On the energy conservation electrostatic particle-in-cell/Monte Carlo simulation: Benchmark and application to the radio frequency discharges

We benchmark and analyze the error of energy conservation （EC） scheme in particle-in-cell/Monte Carlo （PIC/MC） algorithms by simulating the radio frequency discharge. The plasma heating behaviors and electron distributing functions obtained by one-dimensional （1D） simulation are analyzed. Both explicit and implicit algorithms are checked. The results showed that the EC scheme can eliminated the self-heating with wide grid spacing in both cases with a small reduction of the accuracies. In typical parameters, the EC implicit scheme has higher precision than EC explicit scheme. Some ＂numerical cooling＂ behaviors are observed and analyzed. Some other errors are also analyzed. The analysis showed that the EC implicit scheme can be used to qualitative estimation of some discharge problems with much less computational resource cost without much loss of accuracies.

Implicit electrostatic particle-in-cell/Monte Carlo simulation for the magnetized plasma:Algorithms and application in gas-inductive breakdown

An implicit electrostatic particle-in-cell/Monte Carlo （PIC/MC） algorithm is developed for the magnetized discharging device simulation. The inductive driving force can be considered. The direct implicit PIC algorithm （DIPIC） and energy conservation scheme are applied together and the grid heating can be eliminated in most cases. A tensor-susceptibility Poisson equation is constructed. Its discrete form is made up by a hybrid scheme in one-dimensional （1D） and two- dimensional （2D） cylindrical systems. A semi-coarsening multigrid method is used to solve the discrete system. The algorithm is applied to simulate the cylindrical magnetized target fusion （MTF） pre-ionization process and get qualitatively correct results. The potential application of the algorithm is discussed briefly.

Particle-in-cell/Monte Carlo simulation of filamentary barrier discharges

The plasma behavior of filamentary barrier discharges in helium is simulated using a twodimensional（2D） particle-in-cell/Monte Carlo model. Four different phases have been suggested in terms of the development of the discharge： the Townsend phase; the space-charge dominated phase; the formation of the cathode layer, and the extinguishing phase. The spatialtemporal evolution of the particle densities, velocities of the charged particles, electric fields, and surface charges has been demonstrated. Our simulation provides insights into the underlying mechanism of the discharge and explains many dynamical behaviors of dielectric barrier discharge（DBD） filaments.

Calculation of Electron Swarm Parameters of SF_6/N_2 in a Uniform Field Using an Improved Monte Carlo Collision Simulation Method

The electron swarm parameters of SF6/N2 are calculated in the present study using an improved Monte Carlo collision simulation method （MCS）. And some improved sampling techniques are also adopted. The simulation results show that the improved simulation method can provide more accurate results.

Characterization of Nitrogen Glow Discharge Plasma via Optical Emission Spectrum Simulation

Optical emission spectroscopy in nitrogen glow discharge plasma is simulated, and the collision excitations and characteristic emissions of the species （N2, N2^＋, N^＋, N） are investigated by a Monte Carlo model for nitrogen molecular gas discharge. The excitation rates of the main excited states are calculated and the corresponding relation and relative magnitude between the distribution of excitation rate of a certain excited state and the distributions of the emission rates of various lines originating from this excited level are also explored. The simulated results are compared with the experimental measurements in two typical discharge conditions. The luminescence mechanism of the line N2^＋： 391.4 nm is explained based on the microscopic plasma processes. The cathode glow in N2 discharge is found to be mainly caused by N^＋ impact excitation and the intensity of cathode glow decreases with the voltage. The corresponding relation between the emission rate or intensity of the 391.4 nm line and the production rate and the density of N2^＋ is also examined.

Three-dimensional PIC/MCC simulation of electron deposition in JAEA 10 A ion sources

A systematic research on the electron deposition process in the JAEA 10 A ion source is carried out by using a particle-in-cell/Monte Carlo collision simulation, which is based on a full three-dimensional self-developed code. Two parts are studied. One is the space and energy distribution of fast and slow electrons, the other is the vibration excitation collisions between electrons and hydrogen moleculars. The results show that the inhomogeneity of electrons comes from the Y direction drift of the fast electrons （Te ≥25 eV） due to the action of the magnetic fields. This drift also increases the number of vibration excitation collisions in the -Y direction, and results in the increase of Ha in the -Y direction, eventually leading to the -Y drift of H^-. It explains the spatial non-uniformity in the JAEA 10 A ion source.

