Recent Results of the Hanbit Mirror Device

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 2×10¹² and 1×10¹⁴ cm^–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.