The Advanced Photon Source Upgrade (APSU) has transformed the APS into a 4th generation light source. The new 6 GeV, 200 mA multi-bend achromat (MBA) storage ring, along with injector improvements and new front ends will provide an increased brightness and an orders-of-magnitude improvement in coherent flux over the current facility. To take advantage of these new capabilities, we have designed and constructed nine new “feature beamlines” and implemented numerous additional beamline enhancements, all while ensuring the compatibility of existing programs. This talk will present a comprehensive overview of the APSU beamline scope, focusing on successes, challenges, and lessons learned.

The In Situ Nanoprobe (ISN) is a newly constructed, best-in-class experimental instrument at sector 19 of the upgraded Advanced Photon Source (APS-U). The new ISN beamline provides a 5-30 keV monochromatic x-ray beam, high coherence, and focused flux of >3x10^11 photon/sec @ 25 keV. KB mirror focusing offers a focal spot as low as 20 nm. The KB mirrors also provide a long working distance of 61 mm, to enable a versatile suite of sample environments: in-vacuum or in-air operation, heating to >1000˚C, cooling to 40K, flow of liquids & gases, and applied electrical fields. The instrument supports fast fly-scanning of relatively large and heavy samples of ~10x10mm and 2kg at 1mm/s. Measurement techniques include 2D and 3D XRF mapping, ptychographic coherent structural imaging, x-ray diffraction, and x-ray excited optical luminescence. This work presents the first mechanical results from the ongoing technical commissioning in Summer 2025, including the design and architecture of the endstation, vibrational and thermal management, beam conditioning optics, KB mirror alignment, vacuum chamber design, sample scanning, sample environments, metrology, and detector systems design.

We present an active cooling system for the grating mirrors of ID32 soft X-ray beamline at the European Synchrotron Radiation Facility (ESRF). The design combines flexible copper braids to minimize mechanical stress in the grating mirrors with active temperature control to accelerate thermal response. Development followed a model-based approach, integrating dynamic Simulink thermal simulations with static finite element analysis. Under variable beam heat loads, the system maintains mirror temperature stability within ±2 mK and reduces thermal settling time from several hours to under 10 minutes. Interferometric measurements confirm improved optical surface flatness, with the cooling system contributing less than 50 nrad RMS to slope error. This enhancement translates to improved beamline energy resolution from 25.6 meV to 22 meV.

The European Synchrotron Radiation Facility beamline ID01 performs Bragg Coherent Diffraction Imaging and X-ray nano-diffraction experiments with in-situ environments. A new sample environment for nanoparticles has been designed and tested. It combines a furnace and a pressurized X-ray transparent chamber, without the use of beryllium for safety reasons. The required 180°C horizontal and 45°C vertical viewing angles necessitate the use of a dome-shaped pressure chamber. Early in the design phase, the thermal effects of the 500°C furnace on the dome’s mechanical properties were identified as critical. A Finite Element Analysis (FEA) study was conducted, accounting for heat sources, gas turbulence, and static pressure. Aluminium 6082-T6 was chosen for the pressurized dome, providing a safe and easy-to-procure solution. A dome thickness of 0.5mm provides 80% X-ray transmission at 33keV. The sample, a 200nm-diameter palladium nanoparticle, reaches 340°C in a 50-bar hydrogen atmosphere. Unlike beryllium-based pressure domes, this design uses aluminium, avoiding machining difficulties, procurement issues, and safety hazards.

