低气压条件下氢气潘宁放电的模拟分析

为更好地理解低气压、弱电离条件下潘宁离子源放电过程中离子和电子的动力学行为, 通过建立二维轴对称模型, 采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法, 考虑了电子与氢气之间的弹性碰撞、激发、电离以及氢原子、离子之间的弹性碰撞和电荷交换等过程, 对微型氢气潘宁离子源放电和引出过程进行了数值研究. 考察了磁场位形、壁面二次电子发射系数、引出电压和充气压力对放电过程的影响, 得到了实验中难以诊断得到的放电腔内电子与离子数密度分布, 阳极电流、引出极离子电流、单原子氢离子比例和双原子氢离子比例等宏观参数与实验结果相一致. 通过仿真使得对氢气潘宁放电机制的研究从定性过渡到定量, 这对于潘宁离子源的设计和改进具有重要意义. 关键词： 潘宁放电 氢气 粒子模拟 蒙特卡罗     

级联弧放电氦等离子体特性研究

采用另加偏压的单阴极弧氦放电直线等离子体装置对氦等离子体的基本特性进行了研究。对氦轴向输运规律做了描述并与光谱测量数据做了定性地比较。实验结果表明,氦等离子体的电子温度与电子密度均随放电电流、约束磁场的增加而增加。氦原子与氦离子的辐射光谱随放电电流、偏压、磁场的变化规律进行了测量分析,同时氦离子对钨靶积分辐照效应进行了观察。这些结果不但提供了氦等离子体的基本特性,对于研究氦离子与面向等离子材料相互作用导致产生气泡、肿胀、脆化损伤等的评估,特别是对将来伴有(n, α)反应时具有一定的参考价值。     

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采用另加偏压的单阴极弧氦放电直线等离子体装置对氦等离子体的基本特性进行了研究.对氦轴向输运规律做了描述并与光谱测量数据做了定性地比较.实验结果表明,氦等离子体的电子温度与电子密度均随放电电流、约束磁场的增加而增加.氦原子与氦离子的辐射光谱随放电电流、偏压、磁场的变化规律进行了测量分析,同时氦离子对钨靶积分辐照效应进行了观察.这些结果不但提供了氦等离子体的基本特性,对于研究氦离子与面向等离子材料相互作用导致产生气泡、肿胀、脆化损伤等的评估,特别是对将来伴有(n,α)反应时具有一定的参考价值.     

不同成分等离子体鞘层的玻姆判据

在一维平板鞘层中采用流体模型分别研究了不同成分无碰撞等离子体鞘层的玻姆判据.通过拟牛顿法数值模拟了含有电子、离子、负离子以及二次电子的等离子体鞘层玻姆判据.结果表明二次电子发射增加了鞘层离子马赫数的临界值,且器壁发射二次电子温度越高,离子马赫数临界值越小.负离子使离子马赫数临界值减小.而在含有二次电子和负离子的等离子体鞘层中,当负离子较少时,二次电子发射对离子马赫数临界值影响较大;当负离子增加时,离子马赫数的临界值则主要受负离子的影响. 关键词： 鞘层 等离子体 玻姆判据     

氩气微腔放电中特性参数的数值模拟研究

本文采用二维自洽完全流体模型,针对阳极为通孔的高气压微腔放电结构,研究了微腔放电的参数特性.数值计算得到了氩气压强为100 Torr,放电稳态时的电势分布、电子数密度分布和电子温度分布等重要参数.模拟结果表明放电区存在显著的阴极鞘层结构,电子数密度的峰值达到10²⁰ m^-3,电子温度的量级为几个eV至十几eV,该结论与实验结果相一致.数值模拟合理的解释了微腔放电的基本原理. 关键词： 微腔放电 等离子体模拟 流体模型     

圆柱形阳极层霍尔等离子体加速器的质点网格方法模拟

对圆柱形阳极层霍尔加速器内的放电等离子体运用二维质点网格方法（particle in cell）进行数值模拟,用蒙特卡罗碰撞方法处理带电粒子与中性粒子之间的碰撞. 得到了放电通道内离子与电子的分布以及离子流的运动,并且对出口外侧的能量分布进行了统计. 结果发现圆柱形阳极层等离子体加速器的磁场对电子有明显的约束作用,电子集中于阳极附近很小的区域内. 由于电磁场的特殊分布,离子流呈现出双峰式的分布. 离子能量范围从放电电压的20%到接近放电电压,平均能量在放电电压的40%—50%之间. 关键词： 质点网格方法 蒙特卡罗碰撞 数值模拟 阳极层霍尔等离子体加速器     