基于水质特征因子和Monte Carlo理论的雨水管网混接诊断方法

基于水质特征因子法,引入蒙特卡罗理论,建立了分流制排水系统雨污混接诊断的定量分析方法.以上海市某混接分流制排水系统为研究对象,采用安赛蜜和总氮、氟化物、硬度分别作为表征生活污水、半导体工业废水和地下水混接的水质特征因子,对雨水管网混接来源进行了解析.与观测值对比验证表明,由于蒙特卡罗方法考虑了混接来源中多个混接点空间质量浓度差异性以及测量误差等不确定性因素,与目前采用的确定性解析方法相比,可以显著提高解析结果的可靠性,在实现解析结果闭合的同时,解析误差能够控制在10%以内.据此,提出了建立水质特征因子数据库的指导原则.

N_2/H_2辉光放电等离子体电子碰撞电离的Monte Carlo模拟

采用N2/H2直流辉光放电等离子体综合的Monte Carlo模型,通过计算N2/H2混合气体直流辉光放电等离子体电子碰撞电离及离解电离率,电子密度及电子能量分布函数,研究了H2的浓度对氮辉光放电等离子体电子碰撞电离过程的影响.研究结果表明：随着H2浓度的升高,电子的电离及离解电离碰撞率减少;但在一定的放电条件下,加入少量的H2,可以提高电子碰撞电离及离解电离率,即选取合适的放电参数,加入少量的氢,可以提高放电空间的电子及离子的密度.模型考虑了12种和电子相关的反应,在氮气中加氢的比例为0-30%.这些影响能通过放电中发生的碰撞过程及鞘层厚度的改变得到解释.研究结果为认识N2/H2混合气体辉光放电等离子体过程机理提供参考依据.

直流辉光放电氮原子离子的Monte Carlo模拟研究

采用氮直流辉光放电等离子体中快电子和离子(N+2,N+)混合的蒙特卡罗模型,模拟研究了e-+N2N++N+2e和N+2+N2N++N+N2过程离子N+的产生率轴向分布随放电参数的变化规律及其轰击阴极的能量分布.结果表明,两种离解过程中氮原子离子(N+)的产生率均随气压和电压的增加而增大,随放电气体温度的升高而降低;但N+2-N2离解碰撞主要发生在阴极附近.在电压较高时,阴极处的N+主要由N+2-N2离解过程产生;在电压较低时,N+2-N2离解过程可忽略.

Particle-in-Cell with Monte CarloCollisions Gun Code Simulations of a Surface-Conversion H^(−)Ion Source

We present an extended update on the status of a particle-in-cellwithMonte Carlo collisions(PIC-MCC)gun code developed at LosAlamos for the study of surfaceconverter H−ion sources.The programis fully kinetic.Some of the program’s features include:solution of arbitrary electrostatic and magnetostatic fields in an axisymmetric(r,z)geometry to describe the self-consistent time evolution of a plasma;simulation of a multi-species(e^(−),H^(+),H^(+)_(2),H^(+)_(3),H^(−))plasma discharge from a neutral hydrogen gas and filament-originated seed electrons;full 2-dimensional(r,z)3-velocity(v_(r),v_(z),vφ)dynamics for all species;detailed collision physics between charged particles and neutrals and the ability to represent multiple smooth(not stair-stepped)electrodes of arbitrary shape and voltage whose surfaces may be secondary-particle emitters(H^(−)and e^(−)).The status of this development is discussed in terms of its physics content and current implementation details.

电动汽车采用不同充放电策略的影响评价研究

电动汽车由于其显著的节能减排潜力,已成为未来交通领域的重要转型方向。然而,电动汽车的充放电行为主要由用户决定,每辆车接入电网都会引起随机的电力负荷波动。在我国以燃煤为主要电源结构的情况下,未经调控的随机充电行为将导致交通领域的减排效益转移到发电端,使电动汽车发展的节能减排目标失去实际意义。因此,电动汽车的发展需要重点研究充放电策略。充放电策略有无序充电策略、有序充电策略和V2G策略三种方式。本文总结了电动汽车充放电负荷的影响因素,主要包括电动汽车类型、电池容量、日行驶里程、充电起始时间、充放电功率、电价等,根据统计概率对这些主要影响因素建立了概率统计模型,并使用蒙特卡洛模拟法预测电动汽车负荷,得到不同充放电策略下满足电动汽车电力需求的日负荷曲线。然后,使用重庆市实际数据进行仿真,探究在实际条件下,规模电动汽车用户采用无序充电、有序充电、V2G对电网、环境和用户等各方面的影响,为利益相关者提供决策依据,并根据结论提出科学、合理、有前瞻性的管理建议。

