Population kinetics of laser levels of neodymium ions in POCl3 — SnCl4 —235UO22+ — Nd3+ excited by fission fragments

The population kinetics of laser levels of neodymium ions in the uranium-containing POCl₃ — SnCl₄ — ²³⁵UO₂²⁺ — Nd³⁺ laser liquid irradiated in a BARS-6 pulsed reactor is studied experimentally and theoretically. The relations between the populations of the upper and lower laser levels are studied at different time moments with respect to the pump pulse. An inverse population of laser levels is observed and found to be directly proportional to the pump power. The efficiency of pumping of the upper laser level of neodymium ions in the laser medium by uranium fission fragments is determined, and quantitative information is obtained on the inverse population, gain, and their dependences on the pump power.