Prospects of pulsed high-current dischargein nitrogen-filled-capillary for lasing at 13.4 nm

The recombination pumping scheme requires hot dense plasma with abundance of nuclei of active atoms (nitrogen in our case). Then this plasma has to be efficiently cooled to create at recombination of nuclei to hydrogen-like ions and their de-excitation a population inversion on Balmer-alpha transition. Such conditions can be achieved in a capillary discharge that heats plasma during compression (pinching), and cools it during expansion. The time curve (registered by vacuum photodiode) as well as the spectral composition (registered by McPherson 1 m grazing incidence spectrograph) of axially emitted EUV radiation of the pulse, high-current capillary discharge in nitrogen are investigated. It turned out that despite the pinching time is close to its optimum, the pinching process is not yet efficient enough to heat the plasma to temperature at which an abundance of nitrogen nuclei is created.