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...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.展开更多
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...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。展开更多
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 appli...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.展开更多
Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomal...Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomalous-energy RAEs in fast ionisation waves(FIWs)formed during pulsed gas breakdown.Synchronised observation of RAEs and their induced bremsstrahlung X-ray at different locations of the FIW is performed,which is combined with measurement of spatial-temporal evolution of FIW potential.It is revealed that anomalous-energy RAEs,preceding regular RAEs,have an ultrashort beam with a picosecond pulse width,and RAEs tend to maintain their energy during FIW propagation before being deposited into the anode.Particle-in-cell Monte Carlo collision(PIC-MCC)simulation illustrates that the‘pace-matching’between initial electron acceleration through cathode potential drop and potential lift-up during FIW inception opens a narrow window for forming anomalous-energy RAEs.展开更多
基金This work was supported by AFOSR Grant Nos.FA9550-15-1-0094 and FA9550-19-1-0225 and by ONR Grant Nos.N00014-16-1-2352,N00014-16-1-3101,andN00014-19-1-2155.The authors express their gratitude to their AFOSR program managers during this period-Dr.Robert J.Barker(deceased),Dr.John Luginsland(currentlywith Confluent Sciences),andDr.JasonMarshall(currentlywith theNaval Research Laboratory)-and to theirONR programmanagers during this period-Mr.LeeMastroianni,Dr.Joong Kim,andMr.Ryan Hoffman-for their encouragement and support.One of the authors(E.S.)expresses his gratitude to his students and collaborators at UNM over the last 15 years on researching the relativistic magnetron.In particular,he would like to thanks his students who wrote their dissertations and theses on the topic:Sarita Prasad,Christopher Leach,Haynes Wood,David Galbreath,Cassandra Mendonca,Jeremy McConaha,and Andrew Sandoval.The authors acknowledge technical discussions with numerous colleagues from around the world on the subject of the relativistic magnetron.Notable discussions have taken place with Jim Benford,John Swegle,Ron Gilgenbach,Y.Y.Lau,Matt McQuage,Yeong-Jer(Jack)Chen,Brad Hoff,Peter Mardahl,Tim Fleming,Weihua Jiang,Todd Treado,Michael Petelin,Nikolay Kovalev,Yakov Krasik,John Leopold,Meiqin Liu,Renzhen Xiao,and Wei Li,amongmany others.Finally,one of the authors(E.S.)wishes to thank his collaborator of 17 years at UNM(retired since 2017),Professor Mikhail Fuks,for pushing him to begin researching the relativistic magnetron.None of this would have been possible without his creativity,initiative,and impetus.
文摘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.
文摘本文围绕第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。
基金supported by National Natural Science Foundation of China(No.61302010)the Foundation of Science and Technology on High Power Microwave Laboratory,Central University Foundation(2013KW07)Work at the University of New Mexico in USA was supportedby ONR Grant N00014-13-1-0565
文摘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.
基金supported by the National Natural Science Foundation of China(Grants 52350072,52437007,52277167)the Beijing Nova Program(Grant 20240484512)the Beijing Natural Science Foundation(Grant 1242030).
文摘Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomalous-energy RAEs in fast ionisation waves(FIWs)formed during pulsed gas breakdown.Synchronised observation of RAEs and their induced bremsstrahlung X-ray at different locations of the FIW is performed,which is combined with measurement of spatial-temporal evolution of FIW potential.It is revealed that anomalous-energy RAEs,preceding regular RAEs,have an ultrashort beam with a picosecond pulse width,and RAEs tend to maintain their energy during FIW propagation before being deposited into the anode.Particle-in-cell Monte Carlo collision(PIC-MCC)simulation illustrates that the‘pace-matching’between initial electron acceleration through cathode potential drop and potential lift-up during FIW inception opens a narrow window for forming anomalous-energy RAEs.
