Diamond Annual Review 2023/24

60 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 3 / 2 4 Machine Operation and Development RichardWalker, Technical Director 2 023/24 was our 17 th year of operation, and carried out in normal operating mode: six-day running per week, from 09:00 Wednesday to 09:00 Tuesday interspersed with machine development days. A total of 200 days (4,822 hours) were scheduled for user mode operation, including five beamline start-up days. All scheduled operation was in standard multibunch mode (900 bunch train) with total current of 300 mA, apart from six days of hybrid mode in January 2024, consisting of a 686 bunch train with a high charge (3 nC) bunch in the middle of the dark gap. Unfortunately two periods of 200 mA running were required for several days in November and December 2023 due to RF cavity problems. The annual operating statistics are shown in Figure 1. The overall mean time between failures (MTBF) continued to be good at 98.4 hours, and each of the five operating runs during the year achieved individually a MTBF in excess of 72 hours, which is the target minimum. The 97% uptime was however below the target of 98% for many reasons including various new faults which consequently took longer to rectify, as well as an increased amount of scheduled downtime. Using Diamond as a test bed for Diamond-II commissioning In addition to supporting Diamond operations, machine development periods are frequently used for testing the procedures will be used for commissioning Diamond-II. These studies can provide valuable insight into the effectiveness of different methods and highlight real-world effects that are typically absent or neglected in modelling codes. This can be anything from the impact of hysteresis in magnetic fields, charge-dependence of diagnostic equipment or leakage of the RF cavity fields into the adjacent BPM buttons. The first method testedwas tomaximise beam transmission of the injected beam from the booster into the storage ring. The acceptance of Diamond-II is anticipated to be substantially smaller than Diamond, so accurate setting of the dipole steerer magnets to allow beam transmission around the ring forms a vital first step. Distinguishing real signal from the electron beam above the measurement noise floor and adjusting the trajectory of the incoming beam are significant obstacles that must be overcome. As well as adjusting the electron beam steering, corrections to the quadrupole focussing strengths must also be carried out. Standard techniques exist to perform this task, however, in case of difficulties, alternative methods are being explored to achieve this goal. The first is to quantify how the electron beam transverse oscillation frequency (betatron tune) changes as a function of quadrupole strength, the second is to measure how the electron beam trajectory varies around the ring in response to a change in dipole steering magnet strength. These methods are complementary to each other but each face individual challenges and are subject to shot-to-shot fluctuations and measurement noise. Fig. 2 shows clearly the additional noise that is introduced from shot-by-shot measurements compared to measurements with a stored beam. Adapting the fitting routines to overcome the increased measurement noise and to provide a preliminary correction to the machine optics is currently under study. These investigations provide essential input into the procedures that are being developed for the future commissioning of Diamond-II. Figure 1. Mean Time Between Failures (blue bars, left axis) and Uptime (red curve, right axis) since the beginning of operations. Figure 2: Comparison of orbit response matrices for the Diamond storage ring measured at 10 mA stored beam (left) and from shot-by-shot measurements and 0.5 mA injected beam current (right).