CONSTRUCTION OF HIMAC INJECTOR
S. Yamada, T. Hattori~ A. Itano, M. Kanazawa, T. Kohno,
Y. Miyazawa) 0. Morishita! K. Noda, H. Ogawa, K. Sato,
Y. Sato, K. Sawada! T. Yamada and Y. Hirao
National Institute of Radiological Sciences
4-9-1 Anagawa, Chiba-shi, Chiba 260, Japan

Abstract

Table 1.
Injector specification.

At National Institute of Radiological Sciences (NIRS), the J!eavy
Ion Medical Accelerator in Qhiba (HIM A C) is now under construction.
The HIMAC is dedicated to the medical use especially for the clinicaltreatment of tumor and will be the first heavy ion synchrotron complex
in a hospital environment of Japan. This paper describes an outlineof the design and construction of the HIMAC injector.
Introduction
Based on the long experience with the proton and neutron radiotherapy with an AVF cyclotron as well as the conventional photon
therapy, NIRS has decided to construct the HIMAC 1), 2 ) for the clinical treatment of tumor. The HIMAC is an accelerator complex which
consists of a 100 MHz injector linac, two separated function type synchrotron rings and a beam delivery system. The details of the major
components of the accelerator complex are described in other articles
submitted to this conference. 3 )-s) The PIG type ion source 6 l and thecontrol system 7) of the injector are also given in other articles. The
construction of the facility started in 1987 and will continue until afiscal year of 1993 when the clinical treatment is expected to start.
A layout of the injector system is given in Fig. 4 showing that thesystem consists of two types of ion source, an RFQ linac, three cavities
of Alvarez type linac, a debuncher cavity and the beam transportlines between them. The specification of the overall injector system ispresented in Table 1.
The ion species required for the clinical treatment range from 4 He
to 40 Ar. The expected intensities will realize a dose rate of as highas 5 Gy /min·l in a 14¢ X 10 (depth) cm 2 irradiation volume, so thatthe irradiation of heavy ions will be finished within a few minutes. An
intensity schedule to achieve the required values is listed in Table 4 ateach acceleration stage.

*Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo 152!The Institute of Physical and Chemical Research, RIKEN, Hirosawa,Wako-shi, Sa.itama 351-01
ISumitomo Heavy hdustries, LTD., Soukai-cho, Niihama-shi, Ehime 792

~

40 Ar

4 He

Frequency
Repetition rate
Duty factor
Acceptance

100 MHz
3Hz Max.
0.3% Max.
0.6 1rmm·mrad (normalized)

Output beam emittance
Momentum spread::; 1.5 1rmm·mrad (normalized)::; ±I x w- 3

?1/7
PIG & ECR

Table 2
RFQ linac specification
100 MHzkeV/u
1/7-90 ~ -30 deg
0.92

Operation frequency
Input / Output energy
Charge to mass ratio

8/ BOO

Synchronous phase
Transmission efficiency

300
725 em59 em
0.54 em
0.29 em
2.5

Number of unit cells
Vane length
Cavity diameter
Characteristic bore radius
Minimum bore radius
Maximum modulation

3.8
145 1rmm·mrad
0.6 1rmm·mrad

Focusing strength
Acceptance
Nornalized acceptanceIon Sources
Two types of ion sources are adopted: one is a PIG source forlight ions, and another is an ECR source for heavier ions. Both sources
are located independently on high voltage platforms. The maximum
voltage on the platform is about 60 kV to accelerate ions up to 8
ke V fu. A beam emittance of the sources is required to be less than
0.6 1rmm·mrad normalized. Both sources are operated with pulse modein which a duty factor is very low (:S 1%) for the PIG source and high(:S 50%) for the ECR source. The required pulse width of the ion
beam is longer than about 200 J'S, because the injection interval to
the synchrotron is longer than 150 J'S for an effective 20 turns.
The PIG source is a hot cathode type. The typical values for themagnetic field, the pole gap and the extraction voltage are 7 kG, 20 em
and 15 kV, respectively. A beam test of the PIG source is underway,
and the obtained beam intensities exceed the required values given
in Table 4 for ions up to Ne. Pulse operation of the source is very
effective in increasing both intensity and lifetime of the source. The
more detailed information is given in ref. 6.
To improve the heavier ion capability of HIMAC, an ECR sourceis expected to produce heavy ions up to xenon. A compact single
stage structure is adopted for the source. The structure is similar tothat of Caprice 8 l developed at Grenoble. The microwave ferequency
and power are 10 GHz and 2 kW at maximum, respectively. Twosolenoid coils with iron return yokes generate a peak axial magnetic
field of about 1 T. A mirror ratio is designed to be so large thatto

