Theoretical study of a 0.22 THz backward wave oscillator based on a dual-gridded, carbon-nanotube cold cathode

The carbon nanotube (CNT) cold cathode is an attractive choice for millimeter and terahertz vacuum electronic devices, owning to its unique characteristics of instant switch-on and high emission current density. A novel dual-gridded field emission architecture based on a CNT cold cathode is proposed here. CNTs are synthesized directly on the cathode surface. The first separating grid is attached to the CNT cathode surface to shape CNT cathode array. The second separating grid is responsible for controlled extraction of electrons from the CNT emitters. The cathode surface electric field distribution and beam transparency have been improved effectivelyby …% compared to conventional planar devices. Furthermore, a high-compression-ratio dual-gridded CNT-based electron gun is designed to further increase the current density, and a 21 kV/50 mA electron beam is obtained with beam transparency of nearly 100%, along with a compression ratio of 39. A 0.22THz disk-loaded waveguide backward wave oscillator (BWO) based on this kind of electron gun architecture has been realized theoretically with output power of 32 W. The results indicate that higher output power and higher radiation frequency terahertz BWOs can be made using CNT advanced nanomaterial-based cold cathodes electron gun.