Exploration of microscopic physical processes of Z-pinch by a modified electrostatic direct implicit particle-in-cell algorithm

For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-angle cumulative binary collision algorithm is used.In our algorithm,the electric field in z-direction is solved by a parallel electrode-plate model,the azimuthal magnetic field is obtained by Ampere’s law,and the term for charged particle gyromotion is approximated by the cross product of the averaged velocity and magnetic field.In simulation results of 2 MA deuterium plasma shell Zpinch,the mass-center implosion trajectory agrees generally with that obtained by one-dimensional MHD simulation,and the plasma current also closely aligns with the external current.The phase space diagrams and radial-velocity probability distributions of ions and electrons are obtained.The main kinetic characteristic of electron motion is thermal equilibrium and oscillation,which should be oscillated around the ions,while that of ion motion is implosion inwards.In the region of stagnation radius,the radial-velocity probability distribution of ions transits from the non-equilibrium to equilibrium state with the current increasing,while of electrons is basically the equilibrium state.When the initial ion density and current peak are not high enough,the ions may not reach their thermal equilibrium state through collisions even in its stagnation phase.

Particle-in-cell simulations of EUV-induced hydrogen plasma in the vicinity of a reflective mirror

Particle-In-Cell(PIC)simulations were performed in this work to study the dynamics of the EUVinduced hydrogen plasma.The Monte-Carlo Collision(MCC)model was employed to deal with the collisions between charged particles and background gas molecules.The dynamic evolution of the plasma sheath,as well as the flux and energy distribution of ions impacting on the mirror surface,was discussed.It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium mirror coating creates a positively charged wall and then prevents the ions from impacting on the mirror and therefore changes the flux and energy distribution of ions reaching the mirror.Furthermore,gas pressure has a notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors.With greater gas pressure,the sheath potential decreases more rapidly.The flux of ions received by the mirror grows approximately linearly and at the same time the energy corresponding to the peak flux decreases slightly.However,the EUV source intensity barely changes the sheath potential,and its influence on the ion impact is mainly limited to the approximate linear increase in ion flux.

Implementation of a particle-in-cell method for the energy solver in 3D spherical geodynamic modeling

The thermal evolution of the Earth’s interior and its dynamic effects are the focus of Earth sciences.However,the commonly adopted grid-based temperature solver is usually prone to numerical oscillations,especially in the presence of sharp thermal gradients,such as when modeling subducting slabs and rising plumes.This phenomenon prohibits the correct representation of thermal evolution and may cause incorrect implications of geodynamic processes.After examining several approaches for removing these numerical oscillations,we show that the Lagrangian method provides an ideal way to solve this problem.In this study,we propose a particle-in-cell method as a strategy for improving the solution to the energy equation and demonstrate its effectiveness in both one-dimensional and three-dimensional thermal problems,as well as in a global spherical simulation with data assimilation.We have implemented this method in the open-source finite-element code CitcomS,which features a spherical coordinate system,distributed memory parallel computing,and data assimilation algorithms.

不同品系杜洛克、PIC与加系二元母猪杂交后代生长性能及经济效益分析

为了研究猪场引进和选育终端父本以及筛选出符合市场需求的商品猪组合,该试验选取不同品系/品种包括D系杜洛克、F系杜洛克、M系杜洛克和PIC公猪与2~4胎加系长大二元母猪进行杂交,测定母猪繁殖性能、育肥猪日增重、采食量、料肉比、死淘率以及经济效益等指标。结果显示:(1)在繁殖性能方面,D系杜洛克组(DC)总产仔数和产健仔数均显著高于M系杜洛克组(MC)(P<0.05);F系杜洛克组(FC)初生健仔窝重显著高于MC(P<0.05);MC组初生头均重显著高于PIC组(PC)(P<0.05)。(2)商品猪生长性能方面,DC组达校正100 kg日龄最短;MC组170日龄料肉比显著高于PC组(P<0.05);DC组170日龄日增重显著PC组(P<0.05)。DC组出栏重显著高于其他3组(P<0.05);平均日增重显著高于PC组(P<0.05)。MC组出栏料肉比显著高于PC组(P<0.05);FC组出栏死淘率最低为2%。可见,在同等条件下,DC组产仔数最高且在生长速度方面具有明显优势,经济效益最好。

