THE IPCR SEPARATED SECTOR CYCLOTRON PROJECT
presented by H. Kamitsubo
The Institute of Physical and Chemical Research
Abstract
Construction of a separated sector syclotron(SSC) was started at IPCR(Riken) this year. It is the main accelerator of the multipurpose accelerator complex which is composed of the sse and two independent injectors(heavyion linac and AVF cyclotron). The beam energy ranges from 135 MeV/u forfully-stripped light ions to 14 MeV/u for very heavy ions such as uranium.
Introduction
Since 1966 the 160 em cyclotron at IPCR has been used for multidisciplinary studies. However its capabilities are rather limited and a more powerful machine has been required to extend these studies. In 1972 an accelerator complex composed of a separated sector cyclotron and two independent injectors was proposed. Construction of injector linac 1) was started in 1974
and finished recently. The proposal 2) for the energy booster of the linac
was approved by the government last year and the final design studies are
now in progress. The design. goal is to achieve maximum beam energies of 135
MeV/u for fully-stripped light ions and typically 14 MeV/u for very .heavy
ions like uranium. Energy variability down to 10 MeV/u should be realized.
High intensity beams of protons, deuterons and a particles of intermediate
energies are also required for studies of nuclear chemistry and radiation
biology as well as nuclear physics. The beam quality(mainly intrinsic energy·spread and emittance). has to be as high as possible.
General description
Examples of some operating parameters at the maximum energies of .theaccelerator complex a:re given in table 1. . The linac usually accelerates•. ionsin the fundamental mode(i.e.harmonic number h=l). in the fre<tuency range of
17-45 MHz. Considering the matching condition. of the resonance structure of
the beam and the available magnetic field strength of the sse, we take deeangle of 20° for the sse. Then the harmonic number in acceleration in the.
sse is 9 and the frequency range is the same as that of the linac. On theother hand, the injector cyclotron will be operated in the orbit frequency
range of 2.7-7.5 MHz. The harmonic numbers of 3 and 6 are favourable
for the cyclotron and the sse, respectively.
The above values of the harmonic numbers are. different from those i.n ref.
2. The.hannonic number was increased because we reduced the max~mum magnetic
field.of the SSC from .the energy saving point of view.· The maximum value ofBinj-was reduced from 1.7 T to 1.5 T and the injection radius was increase~
to 0.89 m. The beam £rom the linac should be transfered by about 60 m to thesse. The beam transfer system between the injectors and the sse was designed
to transport the beam and to m~tch the beam quality to the accept~nce of theAs for. the,. injection to, the SSC, the a:x;ial inSSG without any beam loss~
jection meth()d wa~:; employed •.. The advantage of this method is. described ref .3.
Separated Sector Cyclotron
The main characteristics of the SSC are shown in table 2. The SSC hasfour sectors of 50° with straight edges. The sector magnet and 30 trim coils-325-yield the required idochronous field of 1.67 T at maximum. The focusing
properties of the sse are calculated with the computer code developed by N.
Nakanishi by using measured field distributio n for a pair of a qurter scalemodel magnets 4 ). In order to avoid the betatron oscillation resonances during
acceleratio n, we have chosen the region defined by v -2v =0 and v =4/3 at highenergy side.
rzr
Ions are accelerated by 20° delta-shape d two dees located at opposite
valley spaces between the sector magnets. The frequency range of the RFsystem is chosen to be 17-45 MHz to realize a synchronous operation with thelinac. RF electric field distributio ns and quality factors were measured fora half scale model cavity for the whole range of frequency. The effective
acceleratin g voltage for the cyclotron injected beams will be 13!2 of thatfor the linac injected beams.
The beam from the injectors is brouggt slantingly into the SSe throughthe valley and bent by 45° into the median plane in the central region. Then
it is inflected by 100° with a bending magnet into a magnetic inflection
channel in the pole tip of the sector magnet. The second magnetic inflection
channel and an electrostat ic inflector bring the beam onto the first equilibrium orbit.
The operating pressure of 1 x 10 -7 Torr is desirable in the medianplane of the sse to limit beam losses due to charge-exca nge less than about
10 % in case of very heavy ions. The vacuum chamber consists of 2 delta-shped
resonators, 2 valley chambers and 4 chambers positioned at the sector magnets.
The total degas rate from the surface of the chambers has been easimat·ed to
be about 2.5 lus. Two cryopumps of 25000 1/s and two titanium-su blimation
pumps of 5000 1/s, for example, will be needed to reach the above mensionedvacuum.
Injectors
The heavy-ion linac at IPeR will be used as an injector of heavy ionswith final energy up to 60 MeV/u. Main characteris tics of the linac isdescribed in ref. 1. For heavy ions with final energy greater than 60 MeV/u
as well as light particles such as deuterons and a particles, an AVF cyclotron
is chosen to be an appropriate injector. The Maximum mean field of the proposed AVF cyclotron is 1. 3 T, the energy constant being K=90 MeV. It ispossible to accelerate p, d, h and a as well as heavy ions up to Ar with theharmonic numbers of 2 and 3. The maximum injection energy into the sse islimited to 7 MeV/u for heavy ions and 10 MeV/u for d, h and a. Main characteristics are given in table 2.
Building
This facility will be devoted to researches in various fields such as nu.clear
and atomic physics, solid state physics, material science, nuclear and radiation
chemistry, radiation biology and RI production. The use for the radiotherap y isalso beirtg considered. All facilities for these purposes are being planned to beconstructed at IPeR. Tentative layout of the beam lines and main facilities together with plan views of the sse and the AVF cyclotron is shown in Fig.l.
In order to keep the radiation dose as lower as possible at the boader ofthe campus of IPeR, thickness of the concrete wall and ciel of the sse vault
should be 4 m and that of other vaults should be 3 m. The shielding effect andthe radiation doses at various points both inside and outside of the building
are calculated.

