The Nitrogen Ion Laser

The characterization and thermal scaling of the nitrogen ion laser pumped by charge transfer from He3 is reported in this work. Intense laser emission in the violet at 427 nm has been observed and found to have a linewidth less than 0.3 A. The pumping ions, He2 and He3, were produced by discharge of a fast-pulsed electron beam gun, APEX-1, into several atmospheres of a mixture of helium and nitrogen. Excitation current densities ranged from 1.1 to 2.5 KAsq cm at 1 MV over a 1 x 10 cm transverse geometry. Under these conditions, the efficiency of the emission of 427 nm laser radiation was found to be proportional to the total pressure raised to the 1.2 power. Efficiencies of 1.6 relative to the energy lost by the electron beam in the radiating volume have been achieved in volumes of 16 cc at room temperature. Outputs of 35 mJ have been obtained from the 16 cc working volume at 30 atm pressure under these conditions. Thermal scaling of the laser has been investigated and a strong inverse dependence of laser output on gas temperature was observed.