Characterization of x-ray lasers at short wavelengths

Experimental measurements of the optimum pulse delay and pulse irradiance ratio for lasing at 7.3 nm in Ni-like samarium are shown to be explained by a simple model. Experimental x-ray laser outputs are also shown to be well fitted with a simple one-dimensional ASE variation of the laser output with increasing target length through saturation. The ASE model is modified to take account of the two lasing lines present in Ni-like lasing and compared to experimental laser output measurements for Ni-like Dy lasing at 5.86 nm and 6.37 nm. The good agreement of experimental data with the ASE model indicates that refraction, non-uniformity of the laser medium and other problems traditionally associated with x-ray lasing are not significant with double pulse pumping.