24P062-P
Characteristics of pulsed plasmas in the magnetized plasma gun device
磁化プラズマガン装置におけるパルスプラズマの特性評価
Daiki Iwamoto, Kyohei Shoda, Ikko Sakuma, Yusuke Kikuchi,Naoyuki Fukumoto and Masayoshi Nagata
岩本 大希，生田 恭平, 佐久間 一行, 菊池 祐介, 福本 直之, 永田 正義
Graduate School of Engineering, University of Hyogo
2167 Shosha, Himeji, Hyogo 671-2280, Japan
兵庫県立大学 工学研究科 〒671-2280 兵庫県姫路市書写2167
The plasma parameters of surface absorbed energy density, velocity and line-averaged electron density ofpulsed H, D and He plasmas produced by the magnetized coaxial plasma gun (MCPG) device at Universityof Hyogo were measured. Dependencies of the plasma parameters on the gas species were observed. The
high energy density of > 1 MJ/m2 was successfully produced for all the gas species at the gun voltage of 6kV.

1. Introduction
A pulsed (~0.1-1 ms) plasmoid is produced by amagnetized coaxial plasma gun (MCPG) device at
Univ. of Hyogo [1, 2] in order to simulate thermaltransient events such as type I edge-localized modes(ELMs) and disruptions. It is important to know
detail characteristics of the pulsed plasmoid forunderstandings of interactions between the pulsed
plasma and candidate materials of divertor in ITER.
In this study, surface absorbed energy density,plasmoid velocity and line-averaged electron
density of pulsed H, D and He plasmas weremeasured in the MCPG device.
2. Experimental setup
A calorimeter is applied to measure the surface
absorbed energy density of the pulsed plasma
produced by the MCPG. The detail of the MCPG
device is shown in [3]. The calorimeter consists ofcylindrical graphite (IG-430U) of 8 mm in diameterand 10 mm in height, in which a thermocouple isinserted. The plasmoid velocity is estimated by atime-of-flight measurement of the magnetic fieldsignals. The line-averaged electron density ismeasured by a He-Ne laser interferometer.
3. Experimental results
Figure 2 shows the velocity of the pulsed H
plasma as a function of the gun voltage. The guncurrent reaches at ~90 kA, which is two times larger
than that of the previous MCPG [1]. The plasma
duration is about 0.2 ms. The resultant ion energy ofthe pulsed H plasma with the gun voltage of 6 kV isabout 40 eV. The line-averaged electron density ofthe pulsed H plasma at z = 175 mm measured by theHe-Ne laser interferometer is shown in Fig. 2. Here,Fig. 1 The velocity of the pulsed H plasma as afuction of the gun voltage.

Fig. 2 The line-averaged electron density of thepulsed H plasma as a fuction of the gun voltage.

z is the distance from the tip of the inner electrode.

Fig. 3 The surface absorbed energy density of thepulsed H, D and He plasmas as a function of the bias
magnetic flux.

The surface absorbed energy of the pulsed H, Dand He plasmas at z = 340 mm was measured withthe calorimeter by changing the bias magnetic flux,
as shown in Fig. 3. Here, the gun voltage was 6 kV.
Figure 4 shows the velocity of the pulsed H, D and
He plasmas as a function of the measured energy
density (Fig. 3). The velocity of the pulsed He
plasma at the energy density of 1.1 MJ/m2 is also
smaller than the others. On the other hand, the line
averaged electron density of the pulsed He plasma
at the energy density of 1.1 MJ/m2 is higher than theothers, as shown in Fig. 5. Thus, the differences ofthe plasma parameters should be considered in thepulsed plasma irradiation experiments [4], eventhough the energy density is the same.
4. Summary
The surface absorbed energy density, the velocity
and the line-averaged electron density of the pulsed
H, D and He plasmas were measured in the MCPG
device. The high energy density plasmoid with thedifferent gas species was successfully generated. Acalorimeter made of W should be performed infuture, because a particle reflectivity between
graphite and W is different.
References[1] Y. Kikuchi et al., IEEE Trans. Plasma Sci. 38 (2010)232.
[2] Y. Kikuchi et al., J. Nuc. Mater. 415 (2011) S55.
[3] K. Shoda et al., Proc. of Plasma Conference 2011
(2011) 24P061-P.
[4] I. Sakuma et al., Proc. of Plasma Conference 2011
(2011) 24P063-P.

Fig. 4 The velocity of the pulsed H, D and He plasmas
as a fuction of the bias flux.

Fig. 5 The velocity of the pulsed H, D and Heplasmas as a fuction of the bias flux.