Gas breakdown by a focused beam of CW THz radiation

This paper presents the results of experimental and theoretical investigations of gas breakdown thresholds in a focused beam of CW THz radiation. During the experiments the source of radiation was CW 1 kW @ 0.263 THz gyrotron. The beam was focused by means of quasi-optical mirrors into the spot with diameter less than 3 mm that provided intensity into the focal spot up to 15kW/cm
²
. The working gas was argon. Achieved electrical field intensity was enough to carry out the gas breakdown into the range of pressure values of 10-300 Torr. The boundary values of field intensity for discharge existence were measured. The results of experiments are in good agreement with theoretical calculations that were made based on a simple breakdown theory of monatomic non-light gases in fields of any frequency.