Research Frontiers 2022 Research Frontiers 2022 118 II. Machine Operation The operation statistics for the last five fiscal years are shown in Fig. 1. In FY2022, the operation time of the storage ring was 5259.3 h, 84.0% of which (4416.0 h) was devoted to the SR experiments. This excellent fi gure for the user time represents a storage ring availability of 99.5 %. The total downtime caused by failures amounted to 19.7 h accounting for 0.45% of the total user time. For 99.4% of the user time in FY2022, the stored beam current was maintained at 100 mA via the top-up operation wherein the stored beam was fi lled up on demand at any time. Extreme stability of the light source intensity better than 0.1% was provided by the top-up operation. The variety of operation modes for SR experiments is one of the characteristics of SPring-8. The operation modes are classified into two types: several-bunch and hybrid-fi lling modes. The several-bunch mode comprises equally spaced bunches or trains of bunches such as 203 bunches or 29 trains of 11 bunches. Whereas, the hybrid-filling mode is composed of a long train of bunches and isolated single bunches. Suffi cient isolated bunch purity is maintained by the SACLA linac's spurious bunch sweeper and the storage ring's bunch cleaning system. The operation modes of SPring-8 are listed in Table 1, along with a share of each operation mode for FY2022. Table 2 summarizes the beam parameters of the storage ring. Fig. 1. Operation statistics for five most recent fiscal years. Table 1. Operation modes in FY2022 Table 2. Beam parameters of SPring-8 storage ring 0 1000 2000 3000 4000 5000 6000 Tuning Refill Downtime User Time Hours 5284.6 5274.8 964.6 3.6 7.4 718.2 4309.0 4464.0 99.7 5300.2 5300.2 860.2 3.1 10.0 553.4 4426.9 4440.0 99.7 5259.3 5259.3 819.3 4.3 19.7 232.4 4416.0 4440.0 99.5 5285.7 5271.2 701.7 5.6 40.5 206.3 4537.9 4584.0 99.0 5329.8 5316.7 721.8 5.3 43.1 168.9 4559.6 4608.0 98.9 Refill Downtime Achieved User Time Planned User Time Availability (%) Accelerator Operation Time Storage Ring Operation Time Tuning & Study (Acc. & BL) Mean Time Between Failures FY2018 FY2020 FY2021 FY2022 FY2019 203 bunches 4 bunch-train × 84 11 bunch-train × 29 1/7-filling + 5 single bunches 2/29-filling + 26 single bunches 1/14-filling + 12 single bunches 4/58-filling + 53 single bunches Single bunch current (mA) Share of operation time (%) 39.5 7.0 17.8 6.5 0 6.5 3.2 3 1.4 1.6 1.0 406 × 11/29-filling + 1 single bunch 19.5 5 Energy [GeV] 8 Number of buckets 2436 Tunes ( / ) 41.14 / 19.325 ν ν x ν ν y Current [mA]: Bunch length ( ) [ psec ] σ σ 13 Horizontal emittance [ nm • rad ] 2.4 * single bunch 12 multi bunch 100 Vertical emittance [ pm • rad ] 4.8 * +2 / +2 * * * Coupling [ % ] 0.2 RF Voltage [ MV ] 14.4 * * ~ 16 Momentum acceptance [%] Beam size ( σ σ x / σ σ y )* [ μ μ m] Long ID section 333 / 7 ID section 316 / 5 BM1 section 94 / 12 3.2 ( ~ 256 MeV) BM2 section 100 / 12 Beam divergence ( σ σ x '' / σ σ y '' )* [ μ μ rad] Long ID section 8 / 0.7 ID section 9 / 1.0 BM1 section 58 / 0.5 BM2 section 68 / 0.5 Lifetime [hr]: Operational chromaticities ( ξ ξ x / ξ ξ y ) 100 mA (multi bunch) ~ 250 1 mA (single bunch) ~ 30 Horizontal dispersion [m]: Long ID section 0.153 ID section 0.146 BM1 section 0.039 BM2 section 0.059 Fast orbit stability (0.1 – 200 Hz) [ μ μ m] : horizontal (rms) ~ 4 ~ 1 vertical (rms) * Assuming 0.2% coupling * * Power saving mode * * * With bunch-by-bunch feedback
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