Abstract
In this paper, in order to enhance the efficiency of the confocal gyrotron travelling wave tube (confocal gyro-TWT), the confocal beam is first introduced based on the field distribution of the operating mode in the confocal waveguide. Besides, a confocal gyro-TWT with a confocal beam operating at 0.34 THz is simulated and designed based on linear and nonlinear theories. It is verified that the confocal beam can enhance the interaction efficiency and output power significantly through simulation. In addition, the effects of electron beam parameters on output power are also analyzed in this paper. The simulation results indicate that the confocal gyro-TWT can operate at TE06 stably with an output power of 17.3 kW when the beam voltage is 60 kV, beam current is 2 A, input power is 40 mW, and transverse velocity spread is 5%. The corresponding frequency and interaction efficiency are 0.34 THz and 14.4%, respectively.
Highlights
Terahertz (THz) technology has received a lot of attention today
Scitation.org/journal/adv In Fig. 7(b), we present the curves of interaction efficiency based on the different electron beams; when the input power is 40 mW, the interaction efficiency based on the confocal beam can reach up to 20.7%, while the interaction efficiency based on the annular electron beam is only 10.7%
It is verified that the confocal beam can improve the output power and interaction efficiency significantly
Summary
Terahertz (THz) technology has received a lot of attention today. It has great potential for applications in spectroscopy, imaging, biology, and medicine. Among all THz sources, the gyrotron is one of the most promising devices based on the electron cyclotron maser (ECM). Among all THz sources, the gyrotron is one of the most promising devices based on the electron cyclotron maser (ECM) It can generate high power radiation with high efficiency; research efforts have been made worldwide on that, and the achievements of this kind of source are remarkable.. The development of the gyro-travelling wave tube (TWT) is still in the research stage despite extensive efforts. In order to alleviate the problems, some new interaction cavities have been introduced, such as the confocal waveguide and photonic-bandgap waveguide.16–18 Both have the ability to reduce the density of the modes so that the mode competition can be suppressed. For the purpose of increasing the efficiency, a novel electron beam called the confocal beam is introduced; we present the linear theory and the self-consistent nonlinear theory to study the beam-wave interaction in the confocal waveguide, in which the velocity spread is considered.
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