Ⅳ. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 51 (2018)

Operation report on the ring cyclotrons in the RIBF acceleratorcomplex
M. Nishimura,∗1 K. Ozeki,∗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 J. Ohnishi,∗2H. Okuno,∗2 N. Sakamoto,∗2 J. Shibata,∗1 K. Suda,∗2 N. Tsukiori,∗1 A. Uchiyama,∗2 S. Watanabe,∗2T. Watanabe,∗2 Y. Watanabe,∗2 K. Yamada,∗2 K. Yadomi,∗1 and H. Yamasawa∗2
In this report, the operation of the ring cyclotrons in
the RIBF accelerator complex from Jan. to Dec. 2017is presented. Table 1 presents a summary of the beams
accelerated by these cyclotrons. The “availability” inthe table represents the ratio of the actual beam time tothe scheduled beam time. For the old facility, multipleexperiments supplying identical beams are shown as ablock. For the new facility, each experiment is shown
separately because each operation is long-running.
In the old facility, the actual beam time was 870.5 h,and the availability was 96.0%. Stable beams were supplied as usual. In the RIBF, six machine times werecarried out. The total beam supply time was 2546.8 h,
and the availability was 91.3%.
The beam supply of 48 Ca was started 1.5 days aheadof schedule. The down time caused by the accelerator
was 4.5 h, which was spent to replace the charge stripperfoils.
The beam supply of 70 Zn (1st) was started about 1
day later than scheduled, was stopped for three days
due to the vacuum leakage at the bellows in the injection beam line to the SRC, and was aborted due to thevacuum leakage at a plastic insulation pipe used for theion source.
The maximum beam intensity of 70 Zn (2nd), 250
particle nA, was about twice higher than ever before.
This intensity was achieved by changing the acceleration
mode from the variable-frequency mode to the ﬁxedfrequency mode using RILAC2. Because of a malfunc-tion of the fRC RF-W, the beam supply was stopped
temporarily for beam tuning.
The averaged beam intensity of 238 U (1st) over a week,
in which a high-intensity and stable beam was supplied,
was 52 particle nA. In order to repair the failed fRC
RF-W and fRC-EDC, the schedule for beam tuning wasreadjusted and the beam time was extended for 0.5 day.
During the beam supply of 18 O, a voltage breakdownof the AVF spiral inﬂector took place. Therefore, themaintenance of the insulator was carried out. The cryogenic pumps for the SRC valley box and the RRC RF#2
failed, possibly caused by radiation.
For the beam supply of 238 U (2nd), the transmission
eﬃciency down to the A02 gas stripper was improved,
owing to the reﬁnement of the RRC tuning and theintroduction of N2 gas-jet system to the gas stripper.
The supply of uranium vapor from the oven used in theion source was greatly reduced ﬁve times because of theblockade in its ejection hole.
For the synthesis of the 119th element, the beam supply of 51 V using RILAC2-RRC acceleration was started.
For the experiment, the beam energy adjuster (D6BEA) was installed in the D-room. In the experimentconducted in Dec. 2017, beams decelerated to 4.50–
4.87 MeV/nucleon using both D6-BEA and rotating
charge strippers with various thicknesses were also supplied. These beams were used for the experiment system
check.

Table 1. Summary of the accelerated beams in 2017.

∗1∗2

SHI Accelerator Service Ltd.
RIKEN Nishina Center- 250 -