Research Frontiers 2019 Research Frontiers 2019 96 The operation statistics for the last fi ve fi scal years are shown in Fig. 1. In FY2019, the total operation time of the entire SPring-8 accelerator complex was 5285.7 h. The operation time of the storage ring was 5271.2 h, 86.1% of which (4537.9 h) was devoted to SR experiments. This excellent fi gure for the user time represents a storage ring availability of 99.0%. The total downtime caused by failures amounted to 40.5 h, accounting for 0.89% of the total user time. For 99.5% of the user time in FY2019, the stored beam current was maintained at 100 mA by the top-up operation wherein the stored beam was filled up on demand at any time. The 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, the several- bunch and hybrid-filling modes. The several-bunch mode consists of equally spaced bunches or trains of bunches such as 203 bunches or 29 trains of 11 bunches. The hybrid-filling mode is composed of a long train of bunches and isolated single bunches. The isolated bunch current is kept constant within 1% through the top-up operation. The isolated bunch impurity is routinely maintained better than 10 –8 by the bunch cleaning system in the booster. The operation modes of SPring-8 are listed in Table 1 with the share of each operation mode in FY2019. Table 2 summarizes the beam parameters of the storage ring. II. Machine Operation Fig. 1. Operation statistics for last five fi scal years. Table 1. Operation modes in FY2019 Table 2. Beam parameters of SPring-8 storage ring 0 1000 2000 3000 4000 5000 6000 Tuning Refill Down Time User Time Hours 5281.6 5270.4 769.6 4.6 28.7 194.7 4478.7 4512.0 99.3 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 4817.9 4804.8 767.2 202.8 4033.9 4056.0 99.5 5.3 16.8 4951.7 4941.1 803.1 23.1 229.2 4125.5 4152.0 99.4 3.4 Refill Down Time Achieved User Time Planned User Time Availability (%) Accelerator Operation Time Storage Ring Operation Time Tuning & Study (Acc. & BL) Mean Time Between Failures FY2015 FY2016 FY2017 FY2018 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 (%) 31.4 3.1 22.5 7.3 3.1 9.4 2.1 3 1.4 1.6 1.0 11/29-filling + 1 single bunch 20.9 5 Energy [GeV] 8 Number of buckets 2436 Tunes ( / ) 41.14 / 19.34 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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