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(EX/P3-02) Confinement Characteristics of ECH Plasmas in Heliotron J

T. Obiki1), T. Mizuuchi1), H. Okada1), K. Nagasaki1), F. Sano1), K. Kondo2), S. Kobayashi1), M. Nakasuga2), K. Hanatani1), Y. Nakamura2), M. Wakatani2), S. Besshou2), Y. Ijiri1), T. Senju1), K. Yaguchi1), K. Sakamoto1), K. Tohshi1), M. Shibano1), Y. Manabe2), H. Shidara2), W.L. Ang2), H. Kawazome2), S. Maeno2), M. Takeda2), K. Tomiyama2), H. Tsuru2), M. Iriguchi2), S. Kaneko2), H. Kubo2), Y. Nishioka2), Y. Ohno2), T. Takamiya2), H. Yukimoto2), Y. Fukagawa2), S. Nishio2), S. Nakazawa2), Y. Morita2), K. Takahashi2), S. Tsuboi2), M. Yamada2), N. Nishino3), V. Tribaldos4), F. Tabares4)
1) Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan
2) Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Japan
3) Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima, Japan
4) Laboratorio Nacional de Fusion, Asociacion EURATOM-CIEMAT, Madrid, Spain

Abstract.  Heliotron J is a flexible, concept-exploration facility ( R0 = 1.2 m, B(0) < 1.5 T) aiming at experimentally optimizing the helical-axis heliotron concept. This paper reports the Heliotron J experiments with special regard to the characteristics of ECH plasmas. The experiments have presented the following results. (1) The energy confinement time was comparable to the ISS95-value. No significant degradation of the density dependence of the electron temperature was observed even in the $ \nu^{\star}_{}$ « 0.1 regime. It was also suggested the existence of discharges with more preferable confinement property. (2) A new effective heating region was found for 53.2GHz ECH in the higher magnetic field (B(0) $ \sim$ 1.4-1.5 T), where there are no resonance layers for electromagnetic waves in the core region. (3) The configuration effects of plasma confinement were observed. (4) Unexpected up-down asymmetry was found in the profiles of diverted plasma density and floating potential at the geometrically up-down symmetric divertor legs.

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IAEA 2003