STUDIES OF CW LASER GAS HEATING BY SUSTAINED PLASMAS IN FLOWING ARGON.

This paper reports the results of an in-depth study of laser-sustained plasmas in flowing argon for application to laser propulsion. The experiments were performed in a pressurized absorption chamber using a 10 kW CO//2 laser. Global absorption measurements have been carried out under a range of laser power, pressure, and flow rate, indicating total absorption near 80%. Thermocouples have been used to map gas temperatures in the downstream mixing zone. These mappings were used to estimate thermal conversion efficiencies. Thermal efficiency ranges from 6% to 25% depending on pressure, flow rate, and laser power. The above thermal efficiencies imply radiative losses above thermal efficiencies imply radiative losses of 64% and 30%, respectively. Spectroscopic relative-intensity surveys of the plasma core indicate peak plasma temperatures of 17,000 K. Finally, an infrared imaging system has been used to study the effects of laser power and flow conditions on the size and location of the plasma.