Non-Equilibrium Effects in High Pressure, High Intensity Arcs

研究发现，平行于阳极表面的冷气流可以导致发光电弧等离子体与阳极表面之间的稳定附着，并扩大了非平衡区域。流向阳极的电流似乎分布在一个相对较大的区域上，从而大大减少了阳极的热通量。在这项研究中，研究了这种类型的电弧附着，其中收缩稳定的电弧附着在垂直于电弧轴的阳极上，并平行于阳极表面的冷气流。利用激光辐射的汤姆逊散射来确定电子温度和密度分布，对阳极和电弧柱之间扩大的非平衡区进行了表征。在阳极中嵌入朗缪尔探针的测量提供了阳极表面相同数量的值，从而确定了电流密度分布，热通量探针测量给出了阳极表面的热通量分布。使用非平衡等离子体的三维有限体积代码的并行建模工作提供了对该非平衡区域的物理过程的洞察，包括电场强度的映射。同时考虑了动力学和成分的非平衡，并采用自洽法处理扩散。更大的冲击强度电弧在材料加工中引起了相当大的兴趣，因为它们可以提供高通量的电子、离子或其他自由基。然而，由于电弧等离子体通常接近平衡，这些通量通常与高热通量相结合，限制了它们在加工应用中的用途。此外，电弧经常以不稳定的方式运行，高热流导致电极的侵蚀，限制了电弧装置的寿命。本研究解决了电弧中高电子密度带来的高热通量问题。这项调查的两个方面有望产生具有实际意义的结果。其一是产生更大的非平衡等离子体体积，可用于表面处理或批量化学处理。第二是存在一个广域漫射附著的高强度电弧明显低热流密度，因此

It has been discovered that a cold gas flow parallel to the anode surface can lead to a stable attachment with an enlarged non-equilibrium region between the luminous arc plasma and the anode surface. The current flow to the anode appears to be distributed over a relatively large area, thus drastically reducing the anode heat flux. In this study, this type of arc attachment, in which a constrictor-stabilized arc attaches to an anode perpendicular to the arc axis with a cold gas flow parallel to the anode surface, is investigated. The enlarged non-equilibrium region between the anode and the arc column is characterized with a newly developed data analysis technique using Thomson scattering of laser radiation to determine the electron temperature and density distributions. Measurements with a Langmuir probe imbedded in the anode provide values for the same quantities at the anode surface allowing determination of the current density distribution, and heat-flux probe measurements give the heat-flux distribution at the anode surface. A parallel modeling effort using a three-dimensional finite-volume code for a non-equilibrium plasma provides insight into the physical processes in this non-equilibrium region including a mapping of the electric field strength. Both kinetic and composition non-equilibrium are considered, and a self-consistent treatment for diffusion is used.Broader impactHigh intensity arcs have attracted considerable interest for materials processing because they can provide high fluxes of electrons, ions, or other radicals. However, because the arc plasma is usually close to equilibrium, these fluxes are usually coupled with high heat fluxes, limiting their usefulness for processing applications. Furthermore, electric arcs frequently operate in an unstable manner, and the high heat fluxes lead to erosion of the electrodes, limiting the life of arcing devices. This study addresses the problems of the high heat fluxes associated with the benefits of high electron densities in electric arcs. Two aspects of this investigation are expected to lead to results of practical importance. One is the generation of larger non-equilibrium plasma volumes that can be used for surface treatment or bulk chemical processing. The second is the existence of a wide-area diffuse attachment for high-intensity arcs with apparently low heat-flux densities and, consequentl