Ⅳ. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 52 (2019)

Operation report of the ring cyclotrons in the RIBF acceleratorcomplex
J. Shibata,∗1 K. Suda,∗2 T. Dantsuka,∗2 M. Fujimaki,∗2 T. Fujinawa,∗2 N. Fukunishi,∗2 S. Fukuzawa,∗1M. Hamanaka,∗1 H. Hasebe,∗2 Y. Higurashi,∗2 E. Ikezawa,∗2 H. Imao,∗2 S. Ishikawa,∗1 O. Kamigaito,∗2Y. Kanai,∗2 M. Kase,∗2 M. Kidera,∗2 K. Kobayashi,∗1 M. Komiyama,∗2 R. Koyama,∗1 K. Kumagai,∗2 T. Maie,∗2M. Nagase,∗2 T. Nagatomo,∗2 T. Nakagawa,∗2 M. Nakamura,∗2 T. Nakamura,∗1 M. Nishida,∗1 M. Nishimura,∗1J. Ohnishi,∗2 H. Okuno,∗2 K. Ozeki,∗2 N. Sakamoto,∗2 N. Tsukiori,∗1 A. Uchiyama,∗2 S. Watanabe,∗2T. Watanabe,∗2 Y. Watanabe,∗2 K. Yadomi,∗1 K. Yamada,∗2 and H. Yamasawa∗2The operation report of the ring cyclotrons in theRIBF accelerator complex from Jan. to Dec. 2018 is presented. Table 1 presents a summary of the beams accelerated by these cyclotrons. The availability is defined asthe ratio of the actual beam service time to the scheduled beam service time, which is an index of the stable
operation of accelerators. Multiple experiments supplying identical beams are shown as a block, whereas theexperiments with the 51 V beam are not shown, because
the new element search experiments are conducted as
the closed beam time under the Nishina Center Director. The total beam supply time was 1719.4 h excluding the V beam supply. The service of RRC was notavailable due to the upgrade of the resonators1) during the period of two months from February. In theold facility (RARF), the actual beam service time was477.0 h, and the availability was 108.5%. Stable beams
were supplied as usual. In the new facility (RIBF), twobeam services were carried out. The total beam supply
time was 1242.4 h, and the availability was 84.2%.
For the synthesis of the 119th element, three beamservices were carried out. The 51 V beams were suppliedwith the availability of 73.5%. The availability was low
due to the vacuum leakages caused by cooling waterleakage at the new resonators of RRC and had to beaborted for repairs.

For the beam supply of 18 O, the maximum beam intensity was 600 particle nA, and the availability was
100.6% for seven experiments. There were failures inthe RRC, namely in the plate and filament power supplies for an intermediate amplifier of RF No. 1 and ina vacuum control system, which seemed to be caused
mainly by radiation.
A 238 U beam at 345 MeV/nucleon was supplied foreight experiments, and the maximum beam intensityof 72 particle nA was the highest ever. The availability decreased to 67.8% owing to several troubles.
The beam supply was started 7.5 d later than scheduled due to the failures and repairs of the SRC-EICand -EDC, abnormal termination of the rotating charge
stripper, and a severe beam tuning to reduce beamlosses. The rotation-stops of the charge stripper occurred frequently even during the beam supply. Finally,a ferrofluidic seal was exchanged to recover stable operation. Furthermore, a vacuum leakage happened again
at the RRC resonator No. 1 in November, and the repair was performed. It took 8 d for the repair and beamtuning to resume the beam supply.
Reference1) K. Yamada et al., “Remodeling of acceleration cavity resonators for RIKEN Ring Cyclotron”, in this report.

Table 1. Summary of the accelerated beams in 2018.

∗1∗2

SHI Accelerator Service Ltd.
RIKEN Nishina Center- 230 -