Review of the relativistic magnetron

The cavity magnetron is the most compact,efficient source of high-power microwave(HPM)radiation.The imprint that the magnetron has had on the world is comparable to the invention of the nuclear bomb.High-and low-power magnetrons are used in many applications,such as radar systems,plasma generation for semiconductor processing,and—the most common—microwave ovens for personal and industrial use.Since the invention of the magnetron in 1921 by Hull,scientists and engineers have improved and optimized magnetron technology by altering the geometry,materials,and operating conditions,as well as by identifying applications.A major step in advancing magnetrons was the relativistic magnetron introduced by Bekefi and Orzechowski at MIT(USA,1976),followed by the invention of the relativistic magnetron with diffraction output(MDO)by Kovalev and Fuks at the Institute of Applied Physics(Soviet Union,1977).The performance of relativistic magnetrons did not advance significantly thereafter until researchers at the University of Michigan and University of New Mexico(UNM)independently introduced new priming techniques and new cathode topologies in the 2000s,and researchers in Japan identified a flaw in the original Soviet MDO design.Recently,the efficiency of the MDO has reached 92%with the introduction of a virtual cathode and magnetic mirror,proposed by Fuks and Schamiloglu at UNM(2018).This article presents a historical review of the progression of the magnetron from a device intended to operate as a high-voltage switch controlled by the magnetic field that Hull published in 1921,to the most compact and efficientHPMsource in the twenty-first century.

基于超材料的高功率微波源技术概要

本文围绕第2作者Schamiloglu教授2020年即将出版的新书《High Power Microwave Sources and Technologies Using Metamaterials》内容,简单介绍了高功率微波新的发展趋势,主要是基于超材料的高功率微波源技术;同时,简单介绍了西安交通大学基于超材料的高功率微波源研究现状,可为高功率微波技术研究提供参考。

Simulation of Secondary Electron and Backscattered Electron Emission in A6 Relativistic Magnetron Driven by Different Cathode

Prticle-in-cell（PIC） simulations demonstrated that,when the relativistic magnetron with diffraction output（MDO） is applied with a 410 kV voltage pulse,or when the relativistic magnetron with radial output is applied with a 350 kV voltage pulse,electrons emitted from the cathode with high energy will strike the anode block wall.The emitted secondary electrons and backscattered electrons affect the interaction between electrons and RF fields induced by the operating modes,which decreases the output power in the radial output relativistic magnetron by about 15%（10%for the axial output relativistic magnetron）,decreases the anode current by about 5%（5%for the axial output relativistic magnetron）,and leads to a decrease of electronic efficiency by 8%（6%for the axial output relativistic magnetron）.The peak value of the current formed by secondary and backscattered current equals nearly half of the amplitude of the anode current,which may help the growth of parasitic modes when the applied magnetic field is near the critical magnetic field separating neighboring modes.Thus,mode competition becomes more serious.