A new hard x-ray fluorescence (XRF) nanoprobe in-strument called Bionanoprobe-II (BNP-II) has been designed and will be constructed at 2-ID-D of the up-graded Advanced Photon Source. BNP-II will take ad-vantage of the orders-of-magnitude increase in bright-ness and coherent flux with advanced sample scanning, metrology, cryogenics, and controls. These advancements will enable high-throughput XRF imaging under cryogenic conditions with 10 nm spatial resolution, 2D survey of mm-sized samples, and fast tomography for 3D visualization. BNP-II also introduces a novel robotic sample transfer system that interconnects a cryogenic plasma focused ion beam (cryo-PFIB) milling station alongside the x-ray nanoprobe. The interconnected instruments enable an iterative workflow between x-ray measurements and cryo-PFIB milling and maintains the integrity of vitrified samples by remaining below 110 K even during transfer. Regions of interest can be identified by fast large-area scans, after which the sample geometry can be optimized for nanoscale x-ray imaging and tomography. This work details the engineering advancements required to examine highly complex, multidimensional systems with BNP-II.

Siam photon source-II (SPS-II) is a new synchrotron facility that is going to be built in Thailand. There are seven beamlines to be constructed together with the new machine. These consist of one soft X-ray beamline, two X-ray absorption beamlines, three X-ray scattering beamlines and one imaging beamline in the lineups. The designs and the selections of insertion devices, front end and beamline components will be presented together with the optical simulation results and the considerations for thermal load management using the combination of front-end components, filters, white/pink beam slits and mirrors along each beamline. New experimental station equipment and the existing equipment from the current Thai synchrotron facility (Siam Photon Source-I) that will be transferred to SPS-II will also be discussed.

The Advanced Light Source Upgrade (ALS-U) will increase soft X-ray coherent flux by 100×. We developed two new beamlines, engineered to minimize loss of brightness and utilize the advanced coherence of the light source. Each beamline uses a minimalist optical layout: a cryogenically-cooled silicon M1 mirror, a monochromator with variable-line-spacing gratings, and a final focusing M3 mirror. Optics are designed for Strehl ratio > 0.8 and sub-100 nrad vibration. A piezo-bimorph M3 mirror paired with a wavefront sensor allows for wavefront optimization. Fabrication is underway. New test data include at-wavelength efficiency measurements for blazed gratings, and motion performance of piezo-actuated pitch/roll flexure systems at cryogenic temperatures, granite air-bearing positioners, and monochromators.

Recent developments on the Spherical Grating Monochromator (SGM) beamline at the Canadian Light Source (CLS) have significantly enhanced its capabilities, particularly through the integration of a vacuum-compatible Physik Instrumente hexapod (H-811.I2V) and the implementation of Bluesky data acquisition software. These upgrades have facilitated the transition from traditional X-ray Absorption Spectroscopy (XAS) measurements to advanced spectromicroscopy techniques. The hexapod allows for sub-micron scale sample manipulation, enabling high-resolution imaging with a 20 mm × 15 mm field of view. Additionally, the modelling of the Kirkpatrick-Baez (KB) mirror system for adaptive focusing has further optimized the beamline's performance providing a beam spot size of less than 10 µm². These developments have not only significantly improved the beamline's capabilities for environmental and catalytic material studies, but also increased the data quality for all routine spectroscopy measurements conducted on the beamline.

As part of the BESSY II+ * upgrade, the new SoTeXS (Soft-to-Tender X-ray Spectroscopy) beamline will enable high-precision, high-throughput studies of battery materials in the 0.5–5 keV energy range. At the endstation, battery cells with varying material combinations will undergo charging and discharging phases while being exposed to the beam. To ensure that, variations in the measurements are attributable to changes within the cells rather than fluctuations in beam properties, a rapid diagnostics procedure will be implemented. This procedure will monitor beam performance in between the battery measurements. This includes measurement of key parameters such as photon flux, energy resolution, and beam focus. The system combines a retractable ionization chamber for energy resolution measurements and a camera-based setup using OpenCV and ChArUco markers for determining beam spot size and position**. These tools allow beam performance monitoring between sample loading cycles and represent an advance over commissioning-only diagnostics on current BESSY II beamlines. This paper presents the technical requirements of the SoTeXS beamline and a selection of potential diagnostic tools.

