Dynamics of target plasma expansion during radiation ablation by a multiterawatt pulse of soft x-ray radiation at the Angara 5-1 facility.

Abstract

The article presents the results of experiments on studying the radiation heating of targets by soft x-rays (SXRs) of the Z-pinch of a wire array. The SXR power pulses had amplitudes of up to 10 TW and a duration of ∼6-10ns at half-maximum. In this series of experiments, the main focus was on the dynamics of expansion of target plasma made of thin films of various substances (Mylar, Ni, Gd, Au, Bi, etc.). Numerical modeling of heating, expansion, and self-emission of the target plasma made of Mylar film with or without a metallization layer was carried out using the two-dimensional radiation hydrodynamics code ralef-2d. We compared the calculated results with experimental data on plasma expansion obtained through laser shadow probing. Already at the stage of the x-ray prepulse, we observed a strong difference in the magnitude of the plasma boundary displacement of the Mylar targets with and without gadolinium deposition, calculated using the ralef-2d model and determined using laser shadow images. After the moment of peak radiation power, the difference between the calculated and experimental data increases. It is shown experimentally that the magnetic field of the discharge current of the SXR source (Z-pinch of a tungsten wire array) has a significant effect on the dynamics of the expansion of the plasma of the targets located in the anode-cathode gap of the facility. Experiments with targets whose plasma expands in magnetic field-free regions show good agreement between the observed expansion dynamics and ralef-2d calculations.