CONSTRUCTION OF THE RCNP RING CYCLOTRON
I. Miura, T. Yamazaki,.A. Shimizu, K. Hosono, T. Itahashi,
T. Saito, A. Ando, H. Ogata, I. Katayama, T. Nakatsnka, M. Kondo and H. Ikegami
Research Center for Nuclear Physics, Osaka University
Minogaoka 10-1, Ibaraki, Osaka 567, Japan
andJ. Abe
Accelerator Business Center, Techinical Department, SumitomoHeavy Industries Ltd.
Niihama, Ehime 792, Japan

Abstract

General description

The main components of the new facility are a six separated
spiral sector cyclotron (ring cyclotron) and a beam circulation ring
linked to a high precision dual magnetic spectrograph system. Theinjector is the RCNP AVF cyclotron. The construction of the newfacility made steady progress along the four year schedule started
from 1987. The main components of the ring cyclotron are fabricatedand passed preliminary tests of the performance. Installation of thering cyclotron system in the new building will be started in February
1990. The first beam is expected early in 1991.

Plan view of the ring cyclotron is shown in Fig. 3. Three single
gap acceleration cavities are used in the ring cyclotron. Frequencyrange of the cavity is 30~52 MHz and harmonic numbers of acceleration is 6, 10, 12 and 18. An additional single gap cavity is used
for flat-topping with third harmonic of acceleration frequency to getenergy resolution better than 10- 4 .

Introduction
The plan view of the new facility is shown in Fig. 1. The main
compmients is a ring cyclotron, a beam circulation ring linked to ahigh precision dual magnetic spectrograph, a neutron TOF facility, aheavy ion secondary-beam facility and a pion spectrometer 1l.
The ring cyclotron is energy quadrupoler of the present RCNP
AVF cyclotron. With this accelerator system, beams of p, d, 3 He,
alpha and light-heavy ions can be accelerated up to 400, 300, 510,
400 and 400·Q 2 /A MeV, respectively. Maximum energies of various
ions from the ring cyclotron and several major projects are shown inFig. 2. An emphasis is placed on the design to produce high quality
beams for precise experiments in the range of intermediate energy. 2 l

A 180°-single-dee acceleration cavity is used in the present AVF
cyclotron. The frequency range of the cavity is 5.5"'19.5 MHz, andfundamental and 3rd harmonic acceleration modes are used. Fig. 4shows relation between orbital frequencies and acceleration frequencies in the present AVF cyclotron and the ring cyclotron for various
ions and energies. the characteristics of the cyclotrons are given in
Table 1.
For the preparation of ideal injection beams for the ring cyclotron in longitudinal phase space, a beam bancher system operated
in 2nd harmonic of acceleration frequencies of the ring cyclotron isbeing proposed.

NEUTRON EXPERIMENTAL HALL

Neutron flight tunnel ( 100 m )H. I.
secondary-b-enm

Beam circulation
IliJ

Fig. 1. Plan view of the new facility.

-54-4000:w

zw

43240

20
105 6 7
NUMBER
MASS

Fig. 2. Expected maximum energies of various ions for the RCNP
ring cyclotron and several major projects .
Rc N p4008+• ....1.12+
Nr' r _Kr16+/.A

I

V/

AVF

Fa-5.5-~9.5M~z

Lv/ 0 6+

jt/, Cs+

2oor---~~~~~~~~/~~~~

1 00::l 80 /E 60"'II~ 40 _L~>
(!)

I iJ

I:IE

Fig. 3. Plan view of the ring cyclotron.

///'/ /

II/////V~_.,_ Nh=3~ I/voltage distribution of the acceleration cavity is convex shape andradially increasing. 6) This voltage distribution is suitable to get wide
phase acceptance with fiat-topping.

17~ Nh= 1 --::f///
202

'A~

1~1//J /

64

8

14

10

A single gap cavity is used for fiat-topping. The upper andlower walls of the cavity can be slid as inductive-tunner-plates. A verymuch similar radial voltage distribution as that of the acceleration
cavity was realized for the fiat-topping cavity.

20a:~5001r---~-+--~--~~~~~le~LJRING

RCNP

4HL

w 400c-- CYCLOTRON -+-"~"'+-"-+J...--l----1-.-l--l
Z 300 Fr =30-52MHz

0;[/Three RF power amplifiers for the acceleration cavities werefablicated. The amplifiers generated 250 kW RF power on a dummyload. Preliminary measurements on the shunt impedance of the cavities and matching condition of the coupling loops have been done. 7 )pI/; d [72oor------+---,~~~~-+~~w
M=2 Nh=!a.j _ 1 . 1 r1Fr=MXFa~~h=~8.1 //I
M- 3 jNh=10RF power test with non-evacuated cavities will be started alsoin August 1990.

Nh=6 I

100·~======l=~~~~~···--~~~M~-~3~3r~

Table 18o,r------+~~~+,f-,+l~,-~~+4~2

4 5 6 7 8 910
3ORBITAL FREQ. MHz

Characteristic of cyclotronsFig. 4. Orbital frequencies, acceleration frequencies and harmonic
numbers of acceleration in the present AVF cyclotron and the RCNP
ring cyclotron. M is ratio of the RF frequency of the ring cyclotron
to the AVF cyclotron.

