A high-power closed-cycle 1 kHz transversely excited atmospheric (TEA) CO/sub 2/ laser with an efficient catalytic CO/sub 2/ regenerator was used to investigate the variations of the average laser output power and the concentrations of the CO/sub 2/, CO, and O/sub 2/ molecules in the laser gas mixture with the operational performance of the CO/sub 2/ regenerator. It was experimentally shown that for the laser gas mixture of CO/sub 2/-N/sub 2/-He=15-15-70% and the output coupler reflectivity of 70%, eta of 0.1 was required to maintain the laser output power greater than 90% of the initial laser output power of 570 W at an input energy density and a clearing ratio of 150 J/L and 3.0, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>