Time-resolved grating spectroscopy of a N capillary discharge plasma for a recombination pumped x-ray laser

•We study the recombination pumping scheme for x-ray laser in nitrogen.•We used a capillary discharge z-pinch apparatus with current pulse of 60 kA in 60 ns.•We measured time resolved x-ray spectra using transmission grating spectrometer.•We developed a collisional-radiative atomic model to analyze the spectra.•The CR model takes opacity effects under account.

Capillary discharge plasmas can serve for recombination-pumped x-ray lasers. We present time-resolved x-ray spectra and density measurements of a nitrogen capillary discharge z-pinch plasma. We use a free-standing transmission grating spectrometer and a gated MCP camera. This is the first time both K-shell and L-shell line emission of the nitrogen plasma are recorded simultaneously. Comparison of the spectra with a 4-ion collisional-radiative atomic model, which accounts for opacity effects, shows that the plasma reaches a maximum temperature of kTe=75-85 eV during the pinch, and adiabatically cools in less than 4 ns. This is slightly less than the newly estimated goal temperature of 110 eV. The fast cooling demonstrates the feasibility of a recombination-scheme laser in the nitrogen Hα line at 13.37 nm, if higher plasma temperature is achieved.