The repetition rate of streamers of a positive corona depends strongly on the concentration of electronegative trace gases in the air. On the basis of this dependence, one can build a simple and cheap detector of trace, gases-a streamer counter. However, the earlier models of the counter are unable to distinguish the strongly electronegative trace gases from additional H2O or CO2 in air. In the present paper, the operation principle of the streamer counter is analysed and a new model of detector together with the method of data processing is elaborated. As a principal technical innovation in the new model of the detector, several discharge gaps are operated simultaneously. These discharge gaps (detector channels) differ from each other in the diameter of the hemispherically capped point electrode. Another technical improvement is the online measurement and processing of data. It is shown experimentally that the relative increase in the formation probability of a streamer with an increase in the concentration of an electronegative admixture is different for different channels as well as for different admixtures. Using these differences, it is possible to distinguish between different admixtures. If the admixture is identified, the evaluation of its concentration is possible from the measured formation probability of a streamer.
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