JAERI-Conf 95-021

la-4
CURRENT STATUS OF THE RCNP RING CYCLOTRON
I. Miura, K. Hatanaka, K. Hosono, T. Itahashi, K. Sato, M. Sato, T. Saito, A. Shimizu,
K. Takahisa, K. Tamura, T. Yamazaki, S. Ano, M, Kibayashi, H. Tamura and M. Uraki

Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567, Japan
Abstract
Experimental studies with the RCNP Ring Cyclotron were started from 1992. Energy resolutionof 25keV was obtained with high resolution spectrograph Grand Raid en for 300MeV proton beamof 80keV energy width by using dispersion matching. A very short polarized proton beam pulse of150ps was achieved for neutron TOF experiment.
A new high intensity polarized proton and deuteronion source, a new axial injection system and injection
beam line for polarized ion source and Neomafios
were installed in August 1994. The old RCNP AVF
cyclotron has been used as injector cyclotron without any modification. On this scheduled summer
shutdown, the control system and the main magnet
power supply of the AVF cyclotron were replaced bya new one. Many improvement on the stability andthe controllability of the AVF cyclotron can be expected. On January 17th, 1995,the Ring Cyclotron
was displaced about 5mm by the earthquake. The
realignment of the system had been made and experimental studies are started in May.

The phase acceptance is 20° for energy deviation
with flat-topping within 10- 4 • A 180°-single-dee acceleration cavity is used in the injector cyclotron.
The frequency range of the cavity is 5.5-19.5MHz.
The phase acceptance of the injector cyclotron is 7°
and 4°, since the ratio of acceleration frequency of
the ring cyclotron to the injector cyclotron is 3 and
5 for proton and alpha, respectively. In order to gethigh quality injection beam for the ring cyclotron,
the six dimensional phase space volume of the injection beam is limited by various slits between the ion
source and the ring cyclotron. The beam intensity
reduction about 10- 2 with these slits is very serious for polarized beam and heavy ion beam. The
beam intensity upgrade project had been done in
19945 ' 6 ' 7 ). Many efforts are being continued to improve beam quality, stability and intensity of thering cyclotron. Injection beam instabilities caused
by main coil and trim coil power supply of the injector cyclotron was serious problem. The beam stability upgrade project of the injector cyclotron wasdone in this summer8 ' 9 ' 10 ).
Table 1 Accelerated Ions and the energies
Proton100,200,250,300,350,365,380,
390,400 MeVDeuteron
150,170,200 MeV
3 He
450 MeVAlpha
300,400 MeV
14N7+
560,980 MeV

I. Introduction

The construction of the RCNP ring cyclotron
was started in 1987. The first extracted beam wasobtained in 1991 1 ). The ring cyclotron is energy
quadrupler of the RCNP AVF cyclotron. Protonand alpha particles can be accelerate up to 400MeV.
The K value for light-heavy ions acceleration is 400.
Table 1 shows the accelerated ions and the energies
by the ring-cyclotron 2 ). For 400Mev proton beam
acceleration, 30-50% of accelerated beam was lostby axial oscillation driven with median plane error
near Vz=l resonance for unproper setting of the trim
coil currents 3 ). However no beam loss was observed
for smooth surface current density distribution of
the trim coil 4 ).
Plan view of the ring cyclotron is shown in Fig.l.
Three single gap acceleration cavities are used in thering cyclotron. Frequency range of the cavity is 3052 MHz. An additional single gap cavity is usedfor flat-topping with 3rd harmonic of acceleration
frequency to get good energy resolution and wide
phase acceptance for single turn extraction mode 1 ).

-II. BEAM INTENSITY UPGRADE PROJECT
1. New axial injection system
Old axial injection line with electrostatic
quadrupole lenses was replaced by new system with
Glaser lenses, sawtooth buncher and spiral infiector to get a high-transmission and stable operation.
Fig.2 shows layout of the injection line. The direction of magnetic field in the Glaser lenses is excitedalternately to cancel the depolarization effect of thelens. The obtained injection efficiency for 65Me V
proton is 14%5 ' 7 ).

8-JAERI-Conf 95-021

4. RF system of the injector cyclotron
2. High intensity polarized ion source
A new atomic beam type polarized proton anddeuteron source with cold(30K) nozzle, NEOMAX
sextuple magnets and ECR ionizer. A maximum
proton current of 8JL A was obtained for 65MeV. The
polarization is about 0. 75. The polarized ion sourceis horizontal type and easy for maintenance. The
polarized protons and deuterons are deflected upward by 6. 7 and 15 degrees respectively with electrostatic deflector and deflected downward by 96.7 and105 degrees with a following dipole magnet to get
longitudinally polarized beam in the vertical beamline 5 •7 ).
3. NEOMAFIONSA 10GHz ECR ion source NEOMAFIOS is used asexternal ion source of the injector cyclotron from lastSeptember. Table 2, shows the beams accelerated
for experimental studies6 •7 ).