基于MPI+CUDA的DSMC/PIC耦合模拟异构并行及性能优化研究

DSMC/PIC耦合模拟是一类重要的高性能计算应用,大规模DSMC/PIC耦合模拟计算量巨大,需要实现高效并行计算。由于粒子动态注入、迁移等操作,基于MPI并行的DSMC/PIC耦合模拟往往通信开销较大且难以实现负载均衡。针对自主研发的DSMC/PIC耦合模拟软件,在原有MPI并行优化版本上设计实现了高效的MPI+CUDA异构并行算法,结合GPU体系结构和DSMC/PIC计算特点,开展了GPU访存优化、GPU线程工作负载优化、CPU-GPU数据传输优化及DSMC/PIC数据冲突优化等一系列性能优化。在北京北龙超级云HPC系统的NVIDIA V100和A100 GPU上,针对数亿粒子规模的脉冲真空弧等离子体羽流应用,开展了大规模DSMC/PIC耦合异构并行模拟,相比原有纯MPI并行,GPU异构并行大幅缩短了模拟时间,两块GPU卡较192核的CPU加速比达到550%,同时具有更好的强可扩展性。

Speeding-up direct implicit particle-in-cell simulations in bounded plasma by obtaining future electric field through explicitly propulsion of particles

The direct implicit particle-in-cell is a powerful kinetic method for researching plasma characteristics.However,it is time-consuming to obtain the future electromagnetic field in such a method since the field equations contain time-dependent matrix coefficients.In this work,we propose to explicitly push particles and obtain the future electromagnetic field based on the information about the particles in the future.The new method retains the form of implicit particle pusher,but the future field is obtained by solving the traditional explicit equation.Several numerical experiments,including the motion of charged particle in electromagnetic field,plasma sheath,and free diffusion of plasma into vacuum,are implemented to evaluate the performance of the method.The results demonstrate that the proposed method can suppress finite-grid-instability resulting from the coarse spatial resolution in electron Debye length through the strong damping of high-frequency plasma oscillation,while accurately describe low-frequency plasma phenomena,with the price of losing the numerical stability at large time-step.We believe that this work is helpful for people to research the bounded plasma by using particle-in-cell simulations.

离子电推进器模拟中Particle-in-Cell模型的发展与应用综述

离子推进器是一种被广泛应用于各类航天器中的重要动力装置。数值模拟在揭示离子推进器的物理机理和辅助结构设计等方面发挥了重要的作用,成为离子推进器研究中必不可少的研究方法。为了推动离子电推进技术的创新发展,并确保其能够持续满足当前和未来航天任务对推进技术的要求,详细总结了Particle-in-Cell(PIC)粒子模型在离子推进器模拟中的发展和应用现状。梳理和总结了放电室、栅极系统、羽流区这三个关键区域及多区域一体化建模的全PIC和混合PIC的研究进展。针对离子推进器数值模拟研究的需求,指出了粒子模型未来的发展方向,为离子推进技术的发展提供理论支撑。

基于PIC-MCC实现空气介质阻挡放电过程的数值模拟

在大气压介质阻挡放电的实际应用中,空气介质阻挡放电具有极其广泛的工业化应用前景。目前,空气均匀放电的获得仍比较困难,且诊断均匀性的依据缺乏可信的依据。文章采用粒子云网格法(Particle in Cell,PIC)与蒙特卡罗碰撞(Monte Carlo Collision,MCC)方法模拟了放电过程中粒子的运动情况,研究大气压下空气介质阻挡放电的发展过程,然后讨论介质厚度、电源频率对形成均匀放电的影响,并研究这两种因素对等离子体密度的影响。模拟结果表明:介质厚度在d≥1.5 mm时可获得没有放电细丝的电流波形;电源频率高于2.5 kHz时,放电细丝是难以避免的。在能够形成均匀放电的条件下,将介质厚度适当的调整在1.5 mm附近,提高电源频率,将产生更高的等离子体密度。

浅析国家药监局加入药品检查合作计划(PIC/S)中广东药监面临的形势与发展展望

国家药监局加入药品检查合作计划(PIC/S)的进程已经进入正式申请阶段,这将加速推动我国药品监管体系国际化现代化发展。本文简要介绍了PIC/S的相关情况,梳理了国家药监局加入该组织的主要进程以及国内近年来在药品GMP检查体系和相关能力建设方面的工作进展,展望了该形势下广东省药监局联合港澳地区协同推进药品监管能力建设、凝聚自身实践经验、助力国家药品监管和药品产业发展的工作脉络。

