The large gap case for high voltage insulation in vacuum

A test set-up able to accommodate dish shaped electrodes for gaps up to /spl sim/20 cm is being used to study the large gap effects. This experience, in connection with other authors' experiences, underlines the three more characteristic aspects of the large gap case: a voltage effect; a current effect; and a gas effect. The difficulty of energy dissipation by surface processes at increasing penetration depth of the energy deposit gives an interesting interpretative perspective to the behaviour of large gap, high voltage devices.