Abstract

We suggest the use of mixtures of light and heavy elements as targets for laser-driven femtosecond time scale x-ray line radiators. We assume that a tightly focused 100-fs laser pulse is incident on the surface of a mixed species target and that some fraction of the laser energy is absorbed in a skin depth of ~150 Å. Electrons in the interior (~5 × 10⁴ Å) of the metal are heated by electron—electron diffusive energy transfer and are cooled by ionizing collisions with heavy metal atoms and also, to some extent, by thermal diffusion further into the interior. Electrons make inner shell holes in heavy metal target atoms, which in turn radiate. The preponderance of light metal allows a much higher electron temperature, and, therefore, at a given absorbed laser energy density, a conversion efficiency to x rays which can be many orders of magnitude larger for a solid density heavy metal alone.

© 1988 Optical Society of America