SOFT-X-RAY AMPLIFICATION IN LITHIUM-LIKE SILICON IONS

Results of our recent experiments on measurement of the recombination-pumped soft x-ray laser gain of Li-like silicon ions are described. The spectra from line-focused laser plasmas on slab silicon targets in the 5-12 nm region are taken with an 1 m non-astigmatic grazing incidence grating spectrograph. The gain coefficients of Si11 + 5f - 3d (8.89 nm) and 5d-3p (8.73 nm) transitions, deduced from the ratio of on-axis to off-axis time-integrated intensities are 1.4 cm-1 and 0.9 cm-1 respectively. The corresponding gain coefficients deduced from the on-axis intensity as a function of the length of the line-focused laser plasma are 1. 5 cm-1 and 1.4 cm-1, respectively.