Establishing Stability Conditions for Sheared-Flow-Stabilized Z-Pinch Plasmas via Fully Kinetic 2-D Simulations¹

Z-pinch configurations with improved stability are a topic of considerable interest, both for understanding the physics underlying the stabilization and for the possibility of extending performance to fusion relevant conditions. The sheared-flow-stabilized (SFS) Z-pinch[1,2] has demonstrated this behavior with stable plasma columns persisting for over 1000 Alfven radial transit times, and the on-going FuZE experiments[3] are scaling this design to higher current. First-ever 2-D fully-kinetic simulations have been performed to determine growth rates and map out stability boundaries for the most destructive instabilities. The simulations use a realistic mass ratio with a direct implicit scheme and a spatial resolution ~1/10 the minimum ion gyroradius, which can resolve ion-scale turbulence. The simulations are performed with plasma conditions that match the on-going experiments, and with the projected conditions of an SFS Z-pinch reactor. In both equilibria stabilization and damping of m = 0 sausage instabilities is achieved when peak flow speeds are less than the plasma sound speed. This is a more favorable result when compared to previous simulations based on fluid approximations that indicated supersonic flows are necessary: a requirement that would preclude scaling the concept to Q>1 reactor conditions.

[1] U. Shumlak, C. W. Hartman, Phys. Rev. Lett. 75 3285 (1995).

[2] U. Shumlak, R. P. Golingo, B. A. Nelson, D. J. Den Hartog, Phys. Rev. Lett. 87 205005 (2001)

[3] E. L. Claveau et al., this conference