In July 2019, a design beam of 8.3 × 1013 protons/pulse, whose 25 Hz operation produced the design beam power of 1 MW, was accelerated for 10.5 h by using the J-PARC 3 GeV rapid cycling synchrotron. During the operation, a J-PARC H- ion source and a 400 MeV linear accelerator (LINAC) were operated with the design beam duty factor (BDF) of 1.25% (0.5 ms × 25 Hz) and ejected beam intensities of 58 mA and 50 mA, respectively. Furthermore, as expected from the transverse emittances measured in an H- ion source test-stand, they were successfully operated with the BDF of 1.5% (0.6 ms × 25 Hz) and ejected beam intensities of 72 mA and 60 mA, respectively. In the operation, the beam pulse accelerated by the J-PARC radio-frequency quadrupole LINAC (RFQ) had a rapid rise-time of about 10 µs and an excellent flatness with a slow variation of ±0.2%. A flat beam pulse was produced by the predicted 100% space-charge neutralization (SCN) in the upstream half of the J-PARC low-energy beam transport (LEBT) with a vacuum pressure of 3.6 × 10-4 Pa and the unpredicted high and almost constant SCN of about 69% in the downstream half of the LEBT with a vacuum pressure of 2.8 × 10-5 Pa. The rapid rise-time was produced by the preformed 100% SCN with a preceding 100 µs 40 keV beam, which was not accelerated by the RFQ due to the low energy outside the RFQ acceptance. In the test-stand operated with the terminal voltage of 62 kV and BDF of 5% (1 ms × 50 Hz), the transverse emittances of a 100-mA beam were also measured to be suitable for the RFQs of high energy LINACs. A 100-mA high energy and high duty factor LINAC could be realized with this source since the transverse emittances were further improved by about 8% with the shortest beam extractor in the test-stand.

中文翻译：

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J-PARC H− 离子源和空间电荷中和 LEBT 用于 100 mA 高能量和高占空因数 LINAC

2019 年 7 月，使用 J-PARC 3 GeV 快速循环同步加速器将 8.3 × 1013 质子/脉冲的设计光束，其 25 Hz 操作产生 1 MW 的设计光束功率，加速了 10.5 小时。在运行期间，J-PARC H-离子源和 400 MeV 直线加速器 (LINAC) 以 1.25% (0.5 ms × 25 Hz) 的设计束流占空因数 (BDF) 和 58 mA 的射束强度运行，分别为 50 mA。此外，正如在 H 离子源测试台中测量的横向发射率所预期的那样，它们在 BDF 为 1.5% (0.6 ms × 25 Hz) 和发射束强度分别为 72 mA 和 60 mA 的情况下成功运行。在操作中，由 J-PARC 射频四极杆 LINAC (RFQ) 加速的光束脉冲具有约 10 µs 的快速上升时间和良好的平坦度，缓慢变化为 ±0.2%。在 J-PARC 低能束传输 (LEBT) 的上游半部预测的 100% 空间电荷中和 (SCN) 产生了平束脉冲，真空压力为 3.6 × 10-4 Pa 和不可预测的高在真空压力为 2.8 × 10-5 Pa 的 LEBT 下游半部几乎恒定的 SCN 约为 69%。快速上升时间是由预制的 100% SCN 和前面的 100 µs 40 keV 光束产生的，它由于 RFQ 接受之外的低能量，RFQ 没有加速。在端电压为 62 kV 和 BDF 为 5%（1 ms × 50 Hz）的试验台中，还测量了 100 mA 光束的横向发射率，以适用于高能 LINAC 的 RFQ。