Simulation studies of the wire-array Z-pinch implosions

Abstract

Fast Z-pinch has produced the most powerful x-ray radiation source in laboratory plasmas and also shows the possibility to drive inertial confinement fusion (ICF). The Z-pinch researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper. The wire array Z-pinch process has three phases: wire plasma formation and wire-array ablation, implosion and the MRT instability development, stagnation and radiation. A mass injection model with azimuthal modulation coefficient is used to describe the wire initiation, and the dynamics of ablated plasmas of wire-array Z-pinches in (r,θ) geometry is numerically studied. Two-dimensional spatio-temporal distributions of magnetic field and precursor current are obtained, and the formation condition of plasma shell in early time is examined. In the implosion phase, a two-dimensional (r, Z) three temperature radiation MHD code MARED has been developed to investigate the development of the Magneto-Rayleigh-Taylor (MRT) instability. It is shown that the instability development corresponds well with the linear theory in the linear, weakly linear and nonlinear stages. We also analyze the implosion modes of nested wire-array and find that the inner wire-array is hardly affected before the impaction of the outer wire-array. While the plasma accelerated to high speed in the implosion stage stagnates on the axis, abundant x-ray radiation is produced. The energy spectrum of the radiation and the corresponding production mechanism are investigated. And the computational x-ray pulse shows a reasonable agreement with the experimental results. We also suggest that using alloyed wire-arrays can increase multi-keV K-shell yield by decreasing the opacity of K-shell lines. In addition, we use a detailed circuit model to study the energy coupling between the generator and the Z-pinch process. Recently, we are concentrating on the problems of Z-pinch driven ICF, such as dynamic hohlraum and capsule implosions.