The 9th Symposium on Accelerator &ience and Technology, Tsukuba, Japan 1993

Status of the RIKEN A VF Cyclotron
Akira Goto, Tadashi Kageyama, Masayuki Kase, Shigeo Kohara, Makoto Nagase,
Takahide Nakagawa, Kumio Ikegami, Osamu Kamigaito, Naohito Inabe,
Ichiro Yokoyama, Jiro Fujita, Tetuo Kawama* andYasushige Yano
The Institute of Physical and Chemical Research (RII<EN)
Wako-shi, Saitama 351-01, Japan

Abstract
The RIKEN A VF cyclotron has been in routine
operation as an injector of the RIKEN Ring Cyclotron (RRC)
since April 1989. The number of ion species accelerated until
now amounts to 15. Beam transmission efficiency through thecyclotron is typically about 20 %. Single turn extraction isachieved and the extraction efficiency of over 75 % isroutinely obtained. Polarized deuterons have been available
since April 1993. Stand-alon e use of the cyclotron for lowenergy experiments also started in June 1993.

I. INTRODUCTION
The A VF cyclotron was completed at the end of March
1989 as one of two injectors (the other is the RILAC) of theRII<EN Ring Cyclotron (RRC).[1,2]It has a K-value of 70 MeV, allowing us to accelerateions whose m/q value is up to 4.5. The number of spiralsectors is 4. The extraction radius is 714 mm, which is 4/5
times the injection radius of the RRC. Beam acceleration is
made, in harmonics of 2, with a couple of 85° RF dees
operating between 12-24 MHz. The cyclotron has external ion
sources: a 10 GHz ECR ion source and a polarized
proton/deu teron ion source. A beam from the ion source isinjected through the upper yoke of the magnet and inflected
onto the median plane of the cyclotron with a spiral inflector.
A beam buncher is located 2m upstream from the inflector. It
consists of a pair of meshes; a sawtooth wave-form electricfield is produced between them. The first beam (7MeV/nucle on 14N5+) was successfully extracted from thecyclotron in April 1989.[1] Since then the cyclotron has
routinely been operated in a combination with the RRC, andits performanc e has gradually been upgraded in terms ofbeam intensity, transmission efficiency, extraction efficiency,
stability and so on.
In this paper will be reported our operational experiences, including the acceleratio n of polarized deuterons. A
brief description on stand-alone use of the cyclotron will also
be presented.

II. OPERATIO NAL EXPERIENCES
Table 1 lists the ions accelerated by the AVF cyclotron
during the past four years since the first beam was obtained.
We have accelerated 15 kinds of ion species. Beam intensities
of several eJ.lA are routinely extracted in recent operation.
The recent one-year statistics of beam time shows that thosefor the following three kinds of ions exceed 50 % of the total

beam time: 5.2 MeV/nucle on (95 MeV/nucle on from theRRC) 40Ar11+ and 7 MeV/nucle on (135 MeV/nucle on)
12c4+ and 18o6+.
The performanc e of the 10 GHz ECR ion source has
been increased in terms of beam intensity and stability byapplying the plasma cathode method to its first stage.[3]Owing to this method, the beam intensities of heavy ions, inparticular like Ar and Kr ions, have been greatly improved,e.g. 80 ejlA of 40 Arll + and 9 ejlA of 84Kr20+. According tothis upgraded performanc e, the extracted beam intensity of5.2 MeV/nucleon 40Ar 11 + from the cyclotron, for example,
has been increased up to about 4 eJ.lA. The upgraded
performance will allow us to accelerate 4.0 MeV/nucleon (70MeV/nucle on from the RRC) 84Kr20+ with practical beam
intensity. To produce metallic ions like Mg, AI, Ni and Zrions, we use ceramic rods of their oxides. The plasma cathodemethod has also remarkably been effective for these metallicions.
A single turn extraction can be achieved by carefully
adjusting the first harmonic field near the extraction and thecurrents of the trim coils near the cyclotron center. The beam
extraction efficiency of over 75 %is routinely obtained. Thebeam bunching efficiency with the sawtooth buncher is 5-6.
The beam transmissio n efficiency through the cyclotron isthen typically about 20 %, though it depends on the kind ofaccelerated ion and in some cases drops as low as about 5 %.
In June 1992 a polarized proton/deuteron ion source wascompleted.[4] It is assembled about 8 m directly above theA VF cyclotron center. During the last one year effort has
been made on the modifications mainly of the dissociator, theECR ionizer and the extraction device. The beam intensity
extracted from the ion source has recently increased up to 140
JlA. Acceleration of a polalized deuteron beam has also been
made with the A VF cyclotron (7 MeV /nucleon) as well as theRRC (135 MeV/nucle on), and the polarizatio n has beenmeasured. Because the AVF cyclotron cannot separate
deuterons and H2+ ions, a charge stripper foil is used after thecyclotron to omit H2+ ions. Polarized dueteron beam of 300
nA and 100 nA have been obtained at 7 MeV/nucleon and
135 MeV/nucleon, respectively, with 50-60% polarization of
the ideal value. The single tum extraction available for both
the A VF cyclotron and the RRC has allowed us to freely
control the spin direction using a spin rotator (a Wien filter)
placed downstream of the ion source, without reducing thepolarization or the intensity. Figures 1 and 2 show examplesof turn patterns measured for polarized deuterons inside thecyclotron and in the extraction region near the entrance of thedeflector, respectively.
Beam emittances were measured before and after the* Sumijyu Accelerator Service, Ltd.
-59-cylotron: the emittance of the beam from the ECR ion source
was about 1501t mm.mrad and the emittance of the extracted
beam about 61t mm.mrad. Pulse width of the extracted beam
was preliminarily measured with a new type of beam phase
monitor.[5] The width (FWHM) of 5.5 MeV/nucleon 18o6+
ion beam was 1.6 nsec corresponding to 8.4 RF degrees.
Precise measurement with the monitor will be made.
Until now, there have been serious troubles with respect
to the, following cyclotron components: a part of the RF
contact fingers of the shorting plate were burnt and melt; andthe deflector became not to work due to its unendurable leakcurrent. In the latter case, white powder-like material
containing very thin and short needle-like material was
adhered to the inside of the septum along the median planelevel. To remove the origin-unknown material, we had todisassemble the cyclotron four times in the recent half year.

