ABSTRACT Helium gas is used as the coolant in high temperature gas-cooled reactor while its insulation property is not good and brings big challenges to insulation design work. In this paper, breakdown voltages of two parallel-plate electrodes in millimeter-scale gaps at atmospheric pressure are calculated numerically with a two-dimensional hydrodynamic model. The Finite-Difference Flux-Corrected Transport method (FD-FCT) is used to avoid spurious oscillation caused by convection and diffusion restrictions. The simulation results are in good agreement with our experimental work. Different discharge characteristics are presented for a breakdown or a non-breakdown voltage. Importantly, when a breakdown is applied, ground-state ionization will make up the most in early stages while later accumulation of metastable atoms and molecules will prompt fractions of penning ionization to increase rapidly. It is predicted that penning ionization will eventually become comparable with ground-state ionization, especially near the anode, as the current density keeps increasing to order of 1 A. Some other simulation results are presented such as time evolutions of the distribution of electrons, ions, field strength and axial potential, etc. Attainment of these breakdown voltages and characteristics of helium discharge is going to help with insulation design work of electric equipment in reactor engineering.

中文翻译：

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大气压下平行板电极间短间隙氦气放电二维模拟与实验

摘要 高温气冷堆采用氦气作为冷却剂，其绝缘性能较差，给绝缘设计工作带来很大挑战。本文采用二维流体动力学模型数值计算了大气压下毫米级间隙中两个平行板电极的击穿电压。有限差分通量校正传输方法 (FD-FCT) 用于避免对流和扩散限制引起的虚假振荡。模拟结果与我们的实验工作非常吻合。针对击穿或非击穿电压呈现不同的放电特性。重要的是，当应用细分时，基态电离将在早期阶段占大部分，而亚稳态原子和分子的后期积累将促使彭宁电离的分数迅速增加。据预测，随着电流密度不断增加到 1 A 数量级，彭宁电离最终将与基态电离相当，尤其是在阳极附近。 还提供了一些其他模拟结果，例如电子、离子分布的时间演变、场强和轴向电位等。获得这些击穿电压和氦放电特性将有助于反应堆工程中电气设备的绝缘设计工作。