Marija Radmilovic-Radjenovic, H. S. Ko, J. K. Lee
Breakdown voltages of a capacitively coupled radio frequency argon discharge at 27 MHz are studied. We use a one-dimensional electrostatic PIC code to investigate the effect of changing the secondary emission properties of the electrodes on the breakdown voltage, particularly at low pd values. Simulation results are compared with the available experimental results and a satisfactory agreement is found.
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We formulate a possible description of the deflection of a relativistic $e^-$ beam in an inhomogeneous copper plasma, encountered by the beam when propagating through a accelerating cell that has undergone a high electric-field RF-breakdown. It is well known that an inhomogeneous plasma forms and may last for up to a few micro-seconds, until recombination in an accelerating structure where a field-emission triggers melting and ionization of RF-cell wall deformity. We present a preliminary model for the beam deflection due to collective plasma response based upon the beam density, plasma densit…
SF6 streamer breakdown induced by floating linear metal particles: Following streamers and side streamers
本研究通过二维流体模型揭示悬浮线性金属颗粒诱发 SF6 流注击穿的微观机制，提出跟随流注与侧向流注两种新机制，并阐明压力与过电压对击穿行为的影响。
In this work, we show that laser induced breakdown spectroscopy (LIBS) with a nanosecond pulse laser can be used to measure the copper and sodium content of CuIn(0.7)Ga(0.3)Se(2) (CIGS) thin film solar cells on molybdenum. This method has four significant advantages over methods currently being employed: the method is inexpensive, measurements can be taken in times on the order of one second, without high vacuum, and at distances up to 5 meters or more. The final two points allow for in-line monitoring of device fabrication in laboratory or industrial environments. Specifically, we report a li…
Experimental and numerical study on Following Streamer mechanism for SF6 breakdown induced by floating linear metal particles
本文通过负脉冲电压实验与二维轴对称流体模拟对比，验证悬浮线性金属颗粒引发SF6击穿的跟随流注机制，并提出扩展物理模型以描述三维离轴及多流注现象。
Metal vapour vacuum arcs are capable to generate multiply charged metallic ions, which are widely used in fields such as ion deposition, ion thrusters, and ion sources, etc. According to the stationary model of cathode spot, those ions are generated by electron-impact single ionization in a step-wise manner, which is M -> M+ -> M2+ -> ... mainly. This paper is designed to study quantitatively the role of double ionization M -> M2+ in the breakdown initiation of copper vacuum arcs. A direct simulation Monte Carlo (DSMC) scheme of double ionization is proposed and incorporated into a 2D particle…
It is demonstrated by three-dimensional quantum electrodynamics --- particle-in-cell (QED-PIC) simulations that vacuum breakdown wave in the form of QED cascade front can propagate in an extremely intense plane electromagnetic wave. The result disproves the statement that the self-sustained cascading is not possible in a plane wave configuration. In the simulations the cascade initiates during laser-foil interaction in the light sail regime. As a result, a constantly growing electron-positron plasma cushion is formed between the foil and laser radiation. The cushion plasma efficiently absorbs …
We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and O$_{2}^-$ ions. When the electric field rises above the breakdown and the detachment threshold, which are similar in air, electrons can detach from O$_{2}^-$ and start ionization avalanches. These avalanches together create one large discharge, in contrast to the `double-headed' streamers found in many fluid simulations. On the other hand, in background field…
We investigate streamer formation in the troposphere, in electric fields above the breakdown threshold. With fully three-dimensional particle simulations, we study the combined effect of natural background ionization and of photoionization on the discharge morphology. In previous investigations based on deterministic fluid models without background ionization, so-called double-headed streamers emerged. But in our improved model, many electron avalanches start to grow at different locations. Eventually the avalanches collectively screen the electric field in the interior of the discharge. This …
Mechanism of Ionization Avalanche in Tokamak Microwave Gas Breakdown
本研究通过三维蒙特卡罗模拟揭示平行布朗运动在托卡马克微波气体击穿电离雪崩中的关键作用，预测的击穿边界经KSTAR验证，并表明ITER条件下D₂预充压力约2 mPa、EC功率1 MW时击穿可行。
Breakdown modes of capacitively coupled plasma I: transitions from glow discharge to multipactor
本文利用一维PIC/MCC模拟研究60 MHz氩气容性放电，发现辉光放电与异常多级电子倍增之间的过渡模式，并揭示其由高二次电子发射系数和高频维持的机制。
Breakdown modes of capacitively coupled plasma II: unsustainable discharges
本文利用一维隐式 PIC/MCC 模拟纯氩极低压高频 CCP 放电，识别正常失效、偏压失效和逃逸失效三类不可持续放电机制，为确定可持续参数和避免工业损失提供依据。
Efficient Dynamic Mesh Refinement Technique for Simulation of HPM Breakdown induced Plasma Pattern Formation
本文提出一种自感知动态网格细化算法，通过粗网格与随等离子体拓扑动态扩展的细网格相结合，在保证精度的同时将高功率微波击穿模拟加速约8倍，并揭示了自组织等离子体丝化的物理机制。
Upon inclusion of collisions, the speed-limited particle-in-cell (SLPIC) simulation method successfully computed the Paschen curve for argon. The simulations modelled an electron cascade across an argon-filled capacitor, including electron-neutral ionization, electron-neutral elastic collisions, electron-neutral excitation, and ion-induced secondary-electron emission. In electrical breakdown, the timescale difference between ion and electron motion makes traditional particle-in-cell (PIC) methods computationally slow. To decrease this timescale difference and speed up computation, we used SLPI…
Laser-driven pointed acceleration of electrons with preformed plasma lens
实验演示了飞秒激光在近临界等离子体板中产生多MeV电子束并利用预等离子体透镜实现高达10度偏转的定向加速，为无磁光学元件的多级加速与原位扫描提供了新途径。
A recent paper by Huang et al. [Computer Physics Communications 207, 123 (2016)] thoroughly analyzed the Finite Grid Instability(FGI) and spectral fidelity of standard Particle-In-Cell (PIC) methods. Numerical experiments were carried out to demonstrate the FGIs for two PIC methods, the energy-conserving algorithm and the momentum-conserving algorithm. The paper also suggested that similar numerical experiments should be performed to test the newly developed Structure-Preserving Geometric (SPG)-PIC algorithm. In this comment, we supply the results of the suggested numerical experiments, which …
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