We have designed and fabricated the world’s first, Additive Manufacture (AM) mirror for X-ray beamlines. For traditional optics, beamline performance is limited by: distortion caused by mechanical clamping; heat-bumps induced by photon-beam illumination; and strain caused by differential thermal expansion when dissimilar materials are cooled. AM enables the creation of intricate internal structures, and the fusion of multiple components into a single piece [$*$]. The optical substrate, beamline mount, and internal cooling manifold were combined into a monolithic structure. The X-ray mirror was 3D-printed in aluminium alloy AlSi10Mg. Single point diamond turning created an optical surface, which was coated in ~ 75 μm of electroless NiP, followed by “super-polishing” using chemo-mechanical processing. Optical metrology demonstrates the AM mirror has surface quality comparable to a traditional silicon mirror, and is virtually immune to clamping deformations, which simplifies beamline installation. AM unlocks exotic internal channel designs, including enhanced cooling performance by turbulent flow, reducing vibrations caused by fluid flow, and conforming to the heat load distribution.

Slope errors on X-ray optics create distortions in the reflected or diffracted X-ray wavefront and reduce energy resolution. This study addresses this challenge by demonstrating a precise and adaptable method for tuning the geometry of liquid nitrogen (LN2)-cooled silicon crystals, with the goal of achieving zero slope errors under specified input power conditions. The findings reveal that an optimal temperature minimizes thermal distortion and slope errors at the X-ray beam footprint. By establishing a straightforward engineering approach to achieve this temperature, the study provides a practical solution for manipulating silicon crystal geometry. This technique ensures minimal slope errors across a broad energy spectrum, enhancing beamline performance and energy resolution. This work overcomes a longstanding limitation in particle accelerator beamlines, where conventional approaches relied on extensive cooling to mitigate thermal effects. The proposed methodology not only improves operational efficiency but also offers a versatile tool for fine-tuning crystal behavior in response to varying energy demands.

In June of 2023, the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory, Berkeley, California, United States, experienced a vacuum interlock event that caused a beam dump. Upon investigation, the vacuum technicians discovered a leak in the cooling system of a custom photon stop in Sector 5 (12 total). This paper will detail the event, the temporary restoration of operations, and the process of how a new photon stop was designed, analyzed, fabricated, assembled, tested, qualified, installed and commissioned in a fourteen week window. Over 20 years had passed since the original photon stop was installed in the ALS. Since then, the technology landscape has changed and many of the manufacturing capabilities have lapsed or become extinct not only in the United States, but across international boundaries. This is especially true of brazing. There is a parallel discussion of the causality for the failure which led to the destructive evaluation of the original photon stop. Finally, engineering looked at the thermal fatigue analysis and provided the operation staff with a specific tool to evaluate and maintain the new photon stop.

The accurate measurement of radiant power is essential for the calibration of X-ray detectors, such as silicon photodiodes. Cryogenic electrical substitution radiometers (ESRs) perform high accuracy, absolute, measurements of radiant power. Material and geometry of the absorber in an ESR are chosen to maximize the absorption in the energy range of interest, while providing a high thermal response and a short time constant. The highest energy design previously reported allowed the measurement of X-rays up to 60 keV. In this work we present a new absorber developed at the Canadian Light Source for energies from 25 keV to 150 keV. Monte Carlo simulations led to a design with an absorption > 99% in the entire energy range while considering all losses due to fluorescence and scattering. Measurements have been successfully performed at the Biomedical Imaging and Therapy beamline (05ID-2), which has a 3.7 T wiggler source and provides X-ray energies up to 150 keV.

