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Spectroscopic Study of Impurity Behavior in Heliotron-J Plasmas

Hayato Kawazome, Shintaro Tsuboi, Katsumi Kondo, T. Mizuuchi, F. Sano, K. Nagasaki, H. Okada, S. Kobayashi, K. Takahashi, H. Shidara, Y. Manabe, M. Kaneko, Y. Ohno, T. Takamiya, Y. Nishioka, H. Yukimoto, S. Nakazawa, S. Nishio, Y. Fukagawa, M. Yamada, T. Obiki

Fusion Science and Technology / Volume 46 / Number 1 / July 2004 / Pages 135-141

Technical Paper / Stellarators /

Behavior of intrinsic and injected impurities has been investigated in Heliotron-J plasmas by spectroscopic methods. Intrinsic impurities are identified with the vacuum ultraviolet grazing incidence spectrometer in neutral beam injection (NBI)-heated plasmas. Na-like Ni XVIII and Mg-like Ni XVIII are observed only in NBI heating phase. Helium gas is injected into electron cyclotron heating plasmas. In the density scan experiments, He II line intensities, which are normalized by the electron density, increase with decreasing electron density. For intrinsic impurities, similar dependence of line intensities on the electron density is observed. The normalized line intensity indicates the particle number of ions penetrated into the core plasma. In addition, the edge electron density is in proportion to the core electron density. These results may reflect the screening effect due to electron collisional ionization at the edge plasma. In the carbon limiter insertion, the CH radical band spectrum is observed. The carbon limiter head is formed in the hemisphere. The spatial distribution of the band emission is asymmetrical to the main axis of the limiter head. A good agreement is obtained between the spatial distribution of emissions of the band spectrum and the camera image with bandpass filter.

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