-326-

Planning.

The four sector magnets will be ordered in this fall. Design study of theRF system,computer controle system and extraction and beam lines to the experimental facilities will be continued.
The first beam will be expected in 1985.
This facility will be 'open not
only for the inside users but also for outside users.
References
1) M.Odera,"Status Report of Rilac, Riken Variable Frequency Heavy-Ion Linac"
this conference.
2) H.Kamitsubo et al,"A Proposed Multi-Purpose Separated Sector Cyclotron at IPC,
R" IEEE Trans.Nucl.Sci. NS-26, (1979) 2065
3) Y.Yano et al, "Design of Injection System for the IPCR SSG (I)",this conference.
A.Goto et al, "Design of Injection System for the IPCR SSG (IT) ",this conference.
4) N.Nakanishi et al, "Orbit Calculation for the IPCR SSG", this conference.

-327-w

I00

""

24

238u 10+

20.4

26

22.1

7.37

1+2+4+

p3He

12c

6.51

19.6

22.1

RF
freq.
(MHz)

Orbit
freq.
(MHz)

7.37

20

20.4

2020

1.28

0. 7270.485

ext(Wb/m2)

B

0.84

1.36

2.2

3.8

799

Energy per
nucleon(MeV/u)Energy per
nucleon(MeV/u)(Rext =0.893 m)

ChargeBeam

159+

l3 2xe3344

Cyclotron

99+

84Kr

58+

40Ar

Accelerating RF
freq. voltage(MHz)(MV)

LINAC

6+2+1+2

1.5

1

6.4
5.9

37+

4.4

3.5

2. 7

m/q 2

40+30+

24+

15+

Charge
(q2)

1.48

1.26

0.838

1.52

1.55

1.43

1.45

1.45

Binj
(Wb/m2)

1.67

1.49

0.994

1.54

1.57

1.46

1.5

1.55

max
(Wb/m2)

B

sse

20.4

19.4

26

33

43.3

99

999

6.5

39.1(26.0) 6(4)7.37 44.2(29.5) 6(4)7.37 44.2(29.5) 6(4)

2.27

2.14

2.88

3.67

4.8

134.6

184

184

13.6

12.2

22.3

36.8

66.6

Orbit
Accelerating Energy per
freq. RF freq. h numbernucleon
(MHz)
(MHz)
(MeV/u)Examples of some operating parameters at the maximum energies in the propoed accelerator complex

Beam Charge m/q 1

Table 1

Table 2

Characteristic s of Separated-Sec tor Cyclotron

Maximum energy for u 37+(u 40+)
Maximum energy for c6+, o8+, NelO+

13.6 MeV

Number of sectors

4

Sector angle

50°

Magnet fraction

0.555

135 MeV/u

Magnet gap

8 em

Maximum Magnetic field

15.5

Main coil power

450 kW

Number of trimming coils

30

Magnet weight2300 tonInjection mean radius

89.3 em

Extraction mean radius

373 emEf/Ei
Number of dees

16-vl82

Dee angle
Peak voltage

250 kVRF power

300 kW X 2

RF frequency range

17 45 MHz

Number of harmonic Acceleration(4), 6,9

Characteristic s of Injector Cyclotron
Energy constant, K

90

Number of sectors

4

Magnet gap at hill-v20 em

Maximum mean magnetic field

13 kG

Extraction mean radius

89.3 emMain coil power

200 kW

Number of dees2

Dee angle

60°

RF frequency range

7.5-v22.5 MHz

Maximum RF voltage

50 kV

RF power

150kW-329-sse vaultphysics(9) Beam transport lines

N~clear

(8)

I0w

w

(7) Atomic' and solidstate physics(6) Nuclear chemistry
and RI productio n(5) Radiation therapy
and radiation biology(4) Nuclear spectrosco py(3) Material science(2) Injector cyclotron(1)

Fig. 1~\·---------}----------,