Two-dimensional MHD simulations of a plasma focus with allowance for the acceleration mechanism for neutron generation

Abstract

The problem is formulated and a numerical model is developed for calculating MHD flows in plasma-focus (PF) devices. An implicit (with respect to the magnetic field) difference scheme and a method for its numerical implementation are proposed. The scheme allows one to describe plasma flows with drastically different densities and, therefore, to take into account the presence of a vacuum region behind the PF current sheath. Taking into account this region is important to numerically simulate the focusing process and adequately describe the acceleration mechanism for the generation of fast ions and fusion neutrons. The results of calculations are compared with the experimental data on the plasma dynamics in two different types of PF device. A model of accelerated ions is proposed to estimate the contribution of the acceleration mechanism to the total neutron yield. The neutron yield calculated in the framework of this model for three different geometries of the PF chamber at currents of 0.5–1.5 MA differs from the measured values by less than a factor of 2.