The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

PRESENT STATUS OF THE RCNP CYCLOTRON COMPLEX
S. Ninomiya, T. Saito, H. Tamura and K. Sato, RCNP, Ibaraki, Osaka, Japan
S. Mine , H. Kanekoa, Z. Taiseia, Y. Inataa, H. Gotoha, H. Yanaa, Y. Ohea, H. Hikakea, Y. Kotakaa,K. Masudaa and K. Yadomia, a Sumiju Accelerator Servics (SAS), Ibaraki, Osaka, JapanaAbstract
In recent years, high-quality beams in momentum
spread have been strongly required and successfully
obtained in a RCNP cyclotron complex. Intense beams
have also been required. Present status of the RCNP
cyclotron complex is described in this report.

1. INTRODUCTION
The Research Center for Nuclear Physics (RCNP) in
Osaka University has a cyclotron complex, which consistsof a large-sized ring cyclotron (K=400) and an injector
AVF cyclotron (K=140). Beams are used mainly for
nuclear physics research. Various kinds of ions wereaccelerated to different energies. Table 1 shows asummary of the beam usage of the cyclotron from 1999 to2002. Mainly light-ion beams, such as proton, deuteronand helium beams, were required. More than 80 % of themachine times were carried out for the light ions in thepast few fiscal years.
Table 1: A summary of the beam usage of the RCNP
cyclotron complex

1999
2000
H
1295.2hrs 989hrs
pol H
952.5
2038
D
00
pol D
374.8
573.2
H2
003
He
262.7
611.7
4
He
967.8
698.7
6
Li
007
Li
295.8
15211B
21.7
012C
93.3
014
N
251.3
11816O
035
18O
282.2
0Total4797.35215.5

2001
2002
1846.8hrs 1050.1hrs
879.71108
42.3
131.3
84.3
1080601338.81304.5647
1189.3
084.5
180
244.1
312
000000000
5331
5279.8In the period shown here, 12C, 16O and H2 molecularions were accelerated to 480 MeV, 1120 MeV and 140
MeV, respectively, by the Ring cyclotron for the first time.
Charge states for 12C and 16O ions extracted from theNEOMAFIOS ECR ion source[1] were 4 and 6,respectively. After acceleration by the injector AVF
cyclotron, both ions were stripped to bare charge state.
The target intensity for the 12C, 16O and H2 molecular ionswere 24 nA, 190 nA and 20 nA, respectively.

For 786 MeV 11B6+ beam, the obtained beam intensity
much increased in the April of 2003, because the vacuum
level in the NEOMAFIOS ECR ion source became better.
Now 30 nA of the beam current can be obtained at thetarget.
For further update detail, see the relevant pages of
http://www.rcnp.osaka-u.ac.jp.
Table 2: A summary of the performance of the RCNP
cyclotron complex
1999

2000

2001

2002

Beam time4797.3hrs

5215.5hrs

5331hrs5279.8hrs

Maintenanceand set up

1695.81625.21367.81395.3

Scheduled
shutdown

2023.5

1791

1843

1921

Unscheduled
shutdown

267.3

128.3

218.2

163.8

Total

8784

8760

8760

8760

A summary of the performance of the RCNP cyclotron
complex is given in table 2. During the last four fiscal
years, unscheduled shutdown periods were always lessthan 270 hours, which were only less than 5 % of thebeam times.

2. HIGH-QUALITY BEAM
High-quality beams are strongly required in theRCNP for light ions, such as proton, deuteron, helium-3
and helium-4. Figures 1, 2 and 3 show the observed
energy spread in each machine time for a proton beam, ahelium-3 beam and a helium-4 beam, respectively, as afunction of the period. Different energies are required forboth ions, especially in the last four fiscal years. For
deuteron beam, we have no enough data comparable.
All lines in these figures seem to decrease, whichmeans that cyclotron operation is still made progress in.
Filled symbols represent the best energy spreads. All of
the best results were obtained between 2000 and 2003.
Without 210 MeV helium-4 beam, The best values of theratios of the energy spread to the beam energy (∆E /E ) inFWHM were achieved as less than 3x10-4. It should be
noted that the reproducibility of the energy spread is quitewell.

The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

achieved for 295 MeV and 392 MeV protons[3],respectively, i.e., ∆E/E ∼ 4x10-5.
Even in the dispersive mode, an energy resolution ofthe beam itself is much important practically. The lateralsize of the beam on a target point is approximately
proportioned to the momentum spread of the beam itself,
which means that a high-quality beam is still
experimentally expected.

delta E/ E (x10- 4)

12840
1995

1998

2001

3. INTENSE BEAM

2004

year

Fig.1 : Observed energy spreads in each machine time for392 MeV proton beam(circle) and for 300 MeV proton
beam(square). Filled symbols represent the best results.

