Annual Review 2024-2025

and replaced with SCC#2, which however needed time to condition with beam and which forced us to have to reduce beam current. Unfortunately SCC#2 then developed a waveguide flange vacuum leak and so had to be removed in Shutdown 3 (August 2024). Due to a simultaneous failure of one of the back-up normal conducting cavities we could only reliably provide a beam current of 200 mA. SCC#2 was repaired in the RAL Space clean-room and re-installed in Shutdown 4 (October 2024), and 300 mA operation was reinstated in Run#1 2025. Other significant problems that occurred during the year were: • load arc trips on one of the Normal Conducting Cavities (NCC), eventually traced to broken ferrite tiles in the load; • a fire alarm-induced shutdown of the machine cooling; • two mains brown-outs; • a fast valve on a front end repeatedly disarming, losing the SR Machine Protection System; • absorber temperature trips on 3 front ends at narrow ID gaps; • major water leak on the DIAD beamline, losing water pressure on the machine side, tripping multiple systems. A Helium compressor failure. 2024/25 was our 18th year of operation, and was carried out in normal operating mode: 6-day running per week, from 09:00 Wednesday to 09:00 Tuesday interspersed with Machine Development days. A total of 204.5 days (4,910 hours) were scheduled for User Mode operation, including 5 beamline start-up days. All scheduled operation was in standard multibunch mode (900 bunch train) with total current of 300 mA, apart from two periods of 6 days of “hybrid” mode in February/March 2025, consisting of a 686 bunch train with a high charge (3 nC) bunch in the middle of the dark gap. Unfortunately several periods of 200 and 250 mA running were required in Runs 3, 4 and 5 in 2024 due to RF cavity problems. The annual operating statistics are shown in Figure 1. The overall Mean Time Between Failures (MTBF) was disappointing at 77.9 hrs, but still above the target minimum of 72 hrs. The 97.2% uptime was slightly below the target of 98%. Various challenges were faced during the year particularly with the RF system. Superconducting cavity SCC#1 had to be removed in Shutdown 2 (June 2024) due to a leak of the insulation vacuum Machine, Buildings and Infrastructure D I A M O N D L I G H T S O U R C E L I M I T E D 43 M A C H I N E , B U I L D I N G S A N D I N F R A S T R U C T U R E Figure 1. Mean Time Between Failures (blue bars, left axis) and Uptime (red curve, right axis) for the last 10 years. MTBF (h) Uptime (%)