High-voltage conditioning at large gaps in industrial vacuum

The improvement of high-voltage insulation in vacuum by ageing the electrodes is well known. This so-called conditioning effect becomes very important if ultra-high-vacuum techniques cannot be employed in systems with large dimensions. For unbaked surfaces this effect allows one to increase the initial field strength by a factor of about 10. In the present paper, the electrode gaps were variable between 15 and 30 cm. For such gaps, the conditioning and also the deconditioning process which occurs when the high voltage is removed have been studied. An attempt has been made to describe these processes mathematically, and to understand the mechanism involved. The results are compatible with the hypothesis that these effects are due to a change in the adsorbed gas layer; that is, a change in the workfunction of the electrode material.