Simulation Study on Balmer Line Emission in the CHS Edge Region

H.Matsuura, S.Iguchi, S.Okamura1)

Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
1)National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

Improvement of plasma confinement such as H-mode is one of urgent issues in the fusion research. Edge transport barrier(ETB) discovered recently in the compact helical system(CHS) [1] is expected to have deep relationship with the profile of atomic/molecular hydrogen. In order to study the neutral particle behavior, we used Monte Carlo simulation code DEGAS[2] and DEGAS2[3].

On the contrary to other helical devices such as LHD, the CHS plasma in the standard configuration has contact with the inner wall like as the material limiter and the neutral recycling become dominant there. So the density of not only atomic hydrogen but also molecular hydrogen has the peak around this wall[4].

Experimentally informations on neutral particles are obtained through Balmer line emission ( mainly H-alpha ). According to CR model calculation[5], we can not neglect the contribution from hydrogen molecules in the H-alpha measurement. As neutral density rapidly decay toward the core plasma, high resolution DEGAS simulation near the inner wall is under way.

References

[1] S. Okamura et al., J. Plasma Fusion Res., 79(2003)977.
[2] D. Heifetz et al., J. Comp. Phys., 46(1982)309.
[3] D. P. Stotler et al., Conrtib. Plasma Phys., 40(2000)221.
[4] H. Matsuura et al., 16th PSI Conference, P1-39, Portland ME, USA, May 24-28, 2004.
[5] T. Fujimoto et al., J. Appl. Phys., 66(1989)2315.

This work is performed with the support and under the auspices of the NIFS Collaborative Research Program.