Was the Livermore X-Ray Laser Pumped by Recombination?

Abstract

We demonstrate that recombination pumping following rapid radiative cooling of an overstripped selenium plasma can quantitatively account for the observed gains of the $J=2 \mathrm{to} 1$ Se xxv transitions in the recent successful Livermore x-ray-laser experiments. The absence of gain in the $J=0 \mathrm{to} 1$ transition, hitherto unexplained, is fully consistent with this scenario.