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A C C E L E R A T O R A N D S O U R C E

The Accelerator and Source Division (ASD) is in charge of the production of synchrotron light from the Extremely Brilliant Source (EBS), the upgrade of the ESRF s 6 GeV storage ring. The EBS has been operating in User Service Mode (USM) for over a year, following its successful construction and commissioning, and launch into operation on 25 August 2020. Remarkable results in the USM operation of EBS have been achieved, with the beam availability increased from 96.1% in 2020 to 96.4% in 2021. The Mean Time Between Failures (MTBF) reached 66.4 hours in the period of USM operation in 2021, and the Mean Time per Failure (MTF) was 145 minutes. In 2021, a total of 4648 hours of beam was officially scheduled for delivery to users despite the COVID-19 pandemic. Besides the EBS operation, much of the Division s development work in 2021 focused on the consolidation and sustainability of EBS operation and the improvement of its beam performance.

With the aim of reaching the nominated beam current in the various timing modes (4-bunch, 16-bunch, and 62-bunch filling patterns), the ASD is working on the replacement of the current injection kicker ceramic chambers, which were found to be problematic in terms of heating when the single- bunch current was increased. The ceramic kicker chambers are still in the prototyping stage at different companies to overcome the technical problems. Meanwhile, the backup scenario of re-coating the current kicker chambers to decrease the impedance is also being implemented.

The HotSwap system, which covers all the power supplies to the quadrupoles around the storage ring, has been connected in the current power supply system. It will be fully operational in 2022, with the expectation of decreasing the beam losses due to power supply failures.

Another measure to consolidate the operation of EBS is the replacement of the klystrons operating with the RF cavities by solid-state amplifiers (SSAs) as a long-term strategy of EBS operation, which was validated by the ESRF management and endorsed by the Machine Advisory Committee (MAC). The procurement of SSAs is ongoing and the whole project is foreseen to finish in 2027.

The newly installed slow power supplies for the injection kickers in the storage ring were commissioned smoothly during Machine-Dedicated Time (MDT), and have been adopted in routine operation since the restart of the EBS in October 2021, with less injection peturbation on the beamlines. A fourth harmonic RF system is still in the design stage, and will be helpful to increase the Touschek beam lifetime in the operation of the timing mode and, in the meantime, to reduce the parasitic heating on the accelerator vacuum elements.

The mini-b scheme, which needs additional quadrupole magnets to be installed during the winter shutdown of 2021, will be conducive for the enhancement of the brightness and coherence for some beamlines. All the preparative work in the tunnel of the EBS storage ring has been finished, and the commissioning of the mini-b scheme is foreseen to be carried out in spring 2022.