Characteristics of the Active Element of a Nuclear-Pumped Cadmium-Vapor Laser

The influence of the active-element characteristics on the efficiency of a cadmium-vapor laser pumped by uranium fission fragments was studied experimentally. The 441.6 nm laser radiation of the cadmium ion was studied. An aluminum tube with diameter ~15 mm and an inner coating of U3O8 with thickness 3 mg/cm2 served as the active element. The neutron source was the BARS-6 pulsed, fast, aperiodic, self-extinguishing reactor. A comparison of the efficiency of the laser with similar data previously obtained under the same conditions for a 48 mm in diameter active element with a ~10 mg/cm2 thick uranium metal coating shows that a three-fold reduction of the diameter of the active element and uranium coating thickness results in a 2.5-fold increase of the laser efficiency. This confirms the hypothesis of internal losses of laser radiation in the active element of a fission-fragment pumped laser which are due to the scattering of light by transverse sound waves of the gas density which appear during a pumping pulse because of the radial non-uniformity of the energy input.