Ion Distribution During the Initial Stages of Spark Discharge in Nonuniform Fields

A method is given whereby a direct study of ion distribution during the initial stages of spark discharges may be made by means of a Wilson cloud chamber and a potential impulse of less than ${10}^{-7\mathrm{}}$ sec. duration. Photographs are shown for ion distribution between a point and plane with the point both negative and positive. The mechanisms responsible for the initiation in these cases has not been discovered. It was found that a maximum field of ${10}^5$ to ${10}^6$ volts/cm was a necessary condition for ionization. With the point negative this could cause sufficient auto-electronic emission to start the discharge. With the point positive it is shown that it is improbable that free electrons in the gas are necessary for initiation of ionization.