Non-Equilibrium Effects in High Pressure, High Intensity Arcs

已经发现，平行于阳极表面的冷气流可以导致发光电弧等离子体和阳极表面之间的非平衡区域扩大的稳定附着。流向阳极的电流似乎分布在相对较大的区域上，从而大大降低了阳极热通量。 在这项研究中，这种类型的电弧附着，其中压缩器稳定的电弧附着到阳极垂直于弧轴与冷气体流平行于阳极表面，进行了研究。阳极和电弧柱之间的扩大的非平衡区域的特征在于与一个新开发的数据分析技术，使用汤姆逊散射的激光辐射，以确定电子的温度和密度分布。 用嵌入阳极的朗缪尔探针进行测量，可以在阳极表面提供相同数量的值，从而可以确定电流密度分布，热通量探针测量可以给出阳极表面的热通量分布。 使用三维有限体积代码的非平衡等离子体的并行建模工作提供了洞察在这个非平衡区域的物理过程，包括电场强度的映射。动力学和成分的非平衡被认为是，和一个自相一致的处理扩散used.broader impactHigh强度电弧材料加工吸引了相当大的兴趣，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耦合，限制了它们在加工应用中的有用性。 此外，电弧经常以不稳定的方式操作，并且高热通量导致电极的侵蚀，限制了电弧装置的寿命。 这项研究解决了与电弧中的高电子密度的好处相关联的高热通量的问题。 这项调查的两个方面预计将导致具有实际意义的结果。 一个是产生更大的非平衡等离子体体积，其可用于表面处理或本体化学处理。 第二个是存在一个大面积的扩散附着的高强度电弧与明显低的热流密度，

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