JAERI-Conf 95-021

PB27

Particle Orbit Simulation for High Energy Heavy Ion Implanter
Takashi ITO, Toshiyuki HATTORI, Yoshiyuki OGURI, Kimikazu SASA, Noriyosu
HAYASHIZAKI and E. Osvath •Research Laboratory for Nuclear Reactors, Tokyo fustitute Of Technology, Meguro-ku, Tokyo,Japan•fustitute for Nuclear Physics, Romania
1. Abstract

3. Calculation and results

We have studied an futerdigital-H type
Quadrupole (IHQ) linac structure for application
to heavy ion implanter. It is possible to vary theoutput energy by changing the voltage between
gaps only. Operating frequency of this IHQ
linac is 30 MHz and the synchronous phase is-30°} with the exception of -90°} at the first gap
that works as a bunching section. The calculated
results show that the output energy can bevaried from 0.48 MeV (30 keV/u) to 1.6 MeV(100 keV/u) for 16 0+.

Table 1 shows the princjpal parameters
for IHQ linac.
Table 1 Basic parameters for calculation
Charge to Mass Ratio [q/A]
Operating Frequency [MHz]Input Energy [keV/u]
Output Energy [keV/u]
Synchronous Phase [de g.]
Maximum Gap Voltage [kV]
Number of Cell

2. Introduction
The Heavy ion accelerator technology
has been expected to be used in the industrial
fields. Conventionally, electrostatic acceleratorsand cyclotron have been used in those fields.
Heavy ion linear accelerators, however,gradually have been developed and used inthose industrial applications. fu particular, radio
frequency quadrupole (RFQ) linacs have beendeveloped and adopted for ion implantation inrecent years l), 2>. However, An RFQ has aproblem for low acceleration rate. To solve thisproblem, we used an IHQ linac that is better
than other kinds of linac for acceleration rate.
This linac has the drift tube with finger tips tofocus the particles, and can vary the output
energy so as to be suitable for industrial
applications.
Normally drift tube linac is not suitablefor variable energy accelerator, because cell
length is not appropriate for particles when thegap voltage is changed. Therefore the particle islost gradually, and it is not able to vary theoutput energy if there are many cells in thecavity. For the linac we have developed,
particles can pass through all drift tubes without
many particle losses because of small gap
numbers. Consequently, this linac accelerates
the particles with variable output energy.
This paper presents the calculated resultsof beam simulation.

~ 1/1630
1530 (Min.)
100 (Max.)-90-+-30
214
10This linac accelerates the particles from
0.24 MeV to 1.6 MeV (maximum) for 160+.
There are 10 cells in the tank and the length
needed to accelerate is 0.53 m, but the cavity
length is 1.04 m as the electric quadrupole lensis mounted in the cavity. Therefore, acceleration
ratio is 1.31 MV/m (2.57 MV/m for onlyacceleration section). The operating frequency is30 MHz and synchronous phase is -90° at thefirst gap and -30° at the other gaps.
By using these parameters, thecalculation wasdone the thinlensapproximation. Fig. 1 shows the output energy
distribution with different values of gap voltage.
V is the normalized gap voltage (1.0 isthe designed value) and E is the output energy.
It was shown that the total output energy can bechanged from 0.48 MeV to 1.6 MeV.
Fig. 2 shows the transmission as afunction of gap voltage. The transmission forthe drift tube with finger tips is better than theother at the high energy region. Therefore
focusing with the finger tips is effective for highgap voltage. On the other hand, for the low gap
voltage,. no - finger - type is superior to theother because the particle is not lost so that the rf
defocusing may be weak if the force due to the-324-

JAERI-Conf 95-021

finger is not added. However, as thetransmission is good, it is not so problem forusing the beam practically ..

40

0 With Finger

30v0 Without Finger

20104. Conclus ion
A new drift tube linac that can vary theout put energy by changing only gap voltage
was presented. This accelerator is suitable forthe industrial application because of theadvantage of high acceleration rate (1.31MV/m). The calculation of beam dynamics
shows the following results:

1.0• The out put energy can be varied from 0.48
MeV (30 keV/u) to 1.6 MeV (100 keV/u) for160+.

• The electric quadrupole field made by finger
tips is effective at high gap voltage.
0.80.7• The cavity length (with the sections thatelectric quadrupole magnets are mounted) is
1.04 m because of the high acceleration rate.

5. Referen ces
1)

Schempp and H. Deitinghoff, Nucl.
Instr. and Meth. B68 (1992) 36.

2)

Robert W. Hamm, Nucl. Instr. andMeth. B68 (1992) 1.

0.6

0.5

E/EoX 100Fig. 1. Output energy distributions at various
gap voltages. V is the normalized voltage and Eo
is the designed output energy (100 keV/u).
rp40-With Finger- e- - Without Finger;!.

II30c"·;r.

?

·e"' 20"'c,...eiO1.1

cr-

1-o-- -o-- d-

0.9

0.8

0.7

0.6

0.5

0.4

Normalized Gap Voltage

Fig. 2. Transmission with different gap voltage-325-