The Siam Photon Source II (SPS-II) is Thailand’s next-generation 3 GeV synchrotron light source, designed to deliver high-brightness radiation for scientific and industrial use. Its storage ring, comprising 14 Double Triple Bend Achromat (DTBA) cells and targeting a natu-ral beam emittance below 1 nm·rad, requires numerous high-precision magnets with strict mechanical and mag-netic specifications. This work presents the development of magnet prototypes, covering the full design process including magnet type and material selection, yoke and pole geometry optimization, and magnetic field simulation with OPERA 3D considering saturation and permeability. Mechanical design involved core and coil material selec-tion as well as structural, thermal, and vibrational analyses using AutoCAD, SolidWorks, and ANSYS to ensure mechanical integrity. Prototypes were fabricated using high-precision machining and vacuum pressure impregna-tion (VPI) for coil insulation, then tested for dimensional accuracy and magnetic field performance. This marks Thailand’s first domestically developed magnet prototype, realized through collaboration with local industry, laying a solid foundation for the SPS-II project.

The girder adjustment system of TPS storage ring can fine adjust each girder in 6 axes with 6 kinematic mounting motorized cam movers. The installation of the TPS had demonstrated this design. However, this design is freely mounted with gravity and the 1st natural frequency is less than 30 Hz even with supplement side locking system. Moreover, the motor controller restricts the beginning power output and sometimes the girder will falling when the electromagnetic motor brake is released. A concept improvement design is thus introduced to modify these situations. In this design, a worm gearbox addition can raised the reduction ratio to prevent the falling and inverse kinematic mounting movers with strong springs not only firmly lack the girder to raise the natural frequency but also preserve the motorized algorithm. This paper describes the design in detail.

The Advanced Photon Source (APS) upgrade from double-bend achromats (DBA) to multi-bend achro-mats (MBA) lattice is completed. All storage ring components and front ends were installed between April 2023 to April 2024 and fully commissioned. Some major changes have been made on front ends since our last front end design paper published in MEDSI2018 proceedings. The changes are: 1) Removed clearing magnet from all front ends, 2) Incorporated a Burn-Through-Mask (BTM) as the first fixed mask for all Insertion Device (ID) front ends, 3) Added a new-design diamond window to replace beryllium window for windowed High Heat Load Front End (HHLFE). The upgraded APS front ends will only have three types: a) HHLFE for single beam, b) Canted Front End (CFE) for canted beam, c) Bending Magnet Front End (BMFE) for bending magnet beam. This paper presents the as-built version of all three types of front ends.

The PETRA IV project involves the refurbishment of the 2.3 km PETRA accelerator to accommodate almost 40 beamlines. It also includes the conversion and construction of numerous buildings, including a large experimental hall, with first light planned for 2032. To support planning and design with a model-based approach, a comprehensive, integrated CAD model has been set up. The model comprises civil infrastructure, the accelerator, beamlines, and infrastructure systems. Serving as a single source of truth, it supports a diverse project team, including civil and mechanical engineers, beamline scientists, and other stakeholders, each with different technical backgrounds and needs. The fully integrated CAD model is tied to systems engineering processes like requirements management, and supports collaboration across disciplines. Multiple levels of abstraction, a structured hierarchy, and explicit modelling of interfaces help bridge communication gaps. They also reduce redundant work and minimize design errors, all critical for efficient design in collaboration.

In order to improve and extend the current diagnostic system of the third-generation synchrotron radiation source BESSY II, a source point imaging system is being developed. This paper presents the conceptual design, including technical requirements, simulation results, and expectations for the optical transport line and mechanical integration. The design aims to ensure beam quality during operation using synchrotron radiation emitted from the dipole magnet. The primary components of this beamline are a CCD camera and a lens system. To enable precise positioning of the achromat, the system is equipped with a motorized linear feedthrough. The entire setup is designed to operate under high vacuum conditions. A basic existing setup is employed to experimentally validate the simulation results, using the same CCD camera as in the final beamline setup.

