Electrical breakdown strength of oxygen-free copper electrodes under surface and bulk treatment conditions

The effects of heating electrodes, and diamond turning of these electrode surfaces to a mirror finish upon an electrical breakdown in a vacuum were investigated. The electrode material used was oxygen-free copper. It was found that the mirror finish obtained by diamond turning reduces the number of repetitive breakdowns to achieve higher hold-off voltages, (conditioning of the vacuum gaps by repetitive breakdowns). Heating the electrodes was effective in improving the breakdown strength after the conditioning process. A higher heating temperature produced a higher breakdown field. A breakdown field of about 250 MV/m was obtained for electrodes heated at 700 degrees C in a vacuum and then finished by diamond fuming. it has been concluded that an improvement in the breakdown field by heating is due to a reduction of the gas contents rather than recrystallization. Copyright (C) 1996 Elsevier Science Ltd.