UPLC-MS/MS的“PICs”功能在分析浓香型白酒5种人造甜味剂中的应用及数据库建立

为了建立UPLC-MS/MS测定浓香型白酒中5种人造甜味剂的快速定量和定性分析方法,本研究将样品直接加水稀释后,采用高速离心进行净化,以ACQUIYT UPLC^(■)BEH C_(18)色谱柱(2.1 mm×50 mm,1.7μm)为分析柱,0.05%氨水水溶液和甲醇为流动相进行梯度洗脱分离,选取电喷雾电离源,利用UPLC-MS/MS的多反应监测模式,在同一时间下完成5种甜味剂的筛选,针对疑似检出的阳性物质以触发PICs功能,得到二级质谱图,通过与标准品比对得到匹配度数值作为定性确认。结果表明,甜蜜素、糖精钠、安赛蜜、三氯蔗糖和纽甜5种人造甜味剂在0.01~0.5μg/mL范围内线性关系良好(r^(2)>0.99),方法检出限LOD(S/N=3)为0.107~1.92μg/L,方法定量限LOQ(S/N=10)为0.358~6.39μg/L;空白样品在3个加标水平下的平均回收率为91.3%~117.1%,相对标准偏差(relative standard deviations,RSDs,n=6)为0.42%~6.67%。该检测方法操作简单、成本低、结果准确,可用于白酒中人造甜味剂的检测。

Modes decomposition in particle-in-cell software CEMPIC

The numerical method of modes analysis and decomposition of the output signal in 3D electromagnetic particle-in-cell simulation is presented. By the method, multiple modes can be resolved at one time using a set of diagnostic data, the amplitudes and the phases of the specified modes can all be given separately. Based on the method, the output signals of one X-band tri-bend mode converter used for one high power microwave device, with ionization process in the device due to the strong normal electric field, are analyzed and decomposed.

加入PIC/S对我国职业化专业化药品检查员队伍建设的思考

目的:对我国职业化专业化药品检查员队伍建设进行深入思考,以期为早日加入PIC/S国际组织,实现我国药品检查国际化,促进我国医药行业走向世界提供参考与借鉴。方法:对照PIC/S审计清单中对检查员要求的模块,概述PIC/S对检查员的要求,对我国检查员队伍现状进行分析,对我国职业化专业化药品检查员队伍建设进行深入思考。结果与结论:为加快建立职业化专业化药品检查员队伍,以满足PIC/S对药品检查员的要求,应扩大职业化专职化检查员的规模,深入推进检查员的分级分类管理。同时,需要建立高素质的检查员培养模式,以提升其检查能力。此外,还应建立具有职业特点的职称评审体系,并完善检查员的薪酬待遇保障机制和激励机制,以充分调动检查员提升能力的积极性和主动性,为我国早日加入PIC/S提供坚实保证。

PIC/S技术标准指南体系分析

国家药品监督管理局已于2023年9月正式提交了加入药品检查合作计划(PIC/S)申请并已成为正式申请者。当前,PIC/S针对申请加入机构和制药行业颁发了大量的技术标准与指南,熟悉并掌握这些技术标准指南,有助于药品监管机构和制药行业更有效地推进和应对加入PIC/S工作。参考PIC/S网站,本文按照GMP标准、机构指南、指导文件、备忘录和其他文件的分类原则,对PIC/S发布的现行技术标准与指南进行了系统分析与梳理,从体系层面对其进行了研究,以期为业内机构和人员更好地理解PIC/S标准指南体系提供参考。

霍尔推进器等离子体鞘层特性的Particle-in-Cell模拟

霍尔(Hall)等离子体推进器鞘层特性对推进器的性能具有重要影响。针对Hall推进器鞘层区域建立物理模型,采用粒子模拟方法(PIC),通过求解泊松方程得到粒子位置产生的电场,确定边界条件,研究了不同磁感应强度和方向、不同推进工质和粒子权重对推进器鞘层电势及壁面二次电子发射系数的影响规律。结果表明:当磁感应强度为0.04T时,随着磁场方位角的增大,鞘层电势绝对值升高,壁面二次电子发射系数降低,变化量在10-3量级;磁场大小对鞘层电势及壁面二次电子发射系数影响较小;对于氩、氪和氙3种工质,鞘层电势和二次电子发射系数依次降低;而当粒子权重大于106时,等离子体鞘层振荡明显,推进器的稳定性降低。

