The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Status Report on the JAERI AVF Cyclotron
Susumu OKUMURA, KazuoARAKAWA, Mitsuhiro FUKUDA, Yoshiteru NAKAMURA,Takayuki NARA,Takashi AGEMPJSU, Ikuo ISHIBORI, Watalu YOKOTA, Hiroyuki TAMURA
Advanced Radiation Technology Center, Takasaki Radiation Chemistry Research Establishment,
Japan Atomic Enetgy Research Institute,1233 Watanuki-machi, Takasaki, Gunma, 370-12 Japan

Abstract

3500

The JAERI AVF cyclotron has been used for experiments since January 1992. The routine operation of the cyclotron began in September 1992. The total operation timeamounted to 18,000 hours in August 1997. We have delivered thirty-three kinds of ion beams and cocktail beams ranging from proton to xenon with enetgies of 10 - 520 MeV.
This paper reports status on performance and operation of
the cyclotron and recent development.

3000~'-'2500

s·.::

2000

d0·~ 1500

1 Introduction""
8The TIARA (fakasaki Ion Accelerators for Advanced
1000

Radiation Application) facilities have been constructed at
Takasaki Radiation Chemistry Research Establishment ofJapan Atomic Enetgy Research Institute (JAERI) since 1987
for R&D in materials science and other irradiation purposes.
The facilities consist of an AVF cyclotron[ 1][2] and threedifferent types of electrostatic accelerators: a 3 MV tandem
accelerator, a 3 MV single-ended accelerator and a 0.4 MV
ion implanter.
The applications of the cyclotron require that manykinds of light and heavy ions can be accelerated in a wide
range of enetgies. To meet the requirement, continuing efforts have been made on new beam development, improvement of beam extraction and transmission, etc.
The operation of the AVF cyclotron for experiment wasstarted from 1992 in daily operation mode on a trial base.
The weekly continuous operation was started from September 1992. The total operation times amounted to 18,000
hours in August 1997.

500

1992 1993 1994 1995 1996
Financial years
Fig. 1 Statistics of the cyclotron operation from 1992 to1996.

3500
3000
HD
4Heg 2500c<I)

E·-= 20000·-=

2 Present Status

0Ne
Ar
KrQ

2.1 Operation

The yearly operation time is divided into three beamtime periods, each of which consists of 11 weeks. Theweekly operation is usually carried out continuously fromMonday morning till Friday evening. Regular over-haul iscarried out for 4 weeks in summer.
Operation statistics of the cyclotron during past 5 years
are shown in Fig. I. The operation time for visitors use withchatge, mainly used for irradiation test of semiconductor
devices for space, is increasing every year. The accelerated
particles and their beam time are also shown in Fig. 2.
In order to meet the requests from many groups of researchers, the accelerated particles, their enetgies and thebeam courses were changed as shown in Fig. 3.
2.2 Maintenance and Status[ 150001000

XeCocktail

019921993 1994 1995 1996

Financial years
Fig. 2 Statistics of the accelerated particles and their beamtime from 1992 to 1996.
It is clear that the power supplies for the magnets, constructed nearly 10 years ago, cannot keep the regulation sta--338-

The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

eMainprobe
Magnetic channel
A
Magnetic channel probe----O--- Deflector

200 -I§J•
f:Cj150•

Particle
EnergyBeamCource

D10050 -Deflector probe·-·~~"'--&-~"- Phase slit

1 .,:,:_::::;:::.::~:.;~;~·::~...................................................
~

0~~-t;::

1991

1992

1993

1994

1995

0.1 ..___..L.----L------1--...___.....__

1996

1991

1992

1993

Financial years

1994

1995

1996

__.
1997

Financial years

Fig. 3 Frequency of particle, ene~gy and course change
from 1992 to 1996.

Fig. 4 Accumulation of induced radioactivity in the acceleration chamber of the cyclotron.

bility. Stability of the current outputted from the power
supply is preserved by monitoring the voltage of the shuntresister. We have replaced the shunt resisters of the power
supplies for the main magnet and the analyzing magnets.
After replacement of the shunt resisters, the stability of thepower supplies for the main magnet and the analyzing magnets is less than w-s for 8 hours and 4 hours, respectively.
It is better than the stability before the replacement.
In a few years, we have had the following machine
troubles:(1) A high voltage of an ECR ion source broke down
by increasing a humidity in the room.
(2) An intlector stem (about 150 kg weight) crashed ona cyclotron upper yoke from a stem carrie[(3) A leakage from bellows, which are used for pressing
the contact fingers of the movable shorting plate
against the wall of the coaxial type resonator withhigh pressure air, caused a vacuum in the acceleration chamber worse.
The accumulation of induced radioactivity in the accel~
eration chamber is making it more difficult to conduct maintenance work inside the cyclotron. The strong sources ofradiation are the electrostatic deflector (100 mSv/h) and themagnetic channel (160 mSv/h) as shown in Fig. 4. For theprotection against radiation hazards, now it will be necessary
to replace some of the strongly activated parts, such as mainprobe-head, magnetic channel and magnetic channel probehead.

e~gy.

