Spatial position of prepulse inducedJ=0→1, 3p-3slasing in low-Zneonlike ions

We report a spatially resolved investigation of lasing on the 3p${\mathrm{}}^1$ ${\mathit{S}}_0$–3s${\mathrm{}}^1$ ${\mathit{P}}_1$ transition in neonlike ions ranging from titanium (Z=22) to germanium (Z=32). Slab targets were irradiated by the Asterix IV iodine laser at an intensity of about 2.0×${10}^{13}$ W/${\mathrm{cm}}^{\mathrm{-}2}$ with a prepulse 5.23 ns before the main pulse. The lasing position was measured as a function of the prepulse energy and the atomic number. It was found that with higher Z, the lasing occurs closer to the target surface and a larger prepulse brings the lasing farther away from the target. A 15% prepulse was found to be favorable for low-Z elements (such as titanium), while a 1.5% prepulse was found to be favorable for elements with Z higher than 26. A simple model taking into account the self-similar expansion of the plasma produced by the prepulse was found to agree qualitatively with the experimental results.