Experiments in the Hanbit Mirror Device with the Kinetic Stabilizer

The Hanbit device is a magnetic mirror machine which has a central cell, one anchor cell and one plug cell. The Hanbit device has been involved in a series of experiments on stabilization of the MHD flute type mode including stability experiments with a divertor. We have undertaken investigations to see if the Kinetic Stabilizer (KS) of R. F. Post can stabilize the MHD instability. According to the theory, by locating a stabilizing plasma pressure on the field lines at a region with a strong second derivative and large radius in the expanding field region outside the mirrors, the main plasma in the mirror central cell in regions with unfavorable field line curvature can be stabilized. The Hanbit KS uses microwave produced plasmas on field lines in the cusp tank region. Two coils on the cusp tank are configured to produce expanding field lines with a large positive radius of curvature. A 5-kW 2.45 GHz magnetron is used to produce the stabilizing electron cyclotron resonant heated (ECRH) plasma pressure in this region. Details of the experimental arrangement and stabilizing plasma parameters were previously reported. For normally terminating plasmas, a reduction in the instability duration has been observed and the range of density where the instability occurs has decreased. However, for higher density plasmas which disrupt due to an m=-1 instability, a prevalent m=+1 instability is removed while the duration of the m=-1 instability is increased.