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

1 8 0 H I G H L I G H T S 2 0 2 3 I

RUN NUMBER 2023-01 2023-02 2023-03 2023-04 2023-05 TOTAL 2023

Scheduled beam time (hours) 1128 1200 1200 908 1056 5492

Delivery time (hours) 1115.10 1197.10 1192.50 895.50 973.80 5374

Availability 98.86% 99.76% 99.38% 98.62% 92.22% 97.85%

Dead time for failures 1.14% 0.24% 0.62% 1.38% 7.78% 2.15%

Number of failures 15 4 10 16 7 52

Mean time between failures (hours) 75.2 300 120 56.8 150.9 105.6

Mean duration of a failure (hours) 0.86 0.73 0.75 0.78 11.74 2.27

Table 1: Overview of storage ring operation in 2023.

Summary of accelerator operation

2023 is the second year with a standard operation schedule since the launch of the Extremely Brilliant Source (EBS) in August 2020. 2022 was already an exceptional year, with 99.06% availability and 88.5 hours of Mean Time Between Failures (MTBF). Compared to 2022, the number of beam failures in 2023 decreased by 16%, from 62 to 52, thanks to high quality maintenance.

The performance of the accelerators was excellent (99.2%) until November, when the longest beam interruption of the year occurred. A copper cooling-water tube in the S3 septum magnet (used to inject the beam into the storage ring) broke, causing a severe water leak. Fortunately, the water did not reach the parts under vacuum. The septum repair and vacuum restoration was limited to 78 hours thanks to the rapid teamwork of the ESRF s experts.

This single failure justifies this year s beam availability of 97.85%, with a nevertheless excellent MTBF of 105 hours, as can be seen in Table 1. In November and December, the Machine-Dedicated Time (MDT) days were reorganised to give 78 hours of beam to users to compensate for the time loss and allow them to perform or finish experiments that were affected by the failure. Taking this compensation into account, the machine availability of 2023 reached 99.28%.

In February, an external event caused an unscheduled pause in beam delivery, when a glitch on the 20-kV electrical network caused the high-quality power supply (HQPS) to trigger the blackout protection system, tripping the power supplies, the RF and reducing the water flow. This happened outside working hours and time was needed to restart equipment.

An intervention was required in August when the Personal Safety System (PSS) triggered, likely due to premature ageing of the cables and emergency push buttons inducing false or spurious contacts. Consequently,

all cables and buttons in SR1 were replaced during the October shutdown of 2023, and remaining zones will be completed in the following shutdowns.

In 2022, certain newly installed cables were found damaged due to high levels of radiation. In 2023, the cables were replaced and plates of lead shielding installed in the straight sections concerned.

The new RF working point of 5.5 MV (implemented in 2022 to reduce the storage ring energy consumption by 1.1 GWh per year) was successfully maintained in 2023. Together with the optimisation of the HQPS electricity consumption, the total reduction in energy consumption from the accelerator reached 1.68 GWh per year.

Filling modes

In 2023, five different modes were delivered with the following distribution: 7/8+1 (55.5%), uniform (12.7%), 16-bunch (23.1%), 4-bunch (6.1%) and hybrid 28 x 12 + 1 (2.6%).

Concerning the 7/8+1 and the uniform modes, all nominal parameters were successfully delivered: an intensity of 200 mA, a lifetime greater than 23 hours and an artificially stabilised vertical emittance of 10 pm.rad.

The 16-bunch mode is still provided with an intensity limited to 75 mA due to the kicker ceramic chamber heating problem. A new design of kicker ceramic chamber that significantly reduces chamber heating has been ordered but not yet delivered. We are confident that this strategy will enable us to deliver the nominal beam current of 90 mA in late 2024.

Injection disturbance has been drastically reduced thanks to hardware optimisation, the compensation system and storage ring optics tuning during USM operation. Consequently, top-up frequency is maintained at one hour in all modes to minimise disturbance.