The distribution of magnetic field in Hall thruster channel has significant effect on its discharge process and wall plasma sheath characteristics. By creating physical models for the wall sheath region and adopting t...The distribution of magnetic field in Hall thruster channel has significant effect on its discharge process and wall plasma sheath characteristics. By creating physical models for the wall sheath region and adopting two-dimensional particle in cell simulation method, this work aims to investigate the effects of magnitude and direction of magnetic field and ion velocity on the plasma sheath characteristics. The simulation results show that magnetic field magnitudes have small impact on the sheath potential and the secondary electron emission coefficient, magnetic azimuth between the magnetic field direction and the channel radial direction is proportional to the absolute value of the sheath potential, but inversely proportional to the secondary electron emission coefficient. With the increase of the ion incident velocity, secondary electron emission coefficient is enhanced, however, electron density number, sheath potential and radial electric field are decreased. When the boundary condition is determined, with an increase of the sinmlation area radial scale, the sheath potential oscillation is aggravated, and the stability of the sheath is reduced.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
在磁场不变的情况下,随着霍尔(Hall)推力器放电电压的提高,其通道内的最大电子温度会在一定的电压区间内出现"饱和"现象。为进一步理解这一现象,在完成了变电压不变磁场PIC(Particle in cell)模拟的基础上,首先分析了电子能...在磁场不变的情况下,随着霍尔(Hall)推力器放电电压的提高,其通道内的最大电子温度会在一定的电压区间内出现"饱和"现象。为进一步理解这一现象,在完成了变电压不变磁场PIC(Particle in cell)模拟的基础上,首先分析了电子能量的平衡机制的构成要素和最大电子温度的影响因素,进而对各个影响因素在变电压下的变化趋势进行了研究。结果显示:最大电子温度点上游区域的电场加热效应是最大电子温度变化的主导因素,而上游区域的电子与壁面碰撞效应对最大电子温度的变化起到一定的调节作用。在高电压下,由于磁场无法有效束缚电子,上游区域的电子数密度急剧降低,导致电子壁面碰撞能量损失大幅降低,使得碰撞损失对最大电子温度的影响变得较为微弱。进一步指出了磁场在霍尔推力器变电压运行中的核心地位,并提出了高电压放电优化的2个方向:增大放电磁场以及更换二次电子发射系数更高的陶瓷壁面。展开更多
基金supported by National Natural Science Foundation of China(Nos.11275034,11175052,11005025,10975026,11375039)Key Project of Science and Technology of Liaoning Province,China(No.2011224007)
文摘The distribution of magnetic field in Hall thruster channel has significant effect on its discharge process and wall plasma sheath characteristics. By creating physical models for the wall sheath region and adopting two-dimensional particle in cell simulation method, this work aims to investigate the effects of magnitude and direction of magnetic field and ion velocity on the plasma sheath characteristics. The simulation results show that magnetic field magnitudes have small impact on the sheath potential and the secondary electron emission coefficient, magnetic azimuth between the magnetic field direction and the channel radial direction is proportional to the absolute value of the sheath potential, but inversely proportional to the secondary electron emission coefficient. With the increase of the ion incident velocity, secondary electron emission coefficient is enhanced, however, electron density number, sheath potential and radial electric field are decreased. When the boundary condition is determined, with an increase of the sinmlation area radial scale, the sheath potential oscillation is aggravated, and the stability of the sheath is reduced.
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.
文摘在磁场不变的情况下,随着霍尔(Hall)推力器放电电压的提高,其通道内的最大电子温度会在一定的电压区间内出现"饱和"现象。为进一步理解这一现象,在完成了变电压不变磁场PIC(Particle in cell)模拟的基础上,首先分析了电子能量的平衡机制的构成要素和最大电子温度的影响因素,进而对各个影响因素在变电压下的变化趋势进行了研究。结果显示:最大电子温度点上游区域的电场加热效应是最大电子温度变化的主导因素,而上游区域的电子与壁面碰撞效应对最大电子温度的变化起到一定的调节作用。在高电压下,由于磁场无法有效束缚电子,上游区域的电子数密度急剧降低,导致电子壁面碰撞能量损失大幅降低,使得碰撞损失对最大电子温度的影响变得较为微弱。进一步指出了磁场在霍尔推力器变电压运行中的核心地位,并提出了高电压放电优化的2个方向:增大放电磁场以及更换二次电子发射系数更高的陶瓷壁面。