MHD STABILITY OF A HOT-ION-MODE PLASMA IN THE GAMMA10 TANDEM MIRROR

Magnetohydrodynamic (MHD) stability of the GAMMA10 tandem mirror is ex tensively studied in ICRF-heated, hot ion plasmas. Stability boundary for a flute interchange mode is predicted to depend on a pressure-weig hted curvature integrated along the magnetic field line. It is found t hat upper limit of the central-cell beta beta(C) increases linearly wi th the anchor-cell beta beta(A). The critical beta ratio beta(C)/beta( A) above which the plasma cannot be sustained strongly depends on the pressure anisotropy P perpendicular to/P-parallel to of hot ions. Stro nger anisotropy greatly expands the stable region up to a higher criti cal beta ratio, owing to the reduction of the pressure weighting in th e bad curvature region of the central cell. On both sides of the quadr upole anchor cells, there are flux-tube-recircularizing transition reg ions where the normal curvature is highly bad. Then the density and io n temperature of the cold plasma in;the transition region are measured , Theoretical prediction on the flute stability boundary calculated by using the measured axial pressure profile of the hot-ion and the cold -plasma pressure can explain well the experimental results.