Research On Low Voltage And Low Current Terahertz Electron Cyclotron Masers Beam-wave Interaction

After CT machine,nuclear magnetic resonance(NMR)imaging technology is another major technological advance in the field of medical imaging.Since the 80 s,NMR began to be adopted in hospital,its development speed is amazing.Because of some self-reasons,the sensitivity of NMR is not high enough.Polarization transfer between electron and the nucleus is called dynamic nuclear polarization(DNP),higher levels polarization of the electron spin is passed to the nuclear spin to increase the sensitivity of nuclear magnetic resonance,this technology can improve the sensitivity of NMR by 1 ~ 2 orders of magnitude,polarization transfer is drived by high frequency millimeter wave or THz wave.The generation and amplification of THz wave is the key technology of the applications of terahertz.At present,the generation of terahertz wave mainly has those ways: by using photonics technology(such as: the effect of laser in some gas or material,etc.)and the use of electronics technology(such as the backward wave oscillator BWO,semiconductor solid-state devices,free electron laser,quantum cascade lasers,tube,etc.).The purpose of this article is to use gyrotron to generate terahertz signals.This topic research is a kind of small power and effective terahertz gyrotron,which has good effect in improving the resolution of the nuclear magnetic resonance instrument.The part of beam-wave interaction is a key part of the gyrotron in this research.The study of the interaction process is base on linear and self-consistent nonlinear theory of beam-wave interaction.The main work of this paper are as follows:(1)according to the requirements of design,this design is the fundamental of 250 GHz terahertz gyrotron.Basing on the working requirement of gyrotron,we choose a appropriate working mode,and design a gyrotron cavity structure,then analyze the parameters,which influence the quality factor and the resonance frequency of the resonance,and design the size of the cavity,use 3d electromagnetic simulation software to verify whether the design meets the requirements.(2)Basing on the linear theory of gyrotron,analysis the dispersion curve?coupling coefficient?start-oscillating current of gyrotron.Getting the parameter of the initial value,roughly for note-wave interaction research.(3)Analysis the nonlinear,and research this theory,make a preparation for numerical analysis,make a theoretical analysis of the relevant parameters that influencing the efficiency of electronic,get a roughly range of parameters of higher efficiency of gyrotron working,then,combine parameters,optimize the working results.