The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

STATUS REPORT ON THE JAERI AVF CYCLOTRON SYSTEM
Y. Nakamura, T. Nara, T. Agematsu, I. lshibori, H. Tamura, S. Kurashima, W. Yokota,
S. Okumura, M. Fukuda, K.Akaiwa*, To. Yoshida*, S. !shiro*, A. Matsumura*,
Y. Arakawa*, Tsu. Yoshida*, S. Kanou*, A lhara * and K. Takano*Japan Atomic Energy Research Institute,* Ion Beam Irradiation Service, Co. Ltd.
1233 Watanuki, Takasaki, Gunma 370-1292, JapanAbstract
The AVF cyclotron system at JAERI Takasaki has
been smoothly operated without serious troubles since thefirst beam extraction in March, 1991. A yearly operation
time is about 3200 hours on an average for recent eightyears.
In last two years, we performed some improvements
and developments as followings: stabilization of thecyclotron beam by addition on an exclusive coolingsystem, designing and investigation of the flat-top systemusing fifth-harmonic RF, reconstruction of the rotary
shutter for radiation shielding and reinforcement of themagnetic channel and its power supply.
Furthermore, the renewal of main circulation pumpfor cooling system, replacement of shunt resistor in thepower supplies and re-alignment of the several magnets
along the trunk beam transport line were also carried out.

frequency of the change of particle, energy and beamcourse increases certainly year by year as shown in Fig. 1.
According as the number of ion species increases, theallotted beam time for users gradually decreases while thetime for scheduled beam tuning including the beam coursechange increases considerably. This means that theutilization efficiency of the cyclotron system is lowering.
300

Fill Particle
250~ 200

c::
~ 150

17.

~v.

u.. 100
500~ll~~~ II~ II~
1m

1m1~

The AVF cyclotron system [1],[2] was introduced topromote various researches of many fields at the Takasakisite of Japan Atomic Energy Research Institute (JAERI).
The cyclotron system can accelerate plenty of ion species
from hydrogen to gold at TIARA (Takasaki Ion
Accelerators for Advanced Radiation Application) facility.
Especially, the cyclotron system has been utilized mainly
for material science such as semiconductor devices, seeds
and plants, organic and inorganic functional materials, andso on for about 10 years.

2.1~
1%~ II~
1%~
1%

II~~~~~~~

1%

1%~~~~~~~~~

1~1~1~1m1m~oo

Fiscal year

1 INTRODUCTION

2----- --------- ---- -----!------ILl Energy• Beam course

PRESENT STATUS

Operation

A cumulative operation time of the cyclotron
amounted to 31009 hours at the end of August in 2001.
In FY 2000, the rate summed up heavy ions and cocktail
ion of M/0=5 occupied about 70 % of yearly operationtime, on the other hand, the rate of light ions consisting ofproton and deuteron was 28 %. A yearly operation time
is kept constantly more than 3000 hours for past several
years in spite of the executions of many reconstructions,improvements and repairs.
A beam time for users has been allotted inconsideration of various demands from them as
Therefore, theconscientiously as possible so far.

Figure 1: Frequency of the change of particle, energy andbeam course.

2. 2 Improvement
It had been pointed out from operational experienceof beam transport that the beam trajectory just behind thecyclotron was shifted upward. As a measurement result,several magnets along the trunk beam transport line had
sunk below maximum about 3 mm as illustrated in Fig. 2.
These magnets were aligned again in original positions
within the precision of 0.2 mm.
A tantalum head of the magnetic channel (MC) probe
was replaced with graphite one to reduce theradioactivation. As this head became rather thick, thefabrication of the reduced-size MC was also needed.
The output current of the power supply for this MC was-193-Figure 2: Sinkage of several magnets along the trunkbeam transport line.