III. BEAM STABILITY UPGRADE PROJECT
1. Control system of the injector cyclotron

The low-level RF system was replaced by new system very similar to the ring cyclotron RF system.
Improvement on the stability is expected.
IV. DAMAGE AND IMPROVEMENT
1. Utility

Old chillers of the cooling water system and old air
conditioning system for the AVF cyclotron were replaced by new one. PID temperature regulator ofthe cooling water was appended.
2. Repair of the cooling pipes
The Dee-electrode of the AVF cyclotron was overhauled to repair perfectly the cooling water leakage
to vacuum.
3. The earthquake
The estimated maximum acceleration of the earthquake( January 17th,1995) on the RCNP is more than300gal. About 5mm slip to north was occurred between the rest and the base-plate of the ring cyclotron. No damage of the elements was occurred.
The rests and the base-plates were welded together
after the realignment of the ring cyclotron system 2 ).

It became difficult to maintain the old control system of AVF cyclotron. A new control system was4. RF current contact of the ring cyclotron
needful to install a new high resolution high stability reference voltage for every power supplies of
After long exposure to the atmosphere during two
the AVF cyclotron. The main computer of the ringmonths realignment of the ring cyclotron, the sliding
cyclotron control system was upgraded from micro
RF current contacts (made of graphite admixed silVAX 4000/200 to micro VAX 4000/500. The controlver) failed on 300MeV proton acceleration position.
and monitor functions of the AVF cyclotron were
The cavity wall was polished and the contacts wereconcentrated to the ring cyclotron control system 8 ).
replace by pure silver contacts in this summer. Thesprings of the RF current contacts of the accelerleaf
2. DC power supplies for the injector
ation cavity were degraded by three years operation
The achieved long-term current stability of the new on high temperature("' 300°C). The leaf spring ismain magnet power supply is 4 X w- 6 • The long- silver plated and made of Be-Cu alloy having electerm current stability better than w- 5 was obtained tric conductivity about 20% lACS. The thermal confor the trim coil power supply by using HOLEC- ductivity of metal is nearly proportional to the elecDCCT-TOPACC. The remained old DCCT of the tric conductivity. Cr-Zr-Cu alloy (85% lACS) leaf
trim coil power supplies will be replaced soon by springs will be installed soon.
the new DCCT9 ).
Table 2 Accelerated ions from Neomafios
Energy AVF Beam current at exit
3. RF system of the ring cyclotron(eJL A)(MeV)
Many efforts were made to improve stability of RF
943.5
dsystem. Typical phase excursion between accelera3 Hl+
432tion and flat-topping voltages are 0.1degfweek. The
3He2+
7.4
92.6
voltage stabilities are 0.01% and 0.1% for the accel4 He2+
3.2120eration and flat-topping voltage respectively 10 ). The
6£i2+0.042
64
development to improve stability of the RF system6£i3+0.088
131.1
is being continued.
1£i3+
0.242
114.0
14N4+
4.4
130.3
14Ns+
2.3
210

-9-JAERI-Conf 95-021

Reference[1] I. Miura, et al., "Commissioning of theRCNP Ring Cyclotron", Proc. of the
13th Conf. on Cyc. and Their Appl.,
Vancouver(Canada)1992,p.3[2] K. Hosono, et al., "Present status of theRCNP cyclotron facility", Proc. of the
14th Conf. on Cyc. and Their Appl.
[3] I. Miura, "The Research Center for Nuclear Physics Ring Cyclotron". Proc. ofthe 1993 Particle Accelerator Conf. p.1650[4] T. Itahashi, et al., "Dynamic behaviourof accelerated particles by using a T.V.
camera and phosphor covered plate". RCNP
annual report 1993, p.193 T. Itahashi, etal., "Radial and vertical betatron oscillation frequencies observed by a scintillation plate and a three wire tomography
monitor", Presented at this symposium.

Fig.1 Plan view of the ring cyclotron.

[5] K. Hatanaka, "The RCNP atomic beamsource", Proc. of the 14th Con f. on Cyc.
and Their Appl.

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!lGlii'-o0 ..
i~ :ICD. ..

~CD[6] M. Sato, et al., "The new external ion
sources and. the new axial injection system at RCNP", Presented at this symposium.

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fromHI PIS

Dipole Magnet[7] K. Takahisa, et al., "Status of the NEOMAFIOS at RCNP", Proc. of the 14thConf. on Cyc. and Their Appl.

Dipole Magnet[8] K. Tamura, et al., "Control system for
RCNP cyclotron", Presented at this symposium.

Quadrupole MagnetSteering Magnet
Glaser Lens~!~~~=tic[9] K. Hosono, et al., "High stability, highcurrent power supplies for the injector",
Presented at this symposium.

Steering Magnet
Glaser Lens

[10] T. Saito, et al., "The fiat-topping system
for the RCNP ring cyclotron", Proc. ofthe 14th Conf. on Cyc. and their Appl.

Beam Buncher

AVF Cyclotron
Upper Yoke
Steering Magnet
Glaser Lens

Median Plane==:!:::==

0.5

Fig.2 Layout of the injection line.

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