JAERI-Conf 95-021

PA01
The Operation of RIKEN Ring Cyclotron
M. Kase, N. Inabe, A. Goto, T. Kageyama, I. Yokoyama, M. Nagase, S. Kohara,T. Nakagawa, K. Ikegami, 0. Kamigaito, J. Fujita and Y. Yario
The Institute of Physical and Chemical Research (RIKEN)·Wako-shi, Saitama 351-01, JapanINTRODUCT ION
Almost nine years has passed since the firstbeam was extracted from the RIKEN Ring
Cyclotron (RRC) successfully, and five years since
the RIKEN Accelerator Research Facility wasfully completedl) as shown in fig.l. Since then,
the RRC has been supplying a variety of beams
with a good stability for a variety of experiments.
As many improvement s have been made, amachine shut-down due to trouble-shoot ing
decreased and a beam tuning time spent in order to
get a high quality beam was shortened .

OPERATION STATUS
All beams, which were accelerated withthe RIKEN Ring Cyclotron (RRC) during tments,
such as medical science, radio-chemistr y, healthphysics, material science, biology, atomic physics.
Although the portion of beam time is so small, avariety of kinds of experiments were behese twoyears, are listed in table 1, together with theirenergy range and total time spent for experiments.

In this period, totally 23 kinds of particles wereaccelerated by RRC and used for experiments.
Their masses as well as their energies cover a very
wide range from 1 to 170. Figure 2 shows the plotsof particles accelerated so far in the region ofenergy-mass space. The plots are ranging almost
everywhere in the available region of the space.
As listed in table 2, the total operation
time for the last one year (from Sept. 1994 to Aug.
1995) amounted to 259 days. Among them, a totalof 70 days were spent for beam tuning. Since abeam was prepared 72 times in this period, ittakes 0.97 days on the average to tune one beam.
The beam tuning time depends on how much an user
requires a high quality beam, for example, a strict
single-turn extraction, an extremely small beamspot, a well-separated single-bunched beam and soTo meet these requirements completely, iton.
takes sometimes longer than 1.5 days.
The beam time, which is used forexperiments, is 189 days. Most of the beam time
(86.7%) was devoted to nuclear physics
experiments and the rest (13.3%) to other field
experiing made, since beam time demanded for one
experiment in these fields are very short ascompared to that of nuclear physics.

Polarized Ion Source
IOGHzECR,(i)/______

Fig 1.
A bird-eye view of acceleratorsin the RIKEN Accelerator Reaerch Facility.
See text for (a) - (i).
-23-JAERI-Conf 95-021

Table 1 A list of particles which were acceleratedbJY the RRC f rpm 0 ct. 1993 to A ug. 1995.
Particle
EnergyTotal time of fraction
range
operation(days)(MeV/u)(%)
p*85-210
26.6
6.9
d**
135
50.0
13.0
12c
92-135
32.5
8.4
13c
100
34.3
8.9
14N
35-135
12.1
3.1
15N
115
11.5
. 3.0
160
135
8.7
2.3
1s0
42-100
51.7
13.4
20Ne
135
8.2
2.1
22Ne
70-110
25.0
6.5
24Mg
100
5.0
1.3
2ssi
135
2.3
0.6
36Ar
7.6
9.3
2.4
40Ar
7.5-95
46.3
12.0
48Ti
7.6
2.9
0.8
son
80
11.9
3.1
59co
80
1.9
0.558Ni
95
5.9
1.5
84Kr
10.5-36
4.5
1.2
130Te
7.5
16.2
4.2
129xe
7.5
9.8
2.5
136xe
26
2.2
0.6
170Er
76.5
1.7
total
385.0
100.0
* H2+ is used for energies lower than 135MeV /u.
** Mostly polarized deuterons.

Table 2An operation statistics of the RRC
from Sep. 1994 to Aug. 1995
Total Operation time
259 days
Beam tunning
70 daysExperiment
189 days
Nuclear Physics(86.7%)
Other fields(13.3%)

210

200
e Ions Accelerated(Aprill987- Aug. 1995)~

0==

u::I 135!l)-->==

AVF Injection!l)hAVF=2,6hRRC=5><c:J..:::~z~50

Linac Injection••••CuH COI\fg ArZn KrXeErTaBi U

Atomic Mass
Fig. 2 Plots of ions accelerated so far by RRC
on the energy-mass space.

