Temporally and spatially resolved investigation of the J = 0–1 and J = 2–1, 3p–3s laser emissions in neonlike germanium

We report a time- and space-resolved investigation of the J = 0–1 and J = 2–1 lasers in neonlike germanium at 19.6, 23.2, and 23.6 nm. Germanium slabs were irradiated by the Asterix IV iodine laser at an intensity of approximately 2.0 × 1013 W cm−2 without and with a prepulse, which was 5.23 ns before the main pulse. The position of the lasing region was measured as a function of the prepulse intensity. It was found that lasing on the J = 0–1 transition at 19.6 nm occurs earlier in time and closer to the target surface than on the two J = 2–1 transisitions at 23.2 and 23.6 nm. The position for the 23.6-nm laser is the farthest from the target surface. A larger prepulse shifted all lasers farther from the target surface. Numerical simulations showed good qualitative agreement with experimental results when a prepulse was applied. For the case without a prepulse, calculations indicated the importance of beam refraction in modifying the effective gain of the soft-x-ray laser beam.