Research On Parallel Multi-electron Beams THz Radiation Source

With the rapid development of terahertz technology,the research on terahertz radiation sources has gradually become a hot spot.With the advantage of the high signal-to-noise ratio,wide frequency band and low photon energy,the terahertz radiation source have made it widely used and rapidly developed in the fields of medicine,science and technology,military and basic research.In the development and the research methods of terahertz radiation sources,the method of using vacuum electronics technology to generate terahertz radiation sources has gradually attracted researchers' attention.The main research in this paper is the parallel multi-electron beams terahertz radiation source.First,the parallel multi-electron beams optical system is designed and optimized to enable the parallel and stable transmission of the electron beam.Then,in order to facilitate the wave interaction of parallel multi-electron beams,a slow-wave structure composed of multi parallel metal grating pins is designed,whose performance is analyzed at the same time.The main work of this article is as follows:1.A brief introduction to the current research status of terahertz technology,terahertz radiation sources and multi-electron beams devices is made.The research of parallel multi-electron beams terahertz radiation sources made in this paper is proposed under these backgrounds.2.According to the theoretical basis of electron gun's design,a model of electron gun that can generate parallel multi-electron beams is designed in the particle studio of CST.Then,the particle trajectory simulation is carried out on the model.The simulation results are analyzed to optimize the size of the electron gun.Finally,the purpose of optimizing the electron trajectory is accomplished.3.According to the relevant theory of the focusing system,two focusing systems that meet the electron gun designed above are designed,which are made of elliptical current-carrying coil and periodic permanent magnet separately.The effects of various parameters of the two focusing systems on electron beam transmission are analyzed separately.Finally,the focusing system composed of elliptical current-carrying coil can generate a parabolic magnetic field with a maximum value of 0.2T on the central axis of the electron channel the focusing system composed of elliptical current-carrying coil can generate a 0.2T magnetic field on the central axis of the electron channel.The focusing system composed of periodic permanent magnet can generate a 0.1T cosine periodic magnetic field on the central axis of the electron channel.Both focusing systems enable the electron beam to pass through the electron channel in parallel and stably,which meet the design requirements of the electron optical system.The structure of the two focusing systems designed in this paper is simple and compact.Due to the small magnetic field required,the size of the focusing system is small,which is conducive to the miniaturization of the overall structure.4.The cold-cavity simulation of the multi-pin slow-wave structure and the hot-cavity simulation of the terahertz radiation source are simulated respectively.First,the influence of different size parameters of single-period slow-wave structure on the dispersion curve and coupling impedance are analyzed in CST microwave studio to optimize the parameters of the model.Then,the multi-electron beams and multi-pin slow-wave structure are used to design the back-wave oscillator,whose particle simulation is carried out in the CST particle studio to analyze the influence of various parameters on the output performance.Finally,when the working voltage is between 12.4kV and 13.4kV,the output signal frequency range from 327 GHz to 331 GHz,and the maximum output power obtained is 180 mW.The parallel multi-electron beams terahertz radiation source can realize wide-band tuning at low voltage.When the working current and working voltage is low,its output power is still high.The overall structure is small in size and simple in structure,which is suitable for matching and assembly.