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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. Tabares^4)
 
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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