Electron Runaway Conditions for a Gas Diode with a Cathode in the Form of the Taylor Cone

Conditions for electron runaway in an air diode with a graphite cathode in the form of the Taylor cone, i.e., the cone with the opening angle of 98.6 deg, are studied experimentally and theoretically. The feature of the conical cathode with this opening angle is that the dynamics of free electrons radically changes for it: at larger angles, electrons are continuously accelerated across the entire gap; at smaller ones, they accelerate near the cathode and then decelerate at the periphery. For various interelectrode distances, the threshold voltages applied to the gap at which runaway electrons are detected have been determined. It has been demonstrated that the experimental voltage values are consistent with the results of calculations of the electron motion in the Laplacian (i.e., not distorted by the influence of space charge) electric field within the framework of both dynamic and kinetic models.