The contribution of space charge in a high non-homogenous electric field to the creation of negative differential conductivity

The paper describes anomaly origination on current or voltage characteristics in time of positive potential on small curvature radius electrode rod against plane electrodes. An anomaly phenomenon occurred in the narrow voltage area in a high non-homogenous electric field close to the electrode (E > 107 V m−1). A mathematical – physical analysis of the observed processes in close proximity to the electrode with the above mentioned form is made. The differential equations, which analytically and theoretically describe this phenomenon, are compiled and solved. The space charge created by element particles (electrons, ions) which causes negative differential conductivity origination in narrow voltage area by their behaviour in electric field, plays a substantial role in this phenomenon. Current–voltage characteristics at both polarities of corona electrode were continuously measured at the study of static and dynamic processes occurring during discharge in the surrounding of a small curvature radius electrode. It was proved that an anomaly, in the form of negative differential conductivity (dI/dU < 0), appeared on a highly curved electrode at positive polarity in a narrow voltage area. This phenomenon was subjected to detailed experimental research including investigation of the influence of the shape and material of the electrode (output voltage), electrode temperature, influence of photoionization on the profile of the anomaly, the contribution of exoelectrons to particle distribution, and study of electrochemical potential of metal electrode. Oscillation of low ionized plasma at positive and negative polarity of small curvature radius electrodes has been analyzed. At the same time, the influence of the external forced electric field on the change of current–voltage characteristic profile was investigated. Theoretical justification of the anomaly phenomenon resulted from a change of energy conditions in the investigated place (the distance limit from the electrode is 10−4–10−6 m).