Recombination and collisional x-ray lasers at LULI

We present our recent efforts to produce X-ray lasers in the 200 angstroms range by using the moderate power drive of the LULI facility in Palaiseau. The 4 - 5 transitions of Li-like sulfur exhibit large gain-length products in recombining plasmas, and appear to be less sensitive to plasma non-uniformity than the 3 - 4 and 3 - 5 transitions previously studied. From numerical simulations this is likely due to smaller radiative and collisional excitation from 4f than from 3d levels. In collisional scheme, neon-like zinc gives analogous results to similar works on other elements for the 3p - 3s, J equals 2 yields 1 transitions, but the J equals 0 yields 1 transition shows a surprisingly large gain coefficient of 4.9 cm-1. From a detailed comparison of time-dependent intensities of the J equals 0 yields 1 and the J equals 2 yields 1 lines, we conclude that transitions from J equals 0 and from J equals 2 are not emitted in the same region of the plasma.