Ion species
Charge to mass ratio
Ion source typeIntervane voltage
Maximum field
Peak rf power

81 kV
205 kV fern (1.8 Kilpatrick)
260 kW (70% Q)

the second order ECR surface contributes effectively to generate highcharge states of heavy ions.
A strong radial sextupole field is produced by NdFe permanent
magnet installed outside the plasma chamber. A bore diameter of themulti pole magnet is 7.6 em. The extraction voltage of the source isabout 15 kV. The development of the source has been performed incooperation with INS, University of Tokyo and with RLNR, Tokyo
Institute of Technology.
RFQ linac
The ions are injected into an RFQ linac through a low energy
beam transport line about 7 m long. A rather low value of 100 MHz
is chosen for a frequency of the linac so as to give sufficient focusing
strength. An acceptance of the injector is 0.6 1rmm·mrad normalized(145 1rmm-mrad unnormalized). The RFQ linac accelerates an energy
range from 8 to 800 ke V /u with a vane length of 7.3 m. The maximum
surface field of the linac is chosen at a very high value of about 200
kV /em (1.8 Kilpatrick) so as not to exceed the experimental value
obtained with an RFQ cavity with almost the same geometry. 9 ) The
main parameters of the RFQ linac are given in Table 2.
A low value of 3.8 is chosen for the focusing strength to obtaina high acceleration efficiency. A calculated transmission efficiency exceeds 90% for a DC beam. A number of unit cells in the radial match-

45 ~Table 3.
Alvarez linac specification.
Tank 1

Tank2

Tank 3

Synchronous phase (de g)
Ion energy (MeV /u)velocity (%)
Average axial field (MY /m)
Effective shunt impedance• (Mf!/m)Transit time factor
Quality factor of cavity•
Tank length (m)Acceleration rate (MeV /m)-300.800- 2.669
4.127- 7.526
1.808
31.5 - 38.7
0.825 - 0.853
132,000
9.768
1.34

-25
2.669 - 4.385
7.526 - 9.634
2.102
41.5- 42.9
0.869 - 0.867
141,000
7.202
1.67

-25
4.385 - 6.060
9.634- 11.31
2.102
45.2 - 45.6
0.888 - 0.880
143,000
6.907
1.70

Tank diameter (m)Drift tube diameter (em)Drift tube length (em)Bore radius (em)Nose corner radius (mm)Corner radius (mm)Unit cell length (em)Gap to cell length ratio
Number of unit cells
Stem radius (em)

2.20
16.0
9.85 - 16.45
1.0
20
10
12.45- 22.47
0.214- 0.265
56
5 and 32.18
16.0
17.99 - 21.72
1.5
30
10
22.67- 28.77
0.210- 0.242
28
5 and 32.16
16.0
22.90- 25.73
1.5
30
10
28.99 - 33.79
0.213- 0.236
22
5 and 3

Shunt impedance• (Mf!/m)Required rf power• (kW)46.29 - 53.16
870

54.93- 57.07
810

57.38 - 58.92
760

FODO
6.0, 8.0
6.0, 4.5
42
67
2.8

FODO
12.0
3.0
49

FODO
15.0
2.4
49

Q-magnet sequence
Q-magnet length (em)Field gradient (kG/ em)
Phase ad vance (de g)
Acceptance (JTmm·mrad)
Normalized acceptance (JTmm·mrad)Fig. 1. Alvarez no.3 tankunder machining.

