Li-LIKE Al XI (10.57 AND 15.47nm)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 1.06μm over an energy range of 17-25J for a 200ps pulse. A 100μm-wide and 12mm-long focused line was produced by means of a cylindrical-aspherical lens system. The aluminum targets were slabs and exploding foils (60nm and 94.7nm thick). The extreme ultraviolet spectra (time-integrated) in a region of 2-32nm were recorded on kodak SWR film with a 1-m grazing-incidence spectrograph. An x-ray pinhole camera photographed the hot plasma in the axial direction. Amplified spontaneous emission was obtained for 10.57nm (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 10.57nm (3d-5f)was 1.78cm^-1 for the 94.7nm exploding foil targets. The gain coefficients of 10.57nm (3d-5f)and 15.47nm(3d-4f) were 1.67cm^-1 and 0.96cm^-1 for 1.2μm targets respectively. Those were 3.18cm^-1 and 2.26cm^-1 for 60nm exploding foil targets respectively. The result confirms that suitable exploding foil targets can create higher gain coefficient.