Stabilization of an axisymmetric mirror cell and trapped particle modes

The criteria for the robust stabilization of axisymmetric tandem mirrors using wall stabilization and hot particle finite Larmor radius (FLR) effects are discussed. It is shown that a stable high-β system can be made compatible with the stability criteria for anisotropy-driven modes. The trapped particle mode formalism is extended to non-eikonal analysis. The effects of radial electric fields and dissipation are studied and it is found that: (1) previously stabilized modes are subject to dissipative instabilities; (2) trapped particle rotational instability is possible even for m=1; (3) there is a new trapped particle mode, driven only by electric fields in the plug; (4) the FLR effect from sharp equilibrium profiles can improve stability. (author)