Li-like Al XI (10.57 and 15.47 nm) x-ray laser gain experiments

Soft x-ray laser gain experiments using Li-like Al XI ions were carried out on the LF-11 (1011 W) laser facility. The single beam of Nd-glass laser was operated at 1.06 μm over an energy range of 17-25 J for a 200 ps pulse. A 100 μm-wide and 12 mm-long focused line was produced by means of a cylindrical-aspherical lens system. The aluminum targets were slabs and exploding foils (60 nm and 94.7 nm thick). The extreme ultraviolet spectra (time-integrated) in a region of 2-32 nm were recorded on kodak SWR film with a 1-m grazing-incidence spectrograph. An x-ray pinhole camera photographed the hot plasma in teh axial direction. Amplified spontaneous emission was obtained for 10.57 nm (3d-5f) and 15.47 nm (3d-4f) transitions of Li-like Al XI ions. The rapid increase of the intensities of the two spectral lines with the target length is very apparent. The gain coefficient of 10.57 nm (3d-5f) was 1.78 cm-1 for the 94.7 nm exploding foil targets. The gain coefficients of 10.57 nm (3d-5f) and 15.47 nm (3d-4f) were 1.67 cm-1 and 0.96 cm-1 for 1.2 μm targets respectively. Those were 3.18 cm-1 and 2.26 cm-1 for 60 nm exploding foil targets respectively. The result confirms that suitable exploding foil targets can create higher gain coefficient