Influence of pump pulse parameters on the collisionally pumped germanium X-ray laser in the transient gain regime

Simulations are presented for the collisionally pumped germanium X-ray lase r working in the transient gain scheme. The influence of the shape, length, intensity and energy of the preforming pulse on the gain and X-ray output are analysed. The hydrodynamics simulations post-processed with 3D raytraci ng give additional information about the effective gain and the output sign als determined by the refraction due to the plasma density gradients. The m odelling presented shows to what extent the plasma preforming plays a decid ing role for the improvement of the lasing conditions. Dependence on the ma in pulse delay is tested as well. There are indications that significant ga in and output signal could be created with a subpicosecond main driving pul se of reduced total energy provided the preforming pulse is optimised. (C) 1999 Elsevier Science B.V. All rights reserved.