High beta toroidal Z pinch

Mhd equilibrium and stability of a high β TZP (toroidal Z pinch) plasma having hollow magnetic field pitch μ are investigated in terms of a hollowness parameter δ. It is shown that both the poloidal beta βp and the beta β0 on the axis raise up as δ increases to make the hollow μ profile deeper. The TZP plasma is stable to ideal modes for moderate δ (0 < δ < 0.4) and the critical βp and β0 increase by a factor of 1.36 and 1.7, respectively. The field configuration of hollow μ profiles of δ = 0.3 is observed during the rising stage of the toroidal current in TZP experiments. In the experiment, however, hollow μ profiles of large δ appears transiently and sustainment time does not exceed 30 μs. We are now developing an intensive plasma beam source since high power injection provides a solution of the problem. (author)