JAERI-Conf

95-021PA08
ACCELERATIO N OF DEUTERON AND ALPHA BEAMSIN THE KEK-PS INJECTORAkira TAKAGI, Kiyoshi IKEGAMI, Chikashi KUBOTA, Zenei IGARASHI,Michikazu KINSHO, Katsuhiro SHINTO*, Shinji MACHIDA, Masahito YOSHII,
Eiichi TAKASAKI, Yoshiharu MORI**
National Laboratory for High Energy Physics(KEK), Oho, Tsukuba, lbaraki, Japan*The Graduate University for Advanced Studies(GUAS), Oho, Tsukuba, lbaraki, Japan**Institute for Nuclear Study, University of Tokyo(INS), Midori-cho, Tanashi, Tokyo, JAPANAbstract
Many experiments have been carried out for helium ion beam acceleration in the KEK 12GeV Proton
Synchrotron throughout in 1994. A helium beam has
been successfully accelerated. the 750 keVPreinjector has a He+ ion source of multicusp typeand a gass stripper cell installed in the low energy
beam transport(LEBT). Maxmum value of 4He2+ ion
current at the exit of the Proton Linac was 1.6 rnA. A
deuteron beam was also produced by carbon stripping foil installed in the LEBT just after high current

D'" ion source for machine tuning.
In addition helium-3 beam acceleration has been
tried in the 40 MeV Proton Linac in 4n-mode acceleration. 3He2+ ion beam current of 1.8 rnA was observed.

been carried out and helium bearri was supplied forthe physics experiment.[4] There were several modifications: A helium ion source of multi-cusp type wasinstalled in the second preinjector for the production
and preacceleration of positive ions.[3]2. Acceleration of He+ ion beam in the preinjector
The injector comprises a 750 keV Cockroft-Waltonpreinjector and a 40 MeV Alvaretz linac. There are
two sets of Cockroft-Walton preinjectors, the firstpreinjector is used to accelerate a high intensity beamof H and n-, whereas the second preinjedor is for aHe Ion Source

100mm

1. Introduction
Acceleration of heavy ion beams in the KEK PS
was discussed about more than 10 years ago. How- •ever, the project was stopped by several reasons andheavy ion acceleration in the KEK PS has not ben realized so far. Very recently, as one of the possible
candidates among the future plans of the KEK PS,
the PS-Collider, which aims to accelerate and collide
heavy ion beams with the beam energy of up to7GeV /u for a gold beam, has been proposed.[1]The PS-Collider is designed to use the present KEK
PS as its injector, therefore a much more simple
scheme compared with the previous one for accelerating heavy ions in the PS has been examined carefully for ease of operation. Simultaneously, possibil-

AnodeElectrodo

L'-------------

ater CoolingFig. 1 Shematic drawing of a helium ion source.

ity of a polarized deuteron beam acceleration in

the PS has been also studied.[2]In the KEK 12 GeV proton synchrotron, the experimental study of helium beam acceleration have

Fig. 2 Multi-hole anode electrode for the helium ion
source.

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CM-6i.~BT

2o~/diY.

4 H e· '?. foto Linac

20.U s/Jiv.
bet1111
6. 0 m A

20:-I<>V

CT-1

0.5mA/div.

2.f.ltts/div.

• H " ' •· hen.

1. 6 m A

Hl{a)D +(d)He""Ion Source
Preinjector Complex

Fig. 3 KEK preinjector complex for the accelerationof positive ions (deuteron and alpha).
polarized beam.
Some modifications of the second preinjector havebeen made in order to accelerate positive ions. Theelectric polarity of the Cockcroft-Walton high voltage
generator and the power supply for bending magnets of low energy beam transport (LEBT) have been
inverted. A multi-cusp ion source is utilized to produce singly charged helium ions.[6] Fig. 1 shows ashematic drawing of a helium ion source. Thisionsource has special anode hole electrode as shownin Fig. 2. An extraction voltage of 50 kV is suppied
to the ion source, and a 50 keV-He+ beam is injected
into the 700 kV accelerating column of theoreinjector. In order to convert a He+ beam to a He 2+
beam, a gas stripper cell has been installed in theLEBT as shown is Fig. 3 .
The 750 keV He2+ ion beam is injected into thelinac. During linac acceleration, the helium beam isaccelereted under the 41t mode operation scheme. Its
velocity is half that in the case of proton acceleration.
As a result, at the end of the linac it has 3% less momentum than that of proton beam. The beam transport parameters and booster injection parametersmust be optimized according to the beam momentum.
3. Production of He2+ion beam
by a charge stripper
Production of He2+ions by the charge stripper.
Two methods of charge stripping: an argon gas celland a carbon foil were tested to convert fro He+ ions
to He2+ions. A gas charge striper device was installedin just after first bending magnet in 750 keV beam

Fig. 4 Waveform of He2+ ion beam at the entrance ofthe Linac and Linac output.
20McV
0.5mA/dh.
3 1l L:

C:T-··1
20Jts/di¥.