experiments were made: a slow-positron experiment using 5.2
MeV proton beam at the port B and measurement of fusioncross sections using 6.7 MeV/nucleon 27 AI beam at the port
C. The. stand-alone use is made while the RRC is operated
with the RILAC beam injection.
IV. ACKNOWLEDGEMENTS
The authors are grateful for the support of the cyclotron
operation by H. lsshiki, H. Akagi, R. Ichikawa, N. Tsukiori,
R. Abe, K. Takahashi, S. Otsuka, T. Maie and T. Honma from
Sumijyu Accelerator Service, Ltd.
V. REFERENCES[1]

III. STAND-ALONE USE OF THE AVF CYCLOTRONStand-alone use of the AVF cyclotron started in June [2]1993. For this three experimental ports have been provided asshown in Figure 3: at port A is installed a chamber for use in [3]radioisotope production; at port B a scattering chamber for ·slow-positron experiments; at port C a scattering chamber for [4]nuclear physics experiments. The port A is located at the endof the extraction straight line in the cyclotron vault, the port B [5]at the end of the vertical line in E7 experimental room and theport C at the end of the horizontal line in E7. So far two

A. Goto, et al., "Status of injector AVF cyclotron at
RIKEN," in Proceedings of the 7th Symposium onAccelerator Science and Technology. Osaka, Japan,
December 1989, pp. 51-53.
Y. Yano,"Current status and future scope on RIKEN
accelerator research facility," in this proceedings.
T. Nakagawa, et al.,"Status on the RIKEN ECRIS," inthis proceedings.
K. Ikegami, et al., "Development of the RIKEN
polarized ion source," in this proceedings.
M. Kase, et al.,"Development of a beam phase monitor
with a micro-channel plate for the RIKEN Ring
Cyclotron," in this proceedings.

Table 1Ions accelerated by the AVF cyclotron from April1989 to June 1993
Particle Charge RFfreq.

Energy*Intensity

Particle Charge RFfreq.

(MHz) (MeV/nucleon) (e~)

pH2dpol. d
12c

13c

1
I
1
I
II
1
11
1
1
4
4
4
4

19.35
21.1
I2.3
I4.0
16.3
I2.3
13.8
14.5
16.0
16.3
16.3
13.95
14.5
16.3
12.3

9.9 (210)
11.8 (270)
4.0 ( 70)
5.2
7.0 (135)
4.0 ( 70)
5.0
5.5 (100)
6.7 (130)
7.0 (135)
7.0 (135)
5.1 ( 92)
5.5 (100)
7.0 (135)
4.0 ( 70)

Energy*Intensity(MHz) (MeV/nucleon) (e~)

14N

5.2
0.07
3.I
5.0
5.4
1.4
2.6
0.6
0.5
3.4
0.3
0.7
0.6
7.3
2.0

15N
t60
ts 02<>Ne
22Ne
24Mg
27AI
40Ar

4
54
556
56
76
78
9
11
11

13.0
16.3
12.3
15.25
13.1
I6.3
12.3
14.5
16.3
12.3
14.5
14.5
16.0
13.0
14.05

4.4 ( 80)
7.0 (135)
4;0 ( 70)
6.1 (115)
4.4 ( 80)
7.0 (135)
4.0 ( 70)
5.5 (100)
7.0 (135)
4.0 ( 70)
5.5 (100)
5.5 (100)
6.7
4.4 ( 80)5.2 ( 95)• The values in the parentheses show the energies obtained by the coupled operation with the RRC.

-60-3.3
12.0
2.6
1.3
7.8
3.3
5.2
12.0
7.4
5.9
0.3
0.3
0.5
0.4
3.8

100

4[flIfJ

XJJ

6[10700000

Radius (mm)Figure 1 Example of turn pattern of 7 MeV/nucleon polarized deuterons inside the cyclotron.

560

680/01)

72D

760

Radius (mm)Figure 2 Example of tum pattern of 7 MeV/nucleon polarized deuterons in the extraction region near theentrance of the deflector. Tum separation is widen with the first-harmonic field perturbation.
From ECRIS I PIS

FromRRC

Figure 3 Schematic drawing of the arrangement of experimental ports A-C in the AVF cyclotron vault and E7
experimental room. Port A: Radioisotope production; Port B: Slow-positron experiment; andPort C: Nuclear physics experiment.

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