Features of a Supersonic Ionization Wave in Argon at Atmospheric Pressure in a Sub-Threshold Microwave Field

• Published in: Plasma physics reports Vol. 46; no. 12; pp. 1220 - 1226
• Main Authors: Artem’ev, K. V., Batanov, G. M., Berezhetskaya, N. K., Borzosekov, V. D., Davydov, A. M., Kolik, L. V., Konchekov, E. M., Kossyi, I. A., Moryakov, I. V., Petrov, A. E., Sarksyan, K. A., Stepakhin, V. D., Kharchev, N. K.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2020
• Subjects: Atomic; Low-Temperature Plasma; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; subthreshold microwave discharge; gyrotron; self-non-self-sustained discharge; gas discharge
• ISSN: 1063-780X; 1562-6938
• DOI: 10.1134/S1063780X20120016

In the subthreshold microwave discharge (the wavelength of 4 mm) in argon at the pressure of 750 Torr at intensities of the wave beam from 3 to 7.8 kW/cm 2 , the velocity of the ionization front, measured from the phase change of the reflected wave, increases approximately as the intensity on the wave beam axis in the power of 3/2 from 0.5 × 10 5 to 2.9 × 10 5 cm/s. This velocity of the discharge front in argon is 20–30 times higher than the velocity of the discharge front in air at the same intensities in the microwave beam. The glow structure of the discharge at intensities higher than 3 kW/cm 2 is similar to the glow structure in molecular gases. An even finer structure of the discharge is observed at glow intensities on the wave beam axis below 3 kW/cm 2 . The gas temperature in the discharge at radiation intensity of 6 kW/cm 2 is 6 kK. It is concluded that the volume of high-temperature regions in the discharge is 0.01 of the volume of the discharge region. The problem of the mechanism of the argon ionization and the possibility of the development of ionization-overheating instability in a non-self-sustained microwave discharge in the UV halo of the discharge front are discussed.