* Superfish value including stem losses.
ing section is chosen to be 40 so that the convergence angle of thematched input beam is reduced to be about 60 mrad.
The RFQ linac has a conventional four vane type structure separated longitudinally into four tanks all of which are fed with a 300
kW peak rf power through a single loop coupler. The tank is made ofcopper plated mild steel, whereas the vanes are solid copper. The rf
contact between vanes and the tank wall is achieved with silver coatedstainless steel 0-rings. The RFQ linac is essentially the same as that
constructed at INS including the beam dynamic design parameters. 10l

Fig. 2. Drift tube end plates and a bore tube.

AI varez type linac
The RFQ linac is followed by an Alvarez type linac operated withthe same frequency of 100 MHz. The linac tank is separated into
three independent rf cavities and each tank is fed with 1.2 MW peakrf power. The maximum surface field is chosen at 150 kV fern (1.3
Kilpatrick). The linac tank is 24 m long in total, and consists of 106
unit cells. The diameter of the cavity is about 2 m and changes with
one tank to the next in order to obtain reasonable values for the transit
time factors. The major parameters of the Alvarez type linac is given
in Table 3.
The beam dynamic calculations through the Alvarez linac are performed with a standard computor code PARMILA. The effects of theerrors in the drift tube alignment and in the Q-magnet field strengthand length are taken into accounts in the calculations. The emittance
growth due to these errors are not so serious when the alignment error
is ::; ±0.1 mm in the transverse direction together with the rotation
error of ±1", the tilt error of ±1", and the excitation error of ±0.5%.
The ellipse parameters in the transverse phase diagram of the accelerated beam are almost kept constant against the error. The centerof the ellipse, however, moves aroud the oringin and needs a set ofsteering magnets in the MEBT line to be matched with the opticalaxis.
The calculations are also made with the errors in the acceleration
field including the field tilt and the phase errors. The phase differences
between three tanks affects strongly on the output beam quality when
they are 2: ±3". The effects of the field tilt, however, are not serious
even when the tilt is as high as 10%.
The tanks are made of copper-dad mild steel, and the drift tubes
are copper-plated mild steel. A photograph of the third Alvarez tankbeing machined is given in Fig. 1. Figures 2 and 3 show two end caps
and a bore tube, and a quadrupole magnet, respectively. Each drift
tube is supported by a horizontal and a vertical stems the diametersof which are 3 and 5 em, respectively. Every second drift tube is

-

(b)

(a)

Fig. 3. A quadrupole magnet before (a) and after (b) assembling.
equipped with a quadrupole magnet for beam focusing. The magnets
have laminated cores and are excited by pulse power sources witha very low fiat-top-duty of 0.3% to reduce the heavy thermal loads.
The Q-magnet loaded drift tube is cooled with a water jacket directly
welded to the inside wall of the tube. The hollow drift tube is alsocooled by water directly flowing through the tube. The cooling water
is treated and very well regulated in temperature (±0.1") to reducethe duty of the automatic frequency tunner. The water which coolsthe. linac tank is not treated but well regulated. Special care is also
taken to the air conditioning system of the accelerator room.
The third Alvarez tank is now its final test stage. The high power
tests will begin at early next year.
RF system
An rf amplifier of the Alvarez linac is designed to deliver morethan 1.4 MW and is equipped with Siemens's RS 2074 SK which isthe same vacuum tube as that adopted by GSI to get more than 1.8
MW peak rf power (25% duty) for 100 MHz Alvarez linac. In the two
driver stages of the amplifier system, the vacuum tubes of RS 2058 CJ
and RS 2032 CL are used to deliver the rf powers of 100 kW and 5
kW, to the next stages, respectively.
Three sets of the 1.4 MW amplifier.system will be used to excite
three Alvarez cavities. The high voltage power supply for the amplifiers, however, is not separated into three independent power supplies

