The 11th Symposium on Accelerator Science and Technology, Harima,Seience Garden City, 1997

Low Power Test of IHQ Linac for Heavy Ion Irradiation
ITO Takashi*, E. Osvath**, SASA Kimikazu*, HAYASHIZAKI Noriyosu*,
ISOKAWA Katsushi*, H. Schubert*** and HATIORI Toshiyuki** Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology,
2-12-1 0-okayama, Meguro-ku, Tokyo, 152, Japan** Institute of Atomic Physics, Institute of Physics and Nuclear Engineering, Bucharest,
P. 0. Box MG-6, Romania* * * HSI, Tiirkenstrabe 28, 80333 Miinchen, Germany

We have proposed IHQ Iinac for industrial
application. An IH structure has the high shunt impedanceand high acceleration ratio[4-7]. Generally, at the drift tube
At Tokyo Institute of Technology (TIT), An
Interdigital-H type Quadrupole (IHQ) linac has been in the linac, the accelerated particles are focused by magnetic
constructed for application of high energy heavy ion quadrupole field generated by the electric or permanent
magnet fitted in the drift tube. However, they have highimplantation. The linac can accelerate the particles withproduction costs to make the drift tube with focusingcharge to mass ratio grater than 1/16 from 0.48 MeV up to16elements. Increase in the cost of linac is serious problem for1.6 MeV (for 0+). As a result of the low power test, theresonant frequency is 36.26 MHz and the shunt impedance practical use. Therefore, we choose to use the drift tube :withis 252 M~:Vm. Therefor, required power to accelerate 16 0+ · fingertips. The fingertip makes quadrupole field between thedrift tubes to focus the particles. It is easy to produce theion is 39.5 kW.
drift tube with fmgertip at little expense. Fig. 1 shows thephotograph of drift tubes in the IHQ cavity.
From a result of beam dynamics calculation, this
1. Introduction
electrode geometry was effective to beam focusing and it
High energy heavy ion implantation has been was possible to accelerate the particles sufficiently. On June
expected to produce semiconductor devices. In a case of 1997, a full scale IHQ linac was installed at TIT. The design
heavy ion implantation (for example P, As, etc.), the linear parameters of an IHQ linac are shown in Table 1. In thisof conventional electrostatic paper, the results of low power tests of IHQ Iinac are
accelerators take placepresented.
accelerators because of a high current acceleration withstrong focusing action. Especially, Radio Frequency
Quadrupole (RFQ) linac has been developed and adopted forTable 1. Design Parameters of the IHQ Linac
ion implantation [1,2]. RFQ linac has the best performance
as low-energy accelerators for high current[3]. However, it
15[keV/u]
Input energy
has disadvantage concerning a low acceleration rate, and its100[keV/u]
Output energy
complicated vane structure causes to be an expensive[em]
200
Cavity inner diametermachine.
[em]
104Cavity inner length20, 28[mm]Gap length
10
Total number of cells
52.84
[em]
Total cell length
14[mm]
Drift tube inner diameter
14[mm]
Fingertip diameter
30[MHz]Operating frequency-90, -30[deg.]
Synehronous Phase
214
[keV]
Maxmum Gap Voltage
Oil: 1/16
Charge to mass ratio

Abstract

2. Resonant frequency and gap voltage
distribution
Fig. 1 Photograph of drift tubes in IHQ linac

An rf measurement for the IHQ linac wasperformed. The measured resonant frequency was 36.26-209.,...

The II th Symposium on Accelerator Science and Technology, Harima Science Garden City, I997

MHz. This increase of resonant frequency .to the designed
value is caused by decrease of tank volume. To endure thevacuum pressure, the tank lid (input and output part ofcavity) was changed from the flat plate to the sphericalshape. Therefore, the resonant frequency was increased. To
accelerate the particles correctly, an input power into thetank should be adjusted.
A measurement of the distribution for the gap
voltage was performed by using the perturbation methods. Acylindrical acrylic rod that fills a whole gap was used as aperturbator. Fig. 2 shows the gap voltage distribution of thehalf scale model and the practical tank. Already the model
test had been performed. The result of the model test wasthat the resonant frequency was higher than the designparameter. Therefore, the cavity diameter was changed to fit
the resonant frequency[4]. In order to investigate the effect ofchanging the diameter on the gap voltage distribution, it
was compared with the gap voltage distribution for themodel tank and the real tank. The gap voltage distribution of
the real tank is quite similar to the model tank. In
conclusion, there is scarcely any influence owing to changeof the tank diameter.

100

101'ii

""'

:i:0:

"'

Stepping
Motor

SignalGenerator____

Pen Recorder ..__)o__.

