This paper reports that a simulation of glow discharge in pure helium gas at the pressure of 1.333×10^3 Pa under a high-voltage nanosecond pulse is performed by using a one-dimensional particle-in-cell Monte Carl...This paper reports that a simulation of glow discharge in pure helium gas at the pressure of 1.333×10^3 Pa under a high-voltage nanosecond pulse is performed by using a one-dimensional particle-in-cell Monte Carlo collisions （PIC-MCC） model. Numerical modelling results show that the cathode sheath is much thicker than that of anode during the pulse discharge, and that there exists the phenomenon of field reversal at relative high pressures near the end of the pulse, which results from the cumulative positive charges due to their finite mobility during the cathode sheath expansion. Moreover, electron energy distribution function （EEDF） and ion energy distribution function （IEDF） have been also observed. In the early stage of the pulse, a large amount of electrons can be accelerated above the ionization threshold energy. However, in the second half of the pulse, as the field in bulk plasma decreases and thereafter the reverse field forms due to the excessive charges in cathode sheath, although the plasma density grows, the high energy part of EEDF decreases. It concludes that the large volume non-equilibrium plasmas can be obtained with high-voltage nanosecond pulse discharges.展开更多
采用粒子-蒙特卡罗模型(Particle in Cell-Monte Carlo Collision,PIC-MCC)对气体电子倍增探测器(Gas electron multiplier,GEM)的倍增放大过程进行了模拟,这对更好的理解和把握GEM的物理机理具有重要的意义。在电场分析的基础上,从GEM...采用粒子-蒙特卡罗模型(Particle in Cell-Monte Carlo Collision,PIC-MCC)对气体电子倍增探测器(Gas electron multiplier,GEM)的倍增放大过程进行了模拟,这对更好的理解和把握GEM的物理机理具有重要的意义。在电场分析的基础上,从GEM空间粒子数和粒子的空间分布随时间的变化分析GEM的倍增过程,并建立GEM增益和各边界层收集到的电子个数之间的关系。研究结果为进一步利用该模型对GEM优化结构、选择工作参数及探讨物理机理建立了基础。展开更多
利用基于PIC-MCC(Particle in cell-Monte Carlo collision)模型的OOPIC-PRO软件计算了107 cm荫罩式PDP实际单元和放大单元的放电,模拟结果表明相似放电单元具有相同的伏安特性,放电相对应时刻的空间粒子浓度分布相同,从数值实验角度验...利用基于PIC-MCC(Particle in cell-Monte Carlo collision)模型的OOPIC-PRO软件计算了107 cm荫罩式PDP实际单元和放大单元的放电,模拟结果表明相似放电单元具有相同的伏安特性,放电相对应时刻的空间粒子浓度分布相同,从数值实验角度验证了气体放电的重要定律:相似定律。在理论模拟的基础上,利用实际单元和放大单元的实验测试系统,测量并比较了放大单元和实际单元的放电电流,结果表明放大单元和实际单元的放电电流强度相当,但实际单元较放大单元的放电快约20倍。展开更多
Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the pl...Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the plasma density.In this work,the variations of the HCE in one RF period are investigated by using a two-dimensional particle-in-cell/Monte-Carlo collision(PIC/MCC)model.The results show that the sheath electric field,the sheath potential drop,the sheath thickness,the radial plasma bulk width,the electron energy distribution function(EEDF),and the average electron energy in the cavity vary in one RF period.During the hollow electrode sheath's expansion phase,the secondary electron heating and sheath oscillation heating in the cavity are gradually enhanced,and the frequency of the electron pendular motion in the cavity gradually increases,hence the HCE is gradually enhanced.However,during the hollow electrode sheath's collapse phase,the secondary electron heating is gradually attenuated.In addition,when interacting with the gradually collapsed hollow electrode sheaths,high-energy plasma bulk electrons in the cavity will lose some energy.Furthermore,the frequency of the electron pendular motion in the cavity gradually decreases.Therefore,during the hollow electrode sheath's collapse phase,the HCE is gradually attenuated.展开更多
The two-layer fluid system and the continuous density system are based on two typical simplified stratification conditions to support the propagation of the internal solitary waves(ISWs).The aim of this study is to es...The two-layer fluid system and the continuous density system are based on two typical simplified stratification conditions to support the propagation of the internal solitary waves(ISWs).The aim of this study is to establish several extension methods of the classical ISW models across the stratification systems in an attempt to find a simple ISW structure that can propagate more stably,and to determine whether the stable ISW structure in the two typical stratification systems can be expressed in terms of a consistent nonlinear model.For the constructed ISW structures,the propagation stability has been investigated by taking the Euler equations as the evolution equations.The results show that the ISW structure constructed from the Miyata-Choi-Camassa(MCC)model undergoes two stages of instability and the re-stable ISW has a larger available potential energy and a smaller kinetic energy than the initialized condition.This illustrates the limitation of the weakly dispersive assumption in the MCC model.In contrast,the ISW structure constructed from the Dubreil-Jacotin-Long(DJL)model for the two-layer fluid system is generally stable,due to the fact that the Boussinesq approximation introduced in the derivation of the DJL model will be automatically satisfied in this system.The initial condition interpolated from the DJL model with a thin pycnocline thickness can be regarded as an appropriate ISW structure for the two-layer system and is even more stable than that initialized by the MCC model.In addition,the effect of the Boussinesq approximation is also included in the discussion.The approximation can be considered equivalent to a weakly dispersive assumption and should not be ignored for the ISW problem in the continuous density system.展开更多
基金supported by the National Natural Science Foundation of China (Grant No 10775027)
文摘This paper reports that a simulation of glow discharge in pure helium gas at the pressure of 1.333×10^3 Pa under a high-voltage nanosecond pulse is performed by using a one-dimensional particle-in-cell Monte Carlo collisions （PIC-MCC） model. Numerical modelling results show that the cathode sheath is much thicker than that of anode during the pulse discharge, and that there exists the phenomenon of field reversal at relative high pressures near the end of the pulse, which results from the cumulative positive charges due to their finite mobility during the cathode sheath expansion. Moreover, electron energy distribution function （EEDF） and ion energy distribution function （IEDF） have been also observed. In the early stage of the pulse, a large amount of electrons can be accelerated above the ionization threshold energy. However, in the second half of the pulse, as the field in bulk plasma decreases and thereafter the reverse field forms due to the excessive charges in cathode sheath, although the plasma density grows, the high energy part of EEDF decreases. It concludes that the large volume non-equilibrium plasmas can be obtained with high-voltage nanosecond pulse discharges.
