Saturated x-ray lasers at 196 and 73 Å pumped by a picosecond traveling-wave excitation

Abstract

Traveling-wave irradiation with a laser pulse of duration $\ensuremath{\sim}1$ picosecond has been shown to achieve saturated operation of Ne- and Ni-like x-ray lasers. Gain at 196 \AA{} was confirmed by observation of both forward and backward x-ray laser beams from a germanium plasma under ideal and nonideal traveling-wave conditions at a small signal gain of $g40 {\mathrm{cm}}^{\ensuremath{-}1}.$ Saturation was observed for targets $g4$ mm long consistent with a model of laser amplification along the plasma medium and with the output of a detailed ray-tracing post-processor coupled to a hydrodynamic and atomic physics code. Ni-like samarium targets, pumped under ideal traveling-wave conditions exhibited a small signal gain of $\ensuremath{\sim}19 {\mathrm{cm}}^{\ensuremath{-}1}$ at 73 \AA{} with saturation observed for targets 8 mm long.