Coaxial Small-orbit Relativistic Electron Maser Loaded With Electrostatic Field

Terahertz (THz) electromagnetic waves occupy a very special position in the electromagnetic spectrum and display a lot of superior characteristics different from electromagnetic radiation in other bands. It has very important academic value and widely potential application in many fields. Currently, research about terahertz science and technology has attracted widespread attention and great interest throughout the international academia and has become one of the forefront areas within international high-tech research.Over the years, lack of effective THz electromagnetic radiation sources is an important reason to restrict the development and application of the THz science and technology. Exploration of new mechanisms and new approaches to generat the terahertz electromagnetic radiation has become the research hot spots in the field of THz science and technology. Free Electron Laser (FEL) and gyrotron devices based on electron cyclotron maser (ECM) are recognized as effective devices to achieve a THz wave output. Where the word 'maser' was the acronym of'Microwave Amplification by Stimulated Emission of Radiation'. Its basic meaning is'stimulated emission amplifier'. So the translation used universally in Chinese is 'maser'in transliteration or'microwave maser'in free translation.In this paper a small-orbit relativistic electron cyclotron maser with external electrostatic voltage loaded is proposed to get some new knowledge of the high-power THz free electron radiation sources. It intends to explore a new type of kilowatt high-power terahertz electromagnetic radiation souce with advantages of larger transverse size; stronger beam-wave interaction; better monochromaticity; lower cost of the project and compacter structure. The major points of the full paper are as follows:(1) By refining a large number of relevant references, the domestic and foreign application and analysis of electrostatic field in electron cyclotron maser and free electron laser are comprehensively reviewed and then the academic methodology is presented.(2) The basic physical model of electron beam-electromagnetic coupling in the coaxial electrostatic system is established. First, the field expressions of TE mode electromagnetic wave in coaxial waveguide are derived. Then, the relativistic electron motion equation with the external electrostatic voltage taken into account is analyzed. Finally, beam-wave coupling equation of energy exchange is derived. These steps lead to the self-consistent nonlinear theory of the coaxial waveguide cyclotron maser with electrostatic voltage loaded, and correspondingly, a program in terms of FORTRAN language is performed.(3) Nonlinear simulation model of a small-orbit relativistic coaxial cyclotron autoresonance maser (CARM) amplifier with external electrostatic voltage loaded for a transverse electric mode at frequency of 0.14THz is given. Simulation results show that, by employing the external electrostatic voltage, the saturation power has an significant increase by 22% and the maximum efficiency changes from 10.2% to 12.5% compared to the situation without electrostatic voltage (V0=0). Influences of initial parameters such as external electrostatic voltage; the ratio of the electron-beam's transverse velocity to the axial velocity and the mean radius of the electron beam on the saturation power are simulated and optimized. Also, the influence of the transverse velocity spread on output power is examined.(4) Theoretical model of a small-orbit relativistic coaxial gyrotron amplifier with external electrostatic voltage loaded is presented and the nonlinear simulation of the situation at the frequency of 0.14THz is given. The initial parameters such as external electrostatic voltage; the ratio of the electron-beam's transverse velocity to the axial velocity and the mean radius of the electron beam are debugged and optimized. Also, the influence of the transverse velocity spread on output power is examined. Simulation results show that, first, the saturation power has an significant improvement by 18.6% compared to the situation without electrostatic voltage (V0=0), and second, the negative influence of the electron beam's transverse velocity spread on output power is weakened by employing the external electrostatic voltage.(5) The corrugated coaxial structure electrostatic system is studied by making use of the electromagnetic simulation software CST. Through the nonlinear simulation we present the electric field distribution in the system and analyze the influence of the ripple depth. Then, we examine the use of the system modulating the motion of relativistic electrons. By tracking the electron's motion, it is found that this electrostatic system can act as an electrostatic wiggler to replace the traditional magnetic-static wiggler in a FEL.