22P055-P
Evaluation of the ion beam generated by bipolar pulse accelerator
両極性パルス加速器におけるビーム特性評価
Kazuki Kitajima, Yusuke Matsugami, Hiroaki Ito and Katsumi Masugata
北島一樹, 松上裕介，伊藤弘昭，升方勝己
Univercity of Toyama
3190, Gohuku, Toyamasi, Toyama 930-0887, Japan
富山大学〒930-0887 富山市五福3190
The development of the bipolar pulse accelerator (BPA) is reported. A double coaxial type bipolar pulse generator wasdeveloped as the power supply of the BPA. The generator was tested with dummy load of 7.5 bipolar pulse with -138
kV, 72 ns (1st pulse) and +130 kV, 70 ns (2nd pulse) was successively generated. By applying the bipolar pulse to thedrift tube of the BPA, nitrogen ion beam of 2 A/cm2 was observed in the acceleratored, which suggests the bipolar pulseacceleration.

ground cathode+V 1

ground anode2nd gap
V1300

VPFL

250
200
150
100
50
0-50-200t

-V 1t1

V0-150

0
1st gap

Fig.2. Cross sectional view of bipolar pulse generator-100

Ion Source drift tube Ion beam (at t )1Ion beam (at t2)

2. Experiment
Figure 2 shows the bipolar pulse generator usedin the experiment. The pulse line is double coaxial,
water field line and on the down stream end of theline between outer and intermediate conductor low
inductance rail gap switch is installed.
Figure 3 shows the waveforms of theintermediate conductor (VPFL) and the output pulse(V0), when dummy load (7.5is connected to theoutput terminal of the generator. From the figure
bipolar pulse of (-138 kV, 72 ns) (+130kV, 70 ns) is
successfully generated.

VPFL, V0 (kV)

1. Introduction
Intense Pulsed Ion Beam (PIB) is expected to beappliedformaterials
sciences
includingsemiconductor
implantation
andsurfacemodifications. However, in the conventional PHIB
accelerators, the purity of the beam is usually very
poor. (1) Hence, the application of the PHIB has
been extremely limited. To improve the purity,
bipolar pulse accelerator (BPA) has been proposedand developed in our laboratory. (2-4) In the paper
the results are described of the acceleration
experiment.
Figure 1 shows the conceptual drawing of theBPA. (2-4) It consists of a grounded ion source, adrift tube and a grounded cathode. The BPA is a
2-stage accelerator and operated with a bipolarpulse. When the bipolar pulse (V1) is applied to thedrift tube, ions produced in the grounded ion source
are accelerator in the 1st gap toward the drift tube
because at first the negative voltage pulse with thepulse duration 0 is applied. After 0 the polarity ofthe pulse is reversed and the positive voltage withthe duration 0 is applied to the drift tube. As aresult, the ions are again accelerated in the 2nd gap
toward the grounded cathode. In the BPA
improvement of the purity of the ion beam isexpected (2). In addition ion source can be installedon the grounded anode. This seems to be favorable
for the active ion source is powered by an external
power supply.

t2

Fig.1. Conceptual drawing of bipolar pulse accelerator

0100

200

300

400

500

600time (ns)Fig.3. Typical waveforms of the charging voltage ofthe intermediate conductor (VPFL) and the output
voltage (V0). Copper sulfite resister of Z0 = 7.5  wasused as a dummy load.

Figure 4 shows the experimental setup for bipolar
pulse acceleration of nitrogen ions. The system
consists of a grounded anode where active ion
source of gas puff plasma gun is installed, a drift
tube where bipolar pulse is applied, and a groundedcathode. Biased ion collectors (BIC) are installed in
the drift tube and in the cathode to evaluate theaccelerated ions.
Figure 5 shows the typical waveforms. From thefigure we see that ions are successfully accelerated
in the 1st gap and ion current density (Ji1) of 40
A/cm2 is obtained. From the time of flight delay ofJi1 (45 ns), ion energy is estimated to be 130 keV if
assuming N+ ion.
Figure 6 shows the track pattern of magnetic ion
energy spectrometer placed in the drift tube. Theion are observed in a drift tube by the spectrometerand the ion energy was evaluated to be 106 keV(N+) and 101 keV (N2+).
In the downstream of the 2nd gap, Ji2 of 2 A/cm2
is observed, which suggest the post acceleration in
the 2nd gap.

N2+N+N. PPFig.6. Track pattern obtained by energy spectrometer

3. SummaryA double coaxial type bipolar pulse generator
was developed as the power supply of the BPA.
The generator was tested with dummy load of 7.5 ,bipolar pulses of -138 kV, 72 ns (1st pulse) and+130 kV, 70 ns (2nd pulse) were successivelygenerated.Energy of N+ and N2+ in the drift tube
were evaluated to 106 keV and 101 keV. Nitrogenion beam of 2 A/cm2 was observed in the cathode,which suggests the bipolar pulse acceleration.
References

Acceleration gap: d = 1 cm
Distance between anode and BIC1 : 6 cmDistance between cathode and BIC2 : 1.5 cm
Fig.4. Cross-sectional view of the experimental system-50-5-100

I0-15045 ns

0-50-5Ji2 (A/cm )30201010-1-100

100

200300Ji220time (ns)96 ns

3-10-1000-15

11.5 ns4

Ji1-10I0-1502

Ji1 (A/cm 2)40

50-100-10

10500

100

200300time (ns)Fig.5. Typical waveforms of the applied voltage, current
to the drift tube (V0, I0), ion current densities in the drift
tube (Ji1) and in the cathode (Ji2).

I0 (kA)

00V0100

I0 (kA)V0 (kV)

55015150

10V0100

V0 (kV)150[1] K. Masugata, H. Okuda, K. Yatui and T.Tazima, J.
Appl. Phys. 80, 4813 (1996).
[2] H. Ito, K. Igawa, I. Kitamura, and K. Masugata,
Bipolar pulse generator for intense pulsed ion beamaccelerator, Rev. Sci. Instrum. 78, 013502 (2007)[3] H. Ito, D. Nakanishi, I. Kitamura, K. Masugata,
Generation of intense pulsed heavy ion beam bybipolar pulse accelerator, The 34th IEEE
International Conference, June 17-22, 2007,
Albuquerque, New Mexico.
[4] K. Masugata and H. Ito, Intense pulsed heavy ion
beam technology, The Trans of IEE of Japan, 130-A(10) pp.879-884 (2010).