Monte Carlo simulation of electron beam air plasma characteristics

A high-energy electron beam generator is used to generate a plasma in atmosphere. Based on a Monte Carlo toolkit named GEANT4, a model including complete physics processes is established to simulate the passage of the electron beam in air. Based on the model, the characteristics of the electron beam air plasma are calculated. The energy distribution of beam electrons (BEs) indicates that high-energy electrons almost reside in the centre region of the beam, but low-energy electrons always live in the fringe area. The energy deposition is calculated in two cases, i.e., with and without secondary electrons (SEs). Analysis indicates that the energy deposition of SEs accounts for a large part of the total energy deposition. The results of the energy spectrum show that the electrons in the inlet layer of the low-pressure chamber (LPC) are monoenergetic, but the energy spectrum of the electrons in the outlet layer is not pure. The SEs are largely generated at the outlet of the LPC. Moreover, both the energy distribution of BEs and the magnitude of the density of SEs are closely related to the pressure of LPC. Thus, a conclusion is drawn that a low magnitude of LPC pressure is helpful for reducing the energy loss in the LPC and also useful for greatly increasing the secondary electron density in dense air.     

临近声速气流条件下电子束空气等离子体特性

为了研究高速动态气流中的电子束等离子体特性,建立了一个由蒙特卡罗模型、多组分等离子体模型与计算流体力学模型组成的多阶段耦合数值模型,在临近声速气流条件下,对1.33×104 Pa空气电子束等离子体特性进行了研究。结果表明,电子束能量沉积具有极强的空间不均性,电子束激发下的风洞流场呈现不同的性质,亚声速流场下游边界区密度减小,而在超声速流场中可诱发弱激波;相比于静止气体,在动态气流中等离子体密度下降,且存在额外的输运行为,使其向气流下游输运,但在临近声速条件下,气流速度大小对气流下游等离子体分布的影响不大;电子束入射角对等离子体空间分布和大小均有影响。     

非结构化网格下自由分子微电热推力器数值模拟

采用非结构化网格,压力边界条件的DSMC-FVM耦合方法对自由分子微电阻加热推力器微喷管内的流动与换热进行了数值模拟.分析了微喷管的流场特征,证明所采用的DSMC-FVM多尺度方法对微喷管内流场与温度场模拟是合适而且必要的.     

Numerical Study on Characteristics of Argon Radio-Frequency Glow Discharge with Varying gas Pressure

A one-dimensional fluid simulation on argon rf glow discharge with varying linearly gas pressure from 1 Torr to 100 Tort is performed. The model based on mass conservation equations for electron and ion under diffusion and mobility approximation, and the electron energy conservation equation is solved numerically by finite volume method. The numerical results show that a uniform plasma with high density can be obtained from rf glow discharge with varying gas pressure, and the density of plasma becomes higher as the gas pressure varies from 1 Tort to 100 Tort. It is also shown that in the range of the gas pressure from 1 Tort to 100 Tort with the slower rate of varying gas pressure, higher density of plasma can be obtained.     

非均匀磁场约束条件下的电子束空气等离子体特性

为了揭示大气环境电子束等离子体的性质,基于蒙特卡罗程序包Geant4建立了一个包含电离、激发以及轫致辐射等物理过程的计算模型,用于模拟非均匀磁场约束条件下高能强流稳态电子束的输运特性、以及大气环境等离子体的性质。结果表明:非均匀磁场可以有效控制电子束在空气中的输运轨迹,显著降低电子束的发散;随着电子束在空气中行程的增加,电子束能谱开始展宽并向低能区移动;输运装置出口能量损失比电子束射程末端高2个量级,且随着电子束输运距离的增加,等离子体密度降低;等离子体密度的高低与电子束能量直接相关。