'~ bco •1.

8 m A

40MeV

CT-1

U.5.nrA/rtiv.

ZO/J. s/djv,

3 H A 2 ...

bf~:t•I .

'I m A

Fig. 5 Waveform of the accelerated 3He2+ion beam atthe Linac.
transport line. The canal size of a stripper gas cellareinner dia. of 30 mm and full length of 600 mm andthe maximum efficiency of charge transfer from 1+to 2+ was 46% in partcle number.
Whereas a carbon foil stripper device which was installed in a straitght section of beam line, a carbon
foil stripper device showed the efficiency of chargetransfer was about 50 %. It was obtained the maximum capture efficiency at the accelerated voltage of759 kV with a gas cell stripper. Whereas, in the caseof a carbon stripper foil, aditional higher acceleration voltage was required: 16 kV for 10 ~g/cm2, 24
kV for 20 ~g/cmz.
4. Acceleration of 4 He2+ion beam
Most of the problems in accelerating heavy ions of
Q/ A=0.5 at the KEK-PS had been solved at the time
when deuteron acceleration succeeded in 1992.
However,in the acceleration of helium ions, there
remains difficulties with respect to multi-turn injection of the positive ions.
In 41t mode acceleration of deuteron in the linac,
the possible injection energy is not only 375 keV,which is a just half of that for proton. A relatively
high energy of 540 keV is also possible. It is found-44-JAERI-Conf 95-021

Gas Cell(Argon)

C-foilto Linac

Beam width:
Beam repetition rate:
Extraction gap /voltage:
After pre-acceleration
He+ beam current:
After gas stripper
He2+beam current:
Linacbeam
Beam current:

C, 0 etc

Low Energy Beam Transport

Acceleration
Ion source
Type of ion source:

16

12Table 1.
Typical Operating Parameters during Helium

multi-cusp ion sourcewith 19 multi-anode hole
20msec20Hz
14mm/ 50kV

C-foilo+D-Ion SourceHe+ron Source

Preinjector Complex

TandemFig. 6 Proposed scheme of the preinjector complex
for the light ion beams with a Tandem accelerator.
preinjector complex for the light ion beams with aTandem accelerator.[1]At present, a heavy ion beam acceleration program has been scheduled for one month every April.

7.6 mA(750 keV)
6.6mA

Polarized deuteron acceleration is also planned.

1.5 mA(20 MeV)
0.8 mA(40 MeV)

The auther thanks all members of the PS groupfor useful discussions and their encouragement.

0.94 I 0.75 mm.mradthat not only the beam energy of 375 keV but thehigher energy such as 540 keV can be acceptable forthe linac. [7][8] In normal operation, 540keV injection was chosen and the optimized beam capture efficiency in the linac was reached to about 30%.
Figure 4 shows a typical waveform of heliumion
beam. Typical operating parameters during 4He2+acceleration is shown table 1.
5. Acceleration of 3He 2+ion beam
He 2\ons was also accelerated by 47t-mode in theLinac A wave form of the 3He2+ion beam is shownin Fig. 5. In this operation, the voltage of Cockcroft
is 567 kV, a beam intensity of 10 rnA was obtained
jast after the accelerating column. It was obtainedthat he capture efficiency of the Linac was 26%, 7.0
rnA at the Linac entrance and 1.8 rnA at the exit of3

the Linac as shown in Fig. 5.
6. Conclusion
Helium beam acceleration is one of the setp to
next step. It is proposed to deveplope the KEK Proton Synchrotorn for acceleration of light ion beams.
Figure 6 shows the proposed scheme of theReferences[1]PS-Colleder design group; KEK Report 89-20,1990(in Japanese), KEK Report 90-13, 1990(in English).
[2] Proc. of the Workshop on Deuteron Beam Acceleration in the KEK 12GeV PS, edited by Y. Mori,
KEK-Proc. 91-12, 1991(in Japanese).
[3] Y. Mori, "Acceleration of deuteron beam in the
KEK proton synchrotron", Proc. 1993 Particle Accelerator Conf. Vol. 5,3754-3756 (Washington, 1993).
[4] I. Sakai et al, "Helium Beam Acceleration in theKEK Proton Synchrotron with A newly Developed
Injection System for Positive/Negative Ions", Proc.
1995 Particle Accelerator Conf.
[5] S. Fukumoto, Z. Igarashi, S. Inagaki, K. Ito, T.
Kato, C.n Kubota, Y. Mori, A. Takagi, E. Tkasaki andT. Takenaka, "Polarized proton preaccelerator program", IEEE Trans. Nucl. Sci., NS-28, 2693-2695(1981).
[6] Y. Mori, T. Okumura A. Takagi and D. Yuan, "Development of the KEK volume H- ion source", Nucl.
Instrum. Meth., A301, 1-8 (1991).
[7]5. Ohnuma, Th. Sluyters; Proc. 1972 Linear Conf.,
Los Alamos, 1972, page 191.
[8]T.Kato;KEK Report 86-5(1986).

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