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The disturbance to the users during each beam injection in USM, and the injection efficiency, are continually being worked upon, with the result of a doubled horizontal emittance during injection and an efficiency of 70-80%, respectively. The S3 septum located at the end of the TL2 transport line will be moved close to the storage ring in the summer shutdown 2024 to lower the injection bump, thus mitigating injection perturbation. Both non-linear kickers (NLK) and stripline kickers (SLK) are candidates for the upgrade of the injector. The physics and technical design, together with the mechanical design of the NLK, progressed in 2023. In collaboration with PSI, the SLK prototyped by PSI will be installed in the EBS for beam tests in 2024. Efforts to lower the natural horizontal emittance further with an off-energy lattice of the storage ring have been made, with an operational beam lifetime and good injection efficiency after the optimisation of beam optics and closed orbit distortion corrections.

The commissioning of the mini-β test straight section of beamline ID31 was continued smoothly during MDTs, resulting in optimised closed orbits and operational beam lifetime. The smaller undulator gap at ID31 reduces the beam lifetime and impacts the injection efficiency. Further tests aiming to optimise beam performance are foreseen in 2024.

New insertion devices (ID) are continuously in procurement, assembly, installation and commissioning, in line with the beamline construction and the medium- term scientific plan. In 2023, two cryogenic permanent magnet undulators (CPMU16.4s), one at ID29 and another at ID03, were installed during the March and summer shutdowns, respectively, and two upgraded APPLE-II 70s were installed at ID32 during the October shutdown. Up to now, eight CPMUs are in operation, and 11 CPMUs will be planned until 2025, with some IDs still in construction and upgrade. In the meantime, ID controls are also being developed, aiming at the standardisation and synchronisation of IDs with beamline double-crystal monochromators, to enable the undulator to be used as the real first element of the beamlines.

Improving the stability of the electron beam and X-rays remains a key project. Following the two X-ray beam position monitors (X-BPMs) installed on beamlines BM08 and BM16, another two second-version X-BPMs and two in-air-X-BPMs were installed in 2023. Comparison of the results from these new X-BPMs will be very helpful to understand their performance and cross-check data from X-BPMs and e-BPMs. Other activities related to the beam diagnostics were carried out, including halo measurements, reduction of the AC-motion due to high water-flow rate, septa-damping system improvement, unification of the BPM system for the fast orbit feedback, cleaning amplifier improvement at the booster and beam emittance blow-up studies.

The ASD is also involved in the EURIZON international collaboration project. Fruitful achievements in the collaboration among European labs on beam physics studies and control-related topics are conducive to strengthening cooperation and the development of AI techniques.

As a result, the operation of EBS reached its objectives thanks to the great efforts and dedication of ASD staff and the valuable support given by the other divisions. I would like to take this opportunity to thank all staff for their continuous contributions and dedication to the operation of the EBS and the accelerator development projects in 2023. Q. QIN