Radiative heating of low-Z solid foils by laser-generated x rays.

Abstract

The x-ray emission and burnthrough of radiatively heated low-Z plastic foils (${\mathrm{C}}_{8}$${\mathrm{H}}_{8}$, n${\mathrm{CH}}_{2}$, or ${\mathrm{CF}}_{2}$) have been investigated in gold cavities of different shape and size, which were heated by the Gekko XII laser up to a radiation brightness temperature of 160 eV. The cavity radiation temperatures were obtained spectroscopically as well as from the speed of the shock that is radiatively driven into aluminum. From measured carbon burnthrough spectra we derived mass ablation rates at drive temperatures ranging from 100 to 180 eV. In addition we measured temporally resolved reemission spectra of carbon. The time- and frequency-integrated reemission was 23% of the gold reemission or 16% when normalized to the driving cavity flux. The measurements are in good agreement with numerical hydrodynamic computer code simulations based on multigroup radiation diffusion. (c) 1995 The American Physical Society