Influence of vibrational nonequilibrium on electron creation and loss kinetics in high pressure molecular plasmas

本项目主要研究强非平衡高压分子等离子体的基本动力学过程。普通的热等离子体是通过简单地将气体加热到高温而形成的，而非平衡等离子体是通过将能量输入到特定的内能状态而形成的，在这种情况下，是分子振动。这提供了一个独特的等离子体环境，其中电离程度是显著的，但温度相当低（数量级室温）。这种低温使各种各样的实际工程设备和工艺成为可能，仅举几例，包括等离子体化学反应器，污染控制系统和分子激光器。然而，要实现这种高压非平衡等离子体系统的全部商业和/或军事潜力，需要将总输入功率降低至少一到两个数量级，低于目前所需的功率。从根本上说，功率要求很高，因为电子在等离子体中通过与正离子重组和/或附着于中性离子的方式耗散的速度非常快，特别是在氧气存在的情况下。克服这种电子快速损失的传统方法是增加输入功率，以提高电子产生的速率。然而，本研究的目的是探索降低损失率的动力学机制。具体来说，实验测量将在交叉电子束/ CO激光非平衡等离子体产生装置中进行，并将利用全套诊断和计算工具，包括用于确定空间和时间分辨电子密度和温度的高灵敏度光谱滤波汤姆森散射仪器。该项目由数学和物理科学局的物理司和工程局的化学和运输系统司共同资助。

This project focuses on the study of basic kinetic processes in strongly non-equilibrium, high-pressure molecular plasmas. Unlike ordinary thermal plasmas, which are formed by simply heating a gas to high temperature, non-equilibrium plasmas are formed by the input of energy into specific internal energy states, in this case, molecular vibrations. This provides a unique plasma environment in which the degree of ionization is significant, yet the temperature is quite low (order room temperature). This low temperature enables a wide variety of practical engineering devices and processes including, to name only a few, plasma chemical reactors, pollution control systems, and molecular lasers. However, achieving the full commercial and/or military potential of such high pressure non-equilibrium plasma-based systems requires that the overall input power be reduced by at least one to two orders of magnitude below that presently required. Fundamentally, the power requirements are high because the rate at which electrons are dissipated in the plasma, by recombination with positive ions and/or attachment to neutrals is quite rapid, particularly in the presence of oxygen. The traditional approach for overcoming this rapid loss of electrons is to increase the input power, in order to increase the rate at which electrons are produced. The goal of this study, however, is to explore kinetic mechanisms for reducing the rate of loss. Specifically, experimental measurements will be performed in an crossed electron-beam / CO laser non-equilibrium plasma generation apparatus, and will feature utilization of a full suite of diagnostic and computational tools, including a high sensitivity spectrally filtered Thomson scattering instrument for determination of spatially and temporally resolved electron density and temperature. This project is jointly funded by the Physics Division in the Mathematical and Physical Sciences Directorate and by the Chemical and Transport Systems Division in the Directorate for Engineering.