用自洽的蒙特卡罗—流体结合模型模拟溅射过程

 采用自洽的蒙特卡罗－流体结合模型对溅射过程进行模拟,以了解等离子体粒子行为与溅射参数的关系。溅射过程包括气体放电和溅射原子传输。对于气体放电,蒙特卡罗部分模拟快电子和快气体原子,而流体部分则描述离子和慢电子。对于溅射原子传输,蒙特卡罗部分模拟溅射原子的碰撞过程,而流体部分则描述溅射原子的扩散和漂移。模拟的结果包括：等离子体粒子的密度和能量分布;不同电离机制对气体原子和溅射原子电离的贡献;不同等离子体粒子对阴极溅射碰撞的贡献;溅射原子的密度分布;溅射场和溅射粒子相对于入射离子能量和角度的分布;溅射原子经碰撞后在整个等离子体区的分布。     

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通过使用数值模拟和实验相结合的方法研究圆柱形霍尔等离子体推进器。应用蒙特卡洛方法和Particle In Cell(PIC)方法对放电通道内等离子体碰撞和行为进行模拟。建立圆柱形霍尔推进器的物理和数值模型;通过对放电和加速区等离子体的产生和输运进行模拟,掌握了等离子体放电和加速机理以及内磁极的刻蚀情况。结果表明:随着电压的升高,内磁极刻蚀较为严重;推进器内部离子能量值约为放电电压值的50%左右。同时通过实验方法测定不同放电电压情况下推进器的放电性能。     

圆柱形霍尔推进器的三维刻蚀模拟与实验研究

通过使用数值模拟和实验相结合的方法研究圆柱形霍尔等离子体推进器。应用蒙特卡洛方法和Particle In Cell (PIC)方法对放电通道内等离子体碰撞和行为进行模拟。建立圆柱形霍尔推进器的物理和数值模型;通过对放电和加速区等离子体的产生和输运进行模拟,掌握了等离子体放电和加速机理以及内磁极的刻蚀
情况。结果表明：随着电压的升高,内磁极刻蚀较为严重;推进器内部离子能量值约为放电电压值的50%左右。同时通过实验方法测定不同放电电压情况下推进器的放电性能。     

电子回旋共振等离子体密度均匀性的数值研究

基于漂移扩散近似,在轴对称假设下,对电子回旋共振等离子体源腔室内的等离子体建立了二维流体模型.采用有限差分法对所建立的模型进行了自洽数值模拟,得到了等离子体密度均匀性随时间演化的数值结果.通过对数值结果的分析,研究了背景气体压强、微波功率和磁场线圈电流对等离子体密度均匀性的影响.研究表明,在电离初期,电子密度的均匀性好于离子密度的均匀性.在电离后期,离子密度的均匀性好于电子密度的均匀性.随着背景气体压强的增大,电子密度和离子密度的均匀性都在增加,且离子密度的均匀性增加的更快.随着微波功率的增大,电子密度和 关键词： 等离子体密度均匀性 背景气体压强 微波功率 磁场线圈电流     

Numerical investigation of the plasma processes for propellant heating in electrothermal plasma thruster for nanosatellites

Numerical investigation of the plasma processes in a cylindrical chamber with small dimensions of a novel microwave electrothermal plasma thruster for nanosatellites has been conducted. The absorbed microwave power from the electrons in the plasma column of the surface wave discharge is included in the computational model as a heat source with Gaussian distribution. The computational model takes into account the elastic and inelastic collisions of the electrons with the atoms in the ground state and two excited states (−s, −p) and the processes of recombination and deactivation of the plasma species in the volume and on the walls of the chamber. The computational model includes the flow of neutral gas and the processes in the plasma for effective heating of neutral particles by collisions not only with electrons but also with ions. Selected combinations of input power and propellant mass flow rates are used as initial parameters for the numerical investigation. The results show that at higher mass flow rates the heating of the neutral gas is more effective and at power levels of 4 W and propellant mass flow rate of 3 mg/s the electrothermal plasma thruster demonstrates effective performance and thrust levels in the order of 1 mN.     

Development and investigation of a metal ion source for accelerators

The design and operation of a new spray-type metal ion source are described. The source is built around a plasma emitter containing metal ions and using a two-step glow discharge with double plasma compression. The necessary temperature of electrons in a discharge chamber is reached by distributing the discharge power without heating. The design of the discharge chamber is optimized. The first set of experimental data for the mass-and-charge composition of a beam generated by this source is presented.     

The Influences of the Magnetic Field Strength on the Magnetic Confinement of Primary Electrons in an Ion Source

This paper deals with the simulation of trajectories of energetic electrons under the influence of a multi-cusp magnetic field produced by a permanent magnet assembly in a ring cusp geometry which is designed for supporting a plasma based ion source. The primary electrons are assumed as being emitted from a cathode located coaxially with the cylindrical discharge chamber. The volume of the region occupied by the electron trajectories and the magnetic trapping time were evaluated and plots are presented showing the effects of the surface magnetic field strength of the magnets on the volume and the mean confinement time of primary electrons in the ion source.     

