and improving refrigerator performance directly reduce entropy generation and improve cryomodule efficiency.

The second-generation high-temperature superconductor (2G-HTS) is under consideration for accelerator applications because its operating temperature, which is higher than 4.2 K, eliminates the need for liquid helium. However, the relatively low engineering critical current, inter-layer insulation challenges, welding reliability and quench protection remain key technical issues. In this work, an insulated 2G-HTS tape was wet-wound using a low-temperature adhesive. The winding method, charging behavior, as well as quench protection were experimentally investigated. A simple liquid-helium-free test dewar is also presented.

At the Taiwan Photon Source (TPS) a cryogenic permanent magnet undulator, CUT18, utilizes the latent heat of vaporization of liquid nitrogen for magnet cooling. After a period of operation, some condensed water, which caused rust at the structure of CUT18, appeared at the flange connecting the cooling system and the vacuum beam chamber of CUT 18. This condensed water was mainly due to deterioration of the thermal insulation vacuum of the liquid nitrogen cooling system. Moreover, the period became much shorter after the maintenance to recover a proper vacuum under cold conditions. This paper presents the efforts to extend the period of sustaining a proper thermal insulation vacuum without the appearance of condensed water. A residual gas analyzer was used to study outgases from the insulation vacuum of the liquid nitrogen cooling system at warm and cold conditions. These efforts succeed to extend the period longer than three months, thus greatly reduced the burden from insulation vacuum maintenance.

Liquid nitrogen (LN2) cooling is widely utilized in the cooling systems of superconducting devices and scientific instruments. During the cooling process, the boiling heat transfer mechanism plays a decisive role. When the solid surface temperature significantly exceeds the saturation temperature of the liquid nitrogen, the Leidenfrost effect occurs, forming a vapor film at the solid-liquid interface that drastically reduces heat transfer efficiency. Previous research has primarily focused on altering the boiling curve and enhancing the Critical Heat Flux (CHF) through surface roughness, micro-nano structures, or various material properties. Few studies have explored the impact of filling modes within the cooling system on disrupting the vapor film and improving boiling heat transfer.This study utilizes a self-developed liquid nitrogen cooling experimental platform to investigate four distinct filling and cooling modes designed for an Oxygen-Free High Conductivity (OFHC) copper test block. By examining the boiling curves under various filling modes, this thesis analyzes the underlying mechanisms influencing the wall superheat at the Leidenfrost point ($\Delta T_{LP}$) and the Critical Heat Flux ($\Delta T_{CHF}$). The results indicate that the bottom-filling method, characterized by impingement kinetic energy, effectively increases fluid disturbance and disrupts the vapor film encapsulation. This significantly reduces the duration of the Leidenfrost effect and facilitates an earlier transition into the high-efficiency nucleate boiling stage.

A sustainability-oriented cryogenic permanent magnet undulator, the LN₂-enabled C³-CPMU, has been success-fully demonstrated at the Taiwan Photon Source (TPS). The system is designed to address cryogenic performance, thermal stability, and cost efficiency for high-current storage ring operation (up to 500 mA). The undulator employs a conduction-cooled architecture combined with an LN₂ reservoir-based cooling scheme with simplified flow and pressure control, eliminating the need for dedi-cated cryogenic units. Operating at an intermediate tem-perature of 150–160 K, the system consumes approxi-mately 8 L/h of LN₂. Active temperature control main-tains the magnet temperature within ± 0.08 K under vary-ing beam conditions, ensuring stable magnetic field per-formance. The enhanced magnetic properties at cryogenic temperatures enable shorter undulator periods, while integration with existing facility LN₂ infrastructure sig-nificantly reduces system complexity and operational overhead. These results demonstrate a scalable and ener-gy-efficient solution for next-generation synchrotron and XFEL light sources.

