Profile and Curvature Depenence of Z Pinch Stability in the Kinetic Ion Regime

The effects of profile variations and curvature of the outer surface of a Z pinch on the stability of the Z pinch are studied theoretically. At the high temperatures relevant to most applications, the ions are collisionless on the timescales of interest unless the density is very high. Stability calculations that account for the collisionless nature of the ions show an enhancement of stability when compared to MHD calculations of the same configuration. The enhancement takes the form of lower growth rates in linear calculations and longer times for the plasma to break up in nonlinear calculations. This report uses the 3D "hybrid" code MERLIN (collisionless ions and charge neutralizing fluid electrons) to investigate the consequences of profile variations and surface curvature. The MERLIN results are compared with MHD simulations of the same configuration done with the MHD code MHRDR to isolate the effects of collisionlessness.