Microwave resonant-cavity-produced air discharges

Air discharges produced in an Asmussen microwave cavity (0-300 W, 2.45 GHz, CW) between 0.5 and 100 torr were investigated. Gas temperatures (1000-2500 K) were estimated from rotational temperatures obtained from optical emission spectroscopy (OES). These agreed with a simple model of the heat transfer of the gas where joule heating was included as the source term. Vibrational temperatures (3700-7300 K) were also determined from OES and followed the electron energy trends. Electron density (10¹¹-10¹³ cm^-3), collisional frequency (10¹¹-10¹² s^-1), and plasma conductivity (0.09-0.3 (Ω-m)^-1) were calculated from a self-consistent electromagnetic model of the cavity where the plasma was assumed to be a lossy dielectric. Absorbed power, electric, and optical probe measurements were used as the input parameters to the model