A. Takayama

E. Kusunoki

K. Sawada

M. Goto

M. Shinohara

N. Ezumi

T. Fujimoto

T. Kido

Y. Kohashi

Y. Tomita

National Institute for Fusion Science (NIFS-Repository)

§19. Effect of Vibrational Excitation of Molecular Hydrogen on Hydrogen Recycling in LHD Edge Plasma Sawada, K., Shinohara, M., Kusunoki, E., Kohashi, Y., Kido, T. (Shinshu Univ.), Ezumi, N. (Nagano National College of Technology), Fujimoto, T. (Kyoto Univ.), Goto, M., Takayama, A., Tomita, Y. We have constructed a neutral particle transport code which contains recent atomic and molecular data espe-cially concerning the molecular assisted recombination (MAR) which may enhance the plasma recombination in the higher temperature region where the cOllventional collisional-radiative recombination becomes ineffective. Figure I shows the rate coefficients of the MAR.') o H2(v)+H+.>H2+.;.H H2++e->H+H' H'.> H D H2(V)+9->H'+H H' + H+ -> H + H' v Fig.1. The MAR rate coefficients from various ini-tial vibrational levels in H2(X'Et). Te = leV, n, = lO'2cm-3 . Because the MAR rate coefficient strongly depends on initial vibrational levels of H2 (X ' Et, v), the v = 0-15 levels are distinguished in our code. All atomic and molecular processes considered are listed below. H+ + e -:> H • H + e -> H+ + e + e • H + H+ -> H+ + H H2(v) + e -> H2(b) + e -> H + H + e H2(v) + e H2(v=14) + e H2(v) + H+ H2(v) + e -) H2(v+l or v-i) + e -> H2(v=contlnuum) -> H -> H2+(v) + H (-> H2+ + e H2* -> H2(b) -> H + H + e + H H2* -> H2(v= continuum) -> H + H + e H2* -> H + H+ + 2e H2* -> H2+(v') + 2e H2(v) + e -> H + H* + e H* -> H H* -> H+ + e · H2(v) + e -> H + H+ • H2(v) + e -> H2+(v') + e H2+(v) + e -> H + H+ + e H2+(v) + e -> H + H* -> H + H+ + e H2+(v) + e -> H + H* -> H + H H2 + H+ • H + H+ 226 -> H2 + H+ -> H + H+ elastic collision elastic collision + e Figure 2 and 3 show some output examples of a cal-culation under a condition that uniform Te = leV and ne = 1012cm-3 are assumed for p 2: 1.0 region where available data of these parameters is few. The vibra-tionallevel of H2 (X ' Et) which is released from the di-vertor plate is set to v = 0 in this calculation. .Hi" Fig.2. Density distributions of H,(X' Et, 11 = 0) and H(ls). For p 2: 1.0 region, uniform T, = leV and n, = l012crn-3 are assumed. Te (~>I):leV ne(P>I):1D'1c:m-1 major radJus (em) 10"13 Te(p>I):leV ne (P>1l"10'lcm"1 """":' 10.1• _H·>H" ._ •• Hz·>H+H" -.~ Hz CXMIIR _. Hz OA MAR major radius (em) Fig.3. (a) Densities ofH2(X'Et,V) and H(ls), and (b) Balmer Q emission intensities originating from various paths, along center horizontal line in Fig.2. Figure 3(b) shows that the Balmer", is emitted uni-formly in p 2: 1.0 region, but no experimental evidence of the emission region is reported: the Balmer 0: is observed in limited region around p = 1.0. Our code can produce the spatial distributions of the densities of the various excited levels of atoms and molecules, and spectral line intensities and profiles emitted by them. However, in order to analyze LHD plasma quantitatively, the follow-ing items should be further investigated: (1) T, and ne for p 2: 1.0 region, (2) a realistic wall reflection model (reflection probability, species, excited levels, direction, energy, etc.). In addition to accumulating information, we will study them by analyzing measured line intensities and profiles emitted by hydrogen atoms and molecules, and helium atoms. Reference 1) K. Sawada and T. Fujimoto, Contributions to Plasma Physics 42, (2002) 603. 

Effect of Vibrational Excitation of Molecular Hydrogen on Hydrogen Recycling in LHD Edge Plasma

Effect of Vibrational Excitation of Molecular Hydrogen on Hydrogen Recycling in LHD Edge Plasma

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