Design and Simulation of Dynamic Screw Pinch Experiments on the Z Facility
Gabriel Shipley, University of New Mexico
Magnetic implosion of cylindrical metallic shells (liners) can effectively compress preheated, premagnetized fusion fuel to thermonuclear conditions but suffers from magnetized Rayleigh-Taylor instabilities (MRTI) that limit the attainable liner convergence, fuel pressure and fuel temperature at stagnation. A novel implosion stabilization method proposed by Schmit et al. employs a magnetic drive field at the outer liner surface that dynamically rotates during implosion and reduces anticipated MRTI growth via a solid liner dynamic screw pinch (SLDSP) effect. Analytical calculations suggest that the (linear) growth of the most deleterious MRTI modes could be reduced by as much as one to two orders of magnitude. Our simulations explore the design features necessary for successful experimental implementation of this concept. The results suggest that an effective helical drive field can be established by using a return current path made from discrete helical conductors that surround the outer liner surface. Apart from liner stabilization, it has also been suggested that use of tilted (helical) return current posts can result in the injection of significant axial magnetic flux into magneto-inertial fusion liners prior to implosion due to the rapid, non-linear magnetic diffusion of an axial field component across materials with large dynamic resistivity gradients. Such field injection could potentially supplant external field coils for premagnetization of the fuel column. We present simulation results aimed at establishing the physics design basis for this experimentally unexplored dynamic z-pinch implosion concept. Detailed evaluation of this concept using transient magnetic and magnetohydrodynamic simulation tools has led to a credible design space for upcoming dynamic screw pinch experiments on the Z Facility.
Abstract Author(s): G.A. Shipley, C.A. Jennings, P.F. Schmit, D.A. Yager-Elorriaga, T.J. Awe