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 2.1 kW. The reduced electric field in the dc sustainer discharge ranges from 0.6 × 10 −16 to 1.2 × 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 Δ → X 3 Σ) infrared emission spectra calibrated using a blackbody source. The yield increases with the discharge power and remains nearly independent of the O 2 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 20 s, 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.