Research Frontiers 2014 Research Frontiers 2014 136 II. Machine Operation The operation statistics for the last five fiscal years are shown in Fig. 1. In the FY2014, total operation time of the accelerator complex was 5099.3 h. The operation time of the storage ring was 5080.7 h, 79.9% of which (4057.8 h) was available for SR experiments. The downtime resulting from failure accounted for 0.42% (17.1 h) of the total user time, and no great loss of user time exceeding several hours occurred. Although the operation time for FY2013 was about 800 h less than that for a typical fiscal year due to the large- scale renovations of the aging cooling water and air- conditioning systems, that for FY2014 was restored to the average. A v a r i e t y o f o p e r a t i o n m o d e s i s o n e o f t h e characteristics of SPring-8. The operation modes are grouped into the multi-bunch mode, several-bunch mode, and hybrid-filling mode. There has been no user operation with the multi-bunch mode since FY2011. The several-bunch mode consists of equally spaced bunches or bunch-trains, i.e., 203 bunches, or 29 trains of 11 bunches, and the hybrid-filling mode is composed of a long bunch train and isolated single bunches, as shown in Table 1, where the shares of user time of the operation modes are also shown. The new operation mode of 11/29-filling + 1 single bunch, which started user operation in 2012, plays an important role. A bunch impurity of less than 10 –8 is routinely maintained in the top-up operation. Table 2 summarizes the useful beam parameters of the storage ring. Fig. 1. Operation statistics for most recent five fiscal years. 0 1000 2000 3000 4000 5000 6000 Tuning Refill Down Time User Time 5125.6 4918.6 5078.8 4330.0 5099.3 5096.3 4904.2 5063.1 4265.5 5080.7 1026.6 803.0 884.0 898.0 1024.7 5.0 4.4 5.2 3.5 5.1 27.5 57.0 39.2 20.0 17.1 178.4 117.7 107.7 213.0 163.2 4071.6 4058.5 4155.6 3408.5 4057.8 4104.0 4120.0 4200.0 3432.0 4080.0 99.2 98.5 98.9 99.3 99.5 FY2010 FY2011 FY2012 FY2013 FY2014 Hours Refill Down Time Achieved User Time Planning User Time Availability (%) Accelerator Operation Time Storage Ring Operation Time Tuning & Study (Acc. & BL) Mean Time Between Failures Energy [GeV] 8 Number of buckets 2436 Tunes ( / ) ν x ν y 41.14 / 19.34 Current [mA]: single-bunch 12 multi-bunch 100 Bunch length ( ) [psec] σ 13 Horizontal emittance [nm • rad] 2.4 * Vertical emittance [pm • rad] 4.8 * Coupling [%] 0.2 RF Voltage [MV] 16 Momentum acceptance [%] Beam size ( σ x / / σ y ) * ) [ 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 x ' σ y ' [ μ rad] Long ID section 8 / 0.7 ID section 9 / 1.0 BM1 section 58 / 0.5 / BM2 section 68 / 0.5 Operational chromaticities ξ x ξ y +2 / +2 * * Lifetime [h]: 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) horizontal (rms) ~ 4 ~ 1 vertical (rms) * Assuming 0.2% coupling * * With bunch-by-bunch feedback ( / ) * ( [ μ m]: Table 1. Beam parameters of SPring-8 storage ring Table 2. Filling patterns in FY2014 203 bunches 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 11/29-filling + 1 single bunch Single bunch current (mA) Share of operation time 22.4% 31.8% 10.0% 0.0% 12.4% 2.9% 20.6% 3 mA 1.4 mA 1.6 mA 1 mA 5 mA
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