Research On Efficiency Enhancement Of ECM By Modulating The Magnetic Field

Electron Cyclotron Maser(ECM)is a type of high power microwave device,which could amplify electromagnetic wave based on the process of electron cyclotron resonance stimulated radiation.Due to the high performance in millimeter and submillimeter bands,it shows a great application potential in high-resolution radar,communication,plasma heating,high-energy particle accelerators.The slow-wave ECM,based on anomalous Doppler effect,presents unique advantages compared with fast-wave devices,such as the wider bandwidth,the weaker guiding magnetic field and the higher tolerance of incident electron beam.Unfortunately,the resonance condition cannot be maintained for a while due to the special working mechanism,which leads to a lower efficiency and severely depresses the development of slow-wave devices.Here,we propose a method to extend the beam-wave interaction by shaping of the magnetic field,and finally realized the enhancement of the efficiency of slow-wave device.Details are as follows:1?Considering the first-order shaping of guiding magnetic field,we carry out theoretical calculations using iteration method and coordinates transformation and obtained the expression of short-range efficiency.In order to explore the time dependence of conversion efficiency,numerical simulations are adopted in Mathmatica code.Indeed,both results manifest that our proposal could enhance the efficiency of slow-wave devices.2?We apply second-order shaping to the magnetic field on the basis of first-order modulation and carry out numerical simulations.The results show that it could further enhance the interaction efficiency,and the optimal efficiency could exceed 90%which is approaching to the theoretical limit.3?We expand the assumption to any other aspects,such as the refractive index of loaded dielectric.And it also presents a good performance in enhancing the efficiency of slow-wave devices in process of theoretical simulations.