Area effect on electric breakdown of copper and stainless steel electrodes in vacuum

The breakdown field strength E/sub b/(= alpha Vb/d) of gaps made with pure copper and stainless steel depends on the effective area S/sub eff/. It can be expressed by the single experimental equation E/sub b/=K/sub 1/S/sub eff//sup -n/, where K/sub 1/ is a constant, n is about 0.24, S/sub eff/ is the electrode area subjected to more than 90% of maximum field strength, alpha is the shape factor, d is the gap length, and V/sub b/ is the breakdown voltage. The field intensification factor beta /sub l/ obtained through the measurement of prebreakdown current can be expressed by a single experimental equation beta /sub l/=K/sub 2/S/sub eff/n, where K/sub 2/ is a constant. This means that the area of effect of E/sub b/ is represented by the area effect of beta /sub l/ and that the vacuum breakdown may be initiated by field emission.>