A computational investigation of the neon-like germanium collisionally-pumped laser considering the effect of prepulses

Simulations of collisionally-pumped germanium slab targets irradiated with prepulses which precede the main pulse by 5 ns are presented. Preforming the plasma is shown to result in increased absorption of the main pulse and lead to larger useful plasma mass, creating more favorable conditions for gain. The electron density gradients within the plasma are found to be reduced for prepulse levels above ~5%. Ray tracing calculations show a large enhancement of the J=0-1, 196 Å transition relative to the J=2-1, 236 Å line. The reasons why the J=0-1 transition is affected more than the J=2-1 are considered. The calculations indicate an optimum prepulse level for both lines in the region of 5-10% of the main pulse, but all prepulse levels which have been ray traced show a significant enhancement over the single-pulse calculation