The rectilinear 6D cooling channel is a key element of the Muon Collider baseline, enabling the large emittance reduction required before acceleration. The Muon Collider Cooling Demonstrator aims to validate, at engineering scale and in relevant conditions, the integration of a single B5-like cooling cell. This paper presents the preliminary design of the Cooling Cell, developed within the MuCol and IMCC collaborations, and based on a high-field HTS solenoid pair, a low-Z absorber, and a 3-cell 704-MHz normal-conducting RF structure. A key point of the design effort is the introduction of the Inter-Cell Cryostat, a compact architecture that closes the magnetic forces inside the cold mass while decoupling the RF and absorber assemblies at room temperature. This solution enables a feasible mechanical integration, compliant with lattice length constraints, and provides sufficient space for waveguides and diagnostics. However, it requires a remote-handling connection between each cell. The final cell layout incorporates the MAG2.4 HTS solenoids operating at 20 K, an updated RF cavity with thin Al foils, a LiH absorber module, cryogenic and thermal-shield structures, and pillow-seal vacuum interfaces designed for remote-handling assembly. The configuration that we present is a step toward demonstrating the feasibility of the cooling channel of the Muon Collider.

A failure of the RHIC superconducting circuit occurred at the end of Run 23 and led to an unplanned shutdown and extensive work to replace a damaged superconducting dipole magnet. After an in-depth investigation, the failure was determined to have originated from an electrical breakdown within a superconducting current lead. The short-circuit through the arc led to large spilling of current through auxiliary superconducting circuits with limited quench stabilization which resulted in a superconducting splice fusing out. This paper will summarize our understanding of the series of events leading to the superconducting circuit damage, describe the repair work undertaken for the remaining RHIC runs and discuss some lessons learned in view of EIC operation.

This paper presents a case study on the reinstallation of heavy weight cryomodule (HWR-B #11, HWR-A #9 & #13) for the SCL3 beamline maintenance. Our HWR-B combines a cryogenic module with a warm section assembled with a quadrupole magnet and a vacuum chamber, with a total weight exceeding 12.5 tons (HWR-A over 7.0 tons). After each annual beam commissioning, some low-efficiency modules were identified to require functional inspection and repair during maintenance for subsequent beam experiments. In particular, the processes of disassembling a large HWR-B or HWR-A cryomodule from the beamline and moving it out of the underground accelerator tunnel needs very strict safety requirements and detailed planning and coordination among related systems and teams. To perform these tasks efficiently and safely, we prepared pre-designed tools and equipment, formed related work groups for collaboration. During the first stage of the maintenance procedure, the HWR-A/B cryomodules was safely removed from the SCL3 beamline using a specially designed moving wheel and then delivered to the contractor for overhaul. After the overhaul & test were completed, the HWR-B #11 cryomodule was returned to the SCL3 tunnel and reinstalled into its original position in the beamline using the dedicated moving wheels and hydraulics. With great effort and attention, This first in-house beamline maintenance experience provided valuable insight and expertise for the ongoing operation of an accelerator beamline.

Cryogenic Current Comparators (CCC) are superconducting devices for beam current monitoring, based on azimuthal magnetic field (fT range) measurement with ultrasensitive SQUID magnetometers. They are able to provide a calibrated non-destructive measurement of beam current with a resolution of 10 nA or better, independent from ion species and without tedious calibrations procedure. We have developed the CCC over the last ten years in an international collaboration with the goal of a highly sensitive and continuous current measurement in the transfer lines and rings at FAIR and CERN machines. Besides the efforts to improve the robustness and current resolution of the device, investigations have been performed on the cryogenic support system, which has to provide stand alone operation in HEBT tunnels without He supply. So far we have achieved standing times in the range of 6 - 9 months after liquid He filling, recently we have demonstrated stand alone He liquefaction from gas bottles within ~ 4 weeks, which would avoid He filling in the tunnels. In this contribution we present the status and results of our current work with focus on the cryogenics aspects.

