Curvature of the cathode and electron emission

An experiment was carried out to investigate the relationship between the initial electron emission and the effective field strength under a nonuniform field, as in the case of the cathode-anode needle-plane and hemisphere-plane geometries. The curvature of the cathode was altered to change the characteristics of the surface field strength, and the initial electron current was measured. The curvatures were 1.2 μm to infinity (plane). The range of the current was 1×10^-19 A to 1×10^-14 A in a high vacuum (2×10^-7 torr). The effect of the effective field strength on the initial electron emission under nonuniform and uniform fields was evaluated. The effective field strength is mostly constant at 10⁸ V/cm, irrespective of the cathode shape. In the case of gas adsorption, the effective field strength of the inception of the electron emission is mostly constant