Nonlocal behavior of the excitation rate in highly collisional RF discharges
Nonlocal behavior of the excitation rate in highly collisional RF discharges
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DOI：
10.1088/0963-0252/24/4/044004
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发表时间：
2015-08-01
影响因子：
3.8
通讯作者：
Mussenbrock, Thomas
中科院分区：
文献类型：
--
作者：
Eremin, Denis;Hemke, Torben;Mussenbrock, Thomas
本文主要研究了欧姆加热欧米伽模式下大气压等离子体正极放电的基本问题、电子加热和激发(电离)速率。我们发现，这两者不一定具有相似的轮廓，可以在不同的位置显示峰，电离率对电场的敏感性比对电子加热电场的敏感性高得多。这为电子吸收的功率分布与文献中报道的和本研究中观察到的激发模式之间的差异提供了一种解释。然后可以通过分析电子加热和电场分布的重叠来解释激发速率分布。令人惊讶的是，已经发现激发动力学表现出非局域行为，其最大值与电场和电子加热率的最大值在空间上分离，这是在欧米茄模式下工作的放电的新效应。这种放电中的强电场导致电子元件的大位移。这会在鞘层附近甚至在大等离子体中产生显著的电荷分离，因为由于高碰撞程度，电子不能绝热地跟随电场并保持准中性。具体地说，这导致鞘结构的显著扭曲和那里的电场增加。
The present work focuses on the fundamental aspects of atmospheric pressure plasma electropositive discharges operated in the ohmically heated Omega mode, the electron heating and the excitation (ionization) rate. We find that the two do not necessarily have similar profiles and can show peaks at different locations, the ionization rate being much more sensitive to the electric field compared to the sensitivity to the electric field of the electron heating. This suggests an explanation for the discrepancies between the profiles of the power absorbed by electrons and the excitation patterns previously reported in the literature and observed in the present study. The excitation rate profile can then be explained by analyzing overlapping of the electron heating and the electric field profiles. Surprisingly, it has been discovered that the excitation dynamics exhibits nonlocal behavior having maxima spatially separated from the maxima of the electric field and the electron heating rate, a new effect in discharges operated in the Omega mode. The strong electric field in such discharges leads to large displacements of the electron component. This can produce significant charge separation close to the sheath or even in the bulk plasma because electrons are not able to follow the electric field adiabatically and maintain quasineutrality owing to the high collisionality. In particular, this leads to a significant distortion of the sheath structure and increase in the electric field there.