In order to understand the physical mechanism of multipactor discharge on dielectric window surface under high power microwave （HPM） excitation in vacuum, an electron movement simulation model based on the particle-...In order to understand the physical mechanism of multipactor discharge on dielectric window surface under high power microwave （HPM） excitation in vacuum, an electron movement simulation model based on the particle-in-cell （PIC） Monte Carlo （MC） is built in this paper. The influences of microwave electromagnetic field and electrostatic field from dielectric surface charging are simultaneously considered in this model. During the simulation, the emission velocity and angle distribution of secondary electrons from the dielectric surface are taken into account. The movement trajectories of electron clusters under complex field excitation are obtained. The influences of emergence angle and microwave electromagnetic parameters on the electron movement are analyzed. It is found that the emergence angle of electrons from the surface has significant effect on its movement, and both the impact energy and return time of electrons oscillate periodically with the phase of microwave field. The number of secondary electrons and induced electrostatic field from multipactoring are also investigated. The results reveal that both values oscillate periodically at twice the microwave frequency, which is due to the electron impact energy oscillating with microwave period. A schematic diagram is proposed to explain the periodical oscillation phenomena.展开更多
This paper provides a review of the compact intense electron-beam accelerators (IEBAs) based on liquid pulse forming lines (PFLs) that havebeen developed at the National University of Defense Technology (NUDT) in Chin...This paper provides a review of the compact intense electron-beam accelerators (IEBAs) based on liquid pulse forming lines (PFLs) that havebeen developed at the National University of Defense Technology (NUDT) in China. The history and roadmap of the compact IEBAs used todrive high-power microwave (HPM) devices at NUDT are reviewed. The properties of both de-ionized water and glycerin as energy storagemedia are presented. Research into the breakdown properties of liquid dielectrics and the desire to maximize energy storage have resulted in theinvention of several coaxial PFLs with different electromagnetic structures, which are detailed in this paper. These high energy density liquidPFLs have been used to increase the performance of IEBA subsystems, based on which the SPARK (Single Pulse Accelerator with spark gaps)and HEART (High Energy-density Accelerator with Repetitive Transformer) series of IEBAs were constructed. This paper also discusses howthese compact IEBAs have been used to drive typical HPM devices and concludes by summarizing the associated achievements and theconclusions that can be drawn from the results.展开更多
Speed is the new stealth and earlier this week America’s top nuclear commander described a grim scenario for U.S.forces facing off against hypersonic weapons.“We do not have any defense that could deny the employmen...Speed is the new stealth and earlier this week America’s top nuclear commander described a grim scenario for U.S.forces facing off against hypersonic weapons.“We do not have any defense that could deny the employment of such a weapon against us,”Air Force Gen.John Hyten,commander of U.S.Strategic Command,told the Senate Armed Services Committee on Tuesday March 20,2018.Russian and Chinese are aggressively developing new weapons that travel at Mach 5 or higher,which is at least five times faster than speed of sound(hypersonic).These weapons travel in excess of 3,600 miles per hour(1 mile per second)and currently,no military possesses a credible defense.Finding,tracking and intercepting something that fast is unprecedented.Given that Russia and China have invested heavily in advanced defensive technologies that now hold most of our traditional forms of power projection at risk,this is a significant advantage—it is one that would impose major costs upon a defending nation.Recently,according to the director of the Army’s Rapid Capabilities and Critical Technologies Office(ARCCTO),The Army will field a battery of truck-borne hypersonic missiles in 2023,with a contract award in August,the service’s new three-star Program Executive Officer said.The service will also field a battery of 50-kilowatt lasers on Stryker armored vehicles by 2021,he said.A program to put a 100-plus-kilowatt laser on a heavy truck,however,is under review and may be combined with Air Force and/or Navy efforts to reach comparable power levels,Lt.Gen.Neil Thurgood told reporters in his interview.In this white paper we are suggesting a new technology as a counter-measure against such an adversary measure and threat that is aggressively being pursued by these two nations,Russia and China both tactically and strategically.We also briefly discuss possible physics and science of aerodynamics involved with these vehicles traveling between range of 5 Mach and higher,where we discuss current status and future direction driven by phenomena of plasma aerodynamics thorough possibly,weakly ionized gases(WIG)program that was started by the former Soviet Republics under AJAX Vehicle and that was direct understanding of the role of plasmas in the performance of this vehicle.展开更多
Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In ...Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In order to improve the power conversion efficiency and eliminate or at least minimize anode plasma formation in the load region and radio frequency （RF） breakdown in the slow wave structure （SWS） section, an X-band MILO is presented and inyestigated nu- merically with KARAT code. The design idea is briefly presented and the simulation results are given and discussed. In the simulation, HPM is generated with peak power of 3.4 GW, maximum electric field of about 1 MV/cm, and peak power conversion efficiency of 14.0%, when the voltage is 559.1 kV and the current is 43.2 kA. The microwave frequency is pure and falls in the X-band of 9.0 GHz. The theoretical investigation and the simulation results are given to prove that the anode plasma formation and the RF breakdown can be effectively avoided or at least minimized, respectively.展开更多
基金supported in part by the National High Technology Research and Development Program of China
文摘In order to understand the physical mechanism of multipactor discharge on dielectric window surface under high power microwave （HPM） excitation in vacuum, an electron movement simulation model based on the particle-in-cell （PIC） Monte Carlo （MC） is built in this paper. The influences of microwave electromagnetic field and electrostatic field from dielectric surface charging are simultaneously considered in this model. During the simulation, the emission velocity and angle distribution of secondary electrons from the dielectric surface are taken into account. The movement trajectories of electron clusters under complex field excitation are obtained. The influences of emergence angle and microwave electromagnetic parameters on the electron movement are analyzed. It is found that the emergence angle of electrons from the surface has significant effect on its movement, and both the impact energy and return time of electrons oscillate periodically with the phase of microwave field. The number of secondary electrons and induced electrostatic field from multipactoring are also investigated. The results reveal that both values oscillate periodically at twice the microwave frequency, which is due to the electron impact energy oscillating with microwave period. A schematic diagram is proposed to explain the periodical oscillation phenomena.