Synchrotron light sources commonly provide users with two types of insertion devices for experiments in biology, medicine, and other fields: in-vacuum undulators (IU) with short period lengths for medium-energy photon sources and cryogenic permanent magnet undulators (CPMU) for higher photon energy. The strong magnetic field generates significant forces on the insertion device magnets, leading to structural deformation and ultimately degrading the magnetic field quality. This paper presents the design and measurement methods of an in-vacuum tapered undulator, analyzes the simulation and measurement results of its structural deformation, and introduces how a flexible structure can be used to establish nonlinear magnetic force compensation to improve system performance

SPring-8 will be upgraded to SPring-8-II, a fourth-generation synchrotron with a multi-bend achromat lattice, by 2028. The beam energy will be reduced from 8 to 6 GeV, substantially lowering emittance. To further reduce the emittance, a damping wiggler is planned for installation in a 30 m straight section. High-energy X-ray above 100 keV are in demand for industrial use, but lowering the beam energy reduces photon flux in this range. A damping wiggler can enhance this flux. We therefore designed the wiggler not only for emittance reduction but also as a high-energy X-ray source. The wiggler will be installed in a straight section with five drift spaces, each about 4 m long, to accommodate the wiggler, masks and related components. Its parameters—unit number, period length, gap and total length—were optimized to achieve low emittance, high photon flux and reduced heat load on absorbers. To handle radiation up to 75 kW and 800 W/mm² over a wide solid angle, the mask aperture was designed to limit angular spread and reduce the heat load on the absorber at the downstream bending magnet chamber. This study presents the optimized wiggler design and power density evaluation at the mask.

The development of a manufacturing plan for the alu-minum straight section vacuum chambers of the Siam Photon Source-II (SPS-II) was undertaken through a multi-stage prototyping program. This work began with the successful reduction of the internal surface roughness (Ra) of domestically produced aluminum extrusions from approximately 19.9 µm to below 0.42 µm by polishing the extrusion die. A dedicated prototype was then used to validate fundamental Ultra-High Vacuum (UHV) processes, confirming the integrity of in-house Tungsten Inert Gas (TIG) welding and establishing a baseline for the chemical cleaning procedure via Photon Stimulated Desorption (PSD) measurements, which showed the cleaning provided an acceptable baseline but requires further optimization. Subsequent full-scale fabrication trials revealed critical lessons. An initial build without a fixture resulted in both significant deformations, confirming the need for mechanical support, and contaminated welds, highlighting the importance of meticulous in-process cleaning. A second trial with a first-generation fixture solved the deformation but caused weld penetration due to obstructed tool access. This iterative development process successfully identified the key challenges of fabrication and has resulted in a de-risked manufacturing methodology, based on an optimized cleaning protocol and a purpose-built fixture, for the final production chambers.

A main application of Laue diffraction in thick bent crystals is on developing high energy/high power monochromators for synchrotron sources. Whereas most of the studies mainly focuses on modelling and simulation of ideal shapes, e.g., cylindrical deformation, this work adds as well a wide set of mechanical and optical measurements performed on 2 mm thickness double bent Laue crystal monochromator currently used at the Biomedical Imaging and Therapy (BMIT) beamline at the Canadian Light Source. Measurements are compared to simulations from tools such as ANSYS and XRT ray-tracing based on Tagaki -Taupin equations. We found real deformed crystal profile is far from ideal cylindrical shape, that the diffracted beam intensity raised 12X due to deformation using an incident white beam. Also, photon flux measurements were performed using a cryogenic radiometer. Measurements have been performed at the 05ID-2 (3.7 T wiggler) and the 05B1-1 (1.35 T bending magnet) BMIT beamlines with energies between 25 keV to 150 keV. Thus, considering the scarcity of experimental data, this work becomes relevant as it presents measurements of a real bent Laue monochromator and compares it to simulations.

The Elettra 2.0 project is upgrading the Elettra synchrotron radiation facility to 4th generation standards. This paper presents the overall photon absorption strategy adopted in the design, which includes both distributed and localized absorption of emitted photons, focusing on discrete photon absorbers and their geometrical configurations within the storage ring. All discrete photon absorbers will be manufactured entirely from Copper-Chromium-Zirconium alloy (CW106C or CuCr1Zr). The components will be produced using wire electrical discharge machining (EDM) for the main geometries, supplemented by conventional milling, with the integration of the flange knife-edge into the absorber geometry without the need for brazing. Two main absorber families are introduced: transversal photon absorbers, designed to protect vacuum chambers near bending magnets and to serve as initial beam-shaping elements, and axial photon absorbers, which function as transitions between different chamber geometries and protect sensitive components, such as RF contact bellows. The paper also presents the current production status and includes photographs of the first manufactured units.

