A double-layer carbon-nanotube cold cathode with enhancing electron beam current

Abstract

Field emission cold cathode has the advantages of room temperature operation, high current density and compact size. Facing to high current electron source application, it has to further raise the emission current and current density. One of the constraints is the low emitter area efficiency and the shielding effect. In this work, a double layer carbon nanotube cathode structure was proposed which comprises a primary cathode and a second cathode. The primary cathode is a traditional array type field emitter. The second cathode serves a dual function: acting as both a mesh stripe type field emitter and an electrode that applies voltage to drive the primary cathode field emission. The two electrodes complementally cover the whole cathode space. This design increases the effective emission area within the cathode space and gets rid of the shielding effect, thus increasing the emission current and enhancing the emission stability. Experimental results demonstrated that the structure attained an anode current of 12 mA at an anode voltage of 1600 V which is double of the traditional array emitter. The current fluctuation was 1.9 % over a 3-h test period. This method offers a feasible solution for achieving a high current electron source further push on the application of cold cathode on microwave/terahertz vacuum electronics devices.