Ion "cocktail" which is composed of ions with thesame or very close mass to chalge ratio (M/Q), is produced
in a ECR ion source, injected into the cyclotron, accelerated
at the same time and extracted separately by a fine tuning of
the magnetic field or a slight changing of the RF frequency.
The cocktail beam has been developed using ions with
M/Q = 5: 15 N3+, 2<N"e4+, 40At+ and 84 Kr17+[3]. Particle identification was carried out by measuring a pulse height from anSSD. The results of the cocktail beam acceleration test aresummarized in Table 1. The extracted beam current for 56
MeV 15 N3+, 75 MeV 20Ne4+, 150 MeV 40A~ and 322 MeV
84 Kr 17+ ions are 0. 7, 1.0, 2.0 J.LA and 0.08 J.LA (electrical ampere) respectively. The time required for changing the ion
species and/or ene~gy is only one minute for the cocktail
beam acceleration.
3.2 Extraction Current and Transmission

Particles accelerated and extracted so far are listed in Table 2. The extraction efficiency is defined by a ratio of thebeam current measured with the main probe at r = 900 mm
to that with the Faraday cup (FC) just after the cyclotron.
The average extraction efficiencies for harmonic 1, 2 and 3
Table 1Results of a cocktail beam acceleration tests.
Ion

3 Beam Development
3.1 Cocktail beam acceleration

Cocktail beam acceleration is one of the most timesaving methods for changing the ion species and/or the en--339-

1sN3+
z<Ne4+
40Af!+
84Krl7+

Ene~gy(MeV)

Frequency(MHz)Extracted
Intensity(eJ.LA)

5675
150
322

13.86713.87313.88114.048

0.7
1.2
2.3
0.08

The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Table 2
Results of extracted intensity and overall transmission.
Ion

Enetgy Extracted(MeV) Intensity
1020
30
45
50

55

100

1607+

84

Kf20+

(%)

(%)

1280
77
67

27
21
22

79
44
63
57

14
14
14

5
530
5
580
90

20
30
50

!606+

(ej.tA)

550

!6o7+

OverallTransmission

60
65
70

1035

!6os+

Extraction
Efficiency

220
100
160
225
335
120
260
350
195195175330460
520

5313
7.7

1l
4020295949

3.7
4.6
7.2

5.5
1.4
2010694262

0.25
1.7773458
54
2953706363
437386637272

1110171022
8.1
21104.2
18
19
23
13

1.9
0.2
0.05

1.6
0.33
1.5
2.5
0.1
3
0.6
0.03
0.05
0.232

An 18-GHz ECR ion source[5] was constructed to generate highly chatge state ions and metal ions, and is now intest operation.
Modification of the microwave feeding and attachmentof an aluminum plate to the inner surface of the plasmachamber resulted in increasing higher chatge state ions, andAr14+ was observed. Iron ion generation was tested by meansof MIVOC (Metal Ions from VOlatile Compounds). We
used vapor of ferrocene Fe(C5H 5 )z to release Fe elements
into the plasma chamber and observed Fe 15+. Nickel ion generation from a ceramic rod of nickel oxide (NiO) was canied
out and we observed Ni ions with chatge state up to 16+ asshown in Fig. 5. Replacing the rod support made of conductive material with non-conductive one, we will obtainhigher chatge state ions.
After completion of the development, the 1on source
will be connected to the cyclotron.

121033.4 Performance of ECR-182212424748

the MCPby an electrostatic field when ions pass through it.
A flight time of an ion is determined using the beam phase
monitor as a start counter and a plastic scintillation counteras a stop counter. 1DF measurements have been earned out
for 225 MeV 160 7+ and 220 MeV 12C 5+ beams. The best
overall time resolutions are 190 ps FWHM for 225 MeV
160 7 + and 230 ps FWHM for 220 MeV 12C 5 +.

0.1
0.01

1.2
152024204Fig. 581012Charge state
Chatge state distribution of Ni ion.
61416References

11are 56%, 63% and 56%, respectively.
The overall transmission efficiency is defmed by a ratioof the beam current with the FC just after the analyzing
magnet at the injection line to that with the FC just after
the cyclotron. The average transmission efficiencies forharmonic 1, 2 and 3 are 13%, 16% and 11%, respectively.

3.3 Measurements of Beam Phase
Time resolutions of a beam phase monitor were evaluated by a time-of-flight (IDF) measurement. The beamphase monitor[4] is a fast timing detector with a microchannel plate (MCP). Secondary electrons emitted from athin tatget, a 3 mm thick aluminum-strip, are collected into

[1] K. Arakawa et ai.,"Construction and First Year's Operation of the JAERI AVF Cyclotron", Proc. 13th Int.
Conf. on Cyclotrons and their applications, 'hlncouver,
Canada, (1992) 119.
[2] K. Arakawa et al.,"Status Report on JAERI-AVF Cyclotron", Proc. 10th Sympo. on Accele. Sci. and Tech., Hitachinaka, Japan, (1995) 32.
[3] M. Fukuda et al. in this proceedings.
[4] S. Okumura et al., "Development of a Beam Pulse
Monitor for the JAERI AVF Cyclotron", Proc. 10thSympo. on Accele. Sci. and Tech., Hitachinaka, Japan,(1995) 150.
[5] W Yokota et al., "Construction and development of theJAERI 18 GHz electron cyclotron resonance ion source",
Rev. Sci. Instrum. 67 (3) (1996) 977.

-340-