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Recently, pre-ionization experiments using thermal electron emission from LaB6 cathode and electron heating by 2 kW@14.5 GHz Klystron installed at cusp and plug cell respectively have been carried out in Hanbit mirror device. Charge exchange collision between ion and neutral atom has been concerned as an important mechanism of ion energy loss in the Hanbit discharges, hence the high pressure of neutral particles is one of the most reasonable cause of low ion temperature. In this work, we investigate low pressure operation mode with help of the pre-ionization to enhance the ion temperature. The ion temperature and temperature anisotropy are measured and also inferred by ELA(End Loss Analyzer) for central cell plasma. We also characterize RF heating properties for different regimes of ɷ/ɷc0iusing simulation code for electromagnetic waves.

The HANBIT device is a non axi-symmetric mirror being operated as a national users’ facility. Plasmas are routinely produced by ICRF at 3.5 MHz with a slot antenna with gas puffing and the line-integrated densities are in the range between 2×1012and 1×1014cm–2. The pulse length is normally 250 msec, but higher wall recycling happened usually after 100 msec into the discharge. Characterization and application of various methods of wall conditioning have been performed. Ion heating had been tried by RF with a double half-turn antenna, however, the heating effects were vaguely seen. Optimum heating schemes have been actively pursued with different heating method and antenna types. RF-induced electric fields have been known to affect the plasma stability. This effect of RF on stability seems important in HANBIT because of lacking of stabilizing mechanisms such as the minimum-B effect and the line-tying effect. In addition, stabilization by a hot electron ring generation and by other methods is being pursued. Detailed experimental results on these topics will be presented.