The A VF-RRC operation was performed for150days (79.6%) and the RILAC-RRC operationfor 38.5 days (20.4%). Stand-alone uses of the two
injector have routinely been made during a time
when the other injector is coupled with RRC. (f, hin fig. 1)

TROUBLE SHOOTINGRILAC injection·AVF injection
Unscheduled shut-down
Highvoltage trouble
A VF magnetic channel
Other reasons
Maintenance or holiday
Total(20.4%)(79.6%)
14 days
8 days
5 days1 day
92 days
365 days-24-In this one year, a total of 14 days of thescheduled machine time had to be canceled. Main
reasons for these unexpected shut-downs wererelating to deflectors of both the A VF cyclotron
and the RRC.
They sometimes did not work
sufficiently due to their unendurable leak currents.
A periodic maintenance with an open of a vacuum
chamber is necessary in both cases.

JAERI-Conf 95-021

Recently, a casing of a magnetic channel inthe A VF cyclotron had small holes due to beamhitting and a serious vacuum leak occurred twice.
The beam has tendency to go lower side in theextraction region. Though the reason for it is notclear at present, the magnetic channel installed at
a vertical position by 2mm lower than theprescribed one.
In the rf system of the A VF, a part of theslide contacts of the movable shorting plate wasmelted and burned. and the vacuum leak occurredfrom the magnetic channel due to beam hitting. In
the RRC rf, the vacuum leak occurred between thealuminum gasket and the ceramics that are used in
the coaxial rf power feeder.

A single-bunched beam is sometimes
required by users as a time trigger for themeasurement of time spectrum. A very compact
single-bunch selector, which consists of a fast beam
chopper (b, c in fig.l) and a sub-harmonic buncher(d in fig.l), has been successfully developed.
Both the devices are installed in a low-energy
injection line of the AVF cyclotron. As long as asingle-turn extraction is strictly achieved in each
cyclotron, a pure single bunched beam with arepetition rate of as high as 1 MHz is available3).

NEAR-FUTURE PROGRAM
NEW TOPICSson Beam
Recently a beam of 50Ti was accelerated andused for an experiment. To get an enough intensity,
we had to use an enriched-material, which isextremely expensive. To save the quantity of it,
when it is charged to the 10 GHz ECR source (a inFig. 1), a thin alumina (Al2.03) pipe, a hole ofwhich was filled with a small amount of powderof enriched (50%) Ti 0, was used in stead of anormal ceramic rod. It could supply a 80MeV /u
50Ti beam with an intensity of 8pnA on a target fora week at least.

An acceleration test of a new injector systemof the RILAC is now under way in a provisionalsite. It consists of a single-stage 18GHz ECR ion
source and a variable frequency RFQ linac.4) It
will be installed at the injection line of RILAC innext spring, being the first-step improvement of
the accelerators in aim of the new project, RI beam·factory5).

Parasite-mode operation
We have routinely begun to make use ofparasite-mode operation. A sub experiment, suchas a detector test, normally demands several timesof short-term irradiation of a faint beam. On theother hand, a main experiment needs a long-term
irradiation of a very intense beam, like a RIPS's
experiment in E6 room. The beam is sent to the subuser as long as they need, normally for several ten
minutes. Switching the beam delivery could bemade in a second each time.
Monitor of single turn extraction
A combination of beam chopper on theinjection beam line of the A VF cyclotron and thetwo beam detectors (e, g in fig. 1) using a microchannel plate (MCP) has routinely been used bothas phase monitors for stabilizing the magnetic
fields of the cyclotrons and as monitors for singleturn extraction2).
Single bunch selector-25-

REFERENCES
Y. Yano, "Status Report on RIKEN Ring
Cyclotron", Proceedings of 12th Int. Con£. on
Cyclotrons and their Applications. Berlin,
1989. pp. 132) M. Kase, N. Inabe, I. Yokoyama, and T.
Kawama. "A Beam Phase Monitor with Useof a Micro -Channel Plate for the RIKEN
Proceedings of Beam
Ring Cyclotron"
Vancouver 1994.
Workshop,Instrumentation
pp. 459.
3) N. Inabe et al. in this proceedings.
4) A. Goto et al. in this proceedings.
5) Y. Yano et al. in this proceedings.

1)