Space-charge and breakdown in artificial tree channels

Auckland et al (1974) were among the first to consider that the electric strength of an electrical tree channel could be high; indeed comparable to that of the surrounding solid dielectric. Their results showed that the electric strength of air in a confined channel increased as the channel diameter decreased below 200 μm. These observations were explained in terms of the avalanche theory in which the diffusion of electrons as the avalanche advances produces a conically shaped volume of negative charge with its apex at the cathode. For long or narrow channels, the head of the avalanche comes into contact with the channel walls. The role of trapped charge was conjecture on the part of Auckland et al. The authors correct this deficiency and investigate the part played by the trapped charge in the process of tree growth