Explosive mechanism of cathode erosion in Trichel pulse negative corona

Summary form only given. Cathode erosion has been investigated in Trichel pulse negative corona discharge in air in point-to-plane electrode configuration on tungsten, copper, graphite and aluminum cathodes. It is found that negative corona causes erosion of the cathode surface in form of nanometer-size craters and fissures. Observed etching may be explained in terms of electro- explosive processes. In Trichel pulse corona current is performed as a consequence of nanosecond pulses due to instability of the cathode sheath. One can assume that erosion process is also performed as a consequence of elementary erosion events. Each event is associated with a single Trichel pulse and causes ejection of erosion fragment from the cathode surface and formation of elementary erosion crater. Current density on the cathode surface equals to relation of Trichel pulse amplitude to erosion crater area and was calculated as 108 A/cm2. The value of integral of specific current action of Trichel pulse which depends on cathode current density and pulse time duration and serves as criterion of electro-explosion was calculated as 109 A2s/cm4. Hence the conclusion has been made that cathode erosion in Trichel pulse negative corona was caused by electro-explosive processes. Formation of micrometer-size craters on the cathode surface is caused by consistent action of discharge at fixed cathode spot. Erosion fissures extend out of such craters due to local heating and thermal tension. On the surface of metal cathodes after treatment oxide nanocrystals were found as result of erosion material redeposition - this recycling demonstrates way of nanoasperities formation for local enhancement of electric field and electro-explosion initiation.