Parametric investigation of the fission-fragment excited helium/argon laser at 1. 79. mu. m

Characteristics of the fission-fragment excited helium/argon laser operating on the 1.79-{mu}m 3{ital d}(1/2){sub 0,1}{sup 0}{minus}4{ital p}(3/2){sub 1,2} argon transition are presented. Laser output occurs for approximately 80% of the 0.9 to 3 ms full width at half maximum thermal neutron pump pulse. Output power efficiency optimizes for a total gas pressure of 760 Torr and argon concentration of 0.3% to 2.0%. Power efficiency was 1.4%{plus minus}0.4% for instantaneous pump rates of 45 to 230 W/cm{sup 3}. The small signal gain and saturation intensity for instantaneous pump rates of 30 to 90 W/cm{sup 3} are 0.55% to 1.05%/cm and 70 to 110 W/cm{sup 2}, respectively. The laser threshold as a function of helium pressure and argon concentration will be presented. The advantages of fission-fragment excitation in predominantly helium gas mixtures will be discussed.