Fig. 3 Block diagram of measurement system of beadpurtabation method:0:..Q... so0::::;.

I.,

~j)

""

60

Model Cavity!
Real Cavity;:::0>0.. 40w<;;

""

C)

20

J v

02

45678910Gap No.

Fig. 2 Gap voltage distribution

!00

0200

II300

u~00500

Position [mm]Fig. 4 Electric field distribution measured by bead pullmethods

3. Shunt impedance and Power Consumption
We measured the field distribution by using thewell-known bead perturbation method to estimate the shunt
impedance. Block diagram of measurement system is shownin Fig. 3.
Fig. 4 shows the electric field distribution in theIHQ linac. In this measurement, a frequency difference fromthe resonant frequency is measured as phase difference 11 a.
The bead (Aluminum: radius is ·1.013 mm) attached on thenylon thread (diameter is 0.07 mm) is moved at the constantvelocity by using stepping mortar. Phase difference ismeasured with vector volt meter, and its signal is recordedon the pen recorder as a function of position.

Shunt impedance Zs is calculated as follows

where-210-Zs

Shunt ImpedanceThe 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

the ECR ion source. With that ECR ion source, this IHQ
linac is useful for not only heavy ion implantation but also
various field applications.
After the low power test, it· will be started thevacuum and the ion source test soon. Then, high power
pulse test will be performed and first acceleratio~with 4He+
ion will plan on September 1997.

Bead Radiuspermittivity of vacuum
Angular Resonant Frequency
Cavity Length
phase difference
Position of bead (longitudinal).

£.[i;;. dz
From Fig. 4, it is possible to obtainand to calculate the shunt impedance. The lliQ linac lengthis 1.04 m (inside the cavity). The length is included thesections where the electric quadrupole lenses are mounted.
Consequently, the shunt impedance and the required power
for acceleration (of 16 0+) were calculated by· using of thetotal cell length (0.5284 m) instead of cavity length L 1•
Table 2 shows the shunt impedance and power consumption
estimated from field distribution.

Acknowl edgments
We would like to thank Mr. AMASAWA for assembling
the drift tube and constructing other parts of the lliQ linac.
The authors also gratefully acknowledge members ofHATTORI Laboratory for helping.

Reference s
Table 2 Shunt impedance and power consumption[MQ/m]
252

Power{kW]39.5** It is the value that the increase of resonant frequency isconsidered

4. Conclusi on
The lliQ linac for application of high energy heavy
ion implantation has been constructed. The following
results were obtained from the low power test.
• The gap voltage distribution of the real tank is very
similar to the result of the model test. Therefore it ispossible to accelerate tlie particles without modificationof the real tank and the drift tubes.
• The resonant frequency is 36.26 MHz• Shunt impedance is estimated at 252 MQ/m
• Power Consumption is 39.5 kW (for 160+)
These results are sufficiently satisfied as a practicalmachine. An Electron Cyclotron Resonance (ECR) ion
source has been developed almost simultaneously at ourlaboratory[8]. This ECR ion source can make the manykinds of multi-charged ion. It is expected to combine with

[1] K. Amemiya, J. Ito, K. Tokiguchi, T. Sato, N.
Sakudo, S. Yamada, Y. Hirao and N. Tokuda.,"Development of a High Current MeV Ion Using a
Variable Energy RFQ Linac," in Proceedings of theTenth International Conference on Ion Implantation
Technology, 1994, pp. 450-453.
[2] H. Vormann, U. Beisel, 0. Engels, D. Li and A.
Schempp., Nucl. lnstr. and Meth. in Phys. Res. B113
(1996) 38-41[3] M. Okamura, M. Okada, T. Ito, and T. Hattori., Nucl.
Instr. and Meth. in Phys. Res. B99 (1995) 694-696[4] H. Suzuki., Masters thesis, Tokyo Institute ofTechnology 1987.
(5] T. Ito, S. Yamaki, M. Okamura, K. Sasa, H. Schubert
and T. Hattori., Nucl. Instr. and Meth. in Phys. Res.
Bll3 (1996) 46-49.
[6] T. Ito, K.Sasa, N. Hayashizaki, T. Yoshida, K.
Isokawa, S. Majima and T. Hattori. , Proc. of the 21stLinear Ace. Meeting in Japan, 1996, P275-277[7] M. Tomizawa, S. Arai, T. Katayama, K. Niki, C.
Belissaris, M Yoshizawa., Proc. of the 1994 Int. Linac
Conf., Tsukuba, Japan, p765-767[8] T. Hattori, T. Katayose, S. Yamada, K. Kitagawa, M.
Sekiguchi and Y.Yamashita., Rev. Sci. Instrum. 67 (3),March 1996, pp. 1186-1188-211-