An Energy Explanation of the Area Effect in Electrical Breakdown in Vacuum

The mechanism of the so called "area effect" in vacuum dis charge studies was investigated. Point-plane aluminum electrodes were used with point radius 1.5 mm and gaps between 0.5 and 10 mm. It was found that a capacitor connected in parallel with an electrode gap reduces the electrical strength in a manner similar to that observed with increasing electrode area. The capacitance was found to play two major roles. On one hand, the larger stored energy associated with a larger capacitance promoted greater cathode damage. As a result, subsequent voltage breakdowns occurred at lower voltage levels. On the other hand, when addi tional stored energy was placed within 15 cm of a discharge site, the initial voltage application resulted in a breakdown voltage less than that observed in the absence of the capacitor during a comparable test. The results presented here advocate an energy based explanation of the area effect rather than a probabilistic weak link theory.