The accelerator complex for the Facility for Antiproton and Ion Research (FAIR) is currently being built in Darmstadt, Germany. After the arrival of the cold box for the central cryogenic facility (CRYO2) in winter 2023, the installation of the accelerator components in the machine and supply tunnels started early 2024. Meanwhile the installation has moved forward. CRYO2 has been handed over to the commissioning team and the commissioning is in progress. The accelerator installation is ongoing in all parts of the beamlines of the High Energy Beam Transfer Lines (HEBT), the Super Fragment Separator (SFRS) and the Heavy Ion Synchrotron (SIS100). In parallel, the installation plans for the experiments (NUSTAR and CBM) are being developed and installation preparations are taking place. In this paper the status and challenges of the machine installation in those areas are presented and an outlook for the next steps towards realisation of the project phases for Early and First Science is given.

Picosecond-long X-ray pulses of moderate intensity and high repetition rate are highly sought after by the light source community, especially for time-resolved fine spectroscopic analysis of matter in the linear response regime. We investigate the upgrade of the Elettra 2.0 diffraction-limited storage ring light source to supercon-ducting radiofrequency transverse deflecting cavities generating a steady-state vertical deflection of selected electron bunches. In this paper, a preliminary design of the cryomodule of the deflecting cavities is reported; both static and dynamic thermal loads are calculated using an analytical approach. The dynamic loads are calculated assuming both bulk Nb and Nb3Sn thin film cavities. The two different solutions involve different cryogenic plants, which will be discussed.

We assess the thermal behavior of a cryogenically cooled copper photocathode integrated into a continuous-wave superconducting radio-frequency injector cavity through direct thermal contact. A coupled three-dimensional thermal-electromagnetic model incorporating both the bulk photocathode and the injector cavity is presented. For the current injector design, the laser heat load is predicted to have a negligible effect on the intrinsic quality factor of the cavity. The cryogenic stability of the copper cathode is identified as the primary operational constraint. To address the associated cooling challenges, we propose a modified cathode plug geometry.

The European Synchrotron Radiation Facility (ESRF) operates a large number of in vacuum undulators (IVUs) and cryogenic permanent magnet undulators (CPMUs). Eight IVUs and nine CPMUs are currently in service, and a few more are under construction or planned. CPMU technology is used to build short period undulators with a wide tuning range. These insertion devices generate intense high order harmonics and can reach high photon energies — typically up to 100 keV at the ESRF. When a CPMU is installed at the centre of a straight section it can be set to a smaller gap, which allows the undulator period to be reduced. Two undulators can also be placed upstream and downstream of each other and phased with a phase shifter. A major limitation of this approach is the heat load on the photon front ends and on the optical elements of the beamlines. This problem can be mitigated by combining a tunable device with a short period, almost monochromatic in vacuum undulator dedicated to a single photon energy. The various layouts of the ESRF IVU/CPMU straight sections will be presented, together with the CPMU operating experience, construction and installation trends, and future developments.

This contribution provides an update on the development of the 4 mA, 100 MeV continuous-wave (CW) superconducting proton linac - the first stage of MYRRHA’s accelerator-driven system (ADS). We present the improved accelerator layout and beam optics design, outline the key design choices for critical components, and report on the latest manufacturing and civil construction progress.

The Figure-8 Storage Ring (F8SR) is an innovative concept designed for storing low energy (<1MeV) proton and ion beams in stellarator-like geometry within strong magnetic field level (B~6-7T). Preliminary studies, presented at previous IPAC conferences, established key design principles and demonstrated the feasibility of a compact ring structure capable of high current beam confinement over extended periods. The unique figure-eight geometry supports long-term beam confinement, essential for fusion experiments within beam-plasma system and colliding beams optics. The experimental program included investigations of the magnetic lattice, orbit stability, beam diagnostics and vacuum performance, supported by simulations and prototype measurements. Results confirmed the reliability of the beam optical design and guided optimization of magnetic field configuration. A Technical Design Concept is now being prepared to define the full-scale implementation of the F8SR, consolidating engineering requirements and scientific objectives toward establishing an international platform for high-current beam studies.