Hot-spot model of K-line emission from laser-heated plasmas

Abstract

A nonhydrodynamic model is developed to describe x‐ray emission from laser‐heated plasmas on a subnanosecond time scale. The model is first correlated with the experiment and then is used to study the conversion efficiency of laser energy to K‐line x rays in carbon, fluorine, and aluminum plasmas as a function of incident laser intensity. It is found that these conversion efficiencies peak at well‐defined values of input energy per area for laser pulse widths smaller than the pumping times for K‐line emission. In this case, the degree and not the rate of plasma heating is important in determining the peak conversion efficiency. It is also found that peak conversion to K radiation in excess of roughly 10 or 20% occurs only when the C, F, and Al plasmas are optically thick to the K_a lines.