Magnets of the ring
the sector magnet of the six separated sector ring cyclotron
were designed by using a computer code FIGER3 l (artificial magnetic
field distribution generator) and the results of model magnet study ofthe previous proposai. 4 l A preliminary measurements of the magnetic
field distribution have been performed in the factory. The results arequite satisfactory. 5 l The complete field measurements are scheduled
to start in August 1990.
Acceleration system
Single-gap type acceleration cavities were used to reduce RF
power loss and cavity size. The size of the cavity reduced much byusing capacitive tunning with a pair of rotatable plates. The radial-55-

No. of sector magnets
Sector angle
Injection radius (em)Extraction radius (em)Magnet gap (em)Max. Magnetic field (kG)
Proton max. energy (MeV)
Alpha particle energy (MeV)
3 He energy (MeV)
Weight of magnet (ton)Main coil magnet (kW)No. of trim coils
Trim coil power (kW)No. of cavities
RF frequency (Mifz)
RF power (kW)Injector
Cyclotron

RingCyclotron

3max 52°6100
20.7 min19.584
130
160
400
450
16265

22~ 27.5°
2004046.0
17.5
400400510
2100
440
363503(Acc.) 1(FT)

5.5~19.5

30~S2

120

250x3

90~15545

Injection and extraction

Vacuum system

The injection and extraction systems of the ring cyclotron 8 lsatisfy the central-position phase matching condition (dispersionmatching). A variable dispersion system follows the extraction system of the ring cyclotron to cancel the velocity dependent momentum
dispersion (D=R,.,(l-,8 2 )) of a relativistic isochronous cyclotron atextraction radius (Rex).

The vacuum chamber of the ring cyclotron consists of six magnet chambers, three acceleration cavity chambers, a flat-topping cavity chamber and two valley chambers as shown in Fig. 3. The gaps
between these chambers are sealed by puneumatic expansion seals.
The reliability of the seals was verified with a prototype of the seai. 9 )Orbit analyses for accelerated beams
The orbital properties of the accelerated beams in the ring
cyclotron were studied in simulated magnetic field distribution.
The sine wave acceleration voltage in the ring cyclotron produce energy broadening of 700 keV for 400 MeV proton beams having
RF phase width 7°. this energy broadening can be canceled perfectlywith only one flat-topping cavity, without evident radial-longitudinal
coupling effect. If the RF phase errors between the cavities are lessthan ±0.1 °, the energy width of the 400 MeV protons is less than
10-4.
The orbit properties of the beam along the injection and extraction elements in the ring cyclotron also studied. The turn separationsat injection and extraction points are lOmm and 3mm, respectively.
The wide phase acceptance for single turn extraction modewith flat-topping is desirable to get high intensity beams. The phase
acceptance depend much for the radial distribution of the acceleration
voltage.
Fig. 5 shows result of calculation on the properties of the accelerated beam in radial and longitudinal phase space. The simulated
magnetic field distribution and the measured radial voltage distributions of the cavities are used for the calculation. Phase acceptancemore than 20° in width can be expected for tlte acceleration frequency.
ga~ LIT cc. u. 1w

Evacuation tests of perfectly assembled magnet chambers andcavity chambers were done. The results were better than designedvalues. After 10 hours of evacuation, the acceleration chamber canbe pumped down to 2x10- 7 Torr.
Beam diagnostic system
Layout of the beam diagnostic system, design of the diagnostic
elements and the format of graphic display for the diagnostic data
has been determined. 10)
Control system
The present control system of the AVF cyclotron will be usedwithout any modification. For the ring cyclotron, new computer control system are developed. 11 l
The control system of the ring cyclotron and the beam transport system consists of a system control computer (micro VAX 3500),
four group control units (one micro VAXII and three RTVAX) andmany universal device controllers.
A twin operator console of the ring cyclotron will be installednear by the present operator console of the AVF cyclotron and connected directly to the system controller.
Each group control computer is connected to the system control
computer through a computer network Ethernet. Each group control
computer is also connected to universal device controllers throughoptical fiber serial lines. The setup sequence of the ring cyclotron
operation can be described by language OPELA and controlled by
the group control computer.

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o.o ooaReferences

1.14ns--...l1---20.6°1) S. Morinobu eta!., Construction of Experimental Apparatuses
and Beam Line, RCNP Annual Report 1987.

N8En
Ez

0-TUAN
Q. DOD 0
9. 75
O. 002) H. Ikegami, Proc. 12th Int. Conf. on Cyclotrons and theirApplications, Berlin (1989),
I. Miura eta!., RCNP Annual Report 1986, Proc. Third JapanChina Joint Symposium on Ace. RIKEN (Japan) 1987.

IMMAl "'INMAl % ~10mrt¥

1-----1.

\• -a.\oo -o.\oo'o.~ooC.."·' a.\oodTooo.'\oo3) I. Miura et a!., A Computer Code FIGER, Proc. of the 4th\f.oooSymposium on Ace. Science and Technology, RIKEN (Japan),
1982.

(a)

4) K. Hosono et a!., Spiral Sector Magnet of RCNP Ring Cyclotron Project, RCNP Annual Report 198·1.
o.o oog•-o.002Bo.ooo 0~R 1c. u. 1o.ruoo

5) K. Hosono et a!., presented at this symposium.

...j6) T. Saito et a!., Proc. 12th Int. Conf. on Cyclotron and their•g 0.59nsApplications, Berlin (1989).

~7) I. :Miura et a!., presented at this symposium.
N8EnEz279- TUAN
Q. 000°~ 5
3. 58 INMAl•Q, 008) A. Ando et al., Proc. 12th Int. Conf. on Cyclotron and their
Applications, Berlin (1989).

INMAl

Q.Q3009) A. Shimizu et al., presented at this symposium.

f.ooo10) T. Itahashi et a!., presented at this symposium.

(b)
Fig. 5. Beam profiles projected in radial and longitudinal subspace
and its coupled space.
(a): before acceleration (63.7 MeV protons).
(b): after acceleration (400 MeV protons) with flat-topping.

11) T. Yamazaki et a!., presented at this symposium.

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