05aE40P
LHDにおけるプラズマ周辺部のダストの三次元輸送シミュレーションとステレオ視高速カメラによるダストの軌道計測
Three-dimensional simulation of dust transport in the plasma periphery andstereoscopic measurement of the trajectory of dusts in the Large Helical Device
主、田中康規1)、ピガロフ・アレキサンダー2)、スミルノフ・ロマン2)、
増崎 貴、河村学思、上杉喜彦1)、山田弘司、LHD実験グループ
SHOJI Mamoru, TANAKA Yasunori1), Pigarov Y. Alexander2), Smirnov D. Roman2), MASUZAKI
Suguru, KAWAMURA Gakushi, UESUGI Yoshihiko1), YAMADA Hiroshi, LHD Experiment
Group
庄司

核融合科学研究所、金沢大・理工研究域、カリフォルニア大・サンディエゴ校
NIFS, 1)Kanazawa Univ., 2)Univ. California San Diego
The transport of dust particles in magnetic
plasma confinement devices has been attracting
attention because it affects plasma operation andperformances. For example, the termination ofsome ICRF heated long pulse discharges in theLarge Helical Device (LHD) was caused by socalled ‘spark’ events on the vacuum vessel,
resulting in accidental injection of a large amountof iron included in dusts into the plasma.
Toroidally non-axisymmetric magnetic fieldcomponents in the LHD form ergodized magnetic
field line structures in the plasma periphery:
divertor legs and an ergodic layer. The LHD
peripheral plasma, which surrounds the main
plasma confinement region inside of the last closed
flux surface (LCFS), has a function of shielding
against invasion of impurity ions into the plasma.
The peripheral plasma possibly has also theshielding effect against dusts which originate fromexfoliated co-deposition layers accumulated on thesurface on divertor plates and the vacuum vessel.
In order to investigate the shielding effect, a dusttransport simulation code (DUSTT) was applied tothe LHD geometry. This code has been originallydeveloped to dust transport analysis in toroidally
axisymmetric configurations such as Tokamaks,
which strongly couples with a two-dimensionaledge-plasma transport code (UEDGE). For
extending the DUSTT to the non-axisymmetricgeometry such as LHD, subprograms for tracking
the trajectory of dusts in the DUSTT weremodularized and implemented in a program module
for tracking ionized test particles in a fully
three-dimensional neutral particle transport
simulation code (EIRENE). The three-dimensional
grid model for the EIRENE provides a geometricalcondition to track the trajectory of dusts in the LHD
vacuum vessel. A fine grid model for athree-dimensional plasma edge transport code
(EMC3) including plasma parameter profiles wasused for the detailed dust trajectory analysis.
Figure 1 shows a three-dimensional model of theLHD geometry for dust trajectory analysis. Small
colored allows indicates the magnitude and thedirection of the plasma flow in the periphery. In thisfigure, the dependence of dust’s trajectory on thedust radius (Carbon), which are released from adivertor plate installed in the upper inboard side of
the torus and dropped from an upper part in thevacuum vessel, are shown in an LHD standard
magnetic configuration (Rax=3.60m).
The shielding effect of the peripheral plasma (aergodic layer and divertor legs) against the dust
invasion into the LHD main plasma will be
numericallyinvestigatedbysophisticatedthree-dimensional dust transport simulation using
the DUSTT implemented in the EIRENE couplingwith the EMC3.

Fig.1 Simulations of the three-dimensional
trajectory of dusts (Carbon) in the LHD geometry.