The Korea-4GSR, to be built in Ochang, South Korea by 2030, is a new 4th generation synchrotron radiation facility. It is designed with an electron beam energy of 4 GeV, a stored electron beam current of 400 mA, and an emittance of 62 pm.rad. In Phase I, 10 beamlines will be constructed, five of which will use the IVU24 undulator. When the undulator gap is set to 5 mm, the X-ray source has a total power of 17.95 kW and peak power density of 165 kW/mrad². The High Heat Load Front-End(HHLFE) system is designed to absorb up to 17kW of heat using a fixed mask and a movable mask, ensuring that only the central cone is transmitted to the beamline optical devices. The main materials are GlidCop or CuCrZr, selected for their high thermal conductivity, and the cooling channels are designed with a rectangular cross-section to maximize the heat exchange area for efficient thermal management. In addition, tungsten is applied to precisely shape and effectively absorb the X-ray beam. The structural design of the heat-absorbing devices was determined based on thermal analysis results$*$. This presentation introduces the structural and mechanical design details of the HHLFE.

As part of the Advanced Photon Source Upgrade (APS-U) Project, all 72 beamlines needed to undergo alignment to the new storage ring installation. Prior to beginning the alignment efforts, beamline geometry files were to identify the location of components with respect to the beam source. For new beamline installations, the remaining process was simpler. New components were fiducialized in a lab, along with their support tables. Tables were then installed and aligned to the beamline geometry configuration and a final report was generated for approval. However, for existing beamlines, the process was more intricate. Fiducial records dating back to 1996 were used to generate fiducial files. However, some information was lost over the years. In response, new techniques were implemented to fiducialize components missing records in-situ to avoid removing components from the beamline. Existing component positions were measured with respect to the new source, then realigned. A report of pre-alignment and a report of realignment were generated for approval. All beamlines have undergone realignment in one year timeline and successfully gone through commissioning process.

The CuCrZr alloy has emerged as a preferred material for thermal absorbers in synchrotron light sources, bal-ancing mechanical strength, thermal conductivity, and cost-effectiveness. However, thermal fatigue design criteria for CuCrZr components under high-intensity X-ray beam exposure are not well established. This gap exists due to a lack of experimental data from test specimens subjected to several thousand cycles of localized high temperatures exceeding 300 °C. To address this gap, thermal fatigue tests were conducted on three CuCrZr photon shutters at the NSLS-II instrumentation front end. The experimental setup, receiving an X-ray beam from an undulator, provided a peak power density ranging from 19.95 W/mm² to 38.80 W/mm² on the photon shutters’ surfaces. Within the beam footprints, calculated peak temperatures ranged from 326.8 °C to 416.5 °C. This paper presents the experimental setup, the test results, and finite element analyses of the thermomechanical response of the photon shutters. Based on both experimental and analytical findings, thermal design guidelines are proposed for CuCrZr absorbers, masks, and photon shutters.

The APS-Upgrade Project (APS-U) built a new electron 1100 meter circumference storage ring within the original APS tunnel. APS-U’s new storage ring vacuum system is a complex assembly of over 2500 custom vacuum chambers. The vacuum pumping system is a hybrid combination of NEG-coated vacuum chambers, ion pumps, and uncoated chambers with NEG strip pumping. APS-U began operations in April 2024 and by early 2025 has successfully commissioned the vacuum system to achieve low UHV operating pressures which helped the machine reach key performance parameters and allows for reliable delivery of beam to the users with minimal downtime. The commissioning performance of the machine indicates the NEG coated chambers are performing reliably even with a relatively minimal bakeout and activation. This presentation will share results and analysis of the vacuum system commissioning and performance along with lessons learned from the installation and operations phases.

