Modeling of Transient Ni-like Ag X-ray Laser

Abstract

Recent high temporal resolution Ni‐like x‐ray laser (XRL) experiments [1] have yielded important insights into the output characteristics of picosecond pumped XRL’s and the shortest XRL pulse was demonstrated. However, important issues were raised that require to enhance our understanding of plasma and population dynamics, namely (a) short pulse duration, (b) XRL pulse occurring before the peak of continuum emission and (c) the role of (over‐)ionization. A numerical study of the Ni‐like transient silver XRL has therefore been undertaken to complement our experimental results. High gain coefficients existing with picosecond lifetimes and restricted in space (∼5 μm FWHM) are predicted, which is consistent with short XRL durations experimentally observed. The simulations suggest that the gain is cut‐off by fast over‐ionization of Ni‐like ions. The late onset of the continuum emission relative to the temporal peak of the XRL output (as observed experimentally) is explained as a signature of a thermal conductivity wave propagating toward the super‐critical density region close to the target surface.