Ar-Xe laser experiments on the Electra rep-rated electron beam generator

Summary form only given. The Electra pulsed-power system at NRL has been used to demonstrate short burst, repetitively pulsed lasing in the 1.73 /spl mu/m line of Xe (5d[3/2]/sub 1//spl rarr/6p[5/2]/sub 2/) at 1 to 5 Hz, attaining an average power of /spl sim/13 W in the latter case. The gas cell was filled with an Ar/Xe mixture, bounded by windows (aperture 30/spl times/30 cm/sup 2/), and configured as a plano-parallel oscillator with a gold mirror and a 7% reflective quartz output coupler. The cell was pumped from one side by an electron beam of 500 kV, 100 kA, and 30/spl times/100 cm/sup 2/ area. Since it is known that high electron densities quench the lasing, various stainless steel mesh screens were installed as anodes on the vacuum diode side of the hibachi to reduce the beam current density. In addition to the rep-rate experiments, single shots were analyzed over a range in Ar pressure of 1.5 to 2.5 atm, a Xe concentration of 0.25% to 2.8%, and an average beam power deposition of /spl sim/40 to /spl sim/700 kW/cm/sup 3/. Diagnostics included a 33/spl times/33 cm/sup 2/ calorimeter to measure the total laser yield, filtered photodiodes to record the lasing temporal profile, a pressure transducer to estimate the beam deposition energy, and visible interferometry to determine the electron density. The maximum observed laser yield in a single pulse was /spl sim/7 J at 2.5 atm, 1% Xe, and /spl sim/230 kW/cm/sup 3/, while the highest intrinsic efficiency was /spl sim/0.9% at /spl sim/40 kW/cm/sup 3/. Improved window transmission and a more reflective output coupler should double the efficiency. At higher power depositions lasing occurred up to 600 ns after the 140 ns long (FWHM) electron beam pulse. Implications for the important kinetic processes in the afterglow leading to lasing will be discussed based on the time dependent response of the 1.73 /spl mu/m lasing line and the measured decay of the electron density.