Preliminary study into the magnetically assisted blocking of reverse current in a cold cathode high current vacuum switch

A program of work to investigate the feasibility of using an external magnetic field to cause the blocking of reverse conduction in a vacuum switch is outlined. The design and build of a suitable device is followed by a program of experimental work during which magnetic fields are applied to the switch in order to attempt to interrupt the current at the first zero crossing of an oscillatory waveform. The design, build and operation of the switch are described and the results of the experimental work outlined. The results show that an effect, which falls short of complete interruption, could be reproducibly observed and that the magnitude of the effect depended upon the position in time of the applied field relative to the current zero crossing point. A number of observations made during the work have indicated possible methods of improving the reverse blocking performance and these will be outlined in addition to general conclusions.