24P042-P
Analysis of plasma behavior near the target plate in divertor simulation
experiment
ダイバータ模擬実験におけるターゲット板近傍のプラズマ挙動解析
Hisato Takeda1, Yousuke Nakashima1, Katsuhiro Hosoi1, Kazuya Ichimura1, Tetsuro Furuta2,Kazuhiko Higashiyama2, Mitunori Toma2, Akiyoshi Hatayama2, Takashi Ishii1, Hedeaki Ueda1,
Shigehito Takahashi1, Satoshi Kigure1, Satoru Hotaka1, Makoto Icnimura1, Masashi Yoshikawa1,Jyunko Kohagura1, Mizuki Sakamoto1 and Tuyoshi Imai1
武田寿人1, 中嶋洋輔1，細井克宏1，市村和也1, 古田哲朗2, 藤間光徳2, 畑山明聖2, 石井貴1, 上田英明1, 高橋樹仁1, 木暮 諭1, 保高 暁1, 市村 真1, 吉川正志1,小波蔵純子1, 坂本瑞樹1, 今井 剛1
1Plasma Research Center, University of Tsukuba,
3-1-1, Tennoudai, Tsukuba 305-8577, Japan
プラズマ研究センター 〒305-8577 つくば市天王台3-1-1
2

Science and Technology, Keio University,
3-14-1, Hiyoshi, Minatokitaku, Yokohama 223-8522, Japan
慶応義塾大学大学院理工学研究科 〒223-8577 横浜市港北区日吉3-14-1
Recently, divertor simulation study was planed using GAMMA 10 tandem mirror device. For organizing
this research, end-loss plasma which is to be irradiated on to target materials has been investigated. As theresult, end-loss plasma in GAMMA 10 has high ion-temperature that is much higher than electron
temperature and is easily controlled. These characteristics do not exist other divertor simulation devices. In
the case of only ion cyclotron resonance heating, heat-flux has strong dependence on diamagnetism which
is time integrated in central-cell. While, particle-flux is proportional to electron line-density in central-cell.
Development of numerical code describing background plasma has been started.

1. Introduction
In the International Thermonuclear Experiment
Reactor and Demo reactor for future nuclear
fusion power generation, heat-load of plasma
particles led to divetor plate approaches tens of
MW/m2 on steady-state operation. In addition itreaches several GW/m2 when ELM occurs.
Therefore, it is important to develop materials
which withstand the level of high heat-load fromthe divertor plasma. For solving this problem, it isneeded to find out the physical mechanism to keep
detaching divertor plate from the plasma influx
steady. The divetor simulation experiments arewidely performed by using linear devices becausemagnetic fields in liner devices are similar tomagnetic field in actual fusion devices.
In GAMMA 10 tandem mirror, divertor
simulation experiments were planed and started[1-3]. In the present experiments, characteristics ofend-loss plasma in GAMMA 10 were measured.
2. Experimental device
GAMMA 10 consists of central-cell, twoanchor-cells two plug/barrier-cells and twoend-cells. Plasma heating systems which are ion

cyclotron resonance heating (ICRF), neutral beam
injection (NBI) and electron cyclotron heating(ECH) are installed for plasma production/heatingand confinement. By applying ICRF in thecentral-cell and anchor-cells, end-loss can begenerated with much higher ion temperature thanelectron temperature. In this plasma state,contribution of ion dominates the heat-flux density.
In the case of superimposing ECH in
plug/barrier-cell on ICRF-produced plasmas, on theother hand, the effects of electron become
significant.

Fig.1. Schematic view of the west end-cell in
GAMMA 10

In this divetor simulation experiments,
directional probes and calorimeters are inserted near
the exit of the end-mirror coil in the west End-Cell(z = 30, 70 cm). By using these diagnostic tolls,
axial and radial profiles of particle-flux andheat-flux of end-loss plasma are measured.
3. Experimental results
In GAMMA 10, main plasma is produced at thecentral-cell and then leeks toward both end-cells
through coulomb collision. Therefore, it isimportant that investigate the relationship between
main plasma parameter of the central-cell and heatand particle flux at the end-cell. In the case ofheat-flux, the result is shown in Fig.2. Heat fluxdepends on the time integral diamagnetism incentral cell. On the other hand, results of particle
flux are shown in Fig.3. Particle-flux is proportional
to electron line-density in the central cell.
zExit = 30 cm

1numerical code is remodeled in simplification of B2
code [4]. A new code is modified to apply theGAMMA 10 end-mirror region. This numericalcode is two-dimensional fluid code and utilizes
finite volume method. Equations in this code arecontinuity equation, momentum balance equation,diffusion equation, electron energy balance
equation and ion energy equation as follows, n   nu  S n(1)tmnu     nmu // u    u //  p  S mu (2)t(3)v   Dn ln n y



 3
 5

e
 neTe      nuTe   Te 
t  2 2

 u e  pe  k Te  Ti   S Ee(4)

 3
1
1
1 2 
 5
 i2 2  niTi  nmu//      nuTi  mnuu//     Ti  u// t  2222 2 u e  pe  k Te  Ti   S Ei

(5)with RF3 (r CM = - 2 cm)
rCM0.4The mesh structure of the magnetic field of
GAMMA 10 end-cell is shown in Fig. 4.

= - 2 cm

rCM = 0 cm

P2(MW/m )

0.6

Heat

0.8

0.2

00

0.2

0.4

0.6

0.8

1

<DM > (x104 Wb)
CC

Fig.2. Heat-flux dependence on diamagnetismin the central cellr7 PrbzAxis= 30 cm

5. Summary
Heat and particle flux of end-loss plasma are
influenced strongly by the central-cell plasma
parameter. Especially, it is founds that the increase
with the central-cell diamagnetism and that theparticle-flux is proportional to the central-cellelectron line density. Numerical simulation which
evaluates the background plasma parameter has
been started.

RF3RF+GP3,4GP7After GP7
RF1

6532i224

 (x10particles/m s)= 0 cm

102

2.5

3

3.5 4 4.5 5
13-2
NL (x 10 cm )Fig.4. Example of the mesh structure of themagnetic fields in GAMMA 10 end-cell.

5.5

6CCFig.3. Particle-flux dependence on electron line
density in the central cell
4. Numerical CodeNumerical simulation study is also important tounderstanding the behavior of background plasmain actual divertor environment. In an collaboration
between Tsukuba and Keio universities, theReferences[1] Y. Nakashima, et al. Fusion Eng. Design 85 issue 6,Nov. (2010) 956-962.
[2] Y. Nakashima, et al. Fusion Sci. Technol. 59 No.1T(2011) 61-66.
[3] Y. Nakashima, et al. 23rd IAEA Fusion Energy
Conference (October 11-16, 2010, Daejeon,Korea) IAEA-CN-180 FTP/P1-33.
[4] B.J. Braams, NET Rep. 68 EURFU/X Ⅱ 80/87/68,
CEC, Brussels (1987).