JAERI-Conf 95-021

2a2-1
PRESENT STATUS OF THE ACCELERATOR DEVELOPMENTAT THE ICR KYOTO UNIVERSITY
Makoto INOUE, Akita NODA, Yoshihisa !WASHITA, Hiromi OKAMOTO, Toshiyuki
SHIRAI, Shigeru KAKIGI, Hiromu TONGUU, Hirokazu FUJITA, Hideki DEWA,Masanori IKEGAMI, Valeri KAPIN, Masaki KANDO, Takaslii SUGIMURA and Hiroshi
FUJISAWA*Institute for Chemical Research, Kyoto University, Uji, Kyoto 611, Japan*R&D Div., Nissin Electric Co., Ltd., Kuze Tonoshiro-cho575, Minami-ku, Kyoto 601, Japanof the extracted beam from the ion source is now designed.

Abstract
The injection system of the 7MeV proton linac has been
Aimproved to transport the high intensity beam.
measurement device for the longitudinal emittance of the7MeV proton beam has been developed. A 100MeV electron
linac has newly assembled to study electron-photon beamphysics. An electron storage ring will follow this linac. A
heavy ion 4-rod RFQ linac was completed and has been
moved to the cooperating company to perform acceleration
test for industry. The cold model study of the improved DAW
structure for the high energy 1inac was done and a power test
model has been designed. A medical synchrotron design hasbeen also studied. An untuned cavity for this synchrotron
has been constructed and a new RF power feeding scheme has
been tested. Theoretical studies of the space charge effect andan improved 4-rod RFQ structure are in progress. An
accelerator-based reactor which consists of a proton linac
and a subcritical assembly has been proposed as a pulsed
neutron source.

Fig. 1. The injection line of the proton linac

1. Introduction
It may be necessary to use a large accelerator for highenergy physics, nuclear physics, photon factory or neutronfactory. Only at a national laboratory we can construct suchlarge machine. While at universities accelerator physicists
are now disappearing in this country because of theconcentration of the budget into the national laboratory. But
it is very important to study fundamental accelerator physics
or beam physics at universities in order to develop advanced
technology and educate younger generation. Our laboratory
was a nuclear physics center with a cyclotron more than
thirty years ago. But now it becomes a unique accelerator
laboratory developing small accelerators and promoting
accelerator physics or beam physics at the university.
2. Proton linear accelerator
Our 433MHz RFQ linac accelerated the first beam of
2MeV protons in 1991. Since January 1992 we haveobtained 7MeV proton beam from a 433MHz Alvarez linac
which follows the 2MeV RFQ linac. So far intensity of thebeam has been limited by small aperture of the injection
line. Recently we have replaced a bending magnet(a mixing
magnet to-be) by a newly designed one which has a larger
gap and an entrance angle against the sector focusing. We
can now transport a wider envelope beam, which reduces
space charge effect. Not only the high intensity beamtransportation during the injection line but also beam
matching to the RFQ acceptance is necessary to increase theaccelerated beam intensity. For this purpose a permanent
magnet symmetric lens(PMS) has been designed!). The
injection line is shown in Fig.l. The designed beamenvelope in this injection line is shown in Fig.2. To ensure
the beam matching a measurement system of the emittanceVtrlial·2!165.S-Fig. 2. The matched beam envelope between einzel lens and
PMS section at current of 20mA (fRACE-3D calculation).
Measurement systems of properties of the 7MeV proton
beam from the Alvarez linac have been constructed andinstalled in the down stream beam line. One of them is adouble-slit emittance monitor2) and the other is a phaseenergy distribution (longitudinal emittance) measuringsystem3).
The principle of the double-slit emittance monitor is not
new but pulse beam detection is necessary in our casebecause the linac is operated in pulse mode with a repetition
rate of 18-180Hz and pulse width of SOJ.Lsec. The typicalmeasured rms emittance of the 7MeV proton beam is
4.8mnrnmrad which varies depending on the RF power fed tothe Alvarez linac2).
The schematic view of the newly developed system of thelongitudinal emittance monitor is shown in Fig.3. It
consists of a narrow gold target, an RF deflector and aposition sensitive detector. A slit and a focusing system arealso included. The phase of the accelerated particle
corresponds to the position of the detected proton at theposition sensitive detector. The energy of the accelerated
particle is also obtained from the measured energy of thedetected particle at the position sensitive detector.

