Upstream and downstream sheath structures near a metal plate in the flow of a diffusive plasma

NUCLEAR FUSION AND PLASMA PHYSICS ›› 2012, Vol. 32 ›› Issue (1): 21-26.

• Plasma Physics • Previous Articles Next Articles

Upstream and downstream sheath structures near a metal plate in the flow of a diffusive plasma

ZHENG Yao-bang1, 2, MA Jin-xiu1, LI Yi-ren1, LI Wei1

(1. Key Laboratory of Basic Plasma Physics and Center for Magnetic Fusion Theory, Chinese Academy of Sciences, and Department of Modern Physics, University of Science and Technology of China, Hefei 230026; 2. China Aerodynamics Research and Development Center, Mianyang 621000)

Received:2011-05-16 Revised:2011-09-18 Online:2012-03-15 Published:2012-03-14

等离子体扩散流中金属平板上下游的鞘层结构

郑尧邦1, 2，马锦秀1，李毅人1，李卫1

(1. 中国科学技术大学近代物理系，中国科学院基础等离子体物理重点实验室和磁约束等离子体理论中心，合肥 230026； 2. 中国空气动力研究与发展中心，绵阳 621000）

作者简介:郑尧邦(1984-)，男，土家族，湖南常德人，硕士研究生，从事等离子体鞘层研究。
基金资助:
国家自然科学基金资助课题(10875121，40831062)；中国科学院知识创新工程资助课题(kjcx2-yw-n28)；国家重点基础研究项目资助课题(2009GB105001，2008CB717800)

Abstract

Abstract:

The potential distributions in the sheath and presheath in the upstream and downstream sides of a metal plate immersed in the flow of diffusive plasma were measured using a fine structured emissive probe. Combining the Child-Langmuir(CL) law and one-dimensional fluid model, the sheath thicknesses and edge electric fields were analyzed. It is shown that the sheath in the downstream side is thicker than that in the upstream side, while the measured edge electric field of the upstream sheath is stronger than that of the downstream sheath. Both experimental and numerical results show that the thicknesses of the CL sheath in the two sides of the plate satisfy a linear relation, with a fitting proportionality of 1.2 between the down- and upstream thickness. The electric field at the CL sheath edge in both up- and downstream sides is consistent with the value given by T_e/(eλ_D), while the measured electric field at the Bohm sheath edge in the upstream side is close to Te/(eλ_D^3/5λ_i^2/5). However, the Bohm sheath edge electric field in the downstream side shows a significant deviation from available models.

Key words: Plasma sheath, Upstream and downstream, Edge electric field

摘要：

利用发射探针诊断了处于扩散等离子体流场中平板两侧的鞘层电势分布并给出鞘层厚度及边界电场。结合Child-Langmuir(CL)定律并利用一维流体模型，分析对比了鞘厚及边界电场。结果显示，上下游的鞘层呈现不对称结构，下游比上游厚，边界电场下游比上游弱，并且下游的预鞘还呈现类似虚阳极的结构。上下游CL鞘的厚度满足线性比例关系，比例系数约为1.2，且实验值与理论值非常接近。上下游CL鞘的边界电场与模型T_e/(eλ_D)比较接近，上游Bohm鞘边界电场的实验结果与过渡区模型较符合，但下游Bohm鞘的边界电场与现有模型有较大差异。

关键词: 等离子体鞘层, 上下游, 边界电场

CLC Number:

O590

ZHENG Yao-bang, MA Jin-xiu, LI Yi-ren, LI Wei. Upstream and downstream sheath structures near a metal plate in the flow of a diffusive plasma[J]. NUCLEAR FUSION AND PLASMA PHYSICS, 2012, 32(1): 21-26.

郑尧邦1, 2，马锦秀1，李毅人1，李卫1. 等离子体扩散流中金属平板上下游的鞘层结构[J]. 核聚变与等离子体物理, 2012, 32(1): 21-26.

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Upstream and downstream sheath structures near a metal plate in the flow of a diffusive plasma

等离子体扩散流中金属平板上下游的鞘层结构

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