Generation and Distribution of Fast Atomic Species(N^+,N_f)in Nitrogen Glow Discharge

Using a combination of the Monte Carlo models of fast electrons, of molecular ions （N＋） and of atomic species （N^＋, Nf）, the influence of the discharge pressure （P） and voltage （Vc） on the energy distributions of fast atomic species （N^＋, Nf） produced by e^--N2s and N2^＋- N2s dissociation reactions at the cathode in a nitrogen dc glow discharge was investigated. Both the angular distributions and the density distributions along the radius of the species （N^＋, Nf） produced by the two dissociations at the cathode were calculated. The results show that： （1） there is an optimum discharge condition for P and Vc in order to obtain the species （N^＋, Nf） at the cathode with high a density and energy, （2） when the voltage is above 800 V, the species （N^＋, Nf） bombarding the cathode are mainly produced by the N^＋-N2s dissociation, whereas when the voltage is below 300 V, they are mainly produced by the e-N2s dissociation, and （3） at high Voltages the incident angles of a considerable number of Nf into the cathode are quite small. The density of the species （N^＋ Nf） at the cathode increases with the voltage, and when the pressure goes up to about 133 Pa, it decreases with the increasing pressure.

基于蒙特卡洛模拟的声电联合局部放电定位阵列设计及快速定位方法研究

针对目前局部放电声电联合定位中传感器阵列和定位算法设计缺乏统一评价指标的问题,通过对到达时间差算法误差来源进行分析,提出通过蒙特卡洛模拟对阵列及定位算法的定位能力进行定量分析的方法。综合考虑空间限制和定位能力,应用上述方法对平面圆形阵列阵元数量和阵列半径进行了优化,并确定平面圆形阵列的最优阵列半径为35 mm,阵元数量为4~6个。随后基于所提方法,针对4阵元平面圆形阵列对到达时间差算法求解过程进行了优化,提出先通过一次方程组解得x、y后,回带误差最小二乘函数计算z坐标的方法,大幅减小了计算量。最后利用有限元仿真软件和油中放电实验平台,对所设计4阵元圆形阵列及局部放电定位算法进行了验证,定位误差小于65 mm。

微型溅射离子泵的阳极筒长度对抽气特性的影响

基于粒子云网格法与蒙特卡罗法,使用VSim软件对微型溅射离子泵内部潘宁放电的工作过程进行了分析.建立了二维仿真模型并得到了氮气离子入射阴极板时的入射能量、入射角度和入射位置等参数.将非垂直溅射产额理论与仿真得到的结果相结合,分析了阴极板上溅射产额的分布规律.根据离子入射参数与溅射产额,计算得到了微型溅射离子泵对氮气的抽速.计算值与实验结果一致性好并且该方法可以给出溅射离子泵抽速阈值对应的压力.仿真结果中增加阳极筒长度可以降低微型溅射离子泵抽速阈值对应的压力,并通过实验证明.

TEM模式同轴谐振腔低气压放电蒙特卡罗仿真和实验研究

随着无线通信系统高频小型化的发展趋势,对微波滤波器设计提出更为严苛的要求。其中功率容量作为衡量滤波器性能的重要指标,在滤波器尺寸不断缩小的情形下面临严峻的挑战。谐振器作为滤波器基本组成单元,对单一谐振器的功率容量准确预测十分重要。本文针对工作频率在2.6 GHz的TEM模式同轴谐振器,将电容加载的耦合结构近似为平行平板结构,利用单粒子蒙特卡罗方法仿真获得同轴谐振器临界击穿电场,实现了对该结构同轴谐振腔的低气压放电功率阈值仿真预测。对所设计同轴谐振腔开展低气压放电实验研究,获得了100~1000 Pa气压范围内击穿功率阈值随气压的变化关系实验曲线,并验证了单粒子蒙特卡罗仿真预测方法的准确性。