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Table 1. Characteristics of the electron linac

Thin Carbon Foil

Output Electron Beam
EnergyBeam Current
Pulse width
Max. Repetition
Electron Gmt (Pierce type)
Cathode assembly
ExtraCtion voltage
grid voltage (typ.)Accelerating structureGold Target
W= 0.3 mm, H= 8 mm

E

-E
..J~

lOOMeV
lOOmA
1~20HzY-796 (Eimac)-100 kV DC
lOOVMode2{31t, Constant Gradient

Number of Cell
Bore Radius85
11.74- 13.4 mm
3m2857MHz
53MW/m15 MV/m at 20 MW input

LengthOperating Frequency
Shunt Impedance
Maximum Electric Field
Klystron (ITT-8568)

Position Sensitive De'tcctor

Cathode250kV, 250 A

Oul:!?ut RF Power

21MW
53 dB

Gain

H=8 mm, W=!5 mm(6.<=0.15 mm, dE=30keV)

Fig. 3. Concept of the longitudinal emittance monitor
3. Electron linear accelerator and storage ringOn the occasion of the shut-down of the JAERI electron
linac and the storage ring JSR some components have beenkindly transferred to our laboratory. We have designed alOOMeV electron linac and our storage ring KSR for thestudy of the electron and photon beams using thesetransferred components and additional parts4)

BeamA:t~l

tltli1\iBu.nc:IMrcJl

Q-mag.l

Q-mq.2

FlAce.J

Q·mii.Jif!!

Q-mas-4~§Q-mag.5

0

B~mDump

Fig. 5. Calculated beam radius (emittance of lOOmnrnmrad)
Table 2. Design parameters of the storage ring KSR

Electron Strage Ring

300 MeV

Maximum energy

100 MeV

Injection energy
5mElectron Injector
Bundler

Accdemor No.1

Quaarupo\eMagnet No.IMagllelNo.2""""'""'

Mqne:rNo.J

25.689 m

Lattice structure

Triple bend doubly achromatic lattice

Superperiodiciwy

2Bending angle

60°

Radius of Curvature

Atcelerlllot No.lq,..o,..po•

Circumference

n-value·~

Dump

Edge angle

Fig. 4. Layout of the electron linac and the storage ring KSR

Length of long straight section
Harmonic number

In Fig.4 the schematic layout of the accelerator is shown.
At JAERI the linac had five accelerator tubes and it wasoperated with repetition up to 600Hz. But our laboratory
area and electricity are limited so that the number of theaccelerator tubes and repetition are reduced to three and 20Hz
respectively. We changed the original triangular shape ofthe ring to a race-truck to have long straight sections,which requires rebuilt of the vacuum chamber. At themoment the electron linac has been completed but thestorage ring KSR is not completed yet, where only the six
bending magnets and focusing magnets are aligned. Maincharacteristics of the electron linac are listed in Table 1 andthe designed values of the KSR are listed in Table 2. Only
three of 3m accelerator tubes are used, while the first two of
five accelerator tubes at JAERI were 2m. Therefore we haveexamined beam transport during acceleration in our case.
The calculated beam envelope is shown in Fig.S. The firstbeam acceleration test is planned in September 1995.

RF frequency
Number of Betation Oscillations

0.835 m000
5.619 mlO

l16.7MHz

Horizontal

2.75

Vertical

0. 75 ( 1.25)

Critical wave length lrom dipole

17 nm

4. Boron beam acceleration with the 4-rod cw RFQ linac
At the ICR Kyoto University the 4-rod cw RFQ linac wasconstructed and the first beam was obtained on December 25,1992. At the University He, N and C ion beams wereaccelerated to test the operation of the system. After one
year test the linac system was moved to Kuze factory ofNissin Electric Co., Ltd. to continue the acceleration test ofthe boron ion beam which would be used in the process ofsemiconductor industry. The characteristics of the 4-rod
RFQ linac are listed in Table 3 and a schematic plan view is- 186-

JAERI-Conf 95-021

Outer Conductor

Table 3. Characteristics of the 4-rod RFQ heavy ion linac
Injector:

Freeman rype

Ion source
Extraction voltagejQ kV'

Mass analyzer

90~max.

magnet with sextupole corrections

Focusing elements

four magnetic quadrupole lenses and one Einzel lensBeam optical lengh

2.5 m, including a beam monitor

Size

1.5 (W)Xl.5 (D)Xl.8 (H)RFQ.·
fixed frequency ·'modified" -+-rod

TypeFrequency

33.3 MHz (design)

Average bore radius

0.8 emFocusing strength

6. 79Inter-electrode \'Oltage

54.9 kV

Charge to mass ratio

1/11 (design}

Injection energy

2.73keV/u

Output energy

83.5 keV/u (w/o half-cell)

Length of electrodeCavity inner diameter60 em

rt- power

50 kW max.

