Review of Ni-like ion X-ray laser research at Lawrence Livermore National Laboratory

Abstract

We have demonstrated saturated output on several nickel-like ion X-ray lasers ranging from niobium to silver by using a psec, high-power, chirped-pulse-amplification, tabletop laser. These results have been achieved at wavelengths from 20.3 to 13.9 nm on the Ni-like 3 d 94 d 1 S 0→3 d 94 p 1 P 1 laser line using a total of 5 to 7 J of energy in a traveling wave excitation scheme. Strong amplification is also observed for Ni-like Sn at 11.9 nm. Gain of 41 cm −1, gain-length product of 18, and output energy of 12 μJ are measured for the Ni-like Pd line at 14.7 nm. For Ni-like Mo, experiments are done using multilayer mirrors to obtain two-dimensional images of the output aperture of the laser and to measure the total laser energy as a function of various parameters such as the delay between the short and long pulses and the energy of the two pulses. For Mo we measure an output energy of 2 μJ and a gain-length product of 16.6. To model the Mo experiments, the LASNEX code is used to calculate the hydrodynamic evolution of the plasma and provide the temperatures and densities to the XRASER code, which then does the kinetics calculations to determine the gain. The temporal and spatial evolution of the plasma is studied both with and without radiation transport included for the 4 f and 4 p→3 d Ni-like Mo resonance lines. High gains are predicted and observed for both the 3 d 94 d 1 S 0→3 d 94 p 1 P 1 laser line at 18.9 nm and the 3 d 94 f 1 P 1→3 d 94 d 1 P 1 photopumped line at 22.6 nm.