Theoretical Basis and Experimental Validation of the Breakdown Induced by Rupture of Dielectric Layer Model

In vacuum (p < 10 -2 Pa) at high dc voltage (>100 kV) and with long gap (>10 -3 m), the Fowler-Nordheim (FN) emission current between metallic anode and cathode has superimposed random bursts which often evolve into breakdown during the voltage conditioning process. Despite the effort made to get a solid understanding of these phenomena, a satisfactory explanation has not been so far attained. A novel approach is here presented based upon the hypothesis that the electrode surface is not an ideal metal but it is instead covered by a dielectric compound layer (oxides mainly). According to the model based on this approach, the process leading to the current burst is associated with electron depletion of the cathode layer due to FN-like emission. When the electric field inside the layer exceeds its dielectric strength, a microbreakdown and a burst of current take place. The equation ruling the current emission has been solved imposing quantum indetermination relations to a solution based on classical theory. It has been found that the bursts can end up into a full breakdown, provided the voltage is high enough to start the avalanche process at the anode.