Population Inversion in Laser-Initiated Vacuum Arcs.

A detailed study of resonant photo-excitation of CII ions in a vacuum arc discharge by line radiation from laser produced, AlIII ions was completed. Although enhanced fluorescence by up to a factor of eight in CII at 2138 A was observed, the collisional-radiative kinetics are such as to prevent a population inversion from building up under the conditions of the experiments. This unfavorable conclusion prompted the identification of a new class of Be-like, photo-excited lasers with potential laser wave-lengths from 2177 A in CIII down to 230 A in MgIX. Design considerations for such lasers are presented. Initial experiments in CIII pumped by MnVI line radiation have shown fluorescence enhancements in CIII at 2177 A by up to a factor of 150. Optimization of the pump plasma geometry has increased this enhancement to a factor of 500. Gain estimates are given which suggest that a laser can be constructed at 2177 A. Originator supplied keywords include Short wavelength lasers, X-ray lasers, Vacuum arcs, Laser plasmas.