Enhancement factor of the electric field in the point-plane configuration

In many dielectric tests a point and plane set of electrodes is used. The point may be tungsten and can be ground accurately to a cone of specified half angle. By grinding and etching the tip may be finished to a spherical shape. The radius may be determined by optical magnification. Given the cone half angle, the tip radius and the gap, it is of interest to find the enhancement factor, i.e., the ratio of the electric field at the tip to the average electric field within the gap. A modification of a technique is outlined, that permits the determination of the enhancement factor by computer for any practical cone angle and radius and for gap lengths of 1 cm and less