Modeling of DC micro-glow discharges in atmospheric pressure helium self-organizing on cathodes
Modeling of DC micro-glow discharges in atmospheric pressure helium self-organizing on cathodes
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DOI：
10.1063/5.0078236
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发表时间：
2022-03
影响因子：
2.2
通讯作者：
M. Bieniek;M. Hasan
中科院分区：
文献类型：
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作者：
M. Bieniek;M. Hasan
在恒定气体温度为300K的条件下，采用自洽数值模拟方法，模拟了氦在金属阴极上的微辉光放电在600-800托压力范围内自组织成三维对称图案的过程。三维模型由泊松方程、单个离子和电子的通量密度守恒方程、输运和反应方程组成，假定了漂移-扩散和局域场近似。对于相同的放电电流范围，找到了模型的多个解，描述了具有不同配置的阴极点的模式。从基模到对应于自组织模式的模式的稳定跃迁被识别为异常辉光中的放电电流被减少。在600Torr时，自组织图案由对称排列的、大小相似的圆形电流密度斑点组成，这些斑点与实验中已经识别的图案非常相似，并通过在较低压力下(例如，在氙气中)建模而确定。在大气压及以上，这些图案出现了一个大的中心圆形斑点，小斑点均匀地出现在其外围，类似于齿轮的形状。在常压下，分别在300K以上、600K和1150K两个恒定温度下进行了模拟，观察到了阴极上电流密度的定性变化。在600K时，第一个稳定的自组织模式在阴极上表现出类似大小的圆形电流密度斑点。在1150K时，没有出现自组织的斑点图案。结果表明，在大气压微辉光放电中可能会出现自组织模式，但气体温度在试图表征这种现象时应该被考虑。
Self-consistent numerical modeling was performed of a micro-glow discharge in helium self-organizing into 3D symmetrical patterns over a metallic cathode in the range of pressures of 600 to 800 Torr, for a constant gas temperature of 300 K. The 3D model employed comprised of Poisson's equation, equations of conservation of flux density, transport, and reactions, for a single ion species and electrons, assuming the drift-diffusion and local-field approximations. Multiple solutions to the model were found for the same range of discharge current, describing modes with different configurations of cathode spots. Stable transitions from the fundamental mode to the modes corresponding with self-organized patterns were identified as current was reduced from a discharge in the abnormal glow. At 600 Torr, the self-organized patterns comprised of symmetrically ordered, similarly sized, circular spots of current density that closely resembled patterns already identified in experiments and by modeling at lower pressures (in, e.g., xenon). At atmospheric pressure and above, the patterns emerged with one large central circular spot with small spots emerging uniformly around its periphery, resembling the shape of a gear. Modeling was also performed at atmospheric pressure for two constant temperatures above 300 K, of 600 and 1150 K. Qualitative changes to the patterns of current density on the cathode were observed. At 600 K, the first stable self-organized mode manifested similarly sized circular spots of current density on the cathode. At 1150 K, no self-organized patterns of spots emerged. The results indicate that self-organized patterns may emerge in atmospheric pressure micro-glow discharges but that gas temperature should be considered in an experiment attempting to characterize the phenomenon.