Nitrogen capillary discharge emission in the wavelength range 1.9 - 2.5 nm

Summary form only given. Pinching capillary discharge in nitrogen is investigated for the purpose of laser recombination pumping. An apparatus, previously realized for argon capillary laser, was used to understand details of pinching mechanism and emission characteristics. The experiments were done with alumina capillary (297 mm long, inner diameter 3.2 mm) filled by nitrogen (pressure 0.1-10 torr). The current profile had the form of dumped sinus (peak value ~21 kA, quasi-period ~260 ns, dumped time ~500 ns). Time dependences of emitted radiation intensities were recorded in the wavelength range (1.9-2.5 nm) determined by the transmission of the 1 mum thick nickel foil. Computer modelling consisted of three steps. Spatial and time dependences of plasma electron density, electron and ion temperatures were evaluated using the code NPINCH. The kinetic code FLY was used as a post-processor. Time dependences of ionisation fractions and energy level populations of helium- and hydrogen-like nitrogen ions on the capillary axis were evaluated. Instantaneous emission spectra were determined separately for helium- and hydrogen-like nitrogen ions using the subprogram FLYSPEC. The pressure dependences of emission delays and amplitudes measured and calculated were compared and a good agreement was achieved. Calculated inversion population on Balmer alpha transition (~13.4 nm) of hydrogen-like nitrogen ions is very low to be measured. To get measurable gain it is necessary either to increase the value of current amplitude or to decrease the quasi-period of the current pulse