22P129-P
Analysis of GAMMA 10 end-loss-ion-flux for application studies ofend-loss-plasma-flux
端損失プラズマの応用研究に向けたGAMMA 10端損失イオン流の分析
Kazuya Ichimura, Yousuke Nakashima, Katsuhiro Hosoi, Takashi Ishii, Hisato Takeda,
Hideaki Ueda, Satoshi Kigure, Shigehito Takahashi, Satoru Hotaka, Makoto Ichimura,
Ryuya Ikezoe, Masayuki Yoshikawa, Mizuki Sakamoto and Tsuyoshi Imai
市村和也, 中嶋洋輔，細井克洋，石井 貴，武田寿人，上田英明，木暮 諭，高橋樹仁，保高 暁，市村 真，池添竜也，吉川正志，坂本瑞樹，今井 剛
Plasma Research Center, University of Tsukuba
Ibaraki 305-8577, Japan筑波大学プラズマ研究センター 〒305-8577 茨城県つくば市天王台1-1-1
Characteristics and capabilities of the GAMMA 10 end-loss-ion-flux are investigated from the view pointof utilizing the end-loss flux for studies which need high performance plasma-flux such as divertor
simulation experiment. The performance of the end-loss-ion-flux in GAMMA 10 is evaluated from themeasurements of the energy distribution and the ion-current density of the ion-flux by using the diagnostics
which is called ELIEA (End Loss Ion Energy Analyzer). Some basic heating and fueling equipments:
ICRFs and gas puffs are revealed to be the key to control the parameters of end-loss-ion-flux. Furthermore,
several additional inputs of heat and particle (Supersonic Molecular Beam Injection (SMBI), ECRH,ICRF…) are found to be effective for the generation of more intense flux of ion.

1. Introduction
The end-loss flux of the world’s largest tandem
mirror: GAMMA 10 has been focused because of
its usefulness to an experiment such as divertor
simulation experiment. GAMMA 10 is a tandem
mirror device which consists of multi cells:
central-cell, anchor-cells, plug/barrier-cells andend-cells (Fig. 1).
The end-loss flux is produced in theconfinement region (central-cell, anchor-cells andplug/barrier-cells) of GAMMA 10 and flows into
the end-cell. Since the typical plasma in theconfinement region has high ion-energy, theend-loss-ion-flux is estimated to be energetic anduseful for an experiment which requires
high-performance plasma flux [1-3]. The
objective of this research is to investigate thecharacteristics of the end-loss flux from the view
point of utilizing the flux.

Fig.1. GAMMA 10 and positions of ICRFs (RF1, 2, 3),Gas Puffs (#3, 4, 7), ECRH and SMBI

2. Diagnostics
Ten units of End Loss Ion Energy Analyzer(ELIEA) are equipped in the west end-cells ofGAMMA 10 (Fig. 2).
The ELIEA is a diagnostic device consists of aslanted-ion-repeller-grid, a secondary-electronrepeller-grid and a collector plate. Positive ion
repeller voltage is applied to the ion-repeller grid
during the measurement and ions reflected by therepeller voltage are detected as ion-current by thecollector plate facing to the ion-repeller-grid. By
sweeping the repeller voltage, ion-energy
distribution and ion-current density of theend-loss-ion-flux are examined (Fig. 3).

Fig.2. ELIEA installed in the west end cell. Arrow is
an example of ion-trajectoryion-energy which occurred in the gas injection is
not observed. In the experiment, the achieved
amount of ion- current increase was not very big sofar.
The additional ICRF is superimposed in the eastanchor cell. Power of additional ICRF produces
more ions in the confinement region and thus, much
more ions flow into end-cells without the loweringof energy observed in gas injection.
Fig.3. Schematic diagram of ELIEA device

3. Typical Parameters of the end-loss-ion-flux
The most typical plasma of GAMMA 10 isheated only by Ion Cyclotron ResonanceFrequencies (ICRF) and fueled by gas puffs
installed in the central-cell and anchor-cells. Theend-loss-ion-flux of such typical plasma isinvestigated and the result shows that at the pointclosest to the center, the ion-current density is about
0.4 mA/cm2 and the energy of the ion flux is about
300 to 400 eV in ion temperature parallel to themagnetic field line. Since the observed energy
distribution of the ion-flux appeared to be
multi-components rather than single-component
Maxwellian distribution, the evaluation of theion-temperature was performed by following theidea of multi-components distribution. Results
showed linear correlations between the ion-current
density and the amount of gas puff (GP #3, 4) input,
and also between the ion temperature and the ICRF
(RF2) power input.
4. Effects of Additional Inputs
Increase of the ion-current density has been
observed during the superimposing of additional
inputs such as gas puff (GP#7), Supersonic
Molecular Beam Injection (SMBI), ECRH andICRF (RF3).
Gas Puff and SMBI increases the amount of gas
in the central-cell drastically and that leads theincrease of ion density. Therefore, more ions flow
in to the end-cells and the ion-current density goesup. However, the injection of gas causes the loss ofion-energy in the central-cell which results thedecrease of energy of the end-loss flux. The valueof end-loss ion temperature in such sequence isevaluated as about 100 to 200 eV which is quite
lower than usual ion temperature (around 400 eV).
The additional ECRH input (Fig. 4) forms
positive confining potential in the east
plug/barrier-cell. Thus, ions escaping to the east
end-cell are reflected and the amount of ion flow
increases in west end-cell. Here, large loss of theFig.4. Time profile of ion-current density in the west
end-cell with ECRH superimposed

Fig.5. Ion-current density with the additional ICRF(RF3) input measured at the west end-cell.

SummaryThe end-loss-ion-flux of GAMMA 10 isanalyzed by using ELIEA device. Typicalparameters are obtained as 0.4 mA/cm2 inion-current density and 400 eV in ion-temperature.
In order to generate more intense ion-flux, effects
of several additional inputs are examined. Injectionof gas results the increase of ion-current density anddecrease of the ion energy. Formation of confining
potential by ECRH input also increases theion-current density. Superimposing of ICRF (RF3)showed the large increase of ion-flux. In future,
sequence of superimposing both ECRH and RF3
will be investigated.
References[1] Y. Nakashima et al: Fusion Eng. Design 85 (2010)
956-962.
[2] Y. Nakashima et al: Trans. Fusion. Sci. Technol. 59(2011) 61-66.
[3] Y. Nakashima et al: J. Nucl. Mater. 415 (2011)s996-s1000.