The influence of secondary avalanches on the development of the cathode-directed streamer

Abstract

Investigations have been made, with an electro-optical streak camera, of the low-current phases of gas discharges (3 cm gap, uniform electric field, and medium over-voltages of some 10% above the DC breakdown voltage). In N₂-CH₄ mixtures (pressure about 100 Torr) the gas discharge develops under these conditions according to the streamer mechanism. Interest was concentrated on the effect of secondary avalanches following the primary avalanche to see if they are necessary for the development of the cathode-directed streamer. It is shown that the cathode-directed streamer can start unsupported by successors. Further, it is demonstrated that an artificial successor very high carrier number accelerates the development.