Industrial application of cold cathodes based on field emission in microwave devices

In cross-field microwave devices the total operating current usually consists of two components: the primary excitation current and the main operating current built up by the secondary electrons. As a source of primary current the cathode based on a cold field emission could be used]. Cold cathodes based on the phenomenon of field emission have a number of advantages over regular thermionic emission cathodes. They emit electrons at room temperature, do not require warm-up time, and are capable of producing very high current densities. However, cold cathodes are very sensitive to the bombardment by ions of residual gases, which sputter the cathode surface material and cause degradation of cathode´s characteristics. Generally the cathode consists of the series of film field and secondary emitters placed on the supporting rod. When the cathode is operated within a strong electric field with sufficient magnitude to cause field emission, electrons will begin to leave the emitter´s surface. Electrons within the interaction space will be accelerated toward the anode and will follow trajectories consistent with the electric and magnetic fields present within the magnetrons interaction space. Some of these dislodged electrons will return to the cathode with enough energy to dislodge further electrons. These dislodged electrons will enter the interaction space and the process repeats itself until high voltage is removed from the device.