Particle-in-Cell等离子体模拟方法的优化研究

由于PIC(Particle-in-Cell)方法在模拟GEO轨道上等离子体与航天器相互作用时计算量较大,因此限制了该方工程上的应用。文章分析了PIC方法在航天器充放电效应模拟中的计算效率问题,针对占用时间最多的泊松方程求解步骤提出了改进方法,并通过模拟验证了该方法的有效性。

5千瓦霍尔推力器磁场优化及Particle-in-Cell性能仿真

为了提升兰州空间技术物理研究所研制的一种5 k W霍尔推力器LHT—140的性能,采用ANSOFT软件进行了磁场优化设计,将磁场径向分量的轴向梯度提高了47%,相同励磁激励下放电通道中的磁场强度提高了38%。建立了一个R-Z平面内的二维particle-in-cell(PIC)等离子体模型,对磁场优化后推力器的性能进行了仿真分析,预估其在300~800 V放电电压、10~15 mg/s流率范围内,推力提升了9.6%~22.1%,效率提升了8.7%~19.3%。性能验证试验表明磁场优化后在相同放电电压与流率下,性能提升的测试值高于仿真值。

Particle-in-Cell/Monte Carlo Collision simulation of planar DC magnetron sputtering

In this paper a numerical simulation of a planar DC magnetron discharge is performed with the Particle-in Cell/Monte Carlo Collision （PIC/MCC） method. The magnetic field used in the simulation is calculated with finite element method according to experimental configuration. The simulation is carried out under the condition of gas pressure of 0.665 Pa and voltage magnitude of 400V. Typical results such as the potential distribution, charged particle densities, the discharge current density and ion flux onto the target are calculated. The erosion profile from the simulation is compared with the experimental data. The maximum erosion position corresponds to the place where the magnetic field lines are parallel to the target surface.

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.

Effects of electron trapping on nonlinear electron-acoustic waves excited by an electron beam via particle-in-cell simulations

By performing one-dimensional particle-in-cell simulations, the nonlinear effects of electronacoustic(EA) waves are investigated in a multispecies plasma, whose constituents are hot electrons, cold electrons, and beam electrons with immobile neutralized positive ions. Numerical analyses have identified that EA waves with a sufficiently large amplitude tend to trap cold electrons. Because EA waves are dispersive, where the wave modes with different wavenumbers have different phase velocities, the trapping may lead to the mixing of cold electrons. The cold electrons finally get thermalized or heated. The investigation also shows that the excited EA waves give rise to a broad range of wave frequencies, which may be helpful for understanding the broadband-electrostatic-noise spectrum in the Earth’s auroral region.

Electromagnetic Particle-in-Cell Simulations of Electron Holes Formed During the Electron Two-Stream Instability

Previous electrostatic particle-in-cell （PIC） simulations have pointed out that elec- tron phase-space holes （electron holes） can be formed during the nonlinear evolution of the electron two-stream instability. The parallel cuts of the parallel and perpendicular electric field have bipolar and unipolar structures in these electron holes, respectively. In this study, two-dimensional （2D） electromagnetic PIC simulations are performed in the x - y plane to investigate the evolution of the electron two-stream instability, with the emphasis on the magnetic structures associated with these electron holes in different plasma conditions. In the simulations, the background magnetic field （Bo = Boer） is along the x direction. In weakly magnetized plasma （Ωe 〈ωpe, where Ωe and ωpe are the electron gyrofrequency and electron plasma frequency, respectively）, several 2D electron holes are formed. In these 2D electron holes, the parallel cut of the fluctuating magnetic field δBx and δBz has unipolar structures, while the fluctuating magnetic field δBy has bipolar structures. In strongly magnetized plasma （Ωe 〉 ωpe）, several quasi-lD electron holes are formed. The electrostatic whistler waves with streaked structures of Ey are excited. The fluctuating mag- netic field δBx and δBz also have streaked structures. The fluctuating magnetic field δBx and δBy are produced by the current in the z direction due to the electric field drift of the trapped elec- trons, while the fluctuating magnetic field δBz can be explained by the Lorentz transformation of a moving quasielectrostatic structure. The influences of the initial temperature anisotropy on the magnetic structures of the electron holes are also analyzed. The electromagnetic whistler waves are found to be excited in weakly magnetized plasma. However, they do not have any significant effects on the electrostatic structures of the electron holes.