The effect of a dielectric electrode coating on discharge inception in a gaseous void of small volume

The author investigated features of the initiation of a discharge in a gaseous void of small volume, and the influence of a dielectric covering one of the surfaces enclosing a gaseous void on this phenomena. The solid dielectric specimens used were made of: (1) synthetic foil (polyethyleneterephtalate) with a thickness of 20 mu m and surface resistivity rho =10/sup 12/ Omega ; (2) transformer paper with a thickness of 100 mu m and rho =10/sup 10/ Omega ; and (3) transformer-oil-impregnated paper with a thickness of 100 mu m and rho =10/sup 8/ Omega . The use of the dielectric with the higher surface resistivity resulted in an increase of the time lag. A positive-polarity charge on the dielectric surfaces was found to considerably reduce the discharge time lag. The results show that the mechanism of discharge inception in small gas cavities is still not clear. The test results support the hypothesis that in this case the effect of a dielectric electrode coating on the discharge-inception mechanism is decisive. It is further evident that the void-enclosing surface is responsible for the emission intensity of the electrons in the rest time range from 1 to 100 s.<>