BREAKDOWN EXPERIMENTS IN A VANDEGRAAFF GENERATOR

Experiments are described which measure the transient radial electric field in the region between the terminal and pressure vessel and also the current flowing in the breakdown channel during terminal discharges of a pressurised Van de Graaff generator. The results show that a dominant frequency is excited which is controlled by the capacitance and inductance of the terminal resonating with the channel inductance. In some cases a higher frequency which is an electromagnetic mode supported by the whole machine is also excited. Calculations show that the inductance of the channel is independent of gas pressure and that the damping of the oscillations is controlled mainly by the insulating gas. It is shown that the gas absorbs a substantial proportion of the initial stored energy within the first few cycles of oscillation. © 1979 North-Holland Publishing Co.