We developed a novel medium energy resolution monochromator(MRM) for Resonant Inelastic X-ray Scattering (RIXS) experiments at the High Energy Photon Source (HEPS) featuring an integrated flexible high-precision positioning system that surpasses conventional designs. Our rotation platform delivers unprecedented performance with a travel range of hundreds of milliradians—three times greater than existing systems—while maintaining sub-microradian precision, with potential for nano-radian resolution if an additional simple configuration is developed. The breakthrough innovation is our two-axis rotation mechanism using parallel decoupled architecture that uniquely combines structural rigidity with precise motion control, solving the longstanding challenge of spatial motion decoupling while enhancing stability. Rigorous simulation and testing confirm all performance metrics exceed design targets. This technology not only meets the exacting requirements for monochromators but extends high-precision capabilities in high-vacuum environments, with our parallel decoupling principle offering transformative potential across multiple precision engineering applications.

As part of the Elettra storage ring upgrade to 4th generation standards, the Nanospectroscopy/nanoESCA beamline is replacing its prefocusing mirror. The new mirror is a 100 mm x 40 mm x 40 mm monocristalline silicon piece, optimized for the maximum heatload produced by the 25 eV horizontal polarity of the beamline's undulators (100.4 mm period, kx = 7.3). This paper presents the layout and strategy followed to ensure a high quality photon delivery as well as and the calculations and the optimization process of the mirror geometry. To minimize the deformations, a notched, top-side cooling design was chosen, with an almost full-illumination of the top surface. The contact length between the cooling circuit and the mirror was optimized shorter than the mirror length, leading to slightly higher temperatures in the mirror extremities, but more preferable heatload-induced slope. Slits positioned before and after the mirror select only the center and least affected portion of the reflected radiation. Additional simulations confirmed that the optimized design performs equally well or better at higher photon energies.

ALBA is working on the ALBA II upgrade to transform the current storage ring, in operation since 2012, into a 4th-generation diffraction-limited synchrotron light source. The vacuum system is designed for a compact geometry with tight magnet apertures, where synchrotron power is distributed directly onto the chamber walls. Nevertheless, crotch absorbers will be used at key locations. Due to the low conductivity in such small chambers, the entire ring will be NEG coated to accelerate vacuum conditioning and achieve the required ultimate pressure. Most of the vacuum chambers of the 268.8 m long ring, divided into 16 arcs of 12.8 m each, will be made of OFHC-Cu or CuCrZr to dissipate synchrotron radiation and reduce resistive wall impedance. The chambers will have a nominal internal diameter of 16 mm, a minimum wall thickness of 1 mm, and clearances of up to 0.5 mm from magnet poles. Launched in 2021, the upgrade includes an R&D program focused on prototyping critical components. This contribution presents the overall vacuum system status, the design and production of vacuum prototypes, and initial component tests.

The SPring-8-II project, upgrading SPring-8 to a 4th generation light source, started in FY2024. SPring-8 will shut down after summer 2027 for removal of existing equipment and installation of new accelerator components. User operation is scheduled to resume in spring 2029. The project requires a vacuum system compatible with compact, reduced-aperture magnets, ensuring sufficient beam lifetime and operational flexibility. An efficient pumping system was introduced for lifetime assurance, localizing photon-stimulated desorption gas near distributed absorbers and utilizing closely placed NEG pumps. A low coupling impedance vacuum system was designed by optimizing chamber geometry etc. to enable various operation modes. Prior to the mass production of vacuum components, prototypes of the main vacuum chambers were fabricated and their performance was verified with magnet arrays. These tests confirmed procedures for rapid installation and vacuum commissioning excluding in-situ baking after installation, checked for interference with other equipment, and verified vacuum performance. We present the design progress and prototype verification results for the SPring-8-II vacuum system.