Trial Low Pressure Triggered Gap Switch for Low Operating Voltage

Abstract

The triggering characteristics of a conventional triggered gap switch at main electrode voltage between 1.25 and 4kV are extremely inferior to those at voltage more than 10kV. Spontaneous discharge or discharge failure will frequently take place in the gap switch as the result of inadequate adjustment of electrode separation. A low pressure triggered gap switch put in a vacuum vessel made of pyrex glass has been made on an experimental basis. This consists of a pair of cylindrical main electrodes opposed to each other with a separation of 2mm, a pair of trigger electrodes made of close parallel wires and disposed at right angles to the main electrode and at a radial distance of 17mm from the axis of the main electrodes and a magnetic field coil provided so as to surround the rear portions of the trigger electrodes. A 100‰ trigger region without spontaneous discharge and discharge failure of the trial triggered gap switch has been obtained with the main electrode voltage from 1.25 to 4kV. The scatter in trigger time lag is evaluated by its standard deviation and it is shown that the standard deviation within the 100‰ bigger region is decreased from 26.4 to 8.8μs by applying magnetic field. The low pressure triggered gap switch was connected in the capacitor bank power source for the vertical field in a small tokamak HAMANA-T. It could be triggered by the detection of the initial phase luminescence in the tokamak and discharge satisfactorily the capacitor bank power source.