A high power CO laser capable of both CW and Q-switched operation has been constructed. Maximum CW power and efficiency obtained from the device are 20 watts and 9%, respectively. Lasing occurs simultaneously on various wavelengths from 5.0 to 5.7 microns, corresponding to transitions between successive vibrational levels azith

. The laser is a flowing system with N
2and He gas additives. The, discharge tube, 60 inches long and 0.75 inches inside diameter, is cooled to 80°K by immersion in a liquid nitrogen bath.