Study on Electron Beam Bunching in a Gigahertz Oscillating Electric-Field Direct-Driven Cold-Cathode Electron Gun

The electron beam of an oscillating electric-field direct-driven cold-cathode electron gun in resonant structure is studied. Such electron gun is capable of providing modulated electron beam and has potential for novel vacuum electronic devices applications. However, the problem of electron beam divergence in the electron gun needs to be solved. By designing the position of cold-cathode and improving the electric field distribution on the cold-cathode surface, the divergence of the electron beam is reduced and the transmission ratio of the electron gun is effectively improved from 75.90% to 94.78
^%
. Further, by applying an axial magnetic field, the transmission ratio is optimized to 97.73%. The method for electron beam bunching optimization is simply and effective, it could find applications in microwave and terahertz vacuum electronic devices.