Toward compact soft x-ray lasers

Abstract

We present recent work on the development of the compact ('table top') soft x-ray lasers (SXLs) using two approaches. In one approach we use low energy Nd/Glass laser (pulse duration, (tau) equals 1.5 nsec, beam energy E equals 3 - 5 J), and in the second approach we use powerful subpicosecond (PSP) laser ((tau) equals 200 fsec, E equals 0.1 - 0.3 J, maximum power density P approximately equal to 2 multiplied by 10<SUP>18</SUP> W/cm<SUP>2</SUP>). We discus generation high gain at 18.2 nm and 13.5 nm in CVI line focussed Nd/Glass laser on a carbon target and the unexplained difficulty to obtain gain-length GL greater than 4.5 in such a configuration. The time evolution of intensities of spectral lines and their correlation with time averaged spectra are analyzed. We also present measurement of plasma refraction as a possible explanation of the limitation of GL. More recently we changed the configuration of this experiment using as a target polyethylene microcapillary with focussing Nd/Glass laser at the entrance of the microcapillary. Very encouraging results were obtained for CVI 18.2 nm line and the possibilities of generation high GL in the near future are discussed.