24P
4P0055-P
Development of Divertor Simulator Enabling Simultaneous Irradiation ofSteady-State High Heat Flux Plasma and Plasmoid
プラズモイド-定常高熱流プラズマ複合照射装置の開発
Takuya Nihashi1, Noriyasu Ohno1, Shin Kajita2, Tetsuya Uchiyama1, Makoto Takagi1,Yusuke Kikuchi3, Kyohei Ikuta3, Iwamoto Taiki3, Ikko Sakuma3, and Masayoshi Nagata3
二橋卓哉, 大野哲靖，梶田 信，内山徹也，高木 誠，菊池祐介，生田恭平，岩本大希，佐久間一行，永田正義
1)Graduate School of Engineering, Nagoya University, Fro-cho, Chikusaku, Nagoya, Aichi 464-8603, Japan
名古屋大学工学研究科, 〒464-8603 名古屋市千種区不老町2)EcoTopia Science Institute, Nagoya University, Fro-cho, Chikusaku, Nagoya, Aichi 464-8603, Japan
名古屋大学エコトピア科学研究所, 〒464-8603 名古屋市千種区不老町3)Graduate School of Engineering, University of Hyogo, Shosha, Himeji-shi, Hyogo 671-2197
兵庫県立大学，〒671-2201 兵庫県姫路市書写2167
For a fusion reactor, it is indispensable to develop the divertor with tungsten which can bear intense transient heat andparticle loads, such as ELMs and disruptions. In order to simulate pulse plasma like ELMs, it is necessary to develop adevice which irradiates transient heat and particle loads to generate with steady-plasma. In this study, the experiments
using the plasma gun are performed. Mo samples were irradiated by a plasmoid in order to investigate the impurities
produced.

1. Introduction
In fusion devices, transient huge heat and particle
loads are critical problems for the damage ofplasma facing components (PFCs). Especially,
type-I edge localized modes (ELMs) anddisruptions, transient heat and particle loads, areconsidered as the damage for divertor plates inITER. It is necessary to investigate the damage oftungsten (W) for transient heat and particle loads,
such as ELMs.
To simulate the condition under ELMs,experiments by using a laser [1], an electron beam[2], and a plasma gun [3] were conducted. However,these experiment were not enough to simulate
ELMs. Therefore, an experimental device which
irradiates pulsed heat and particle loads understeady-plasma is required to simulate ELMs. The

purpose of this study is to develop the divertor
simulator enabling simultaneous irradiation ofsteady-state high heat flux plasma and plasmoid.
In this study, experiments by using the plasma gun
are shown, as the first step.
2. Experimental setup
Figure. 1 shows a schematic of a plasma gun that
we developed [4]. An internal electrode is coatedwith W in order to prevent scattering of theimpurities from the electrode. However, it may bepossibility that W scatters. To investigate thedistance dependence of the amount of scattered W
from the electrode, we conducted following
experiments. Molybdenum (Mo) samples wereirradiated with five shots of hydrogen discharges. In
these shots, gun voltage was 5 kV. The size of theseFig. 1 A schematic of the plasma gun [4].

samples was φ24 mm and the thickness was 2 mm.
The positions of the samples were 327.5 mm, 467.5mm, and 607.5 mm from the electrode respectively.
We observed the surface structure of the irradiatedsamples by scanning electron microscope (SEM)
and these samples were analyzed by energy
dispersive x-ray spectroscopy (EDX) and rutherford
backscattering spectrometry (RBS) to measure theelemental ratio. Additionally, the spectroscopic
measurement was conducted using a high speed
camera with a visible spectroscope to observe time
evolution of emission of the plasmoid.
3. Results and Discussion
Figure. 2 shows the result of RBS of Mo samples.
It shows the relationship between the distance fromthe internal electrode and the concentration of W.
From this result, it was found that the amount of W
deposition on Mo samples decreases with distancefrom the internal electrode.
Figure. 3 (a) and (b) show the characteristic
spectra of the emission of the plasmoid measured
by the spectroscopic measurement and the time
evolution of the emission of Hb, W I, and Cr I. Theemission of Cr I was observed because we use thestainless screwes in a vacuum vessel in order to fix
Mo samples. From Fig. 3 (b), it was found that Cr Iemission was delayed approximately 0.05 ms, ascompared with that of Hb and W I. This was causedby the fact that Cr I emitted light after thetemperature rise of stainless screwes. Moreover,about Hb and W I, the second peak was observed at0.5 ms. This suggests that the plasmoid wasirradiated twice in a single shot.

Fig. 2 Result of RBS for Mo samples.

(a)(b)

Fig. 3 (a) The characteristic spectra of the emission ofthe plasmoid (b) Time evolution of emission of Hβ, W I,and Cr I
References[1] Y. Ueda et al., Fusion Eng. Des. 82 (2007) 1904.
[2] T. Hirai et al., J.Nucl. Mater. 390-391 (2009) 751.
[3] N.Kilmov et al., J.Nucl. Mater. 390-391 (2009) 721.
[4] Y. Kikuchi et al., J.Nucl. Mater. (2011),
doi:10.1016/j.jnucmat.2010.12.019