基金This work was supported by the National Natural Science Foundation of China under Grant No.51677190the Hunan Provincial Natural Science Foundation of China under Grant No.2017JJ1005.
文摘This paper provides a review of the compact intense electron-beam accelerators (IEBAs) based on liquid pulse forming lines (PFLs) that havebeen developed at the National University of Defense Technology (NUDT) in China. The history and roadmap of the compact IEBAs used todrive high-power microwave (HPM) devices at NUDT are reviewed. The properties of both de-ionized water and glycerin as energy storagemedia are presented. Research into the breakdown properties of liquid dielectrics and the desire to maximize energy storage have resulted in theinvention of several coaxial PFLs with different electromagnetic structures, which are detailed in this paper. These high energy density liquidPFLs have been used to increase the performance of IEBA subsystems, based on which the SPARK (Single Pulse Accelerator with spark gaps)and HEART (High Energy-density Accelerator with Repetitive Transformer) series of IEBAs were constructed. This paper also discusses howthese compact IEBAs have been used to drive typical HPM devices and concludes by summarizing the associated achievements and theconclusions that can be drawn from the results.
文摘Speed is the new stealth and earlier this week America’s top nuclear commander described a grim scenario for U.S.forces facing off against hypersonic weapons.“We do not have any defense that could deny the employment of such a weapon against us,”Air Force Gen.John Hyten,commander of U.S.Strategic Command,told the Senate Armed Services Committee on Tuesday March 20,2018.Russian and Chinese are aggressively developing new weapons that travel at Mach 5 or higher,which is at least five times faster than speed of sound(hypersonic).These weapons travel in excess of 3,600 miles per hour(1 mile per second)and currently,no military possesses a credible defense.Finding,tracking and intercepting something that fast is unprecedented.Given that Russia and China have invested heavily in advanced defensive technologies that now hold most of our traditional forms of power projection at risk,this is a significant advantage—it is one that would impose major costs upon a defending nation.Recently,according to the director of the Army’s Rapid Capabilities and Critical Technologies Office(ARCCTO),The Army will field a battery of truck-borne hypersonic missiles in 2023,with a contract award in August,the service’s new three-star Program Executive Officer said.The service will also field a battery of 50-kilowatt lasers on Stryker armored vehicles by 2021,he said.A program to put a 100-plus-kilowatt laser on a heavy truck,however,is under review and may be combined with Air Force and/or Navy efforts to reach comparable power levels,Lt.Gen.Neil Thurgood told reporters in his interview.In this white paper we are suggesting a new technology as a counter-measure against such an adversary measure and threat that is aggressively being pursued by these two nations,Russia and China both tactically and strategically.We also briefly discuss possible physics and science of aerodynamics involved with these vehicles traveling between range of 5 Mach and higher,where we discuss current status and future direction driven by phenomena of plasma aerodynamics thorough possibly,weakly ionized gases(WIG)program that was started by the former Soviet Republics under AJAX Vehicle and that was direct understanding of the role of plasmas in the performance of this vehicle.
基金supported by National Natural Science Foundation of China(No.11075210)the Special Financial Grant from the China Postdoctoral Science Foundation(No.201104761)
文摘Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In order to improve the power conversion efficiency and eliminate or at least minimize anode plasma formation in the load region and radio frequency （RF） breakdown in the slow wave structure （SWS） section, an X-band MILO is presented and inyestigated nu- merically with KARAT code. The design idea is briefly presented and the simulation results are given and discussed. In the simulation, HPM is generated with peak power of 3.4 GW, maximum electric field of about 1 MV/cm, and peak power conversion efficiency of 14.0%, when the voltage is 559.1 kV and the current is 43.2 kA. The microwave frequency is pure and falls in the X-band of 9.0 GHz. The theoretical investigation and the simulation results are given to prove that the anode plasma formation and the RF breakdown can be effectively avoided or at least minimized, respectively.
