Time-dependent subsonic ablation pressure scalings for soft X-ray heated low- and intermediate-Z materials at drive temperatures of up to 400 eV

The soft X-ray driven subsonic ablation of five different materials with atomic numbers ranging from 3.5 to 22 is investigated for radiation drive temperatures of up to 400 eV. Simulations were performed using the one-dimensional radiation hydrodynamics simulation code HYADES. For each material, ablation pressure scaling-laws are determined as a function of drive radiation-temperature and time, assuming that the irradiation lasts for a period of a few nanoseconds and that the drive temperature remains constant during this period. For all the materials, the maximum drive-temperature for subsonic operation is identified. As expected, lower-Z materials demonstrate a stronger scaling of ablation pressure with radiation temperature and a more gradual fall off with time. However, the lowest-Z materials transition to trans- and super-sonic ablation at temperatures of only a few hundred eV.