Theoretical Basis and Experimental Validation of the BIRD Model

At high de voltage (>100 kV) and with long gap (>10
^-3
m) (p<;10
^-2
Pa), the current flowing in vacuum between metallic electrodes follows the Fowler-Nordheim (FN) emission, with superimposed random bursts during the conditioning processes, eventually ending in a breakdown. Despite the effort made to get a solid understanding of these phenomena, satisfactory explanation hasn't been so far attained. A novel approach is here presented, based upon the hypothesis that the electrode surface is not an ideal metal but instead it is covered by a dielectric compound layer (oxides mainly). According to the model the process leading to the current burst is associated to electron depletion of the cathode layer, due to FN-like emission. Under certain conditions, the electric field inside the layer exceeds its dielectric strength, producing a micro-breakdown and a burst of current. The evaluation of the FN-like current has been set and solved imposing quantum indetermination relations to a solution based on classical theory. The burst can therefore end up into a full breakdown, provided the voltage is high enough to start avalanche process at the anode.