2D R-Z MHD simulations for sphinx experiments numerical study of single wire array Z-pinches with multi-microsecond current prepulse

The Sphinx machine based on microsecond LTD technology was used to implode single wire arrays. These z-pinch experiments were performed on Sphinx driver using a multi-microsecond current prepulse. This prepulse dramatically changes the ablation phase leading to an improvement of the axial homogeneity of both the implosion and the final radiating column. As a consequence, the number of parameters and the complexity of the load description can be reduced and a 2D numerical study of these shots becomes of great interest. In this paper the following parameters were identified and quantified: the wire ablation velocity Vabl and the rate tau of cell-by-cell mass random perturbation of the wires along z. Numerical simulations presented here were done with Marple2D (Fortran version), a 2D(r,z) MHD code developped by IMM (Moscow). The rocket model is used to calculate the mass injected at each time step. Both simulations using experimental and simulated currents have been done. These MHD simulations allow us to quantify possible variations of Vabl and tau in order to fit experimental results and to link them to load parameters : the inter-wire array gap and the distance between the wire array initial radius and the current return radius.