22P149-P
Selective removal and collection of Ion by ICR heating in magnetized sheet plasma
シートプラズマを用いた ICR 加熱法による He イオンの選択的分離・回収
Daiki Hamada, Satosi Hagiwara, Akira Tonegawa, Kazutaka Kawamura, Kounosuke Sato濵田 大樹, 萩原 聡, 利根川 昭, 河村 和孝, 佐藤 浩之助
Department of Physics, School of Science, Tokai University,
1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan
東海大学 理学部 物理学科 〒259-1292 神奈川県平塚市北金目 411
The pumping of helium ash has become important for the control in the edge plasma of the divertor
because of the helium ash has limit of concentration. We have demonstrated the ion cyclotron resonance(ICR) method of the helium or helium/hydrogen sheet plasma by the RF electrodes of two parallel
plates, sandwiching the plasma. Measurements of the ion temperature in the plasma were carried out afast scanning Faraday cup. In addition, the ion densities in the plasma were measured by an omegatronmass analyzer and the neutral densities of resonant ions was measured by a quadruple mass analyzer.
The ion temperature shows maximum amount when the rf frequency is nearly equal to ion cyclotronfrequency. When the rf power is applied to 0 W to 400 W, the ion temperature in the periphery of the plasma
is increase than that of the central region.

1. Introduction
It has been shown that the end loss from the line cusp
can be plugged effectively when an RF field near theion cyclotron frequency is applied at the line cusp [1].
Also, the methods to improve the helium removal
performance of a pump limiter by using a RF
ponderomotive force (RF-filter) were presented [2].
The selective removal of helium ash using by ion
cyclotron resonance (ICR) method has been studied ina linear divertor simulator, TPD-SheetIV [3]. We havedemonstrated the ICR method of the helium orhelium/hydrogen sheet plasma by the RF electrodes of
two parallel plates, sandwiching the plasma.
Measurements of the ion temperature in the plasma
were carried out a fast scanning Faraday cup. Inaddition, the ion densities in the plasma were measured
by an omegatron mass analyzer and the neutral
densities of resonant ions was measured by aquadrupole mass analyzer.
2. Experimental apparatus
A schematic diagram of an experimental apparatus
TPD-SheetIV is shown in Fig.1[3]. The
TPD-SheetIV device consists of the sheet plasma
source, magnetic coils, RF heating part, ameasurement part, end chamber, a vacuum exhaust,

the Faraday cup and a omegatron mass analyzer
apparatus. Figure 1 shows the schematic diagram ofthe measuring system and the RF applying circuit.
The RF applying circuit consists of the RF power
supply, a matching circuit and RF electrodes. TheRF power supply consists of a function generator, aFunction generator
RF amplifier Power meter

RF electrodes

Matching circuit

Fig.1 Schematic diagram of the measuring system
and a RF power supply. Ti⊥ was measured by afast scanning Faraday cup system.

RF amplifier and a power meter. The maximum
output of the RF power supply is about 500 W. The
matching circuit consists of a LC circuit andBAL-UN circuit and transmits the electric power
without loss. The RF electrode is two parallel plateelectrodes which are 200mm in length and 60 mm inwidth which are faced 38 mm apart from each other.
The plasma is sandwiched between the two parallelplate electrodes.
3. Experimental Results
Figure 2 shows mass spectrum of the omegatronmass analyzer at a discharge current Id of 45 A in
the helium and hydrogen mixture plasma. The
applied RF frequency fRF is 500 kHz corresponding
to the resonance frequency of helium plasma. The
RF power changes from 0 to 450 W. Mass
spectroscopy is performed by applying an RF field
to the parallel plate of the omegatron and measuring
the resulting current on the collector plate. Analysisof the ion trajectories in a uniform rf field applied
perpendicular to a constant uniform magnetic fieldshows that the ions execute spiral orbits with amaximum excursion radius. From a typical plasma
omegatron spectrum, it can be seen that the peaks
correspond to H+, H2 + and He+ without RF power.
The peak identification is carried out by comparing
the observed peak frequencies, which is thecyclotron frequency decided by the magnetic field in
the omegatron. The ion current of He+ gradually
decreases with increasing RF power.
Figure 7 shows the dependence of the RF power
PRF on the content of the He+ ion  at the RFfrequency is 500 kHz corresponding to the resonancefrequency as shown in fig.4. The ion density is given
byN i  Ii Mi ,where Ii and mi are the ion currents of omegatronand the ion masses, respectively. The content of theHe+ ion is defined asN He,


Fig.2 Typical mass spectrum of the omegatron mass
analyzer at a discharge current Id of 45 A in thehelium and hydrogen mixture plasma.

Fig.3 Dependence of the RF power P RF on thecontent of the He+ ion  at the RF frequency is 500
kHz corresponding to the resonance frequency.

in the sheet plasma is successful by using ICRF.
4. Conclusions

N HeN He NNH 2H 2NNHH

We have demonstrated the ICRH of the helium
sheet plasma by two parallel plate electrodes,
sandwiching the plasma. The ion densities Ni of He+
rapidly decreases with increasing the PRF, although
H+ and H2+ gradually decrease. As the result, increases from 34.5% to 37.5%. It is found that theselective heating of the helium ions in the sheet
plasma is successful by using ICRF.

where NHe, NH2 and NH are the density of He+, H2+and H+, respectively. The ion densities Ni of H+and H2+ gradually decrease with increasing the P RF,
although He+ rapidly decreases with increasing PRF.
As the result, α increases from 34.5% to 37.5%. It
is found that the selective heating of the helium ions

References[1] T.Shoji, et al., Journal of Nuclear Materials,313-316, 1262 (2003).
[2] S.Hidekuma, et al., Phys.Rev.Lett. 33,537 (1974).
[3]Y.Ohara, S.Yasuda, M.Ono, A.Tonegawa,K.Kawamura, JPFR SERIES 8(2009)888.