Proceedings Article | 21 February 2008
Steven Davis, Seonkyung Lee, David Oakes, Julie Haney, John Magill, Dwane Paulsen, Paul Cataldi, Kristin Galbally-Kinney, Danthu Vu, Jan Polex, William Kessler, Wilson Rawlins
Proc. SPIE. 6874, High Energy/Average Power Lasers and Intense Beam Applications II
KEYWORDS: Mirrors, Resonators, Diagnostics, Oxygen, Throat, NOx, Microwave radiation, Information operations, Temperature metrology, Absorption
Scaling of EOIL systems to higher powers requires extension of electric discharge powers into the kW range and
beyond with high efficiency and singlet oxygen yield. We have previously demonstrated a high-power microwave
discharge approach capable of generating singlet oxygen yields of ~25% at ~50 torr pressure and 1 kW power. This
paper describes the implementation of this method in a supersonic flow reactor designed for systematic investigations of
the scaling of gain and lasing with power and flow conditions. The 2450 MHz microwave discharge, 1 to 5 kW, is
confined near the flow axis by a swirl flow. The discharge effluent, containing active species including O<sub>2</sub>(a<sup>1</sup>Δ<sub>g</sub>, b<sup>1</sup>Σ<sub>g</sub><sup>+</sup>),
O(<sup>3</sup>P), and O<sub>3</sub>, passes through a 2-D flow duct equipped with a supersonic nozzle and cavity. I2 is injected upstream of
the supersonic nozzle. The apparatus is water-cooled, and is modular to permit a variety of inlet, nozzle, and optical
configurations. A comprehensive suite of optical emission and absorption diagnostics is used to monitor the absolute
concentrations of O<sub>2</sub>(a), O<sub>2</sub>(b), O(<sup>3</sup>P), O<sub>3</sub>, I<sub>2</sub>, I(<sup>2</sup>P<sub>3/2</sub>), I(<sup>2</sup>P<sub>1/2</sub>), small-signal gain, and temperature in both the subsonic and
supersonic flow streams. We discuss initial measurements of singlet oxygen and I* excitation kinetics at 1 kW power.
