These experiments map out the ionization balance present in a recombination x-ray laser plasma as a function of time and space. The plasma is created by irradiating an Al strip target with a 600-ps Nd:glass laser, and is probed by an x-ray backlight at several times as it cools and recombines. The primary diagnostic is an x-ray spectrometer which spatially resolves the He-like to Be-like Kα absorption spectra as a function of distance from the target surface. The experimental results indicate that the plasma ions important to the lasing are observed much farther from the target than expected from simulations. These results are consistent with x-ray gain measurements, and demonstrate the effect of non–local thermal equilibrium cooling on the ionization balance. © 1996 The American Physical Society.

• Received 5 January 1996

DOI:https://doi.org/10.1103/PhysRevE.53.5315