IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Operation report on the RIKEN AVF cyclotron for 2021
S. Fukuzawa,∗1 K. Suda,∗2 M. Fujimaki,∗2 N. Fukunishi,∗2 A. Goto,∗2 M. Hamanaka,∗1 H. Hasebe,∗2Y. Higurashi,∗2 E. Ikezawa,∗2 H. Imao,∗2 S. Ishikawa,∗1 K. Kamakura,∗3 O. Kamigaito,∗2 M. Kase,∗2
M. Kidera,∗2 K. Kobayashi,∗1 M. Komiyama,∗2 Y. Kotaka,∗3 R. Koyama,∗1 K. Kumagai,∗2 T. Maie,∗2T. Nagatomo,∗2 T. Nakagawa,∗2 T. Nakamura,∗1 M. Nishida,∗1 M. Nishimura,∗1 J. Ohnishi,∗2 H. Okuno,∗2K. Ozeki,∗2 N. Sakamoto,∗2 J. Shibata,∗1 N. Tsukiori,∗1 A. Uchiyama,∗2 S. Watanabe,∗2 T. Watanabe,∗2Y. Watanabe,∗2 K. Yadomi,∗1 and K. Yamada∗2
The annual report on the operation of the RIKEN
AVF cyclotron (hereafter denoted as AVF) for the period January–December 2021 is presented. The beams
accelerated using AVF in the period are listed in Table 1, where beam currents are the maximum values
measured by the Faraday cup FC-C01 at the exit ofAVF. The operation statistics are summarized in Table 2. The operation time for stand-alone operation
was increased to 2100 h from 1520 h, which was reduced because of the COVID-19 outbreak in 2020.
Moreover, the operation time for injection to RRC wasalso increased to 1816 h from 1182 h because the acceleration in the AVF-RRC-SRC mode was performed
for the ﬁrst time in three years from May to June, and2H, 4 He, and 12 C beams were supplied to experimentsfor 28 days.
To supply high-quality beams required for the experiments and to reduce beam losses in two cyclotrons(RRC and SRC) downstream of AVF, AVF was tuned
to extract single turn beams so that components of different turns were minimized in the extracted beams.
The minimum mixing rate for 2 H beam was 2.3% ±1.3%.
In the stand-alone operation which supplied 7 Li3+
at 8.3 MeV/nucleon, the highest beam current of 5670
particle nA was achieved at FC-C01, which was increased by 2.4 times compared with that recorded ata slightly diﬀerent energy of 8.6 MeV/nucleon in an
acceleration test performed in 2011. The increase wasbecause of a high beam current of 70000 particle nA
extracted from the Hyper ECR ion source owing to a
modiﬁcation of an extraction electrode, as well as a
research for supporting gases.
A main trouble occurred at each compensator for
two Dees, which was used to tune a resonant frequency
by changing the capacitance. When compensator #2
was rotated, a vacuum was leaked through a driving
shaft, so that a vacuum degree of the main chamber
deteriorated from 10−5 Pa to 10−3 Pa. In the repair
process, the other leakage was found from compensator#1. The vacuum was recovered by replacing the Xrings.
As a recent improvement, we started monitoring
temperatures at the tips of septum electrodes for the∗1∗2∗3

SHI Accelerator Service Ltd.
RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo- 179 -

Table 1. AVF beam list in 2021.
Particle
1+H

Energy[MeV/nucleon]
1930
4.93

2H+

1215
4.17

Acceleration
Mode
AVF
ˢRRCˢSRC
AVF
ˢRRCˢSRC

6.5
4

He2+

Li2+

7

Li

3+

12C4+

14N

16
18
20

8.3

40

84

5.54

O

6+

6.8

O6+

7

Ar11+

56

75+

Ne7+

AVF

64.93

Beam Current
at C01[particle nA]

E7V/RI production

10000

C03/RI production

10000

BigRIPS

7000

C03/RI production

19800

C03/RI production

13000

BigRIPS

1670

E7B/Student

6000

C03/RI production

7.25
12.5

7Experimental
CourseˢRRCˢSRC

25000

E7B/RI Production
C03/RI production

3850

C03/RI production

8000

E7A/CRIB

5670

BigRIPS

1130

E5B/Biology
ˢRRC

880

E5A/Industry
E3B/Industry

AVF

450

E7A/CNS

4080

E7V/CNS

4580

7ˢRRC

E5B/Biology

540

3.8

ˢRRCˢIRC

E5B/Biology

390

E5A/Industry

520

ˢRRC

E5B/Biology

110

E5A/Industry

230

5.2

Fe15+

5.01

Kr20+

3.97

Table 2. Comparison of AVF operation statistics with thatin the previous years.
AVF stand-alone operation
Tuning of AVF [h]Trouble of AVF [h]C01 MS [h]C03 Exp [h]E7V Exp [h]E7A Exp [h]E7B Exp [h]Sub total [h]AVF operation as injector of RRC
Tuning of AVF [h]Trouble of AVF [h]RRC-Exp (-IRC-Exp) [h]RRC-SRC-Exp [h]Sub total [h]Total [h]Year 2019
1314
00873
36790
153
3166
Year 20191180320
0438
3604

2020
744
112631
1812101
1519
2020
178
599901182
2702

20211149
535672
9548
96
2100
2021
214
1834767
18163916

electrostatic deﬂector using a pair of thermocouples.
The monitor signals are fed into the beam interlock
system (AVF-BIS), so that beams are stopped automatically by a chopper and a Faraday cup, which arelocated before injection to AVF, if an increase of thetemperature caused by beam loss exceeds a certainvalue. Currently, the preset value is 45◦ C.

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