Towards Recombination Pumped H-Like N X-Ray Laser

The recombination pumping scheme for soft X-Ray lasers has better energy scaling, in comparison to the collisional pumping scheme. Implementation of an H-like $3\to 2$ Nitrogen recombination laser, at $\lambda \sim $13.4 nm requires initial conditions of 50{\%} fully stripped Nitrogen, Te$\sim $140eV and N$_{e}\sim $10$^{20}$cm$^{-3}$. The cooling period to below 60eV should be faster than the typical three-body recombination time. Here we study the possibility to achieve the required plasma conditions using a capillary discharge Z-Pinch apparatus. The experimental setup includes a 90mm long ceramic capillary with an inner diameter of 5mm, coupled to a pulsed power generator supplying a peak current of $\sim $60 kA, with a quarter-period of 60 ns. We used various diagnostics techniques to measure the plasma dynamics including X-Ray diodes, time-integrated spectrometry and time-resolved pin-hole imaging (using a framing MCP camera). Analysis of the results shows a rapid cooling period to a temperature below 60eV, demonstrating the feasibility of recombination-pumped capillary discharge lasers.