Intense beams have also been required. It should be
noted that a beam current is limited to less than 1100 nA
by means of radiation control of the Ring cyclotron.
Table 3: Typical beam current at a targetprotondelta E/ E (x10- 4)

12844

He0
1995

1998

2001

2004

year

Fig.2 : Observed energy spreads in each machine time for
450 MeV 3He beam(circle) and for 420 MeV 3Hebeam(square) . Filled symbols represent the best results.

delta E/ E (x10- 4)

Current(nA)
330
1000
1000
720
700
690
440

Typical beam intensity at a target is shown in table 3. A
few hundreds of nA beams were obtained. Especially for
150 MeV and 200 MeV proton beams, beam intensities are
just below the radiation control limitation of the Ring
cyclotron. We also have ~ 5 µA limitation by means ofradiation control of the AVF cyclotron. Therefore,transfer efficiencies through the Ring cyclotron are very
important to obtain intense beams in the RCNP.

4. QUASI-SINGLE TURN EXTRACTIONFROM THE AVF CYCLOTRON

12840
1995

Energy(MeV)
100
150
200
250
300
392210

1998

2001

2004

year

Fig.3: Observed energy spreads in each machine time for
400 MeV 4He beam(circle) and for 210 MeV 4Hebeam(square) . Filled symbols represent the best results.
A new beam line which accomplish both lateral andangular dispersion matching with the Grand Raiden
spectrometer[2] in the RCNP was constructed[3]. In thedispersive mode, the energy distribution of the beam itself
can be principally cancelled out. Energy resolutions of ∆E= 13.0±0.3 keV and ∆E = 16.7±0.3 keV in FWHM wereIn order to realize high-quality beams, singlecomponent beam is required. Therefore, single-turnextraction from a cyclotron is desirable. In the RCNP
cyclotron complex, single-turn extraction from the Ring
cyclotron is carried out. However, single-turn extraction
from the AVF cyclotron was not realized for a normaloperation.
Using a phase defining slit located in the central regionof the AVF cyclotron, a single or two turns extraction was
already achieved[4]. Recently, practical method to obtain
quasi-single-turn-extraction beam with finite intensities
have been found out mainly by the operators.
Detailed technique was described elsewhere[5]. It
should be noted that the suitable magnetic field for quasisingle-turn-extraction needs to be searched by adjusting
the main coil current by 0.02 A, i.e., the magnetic field issearched on the order of 10-5.

The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

AVF cyclotron and of the Ring cyclotron can becontrolled on the order of 10-7.
A newly phase probes for the AVF cyclotron were also
installed. Comparing the old ones, noise levels became
quite small and we can get signals from a few nA of thebeam.
Fig.4 : 3He beam current as a function of a position of
the beam probe of the AVF cyclotron
Figure 4 shows observed herium-3 beam current as afunction of a position of the beam probe. Extractionenergy from the AVF cyclotron was 93 MeV. The rightside of the figure corresponds to an extraction point. Notwell, but separated peaks were observed, which meansthat quasi-single-turn extraction is realized.

5. R & D
Past a few years, we have stressed an importance ofcooling systems for the RCNP cyclotron complex toobtainhigh-quality
beam[6]-[9].
Here,
other
improvements in the last four years were very briefly
described.
One-turn-coil systems were installed both to the AVF
cyclotron and to the Ring cyclotron to correct the main
coil currents. As a result, the magnetic fields both of theREFERENCES[1] K. Takahisa et al., RCNP Annual Report, p.190(1994)[2] M. Fujiwara et al., Nucl.Instrum. Meth. A, 422,p.484, (1999)[3] T. Wakasa et al., Proc. of the 16th Int. Conf. on
Cyclotrons and their Applications, East Lancing,
2001, p.458[4] K. Hatanaka et. al., RCNP Annual Report p.172(1982)[5] S. Ninomiya et. al., RCNP Annual Report (2002) inpress[6] S. Ninomiya et al., Proc. of the 16th Int. Conf. on
Cyclotrons and their Applications, East Lancing,2001, p.110[7] T. Saito et al., Proc. of the 13th Symp. on Accl. Sci.
and Tech., Osaka, 2001, p.68
[8] S. Ninomiya et. al., in these proceedings[9] T. Saito et. al., in these proceedings