1 Scaling of an Electric Discharge Excited Oxygen-Iodine Laser1

Electric discharge excited oxygen-iodine laser apparatus has been successfully scaled to increase the electric discharge volume and power, the laser mixture flow rate, and the gain path in the M=3 laser cavity. Singlet delta oxygen (SDO) generator discharge power has been increased up to at least 4.5 kW, laser mixture flow rate up to approximately 0.5 mole/sec, and gain path up to 10 cm. The steady-state run time of the new scaled-up laser apparatus at these conditions is up to 10 sec. Two different discharge configurations have been used to generate singlet delta oxygen, crossed nanosecond pulser / transverse DC sustainer discharge and capacitively coupled transverse RF discharge. Flow temperature downstream of the discharge, singlet delta oxygen yield, and laser gain have been measured in a wide range of discharge powers, nitric oxide mole fractions in the main oxygen-helium flow, and oxygen percentage in the mixture, at discharge pressures ranging from 60 to 86 torr. The results demonstrate that SDO yield increases with the discharge power for both discharge configurations, although highest yields achieved so far remain rather low, 3.6-3.7%, due to fairly low energy loading per oxygen molecule in the discharge. Small signal gain measured in the M=3 cavity of the new laser apparatus is up to 0.116%/cm (2.3 % gain per double pass), at the flow temperature of T=125 K. Laser gain remains steady during operation and decreases along the cavity, although the flo