Abstract

The results reported here, are time integrated measurements of soft X-ray amplification obtained with our new experimental set-up involving a single normal incidence multilayered mirror, put at the rear of a 60mm laser-plasma column. After a brief description of the experimental system, we report the first results obtained at 10.57nm by comparing intensities of single-pass ASE and of double-pass with the mirror. The target is a thin aluminum layer with a thickness optimizing the population inversion on lithium-like Al+10 ions. The pumping is produced by recombination mechanisms during the plasma cooling.

From the single to the double pass X-ray beam, the lines exhibit significant differences, both in peak intensities and widths. First, double-passing enhances the 10.57nm line intensity much more than mirror reflection would do without any amplification by the plasma. Secondly, and concomitantly, one observes a line width decreasing of about 30%.

This is supposed due to a core size decreasing of the zone emitting the line. To explain how the cross-section of the double pass beam can be reduced during propagation trough the plasma column we suggest to consider the focussing effects due to the gain coefficient profile.

© 1988 Optical Society of America