23P059-P
Investigation of neutral particle transport in GAMMA 10 SMBI experiments
GAMMA 10 SMBI実験における中性粒子輸送解析
Katsuhiro Hosoi1, Yousuke Nakashima1, Shinji Kobayshi2, Nobuhiro Nishino3, Tohru Mizuuchi2,Takashi Ishii1, Kazuya Ichimura1, Hisato Takeda1, Hideaki Ueda1, Satoru Kigure1,
Shigehito Takahashi1, Satoru Hotaka1, and T. Imai1
細井克洋 1、中嶋洋輔 1、小林進二 2、西野信博 3、水内 亨 2、石井 貴 1、市村和也 1、
武田寿人 1、上田英明 1、木暮 諭 1、高橋樹仁 1、保高 暁 1、今井 剛 11

Plasma Research Center, University of Tsukuba
1-1-1, Tennodai, Tsukuba, Ibaraki 305-8577, Japan筑波大学プラズマ研究センター 〒305-8577 つくば市天王台1-1-1
Institute of Advance Energy, Kyoto UniversityGokasyo, Uji 611-0011, Japan京都大学エネルギー理工学研究所 〒611-0011 京都府宇治市五ヶ庄
Grauate school of Engineering, Hiroshima University
Hiroshima 739-8527, Japan
広島大学大学院工学研究院 〒739-8527 東広島市鏡山1-4-1
SMBI system has been installed in GAMMA 10. SMBI is located at the bottom of the central-cell
mid-plane. The first results of the SMBI experiment showed that SMBI achieved higher density plasmas at
the core region than the conventional gas puffing case. A high-speed camera at the central-cell was used inorder to observe plasma behavior during SMBI. In order to analyze neutral transport from SMBI fueling,
three-dimensional Monte-Carlo simulation code has been applied to GAMMA 10. In this paper a discussion
on the neutral transport due to SMBI follows a comparison between the experimental results andsimulations.

1. Introduction
Control of gas fueling is one of the mostimportant issues to obtain good performance
plasmas. Fueling control enables the profile controlof the core plasma density and reduction of neutral
particles in the peripheral area. Supersonicmolecular beam injection (SMBI) technique, which
has been developed by L.Yao et al.[1], is a new
method of gas fueling. SMBI can inject neutral
particle deeper into the core plasma compared to thegas puffing. SMBI is successfully applied to somedevices [2, 3].
GAMMA 10 is open magnetic plasma-confining
device [6]. SMBI is located at the bottom of thecentral-cell mid-plane. The central-cell has a simple
solenoidal magnetic configuration by a number ofpancake coils. In addition, GAMMA 10 has manyobservation ports. Thus, GAMMA 10 is suitable foranalyzing the neutral transport. The first results ofSMBI showed that SMBI achieved higher density
plasmas at the core region than the conventional gas
puffing case. The purpose of this study is that theneutral particle behavior due to SMBI isinvestigatedbasedon
three-dimensional
Monte-Carlo simulation.

2. Experimental set up and the typical results
GAMMA 10 consists of central-cell, anchor-cells,
plug/barrier-cells and end-cells. Mid-plane of thecentral-cell is located at z = 0 cm and west and east
correspond to plus and minus in z-axis respectively.
The central-cell is the main region to confine
plasma. Mirror-throat regions which exist between
the central-cell and anchor-cell have the first mirror
with strong magnetic field for confining the plasma
in the central-cell. The initial plasma is produced byplasma guns located in both ends. Then plasma isproduced and heated by ion cyclotron range of
frequency (ICRF) waves. Two conventional gaspuff systems are installed for sustaining plasma at
both mirror throat region.
Figure 1 shows the cross-section view of theGAMMA 10 central-cell and locations of thehigh-speed camera and SMBI system. A high-speed
camera has been installed at central-cell in order toobserve the plasma behavior. The camera system
has two lines of sight in the horizontal and verticaldirections of the plasma cross-section by using dual
blanch optical fiber bundles. SMBI system consistsof a fast solenoid valve with a magnetic shield. The

plenum pressure is usually 1MPa and pulse width is
0.5-1.0 ms. SMBI pulse was injected to typicalplasma heated by only ICRF. Figure 2 shows 2-Dimage of visible light-emission from GAMMA 10
plasma by high-speed camera. Z-axis distribution ofthe emission intensity was estimated based on this2-D image.

diffusion of cosine distribution. Maximum valueof intensity of each distribution was normalized 1in Fig. 4.

Fig.3. The fully 3-dimensional DEGAS mesh model

Intensity [Arb.U.]

1.2

1
1/2
1/3

1
0.8
0.6
0.4
0.2
0-100

-50

050100z [cm]Fig.1. Cross-section view of the GAMMA 10
central-cell and locations of high-speed camera andSMBI system

Fig.4. The dependence of z-axis distribution ofemission intensity on the diffusion degree.

4. Summary
Using 3-D Monte-Carlo simulation code, theneutral transport in the GAMMA SMBI
experiments were simulated. A profitable findingof the neutral transport due to SMBI will beobtained by discussing a comparison between theexperimental results and simulations.

Fig.2. 2-D image of plasma during SMBI injection.
(left side: horizontal right side: vertical)

3. Simulation model
Monte-Carlo simulation code (DEGAS [5]) wasused in order to analyze the behavior of neutral
particle in GAMMA 10 [6]. Three-dimensional
mesh-model for DEGAS has been applied to thecentral-cell [7]. The mesh-model was upgraded formodeling of SMBI experiment as shown in Fig. 3.
The dependence of diffusion degree wasinvestigated in order to interpret the configurationof diffusion corresponding to the results of SMBIexperiments. Figure 4 shows the dependence ofz-axis distribution of emission intensity on thediffusion degree. In the case of cosine distribution,
the diffusion degree is 1. In the case that thediffusion degree is 1/2, that means a half ofAcknowledgments
This study was supported by the bilateralcollaboration research program in the University ofTsukuba, Kyoto University, Hiroshima University.
The authors would like to thank the members of theGAMMA 10 groups fort their collaboration in theexperiments and for helpful discussion.
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[6] Y. Nakashima: J. Nucl. Mater. 196-198 493(1992).
[7] Y. Nakashima: J. Plasma Fusion Res. SEREIS 6, 546(2004)