A. Tsushima

M.Y. Tanaka

Y. Amagishi

Y. Saitou

National Institute for Fusion Science (NIFS-Repository)

§s. Behavior of Neutral Particles in a Large Diameter Plasma Tsushima, A. (Yokohama National Univ.), Saitou,Y. (Utsunomiya Univ.), Amagishi, Y. (Shizuoka Univ.), Tanaka, M.Y. Spatial distribution of neutral particles is important from the viewpoint of plasma production, because a pair of ion and electron are generated from one neutral particle by electron impact ionization. In addition, the existence of neutral particle influences the propagation characteristics of various waves in plasma, for example, the field pattern of the kinetic Alfven wave is drastically changed by the existence of neutral particles. [1] The purpose of this study is to investigate the radial distribution of the neutral density in the HYPER-I device [2] through the spectroscopic measurement. The intensity of line emission from the neutral particles is expressed by 10 = nonefoCTe) and that from the singly ionized particles by 1 I = n 1 nell (T e ) where, no is the density of neutral particle, nl the density of singly ionized particles, ne the electron density, and to (Te) and fi (Te) are the line-excitation rate coefficients of the neutral particle and the singly ionized particle, respectively, which are functions of electron temperature Te. In an argon plasma with a electron temperature Te =10 eV, the most of ions are singly ionized, and the quasi-neutral condition, ne = n 1, is satisfied. Then we have the neutral density profile: no and the ion density profile: from which we easily obtain the radial distribution of the neutral density no if the electron temperature is uniform. Figure 1 (a) shows the radial distributions of the emission intensity at A = 811nm and 436nm, which correspond to the emission lines from the neutral argon atom and the singly ionized one, respectively, in the HYPER-I plasma (p = 1 X 10-3 Torr and P = 5 kW). It is worthwhile to note that the radial distributions of these line intensities are obtained by using the Abel inversion under the assumption of ax i-symmetric distributions. Figure 1 (b) shows that the radial profiles of the neutral and ion densities determined from the results presented in Fig. l(a). The radial distribution of the neutral density agrees with the result obtained in the numerical calculation with the Monte CaIro method. (a) 4 ~ CI) 3 -+-J ·c 0 436nm ;::j 2 • ...0 $.....; • • 0 cc:l 1 • • '-../ • 0 0 • 0 0 0 » 0 .-t::: 0 CI) C 0 50 100 150 Q) +-' C Radius (mm) ~ (b) 4 ~ CI) neutral +-' 3 • ........ c ;::j 0 ion ...0 2 • • • $.....; • cc:l '-../ 1 0 Q) o 0 ta 0 0 $.....; 0... 0 50 100 150 Radius (mm) Fig.l. (a): radial distributions of emission intensity at 811 nm and 436 nm, (b): radial distributions of neutral and ion densities. References 1) Amagishi Y. and Kitagawa S. , J. Phys. Soc. Jpn. 63 (1994) 2021. 2) Tanaka M.Y. et aI., Ann. Rep. NIFS (1998--1999) 259. 283 

Behavior of Neutral Particles in a Large Diameter Plasma

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