Apparatus and method for generating a glow discharge

Abstract

This invention provides a laser or high voltage switch which has two spaced apart main discharge electrodes which define between them a main discharge gap, a discharge inducing member that is of an insulating material and which provides a planar or curved trigger discharge surface adjacent the electrodes and partially or completely bridging the main discharge gap, and an auxiliary conductor on the other side of the discharge inducing member to the main discharge electrodes and capacitively coupled to one of them by a distributed stray capacitance, such that when an excitation pulse is applied across the main discharge electrodes an initial capacitively initiated low order trigger discharge occurs onto the trigger discharge surface, and preferably across the surface from one main discharge electrode to the other. This trigger discharge photo-ionises a gas in the main discharge gap to cause a glow discharge between the main electrodes. The auxiliary conductor may be sheet like and may be either part of a pulsing circuit or it may be directly electrically coupled to one of the main discharge electrodes. The conductor may be shielded by a shielding member to vary the capacitive coupling between the conductor and the main discharge electrode. One or both of the main discharge electrodes may have a curved portion and a sharpened portion to induce a corona discharge.