46-

Table 4.
Beam intensity schedule for typical ions
He2+

c6+

Ne10+

Si14 +

Ar 18+

Extracted intensity (pps)

1.2 X 10 10

2.0 X 109

8.5 X 108

4.5 X 10 8

2.7 X 108

Injected ion intensity (pps)
Injected ion current (ellA)

1.1 X 10 15340

1.8 X 10 14170

7.8x10 13
120

4.1 X 10 1391

2.4 X 10 13
69

1.0(1+ --> 2+)

0.93(2+ --> 6+)

0.75
0.67
(3+ --> 10+)0.52
(4+--> 14+)(6+ --> 18+)

Ion species

Beam transport transmission
Stripper efficiency(Charge states)

0.18

0.9
0.8
0.7

Alvarez linac transmission
RFQ Jinac transmission
Beam transport transmission
Source electrical current (ellA)

630

160

140

130

340

Ions from source

Hel+

C2+

Ne3+

SiH

Ar6+

HIMAC INJECTORI I I•' II. 111111111 I I I'

Fig. 4. A layout of the HIMAC injector.
but a unified one having a large condensor bank. The construction of
the amplifier system for Alvarez tank no.3 is already finished including
the dummy load tests.
In a 300 kW amplifier for the RFQ Jinac, the Eimac tubes are
adopted: 4CW 100,000 E for the final stage and 4CX 20,000 C for thedriver stage. The 4CX 20,000 C tube is also used as a final tube forthe debuncher cavity which requires 30 kW peak rf power.

Ackowledgements
Heartfelt thanks go to Drs. K. Kawachi, J. Staples (LBL) andthe members of Division of Accelerator Research of NIRS who havegiven continuous encouragement and fruitful discussions. The authors
also express their sincere thanks to Dr. Kimura and to the engineersof Sumitomo Heavy Industries, LTD. for their so much assistance anddiscussions.

Charge stripper & debuncher

References

At the output end of the Alvarez linac, an automatic changer for
carbon stripping foils is installed. Only one stripping section is used
at a relatively high ion energy because of the reliability of the systemand of future expansion to the acceleration of the heavier ions.
After the foil, the fully stripped ions are obtained more than 18%
up to Ar. The charge to mass acceptance of the medium energy beamtransport (MEBT) line is designed to be qfA;?: 1/4 in order to ensure
the heavier ion capability of the HIM AC.
A 100 MHz debuncher cavity is introduced in the MEBT line
to suppress the momentum spread of the accelerated beam. A distance between linac end and the debuncher cavity is optimized to beabout 9 m. The maximum phase spread at the acceleration gap in the
debuncher cavity is estimated to be ±45° from the PARMILA calculations. An rf voltage of 300 kV (for qfA = 1/4) rotates the beam
bunch in longitudinal phase space, and reduces the energy spread of
the Jinac beam from Ll W /W = ±1.2% to a satisfactorily good valueof ±0.11 %. Some kind of tuning error of the Alvarez linac, however,tends to increase the energy spread up to more than ±0.2%.

(1) S. Yamada, et al, Proc. of 6th Symp. on Accel. Sci. & Techno!., INS,Tokyo, Japan, 1987, p33.
(2) S. Yamada, Proc. of 12th Symp. on Ion Sources & Ion-Assisted Techno!. (ISIAT '89), Tokyo, Japan, 1989, pl77.
(3) M. Kanazawa, et a/, this conference.
(4) A. Itano, et a/, this conference.
(5) H. Ogawa, et a/, this conference.
(6) Y. Sato, eta/, this conference.
(7) T. Kohno, et a/, this conference.
(8) B. Jacquot & R. Geller, Proc. of Int. Conf. on ECR-IS & Their
Applications, MSU, USA, 1987, p254.
(9) T. Nakanishi, et a/, Particle Accel. lQ (1987) pl83.
(10) N. Ueda, et a\ Proc. of 3rd Japan-China Joint Symp. on Accel.
for Nucl. Sci. & Applications, RIKEN, Wako, Saitama, Japan, 1987,
pl49.

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