Abstract-Design and Simulation of a Multi-Sheet Beam Terahertz Radiation Source Based on Carbon-Nanotube Cold Cathode

Yifan Zu, Xuesong Yuan, Xiaotao Xu, Matthew T. Cole, Yu Zhang, Hailong Li,  Yong Yin,  Bin Wang, Yang Yan 

https://www.mdpi.com/2079-4991/9/12/1768

Carbon nanotube (CNT) cold cathodes are proving to be compelling candidates for miniaturized terahertz (THz) vacuum electronic devices (VEDs) owning to their superior field-emission (FE) characteristics. Here, we report on the development of a multi-sheet beam CNT cold cathode electron optical system with concurrently high beam current and high current density. The microscopic FE characteristics of the CNT film emitter is captured through the development of an empirically derived macroscopic simulation model which is used to provide representative emission performance. Through parametrically optimized macroscale simulations, a five-sheet-beam triode electron gun has been designed, and has been shown to emit up to 95 mA at 3.2 kV. Through careful engineering of the electron gun geometric parameters, a low-voltage compact THz radiation source operating in high-order TM5,1$$ mode is investigated to improve output power and suppress mode competition. Particle in cell (PIC) simulations show the average output power is 33 W at 0.1 THz, and the beam–wave interaction efficiency is approximately 10%

Abstract-Theoretical Study of a 0.22 THz Backward Wave Oscillator Based on a Dual-Gridded, Carbon-Nanotube Cold Cathode

Qingyun Chen,  Xuesong Yuan,   Matthew T. Cole, Yu Zhang , Lin Meng,  Yang Yan

Figure 1. Schematic of the dual-gridded field emission structure based on carbon nanotube (CNT) cold cathode. SSG: second separating grid; FSG: first separating grid.

 https://www.mdpi.com/2076-3417/8/12/2462/htm

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

Abstract-Study on calculation method of terahertz gyrotron with special cross-section cavity

Xuesong Yuan ; Terahertz S&T Res. Center, Univ. of Electron. Sci. & Technol. of China, Chengdu, China ; Yu Han ; Yang Yan

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6092205

In order to develop high power terahertz sources, high harmonic terahertz gyrotrons with special cross-section cavity have been proposed. The calculation method of the gyrotrons mentioned above has been investigated based on the three-dimensional electromagnetic simulation software CST and traditional nonlinear theory of gyrotrons in this paper. In this method the analytical solution of the high frequency fields is replaced by inserting the simulation results of CST, the beam-wave interaction efficiency, coupling coefficient and starting current have been obtained. A 0.4THz third harmonic TE33 mode gyrotron with corrugated interaction cavity has been designed by making use of this calculation method.