文摘采用粒子-蒙特卡罗模型(Particle in Cell-Monte Carlo Collision,PIC-MCC)对气体电子倍增探测器(Gas electron multiplier,GEM)的倍增放大过程进行了模拟,这对更好的理解和把握GEM的物理机理具有重要的意义。在电场分析的基础上,从GEM空间粒子数和粒子的空间分布随时间的变化分析GEM的倍增过程,并建立GEM增益和各边界层收集到的电子个数之间的关系。研究结果为进一步利用该模型对GEM优化结构、选择工作参数及探讨物理机理建立了基础。
文摘利用基于PIC-MCC(Particle in cell-Monte Carlo collision)模型的OOPIC-PRO软件计算了107 cm荫罩式PDP实际单元和放大单元的放电,模拟结果表明相似放电单元具有相同的伏安特性,放电相对应时刻的空间粒子浓度分布相同,从数值实验角度验证了气体放电的重要定律:相似定律。在理论模拟的基础上,利用实际单元和放大单元的实验测试系统,测量并比较了放大单元和实际单元的放电电流,结果表明放大单元和实际单元的放电电流强度相当,但实际单元较放大单元的放电快约20倍。
文摘Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the plasma density.In this work,the variations of the HCE in one RF period are investigated by using a two-dimensional particle-in-cell/Monte-Carlo collision(PIC/MCC)model.The results show that the sheath electric field,the sheath potential drop,the sheath thickness,the radial plasma bulk width,the electron energy distribution function(EEDF),and the average electron energy in the cavity vary in one RF period.During the hollow electrode sheath's expansion phase,the secondary electron heating and sheath oscillation heating in the cavity are gradually enhanced,and the frequency of the electron pendular motion in the cavity gradually increases,hence the HCE is gradually enhanced.However,during the hollow electrode sheath's collapse phase,the secondary electron heating is gradually attenuated.In addition,when interacting with the gradually collapsed hollow electrode sheaths,high-energy plasma bulk electrons in the cavity will lose some energy.Furthermore,the frequency of the electron pendular motion in the cavity gradually decreases.Therefore,during the hollow electrode sheath's collapse phase,the HCE is gradually attenuated.
基金supported by the National Natural Science Foundation of China(Grant Nos.52231011,52071056)This work was supported by the Liaoning Revitalization Talents Program(XLYC2007109)+1 种基金Dalian Science and Technology Innovation Fund(Grant No.2020JJ25CY012)the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(Grant No.2021QNLM020003-5).
文摘The two-layer fluid system and the continuous density system are based on two typical simplified stratification conditions to support the propagation of the internal solitary waves(ISWs).The aim of this study is to establish several extension methods of the classical ISW models across the stratification systems in an attempt to find a simple ISW structure that can propagate more stably,and to determine whether the stable ISW structure in the two typical stratification systems can be expressed in terms of a consistent nonlinear model.For the constructed ISW structures,the propagation stability has been investigated by taking the Euler equations as the evolution equations.The results show that the ISW structure constructed from the Miyata-Choi-Camassa(MCC)model undergoes two stages of instability and the re-stable ISW has a larger available potential energy and a smaller kinetic energy than the initialized condition.This illustrates the limitation of the weakly dispersive assumption in the MCC model.In contrast,the ISW structure constructed from the Dubreil-Jacotin-Long(DJL)model for the two-layer fluid system is generally stable,due to the fact that the Boussinesq approximation introduced in the derivation of the DJL model will be automatically satisfied in this system.The initial condition interpolated from the DJL model with a thin pycnocline thickness can be regarded as an appropriate ISW structure for the two-layer system and is even more stable than that initialized by the MCC model.In addition,the effect of the Boussinesq approximation is also included in the discussion.The approximation can be considered equivalent to a weakly dispersive assumption and should not be ignored for the ISW problem in the continuous density system.
