Design and operation of a supersonic flow cavity for a non-self-sustained electric discharge pumped oxygen-iodine laser

The paper presents results of a high-pressure, non-self-sustained crossed discharge -M =3 supersonic laser cavity operation. A stable and diffuse pulser-sustainer discharge in O-2-He flows is generated at pressures of up to P-0=120 Torr and discharge powers of up to 2.1kW. The reduced electric field in the dc sustainer discharge ranges from 0.6 x 10(-16) to 1.2 x 10(-16) V cm(2). Singlet delta oxygen (SDO) yield in the discharge, up to 5.0-5.7% at the flow temperatures of 400-420 K, was inferred from the integrated intensity of the ( 0,0) band of the O-2 (a(1)Delta -> X-3 Sigma) infrared emission spectra calibrated using a blackbody source. The yield increases with the discharge power and remains nearly independent of the O2 fraction in the mixture ( in the 10 - 20% range). Static pressure and temperature measurements in the supersonic cavity show that a steady-state M = 3 flow in the cavity can be sustained for up to 20s, at the flow temperature of T = 120 +/- 15 K. The results suggest that the measured SDO yield exceeds the threshold yield at the cavity temperature by up to a factor of 2.5. PLIF iodine vapour visualization in the supersonic cavity, which showed the presence of large-scale structures, suggests the need to improve iodine vapour mixing with the main oxygen - helium flow.