Parameters of a Subthreshold Microwave Discharge in Air and Carbon Dioxide as a Function of Microwave Field at Different Gas Pressures

Propagation velocity of a subthreshold microwave discharge in air and carbon dioxide is measured at various gas pressures and intensities of microwave radiation. At air pressures of 200, 390, and 738 Torr and carbon dioxide pressures of 390 and 750 Torr, the propagation velocity of the head part of the self-non-self-sustained discharge closely follows a quadratic power law as a function of microwave-beam intensity in the range from 4 to 16 kW/cm2, while decreasing directly proportional to the initial gas density. In the process, the discharge propagation velocities in carbon dioxide are twice lower that those in air at equal intensities of the microwave radiation. The temperature in the head part of the discharge in air reaches 3.5–5.5 kK, while that in carbon dioxide reaches 9–15 kK.