Towards a 38 Å x-ray laser

Space-resolved keV spectroscopy study of neonlike x-ray laser plasmas created with low-level prepulse irradiation

“…This line finally displays the largest gain and becomes the dominant feature in the XUV spectra, as it was predicted in the early days of collisional pumping X-ray lasers;4'9'10 the two principal 3p-3s J =2-1 lines are seen to react very little to the addition of a prepulse. This difference in behavior between the J = 0-1 and J = 2-1 lines, and the fact that they are observed to be emitted at different distances from the target and with different time ri31 suggest that the prepulse changes conditions in the plasma for which the J=O-1 line is more sensitive: direct collisional excitation from the ground state (sensitive to the neon-like population density and the electron temperature)9 and X-ray laser propagation (through the size of the gain region, the density gradients, and the homogeneity of the plasma parameters).12'5 For the most part, studies of prepulsed X-ray lasers has been limited mostly to the phenomenological observation of the lasers performances under different prepulse conditions, and to computer simulations.2'7'15' 16 We present here a quantitative experimental characterization of zinc, copper and nickel X-ray laser plasmas created with prepulsed irradiation. Through a determination of the plasma conditions and their dependence on the prepulse level, we aim to gain a better understanding of the physics involved in the improvement of X-ray lasers using prepulses.…”