大气压管板结构纳秒脉冲放电中时域X射线研究

纳秒脉冲放电能在大气压下产生高电子能量、高功率密度的低温等离子体,由于经典放电理论无法很好地解释纳秒脉冲放电中的现象,近年来以高能逃逸电子为基础的纳秒脉冲气体放电理论受到广泛关注.纳秒脉冲放电会产生高能逃逸电子,伴随产生X射线,研究X射线的特性可以间接反映高能逃逸电子的特性.本文利用纳秒脉冲电源在大气压下激励空气放电,通过金刚石光导探测器测量放电产生的X射线,研究不同电极间隙、阳极厚度下和空间不同位置测量的X射线特性.实验结果表明,在大气压下纳秒脉冲放电能产生上升沿约1 ns,脉宽约2 ns的X射线脉冲,其产生时间与纳秒脉冲电压峰值对应,经计算探测到的X射线能量约为2.3×10-3J.当增大电极间隙时,探测到的X射线能量减弱,因为增大电极间隙会减小电场强度和逃逸电子数,从而减少阳极的轫致辐射.电极间距大于50 mm后加速减弱,同时放电模式从弥散过渡到电晕.随着阳极厚度增加,阳极后方和放电腔侧面观察窗测得的X射线能量均有所减弱,在阳极后面探测的X射线能量减弱趋势更加明显,这说明X射线主要产生在阳极内表面,因此增加阳极厚度会使穿透阳极薄膜的X射线能量减少.     

The characteristics of surface arc plasma and its control effect on supersonic flow

The characteristic of surface arc plasma included millisecond and microsecond actuation in supersonic flow is investigated both experimentally and numerically. In the experiment, the discharge characteristic of surface arc plasma in quiescent air and supersonic flow is recorded. The stable oblique shock could be observed with millisecond actuation. And the unstable compressive wave could be also observed with microsecond actuation. In the numerical investigation, plasma actuation is defined as a source term with input power density from discharge V–I characteristic, which is expected to better describe the influence of heating process. The numerical results are coincident with experimental results. In order to confirm the capability of surface arc plasma actuation to control supersonic flow, experimental investigations on control shock induced by ramp and separation of boundary layer induced by impinging shock are performed. All the results demonstrate the control effect of surface arc plasma actuation onto supersonic flow.     

HT-7托卡马克等离子体slide-away放电研究

在HT-7托卡马克上,只在等离子体放电击穿阶段充气,击穿后关闭充气阀门,让装置内真空室器壁的出气维持放电的进行,通过密度衰减实现了slide-away放电.实验分析了不同等离子体电流平台下的slide-away放电模式的密度阈值,以及相同充气量的条件下放电等离子体电流对实现slide-away放电的影响.研究了slide-away放电模式下密度提升对等离子体放电状态的影响.结果发现,slide-away放电模式下的密度提升使得H_a线辐射强度增强,等离子体中超热电子的约束性能变差,等离子体芯部的超热电子减少,高能逃逸电子厚靶轫致辐射增加. 关键词： slide-away放电 托卡马克 等离子体 逃逸电子     

Beam-plasma discharge in the propagation of a long-pulse relativistic electron beam in a medium-pressure rarefied gas

A theoretical model is given, along with a numerical analysis of the evolution of beam-plasma discharge in the propagation of a long-pulse relativistic electron beam in a rarefied gas at medium pressure. It is shown that the self-stabilization of beam-plasma discharge as a result of longitudinal inhomogeneity of the density of the discharge plasma makes it possible for the beam to traverse the beam chamber with relatively low total energy losses, including ionization losses and energy losses in the generation of oscillations. During the dissociative recombination of electrons and ions of the discharge-driven plasma, heat is released and spent in raising the temperature of the gas. The investigated collective-discharge mechanism underlying heating of the gas for a relativistic beam can be more efficient than the classical heating mechanism due to ionization losses of the beam in pair collisions of its electrons with gas particles. Zh. Tekh. Fiz. 67, 94–98 (May 1997)     

会切磁场多极离子源中磁场对等离子体特性的影响

本文提出了会切磁场多极离子源中,磁场对等离子体参数以及可引出离子束流和放电室阳极收集的离子电流影响的实验研究结果,并对该结果进行了分析讨论。     

Simple Physical Model of Generation of the Low-Pressure Radio Frequency Supersonic Plasma Jet

The paper presents a simple theoretical model of the breakdown of the supersonic plasma jet generated by the hollow cathode discharge inside the nozzle in the low pressure RF plasma-chemical reactor. Through the nozzle which is drilled in the RF electrode the working gas flows to the reactor chamber. If at the outlet of the nozzle the gas flow is supersonic the well defined plasma jet is created inside the reactor chamber. The results of our model are in qualitative agreement with experimental data.