Improved electrical insulation of vacuum gaps utilizing SiOx coatings

Thin film coatings have been applied to metal electrodes in a vacuum insulation system to increase the breakdown voltage. Through careful cleaning and polishing of uncoated stainless steel electrodes, a breakdown field of >50MV/m was obtained with a uniform field over a 1cm/sup 2/ cathode area. When coated with 2 /spl mu/m of SiO/sub x/, the field emission current was reduced by up to at least three orders of magnitude and the breakdown field was increased to >100MV/m in every case. Recent improvements in the cleaning procedure of the metal surface have resulted in an increase of the breakdown strength to more than 140MV/m which is the largest field known to have been measured over a large area cathode.