NUCLEAR-PUMPED HE-3-AR LASER MODELING

Theoretical models of nuclear-pumped lasers are of interest for the purpose of system optimization and identification of new and more efficient nuclear-pumped laser systems. A first-order model of the 3He-Ar 1.79-μm laser is developed, compared to experimental results, and used to explain the qualitative features of this system. The results indicate that direct excitation of the argon upper level is at best very inefficient for population inversion. For argon concentrations which give the most efficient laser operation, the 3He(n,p)3H energy is used to produce atomic helium ions that quickly convert into helium molecular ions. These molecular ions subsequently form argon atomic ions through charge transfer. The dominant pumping mechanism is collisional-radiative recombination of the argon atomic ion and subsequent radiative cascading into the upper laser level. The formation of argon molecular ions is in competition with argon atomic ion recombination; this combined with the dissociative recombination of argon molecular ions into the lower laser level terminates laser action for argon concentrations above 20%.