EXPERIMENTAL STUDIES ON SOFT X-RAY LASER GAIN

Soft X-ray laser gain experiments were successfully carried out to test recombination pumping scheme at the 6-beam laser facility and the LF12 laser facility of Shanghai Institute of Optics and Fine Mechanics, Academia Sinica. Amplifications of soft X-ray spontaneous emission （ASE） have been observed in Li-likealuminium and silicon ions in plasmas produced by irradiation of slab targets with line-focused lasers. Time-integrated intensities of the Li-like aluminum and silicon ion spectral lines emitted along the axis of the plasma show that the intensities of the spectral lines for Al10+ 5f—3d （105.7） and Si11++5f—3d （88.9） and 5d—3p （87.3） transitions increase nonlinearly with plasma lengths, and the corresponding gain coefficients are 3.1±0.9, 1.5±0.5, and 1.4±0.5cm-1, respectively, the maximum gain-length product being about 2.5. These results were obtained at much lower intensity of driving laser, 1.5—2.0×1012W/cm2.