Indication of recombination-pumped population inversion in O VI and Li III ions using an ablative capillary discharge

摘要

Abstract: In order to investigate the possibility of recombination - pumped lasing in the extreme ultraviolet (XUV) spectral range a fast ablative capillary discharge has been developed. Discharge currents of up to 15 kA with minimum rise-times of 20 ns could be achieved using Li$-2$/CO$-3$/ and SiO$-2$/ capillaries with diameters ranging from 1 mm to 2 mm and lengths ranging from 1 cm to 5 cm. Time-integrated as well as temporally and spatially resolved spectroscopic measurements have been performed. Using a Li$-2$/CO$-3$/ capillary (diameter: 2 mm, length: 5 cm) the Li III (2 $IMP 3) 729 angstrom line showed a significant increase of intensity during the cooling phase of the discharge while its spatial divergence was found to be decreasing. Indication of gain on the O VI (3d $IMP 4f) 520 angstrom transition could be obtained by varying the length of a SiO$-2$/ capillary (radius: 0.5 mm) from 3 cm to 5 cm. !10