Recombination and collisional X-ray lasers at Luli

We present our recent efforts to produce X-ray lasers in the 200 A range by using the moderate power driver of the LULl facilityin Palaiseau. The 4-5 transitionsofLi-like sulfur exhibit large gain-length products in recombining plasmas, and appear to be lesssensitive to plasma non-uniformity than the 3-4 and 3-5 transitions previously studied. From numerical simulations this is likelydue to smaller radiative and collisional excitation from 4f than from 3d levels. In collisional scheme, neon-like zinc givesanalogous results to similar works on other elements for the 3p-3s, J =2-1 transitions, but the J = 0-1 transition shows asurprisingly large gain coefficient of4.9 cm. From a detailed comparison of time-dependent intensities of the J =0-1 and theJ = 2 ± I lines, we conclude that transitions from J=O and from J=2 are not emitted in the same region of the plasma.