真空高功率微波介质窗表面击穿破坏现象的研究进展

综述了国内外真空中高功率微波(HPM)下介质窗表面击穿问题的研究现状和进展。在介质窗表面击穿实验研究方面,介绍了国外最具代表性的研究成果,给出了介质窗材料表面及内部的破坏发展规律,并提出相应的理论模型。在理论仿真方面,重点介绍了国外在运用蒙特卡罗(Monte Carlo)程序和PIC模型对认识HPM下介质窗表面倍增放电机理上做出的突出贡献,给出了HPM下介质窗表面电子在不同影响因素下的运行状态,并提出了一个理论模型,从本质上解释了倍增电子数目和表面静电场以微波频率的2倍振荡的原因。介绍了目前几种可有效抑制介质窗表面微波击穿的技术手段。

电动汽车充放电特性及其对配电系统的影响分析

随着电动汽车技术特别是电池技术的发展和一些发达国家在政策方面的大力支持,电动汽车在最近几年得到快速发展。大量电动汽车的广泛应用肯定会对电力系统尤其是配电系统产生影响,因此就很有必要研究电动汽车充电时的需求特性和电动汽车接入网络(Vehicle to Grid,V2G)时的放电容量曲线。在此背景下,采用蒙特卡洛仿真方法首先对此问题做了研究,之后分析了电动汽车单向无序充电和V2G下对系统负荷、网损和电压的影响。最后,以美国PG&E 69节点配电系统为例,通过仿真分析了在不同的电动汽车渗透率下,电动汽车单向无序充电和V2G方式下对系统负荷、网损和电压的影响。计算结果表明:在电动汽车渗透率较高的情况下,无序充电会对配电系统的安全与经济运行带来比较明显的影响甚至挑战,而合理的充放电管理则可以改善这种状况。

高功率微波沿面闪络击穿机制粒子模拟

针对高功率微波介质沿面闪络击穿物理过程,首先建立了理论模型,包括:动力学方程、粒子模拟算法、二次电子发射,以及电子与气体分子蒙特卡罗碰撞模型、电子碰撞介质表面退吸附气体分子机制;其次,基于理论模型,编制了1D3VPIC-MCC程序,分别针对真空二次电子倍增、高气压体电离击穿和低气压面电离击穿过程,运用该程序仔细研究了电子和离子随时间演化关系、电子运动轨迹、电子及离子密度分布、空间电荷场时空分布、电子平均能量、碰撞电子平均能量、碰撞电子数目随时间演化关系、电子能量分布函数、平均二次电子发射率以及能量转换关系。研究结果表明:真空二次电子倍增引发的介质表面沉积功率只能达到入射微波功率1%左右的水平,不足以击穿;气体碰撞电离主导的高气压体电离击穿,是由低能电子(eV量级)数目指数增长到一定程度导致的,形成位置远离介质表面,形成时间为μs量级;低气压下的介质沿面闪络击穿,是在二次电子倍增和气体碰撞电离共同作用下,由于数目持续增长的高能电子(keV量级)碰撞介质沿面导致沉积功率激增而引发的,形成位置贴近介质沿面,形成时间在ns量级。

氮气空心阴极辉光放电等离子体离子的蒙特卡罗模拟研究

采用蒙特卡罗模型对氮空心阴极放电等离子体鞘层离子(N2+、N+)的输运过程进行了模拟研究,计算了阴极鞘层中氮离子(N2+、N+)的能量及角分布的空间变化和粒子密度及平均能量随放电参数的变化规律。研究结果表明:空心阴极放电产生的氮离子,在鞘层输运过程中,N2+是密度几乎不变的低能粒子;N+是密度逐渐减少的高能粒子。随着电压增加,N+密度减小,平均能量增加;N2+密度和平均能量变化不明显。能量及入射角的相对分布规律与平板电极氮直流辉光放电基本类似,但圆筒空心阴极放电更有利于氮离子的产生。

氩直流辉光放电等离子体中电子运动及能量的模拟

采用自动调节时间步长的蒙特卡罗模拟,对平行板放电系统中的氩气直流辉光放电系统中的等离子体区内电子的运动过程进行了跟踪和抽样。统计结果表明:在我们的实验条件下,等离子体中的电子在电场作用下出现明显的轴向漂移;在40000次抽样中,出现能量为E的电子数目随能量E增大呈下降趋势,场强增大将引起能量分布展宽和电子平均能量增加;即使场强达到15V·cm-1,等离子体激发和电离仍是很少的;场强和气压都能明显改变电子的平均自由程。