The Influence of Preparatory Furnacing of Electrodes on Vacuum Breakdown

The relative importance of prefiring of copper electrodes in hydrogen or vacuum, as well as that of varying their area, on the determination of the vacuum insulation strength has been investigated using the factorial design technique of experimentation. In the gap range from 0.5 to 3.0 cm, at 6×10-7 Pa, control of this prefiring process led to results with an extremely high degree of confidence during the early conditioning stages of the stress history. Early effects of anode prefiring in vacuum were detrimental but rapidly conditioned out, while the influence continued to persist in cooperation with the influence of electrode area. The preparatory procedure was chosen to approximate that employed in the furnace brazing of electrode sub-assemblies. A complete set of factorial influences and interactions is presented to assist in the resolution of conflicting test experiences on tubes fabricated in these different ways.