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

reinforced up to 1430 A from 1300 A to guarantee thesame performance as the old MC.
Five controllers for TMP's installed in the switchingmagnet room on the first floor were moved to thecyclotron pit room on the basement where the radiationlevel is lower, because they had to be sometimes repairedso far owing to accumulated radiation damage.
A rotary shutter (RS) for one of beam lines embeddedin the shielding wall through the HB course was renewedsince significant air leakage through the driving shaft had
been observed whenever it was operated. This RS wasoperated most frequently among nine RS 's in thecyclotron facility. The number of operations alreadyexceeded 3500 before the renewal.
Someimprovements were performed
for the new RS [3] asfollows:1)
thealteration of vacuum
seal structure fromdouble 0-rings (Capseal "A" and "B") tomagnetic fluid seal as
shown in Fig. 3, 2) themodificationof
drivingmechanism
from a pneumatic
rotary actuator to anelectricstepping
motor, 3) the reconstructiontothepolyethylene
shieldFigure 3: Sectional view of thecovered with stainlessvacuum seal part around thesteel
plate to diminish
new driving shaft (upper) andtheoutgassingin thethe old (lower).
vacuum.
The control system constituting of personal computersfor cyclotron was renewed completely in March, 1999 [4].
A pair of liquid crystal displays were further installed oneach control console to always monitor the operating
condition.
In order to improve the uniformity of beam fluence ofthe scanner, the phase control of triangular scanning wave
was added on three beam scanners so that the scanning
pitch on the target plane became to be narrower. A new
scanning frequency of 0.25 Hz was also added on thescanner equipped with LD course.

2.3 Maintenance and Repair
Four mechanical-seal pumps with electric motors forthe circulation of cooling water were renewed
preventively. The manufacturing period for these pumps
is more than three months as they are usually begun tomake after the order from a customer. They had been
operated for about 35000 hours since the installation in1990. In addition, the control mode for cooling tower on

the building roof was also modified to the continuous
operation using an inverter from the intermittent ON-OFFmotion.
Serious water leakage from the MC occurred at the"Vebeo" fitting for both introductions of coil current andcooling water. The Vebeo fitting contacted directly withneighbor one because the shrinkable tube covering thefitting suffered from deep damage by heating for a longterm operation. Therefore, the localized meltdown wascaused by rare-shortening of this metal fitting where thelarge coil current was flowed.
We altered the fitting type from Vebeo to "Swagelok"on account of mechanical property and contact condition.
Then, we examined the difference of surface temperature
between stainless steel and brass fitting. A measurement
result of saturated temperature is shown in Fig. 4. Since
the surface temperature on the shrinkable plastic tube wasrestrained below 70 "C with maximum coil current of1430 A, finally we chose the Swagelok fitting made ofbrass.

Figure 4: Comparison of surface temperature between
stainless steel and brass fitting.
The vacuum chamber of the OCfOPUS was filled
fully with cooling water for serious leakage.
TheOCfOPUS was disassembled completely for internalcleaning, polishing and replacement of gaskets. The
HYPERNANOGAN was operated for the experiments forabout two weeks instead of the OCfOPUS.
Many shunt resistors in the power supplies were
replaced with new type made of "Zeranin" or "Manganin"
due to the deterioration of electrical property and thepossibility of internal corrosion.
As one of the preventive countermeasures, a greatamount of plastic (nylon) tubes used for cooling water andcompressed air was replaced with new ones along thebeam lines. Total length of theirs was about 520 m andthe number of replaced tubes was 720.

33.1

DEVELOPMENT

Cocktail Beam and Scaling Acceleration

Two kinds of 58Ni15+ and 82Kr20+ ion were newly
added on the previous series of cocktail beam of M/0=4.

-194-

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

It is considerably difficult to separate clearly a single
species from several cocktail ions when the difference ofthe M/Q ratios between an objective ion species and theothers is less than proper M/Q resolution of the cyclotron(about 3x104 ). However, we fmd out that the reductionof dee voltage is very effective to eliminate impurities incombination with slight shift of RF freguency [5].
The series of 2~e8 + 350 MeV, 2~e7 + 270 MeV and2~e6+ 200 MeV beam was developed for the purpose ofquick change of the ion species using a "scaling method".
Actually, the magnetic field generated by twelve pairs oftrimming coils was adjusted mainly on condition that themain coil current was maintained constantly.

Table 1: List of ion species accelerated by JAERI AVF
cyclotron. The symbol of "Text" in the table is definedby a ratio of the beam current at frrst Faraday cup justbehind the cyclotron to that at 900 mm of the cyclotron
radius. The "Tall" is a ratio of the beam current
extracted from the cyclotron to that injected into.

