Gas Lasers (Used for Light Propagation Studies, Light Scattering Experiments, Photo-Elastic Stress Analysis, Optical Communications, Longpath Interferometry, Magnetic and Electric Field Studies, Plasma Diagnostics, Optical Testing and Alignment, Precision Ranging and Velocity Determinations, Optical Data Processing, Spectroscopy, Micro-Heating, Coherent-Light Photography, and the Like) and Discharge Exciters Therefor