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Modeling and Simulation of Electrical Breakdown in DC for Dielectric-Loaded Systems with Non-Orthogonal Boundaries Including the Effects of Space-Charge and Gaseous Collisions.

机译：具有非正交边界的电介质负载系统（包括空间电荷和气态碰撞的影响）的直流电击穿建模和仿真。

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摘要

Improved modeling of angled-dielectric insulation in high-voltage systems is described for use in particle-in-cell (PIC) simulations. Treatment of non-orthogonal boundaries is a significant challenge in modeling angled-dielectric flashover, and conditions on boundaries are developed to maintain uniform truncation error in discretized space across the dielectric angles studied. Extensive effort was expended in isolating particular operating regimes to illustrate fundamental phenomenological surface effects that drive the discharges studied herein; consequently, this document focuses on the phenomenology of two specific dielectric angles at 6.12° for multiplicative breakdown (the so-called single-surface multipactor) and 22.9° for a non-multiplicative discharge that evolves into a dark current at steady state.;Phenomenological results for simulations in vacuum through "ultra-low pressures" on the order of a few hundred mTorr are presented. A multipactor front forms via net emission of electrons from impact on the dielectric surface, where emission leads to saturated field conditions in the wake of the front, producing a well-defined forward-peaked wave. A treatment of the gain and saturation characteristics is presented, isolating the surface electric fields as the driving contributor to both metrics. Physical models include oftenneglected effects such as space-charge, dielectric-surface charging, and particle distributions in energy and space. For the discharges treated in this study, breakdown voltages of the typical Paschen form are not applicable, since multiplicative conditions are driven primarily by surface effects.;Phenomenological results are also presented for simulations at low pressure (~ 1Torr), which is shown to be a transitional limit where volume effects become appreciable compared to surface effects. A coupling between space charge and surface charge is shown to lead to oscillatory effects in otherwise DC discharges. Surface multipactor leads to increased ionization and space charge, and the ensuing space-charge momentum alters what would have been a steady-state saturation as in the case of vacuum-like discharges. Models for diffusive outgassed species are developed and implemented, extending the capabilities of the PIC suite.;The overarching theme of this study is to communicate the dependence of multiplicative discharges dominated by surface effects on near-surface electric field conditions. It is shown through various examples from vacuum through low pressures, and in diffusive gases, that single-surface multipactor conditions can be expressed solely in terms of the dielectric surface field angles. This treatment lays the foundation for a novel extension of RF breakdown susceptibility theory [1] to the DC regime, grounding breakdown susceptibility to the well-established fundamentals on secondary emission [2, 3]. This theory shows that breakdown characteristics can be modeled in an a-priori framework, hence the lack of a Paschen-type curve.;Finally, the effect of the seed source on discharge characteristics is also studied. A comparison between a constant-waveform source, a Fowler-Nordheim source, and an application of a modified source based on theoretical treatment from [4] are presented, showing that the seed is a necessary but insufficient condition for surface flashover, where the dominant contributor is the configuration of the surface fields downstream of the seed source. While the seed can influence upstream conditions to alter the injected current, the gain characteristics of the downstream region are still well described by the framework developed in the remainder of this document.
机译：描述了用于电池中粒子（PIC）模拟的改进的高压系统中角电介质绝缘模型。在对角介电闪络进行建模时，非正交边界的处理是一个重大挑战，并且边界条件已开发出来，可以在整个介电角内的离散空间中保持均匀的截断误差。在隔离特定的工作方式上花费了很多精力，以说明驱动本文研究的放电的基本现象学表面效应。因此，本文着重研究了两个特定介电角的现象学，分别用于倍增击穿（6.12°）和所谓的非倍增放电（22.9°）的非介电角，该非稳态放电在稳态下演化为暗电流。给出了在真空中通过几百毫托的“超低压”进行模拟的结果。通过撞击电介质表面产生的净电子发射，形成了一个多端电子前沿，该发射会导致电子束在前沿唤醒后达到饱和场条件，从而产生清晰的前向波。提出了一种增益和饱和特性的处理方法，隔离了作为两个指标的驱动因素的表面电场。物理模型包括经常被忽略的效应，例如空间电荷，介电表面电荷以及能量和空间中的粒子分布。对于本研究中处理的放电，典型的帕申形式的击穿电压不适用，因为相乘条件主要是由表面效应驱动的;现象学结果还提供了在低压（〜1Torr）下进行模拟的现象，证明是与表面效果相比，体积效果变得明显的过渡极限。结果表明，空间电荷与表面电荷之间的耦合会导致直流放电中的振荡效应。表面多重放电导致电离和空间电荷的增加，并且随之产生的空间电荷动量改变了本来是饱和状态的饱和状态，如在类似真空的放电情况下。开发并实施了扩散性除气物种的模型，扩展了PIC套件的功能。本研究的总体主题是传达由表面效应主导的倍增放电对近地电场条件的依赖性。通过从真空到低压​​以及在扩散气体中的各种示例可以看出，单表面多间隔条件可以仅根据介电表面场角来表示。这种处理为将射频击穿敏感性理论[1]扩展到直流机制奠定了基础，使击穿敏感性基于已建立的二次发射基本原理[2，3]。该理论表明，击穿特性可以在先验框架内建模，因此缺少Paschen型曲线。最后，还研究了种子源对放电特性的影响。对比了恒定波形源，Fowler-Nordheim源和基于[4]的理论处理的改进源的应用，结果表明，种子是表面闪蒸的必要条件，但条件不足，其中主要贡献者是种子源下游表面场的配置。尽管种子可以影响上游条件以改变注入的电流，但本文其余部分开发的框架仍然很好地描述了下游区域的增益特性。

著录项

  • 作者

    Aldan, Manuel Thomas Pangelinan, III.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Nuclear engineering.;Plasma physics.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 212 p.
  • 总页数 212
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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