No abstract

Amplification of spontaneous emission (ASE) at 23.6 nm has been studied in a Ge plasma heated by a 1 TW infrared laser pulse. The exponent of the axial gain reached 21 in a geometry with Fresnel number < 1. Two plasma columns of combined length up to 36 mm were used with an extreme ultraviolet mirror giving double-pass amplification. Saturation of the ASE output was observed. The beam divergence was about 8x diffraction limited with a brightness estimated at 10 14 Wcm~2sr _1 . The feedback from the mirror was significantly reduced probably by radiation damage from the plasma.

The existence of modes of compressible fluid flow involving a separation of variables into a similarity solution in two dimensions and one-dimensional flow in the third is demonstrated. The numerical integration of such flows by a modified von Neumann–Richtmyer scheme is proposed, and the stability conditions investigated, showing that a generalized Courant–Friedrichs–Lewy condition is necessary. The inclusion of dissipation in the forms of artificial viscosity and thermal conduction into the model is discussed. The results of some test calculations are presented to demonstrate the behaviour of this model.