Ion
speciesH•

3.2 Others
We have found out that the instability of cyclotron
beam comes from the slight reduction of magnetic field in
the accelerating gap because of temperature rise of thecyclotron body by large amount of heat transferred fromthe main coils. The comprehensive measures for thebeam stabilization were carried out in March, 2000 [6].
As a result, the stabilization of the cyclotron beam wasimproved within 10 % decreasing by means of continuous
operation of an exclusive cooling system [7].
A flat-top (Ff) acceleration system for the JAERIAVF cyclotron has being designed to minimize the energy
spread for the micro beam formation.
The fifth
harmonics of the main RF frequency will be used toconstruct the Fr system. We investigate carefully thestructure, characteristics and power consumption for theFrsystem using a MAFIA code [8].
All of the ion species accelerated by JAERI A VF
cyclotron so far is summarized in Table 1.

REFERENCES[1] Y. Nakamura, T. Nara, T. Agematsu, et al., Proc. 16th
Int. Conf. Cyclo. Their Applic., East Lansing, Ml,USA(2001)[2] Y. Nakamura, T. Nara, T. Agematsu, et al., JAERIReview 2000-024 (2000)[3] I. Ishibori, Y. Nakamura, T. Torii, et al., JAERIReview 2000-024 (2000)[4] T. Agematsu, K. Arakawa, S. lshiro, et al., Proc. 12th
Sympo. Accel. Sci. Technol., Wako, Japan (1999)[5] M. Fukuda, K. Arakawa, S. Okumura, et al., Proc.
1999 Particle Accel. Conf., Yew York, USA (1999)[6] Y. Nakamura, S. Okumura, M. Sano, et al., JAERIReview 2000-024 (2000)[7] S. Okumura, S. Kurashima, T. lshimoto, et al., in thisproceedings[8] S. Kurashima, M. Fukuda, Y. Nakamura, et al.,Proc. 16th Int. Conf. Cyclo. Their Applic., East
Lansing, MI,USA(2001)

o•

4He2+

12c3•
12cs•
12r.ll+
14N3+
'"N3+
••o4+
1a0 s.
1606+
1a0 7.
11Q7+
1a0 a.
20Ne4+
2uNe5+
20Ne&+
20Ne&+
2oNe7+
2oNe7+
20NeB+
20NA10+311AfB+
36Ar10+
3&Ar1B+40~+

40Ar10+40Ar11+
40Ar13+
4ocas+
ssFe11+
5&j:,.15+
saNi15+a2K~+

84Kr17+
84Kr18+
114Kf20+
84Kr21+129)(A23+
197 AI 31+

M/Q

-195-

Energy

Beam

Text

Tall

(MeV)
102030
45
50
55
60
65
70
80
90
10
20
25
35
50
20
30
50
100
108
75
220
320
67
56
100
100
160
225
335
430
75
125
120
200
260
270
350
540
195
195
970
150
175
250
330
460
200
200
400
388
488
320
400
520

(e11A)
12753055575310
115.6
11
40
20
5.5
1020101.6
2.0
1.0
0.0025
40.70
54
1.9
1.0
0.1
0.00451.5
0.01
1.6.0.80
0.33
0.28
1.5
105 coS
2.5
0.1

(%)

(%)

80

27
23
22
14
14
14
22
12
12
13
7.7
3.7
16
31
13
7.2
12
10
22
10

1ns"'""

!

2.4
3.0
0.2
0.7
0.03
2.0
1.4
0.59
0.012
106 cos
0.08
0.04
0.06
o.c1032!

0. 0:!3c

77

67
79
44
63
57
62
42
47
48
29
80
88
59
49
69
42
62
32
M/0=2
M/0=4
77

M/0=2
43
M/0=5M/0=4
34
58
82
41
M/0=2
M/0=5M/0=453
Scalina70
Scalina--~22~105.0
22
21
21
136--

~

6.6
18
1019
14
23

63
M/0=2 .....-""""'
73
13
43
1.2
M/0:2·
M/0=56.2
73
15
M/0=4
86
2263
24
61
11
M/0=516
66
28
M/0:4
M/0:-45.0
M/0=5260
72
22
M/0=41172
49
3=2, 4 ana 5: Goc<tai Deams..------------