Electrostatic insulation of a high-voltage gap

The self-electric field of an intense relativistic electron beam with a current in the kA range can be of the order of >or=1 MV/cm. When such an electron beam traverses a high-voltage (HV) gap, the self-electric field modifies the equipotential lines at the gap in such a way that the voltage gradient on the negatively charged electrode is reduced. This effect eliminates emission of secondary electrons and prevents conditions necessary for breakdown to occur. Theory and experiments showed that a voltage of 3 MV can be applied on a HV gap of 2 cm length, without breakdown, when an electron beam of 70 kA current propagates through it.