Repetition rate of streamers as a measure of content of electronegative additives in the air

Abstract

This paper demonstrates that the positive streamer corona may be useful for the detection of electronegative impurities in gas (ambient air). The measurements of the repetition rate of streamers are carried out in a point-to-coaxial cylinder gap where DC voltage and AC voltage at a frequency of up to some kilohertz (the so-called `mixed voltage') are applied simultaneously. The repetition rate of streamers is investigated depending on the airflow rate, on the amplitude and frequency of the AC voltage, on the level of gas preionization and on the amount of moisture and impurities of different kinds in air. Results presented in the form of counting-rate characteristics of streamers show that under the action of halogens the detectable changes in characteristics take place if the halogen concentration exceeds 1 - 10 ppb. Principles of operation of the proposed detector and possible basic physical mechanisms of the influence of impurities on the counting response are discussed. It has been demonstrated that a simple statistical model for the inception of streamers under the conditions of a mixed voltage enables calculation of the counting-rate characteristics of streamers in satisfactory agreement with the experimental results.