~22 emcoupling caseS). The power model test is being carried out incooperation with Hitachi Ltd..

(w/o half-cell)

7. Other studies

Operation mode

Space charge effect and halo formation in case of highintensity linac are investigated by analytical and simulation
methods. A simulation code is developed at our laboratory9).
A normal mode analysis of transmission lines for TEM
mode waves is applied to a 4-rod RFQ resonatorlO). Resultsof this analytical method are in good agreement withcalculations by MAFIA code. A 2.5-D RF cavity code
PISCES II is also developedll).
A pulsed neutron source which consists of a proton linac
and a subcritical assembly is proposed for a future project ofKyoto University Research Reactor lnstitute12). The linac
will accelerate a 300MeV-30mA proton beam and the power
gain of the subcritical assembly will be 20. Characteristics
of an example of the proposed pulsed reactor with a proton
linac are listed in Table 4.

~80%

Transmission

Descriptions of icons:CFi.l.ed Faraday cup.

1 Rctr~ctableIj,,

Faraday .:;up. {(b) Yiulti-feed coupling.

(a) Direct coupling.

Fig. 7. Setup of the direct and multi-feed coupling

Beam defining slit.
Emittance monitor.

Gate vulvc.

!on source

1.5 m

Table 4. A proposed pulsed reactor with a proton linac
Accelerator

Fig. 6. Experimental setup of the 4-rod RFQ linac system

multi-cusp field type

Ion source

shown in Fig.6. We have obtained the singly charged boron
beam intensity of 3301J.A with total beam transmission of80% 5). The measured beam emittance was about
101tmmmrad at the accelerated beam energy of 0.92MeV.

5. DAW cavity
The disk-and-washer (DAW) structure of the linac has beenstudied in our laboratory. Recently a biperiodic L-support
structure has been proved to have high quality without themode overlapping problem. MAFIA and SUPERFISH
calculations and cold model study have been made6). Then apower model is now under construction for S-band electron
linac because the S-band RF power sources have become
available as mentioned above.
6. Medical proton synchrotron
A compact 230MeV proton synchrotron with a combinedfunction lattice has been designed for medical use. A proton
linac like our existing ?MeV linac may be used as aninjector. Slow beam extraction of diffusion-resonant
scheme has been studied?). A ferrite-loaded untuned cavity
with multiple RF power feeding has been designed andconstructed8). The concept of the feeding is shown in Fig.?.
According to the cold model test the reflection power fromthe cavity is reduced from 75% of the forward power in the
direct coupling case to 20% in the multi-feed coupling case.
It is also confirmed that the cavity voltage is increased byfactor 1.5 for multiple coupling case comparing to the direct

RFQ section

2 MeV,433 MHz

DTL section

lOOMeV,433 MHz

DAW section

300MeV, 1,300MHz

Beam intensity

SOmA at peak

Pulse width

50 J-ISec

Repetition

60Hz

Neutron yield

10 18 n/sec at peak

Subcritical assembly
Fuel
Peak power

l80MW

Average power

600kW

Neurrons

10 19 n/sec at peak

References
1) M. Kando et al., Proc. Particle Accel. Conf.1995
2) M. Ikegarni et al., Bull.lnst.Chem.Res. Kyoto Univ.
Vo1.73, 1, 1995
3) H. Dewa et al., ibid. Vol. 73, 90, 1995
4) T. Shirai et al, ibid. Vol. 73, 78, 1995
and A. Noda et al., ibid. Vol. 73, 27, 1995
5) H. Fujisawa et al., ibid. Vol. 73, 33, 1995
6) Y. !washita et al., ibid. Vol. 73, 97, 1995
7) K. Hiramqto et al., ibid. Vol. 73, 11, 1995
8) J. Hirota et al., ibid. Vol. 73, 41, 1995
9) M. Ikegami and H. Okamoto private communications10) V. Kapin et al., BulllCR K.U. Vol. 73, 50, 1995
11) Y. !washita, Proc. Int. Linac Conf.94, 239, 199412) M. Inoue et al., Bull.ICR K.U. Vol. 73, 106, 1995

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