Optimizing the Ar-Xe infrared laser on the Naval Research Laboratory's Electra generator

The Ar-Xe infrared laser has been investigated in several series of experiments carried out on the Naval Research Laboratory's Electra generator. Our primary goals were to optimize the efficiency of the laser (within Electra's capabilities) and to gain understanding of the main physical processes underlying the laser's output as a function of controllable parameters such as Xe fraction, power deposition, and gas pressure. We find that the intrinsic efficiency maximizes at ∼3% at a total pressure of 2.5 atm, Xe fraction of 1%, and electron beam power deposition density of 50-100 kW cm-3. We deployed an interferometer to measure the electron density during lasing; the ionization fractions of 10-5-10-4 that it detected well exceed previous theoretical estimates. Some trends in the data as a function of beam power and xenon fraction are not fully understood. The as-yet incomplete picture of Ar-Xe laser physics is likely traceable in large part to significant uncertainties still present in many important rates influencing the atomic and molecular kinetics