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K. Yatsu, L. G. Bruskin, T. Cho, M. Hamada,
M. Hirata, H. Hojo, M. Ichimura, K. Ishii,
A. Itakura, I. Katanuma, Y. Kiwamoto, J. Kohagura,
S. Kubota, A. Mase, Y. Nakashima, T. Saito,
Y. Sakamoto, T. Tamano, Y. Tatematsu, T. Tokuzawa,
M. Yoshikawa
Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
Abstract. The central-cell density and the diamagnetic signal were doubled due
to plug potential formation by ECRH in the hot ion mode experiments on the
GAMMA 10 tandem mirror. In order to obtain these remarkable results, the
axisymmetrized heating patterns of ECRH and ICRF were optimized. Furthermore,
conducting plates were installed adjacent to the surface of the plasma along
the flat shaped magnetic flux tube located at the anchor transition regions;
the plates may contribute to reduce some irregular electric fields produced
possibly with ECRH in these thin flux tube regions. The conducting plates
contributed to the reduction of the radial loss rate to be less than 3% of
the total particle losses along with the improvements in the reproducibility
of the experiments and the controllability of the potential confinement. The
increases in the central-cell density and the diamagnetism in association with
the increase in the plug potentials scaled well with increasing the ECRH
powers. A plug potential of 0.6 kV and a density increase of 100% were
achieved using an ECRH power of 140 kW injected into both plug regions. The
plasma confinement was improved by an order of magnitude over a simple mirror
confinement due to the tandem mirror potential formation.
IAEA 2001
