【作者】 赵颖；

【导师】 巴德纯；

【作者基本信息】 东北大学 ， 流体机械及工程， 2008， 硕士

【摘要】 对于低压、稳定等离子体的诊断,应用最多的仍然是探针法,其中以朗缪尔探针最为人们所熟悉。朗缪尔探针作为20世纪20年代出现的一种等离子体诊断方法及工具,具有设备简单,使用方便的特点,而且它的诊断能力也比较强,诊断得到的信息也比较丰富,适用的范围除主要在低温低压等离子体领域外还在逐渐扩大。朗缪尔探针设备简单的优点也带来了弊端,就是抗干扰性较差,采集数据的过程中很容易受到干扰。计算机的出现在世界范围内引起了科技革命,利用计算机技术进行复杂的数据处理已经成为一种趋势,数值模拟在科学研究中的地位和实用性已经凸显出来,关于朗缪尔探针的计算机数值模拟也在不断发展。本文以圆柱形朗缪尔探针为模型基础。建立一个PIC-MCC模型,将探针浸入Ar等离子体中,不考虑等离子体与预鞘层之间的“过渡层”,并且为了验证模型,将所得的低压Ar等离子体的模拟结果与Sternovsky等人的理论结果和实验结果进行比较。关于假设电子与离子的热能(温度)的比值问题和波尔兹曼电子分布也有所讨论。以往的学者都是采作传统的流体动力学模型或蒙特卡罗模型,这样在模型的建立上,就人为地增加了计算误差。与以往的研究不同之处是,本文采用PIC-MCC模型,用PIC法进行数值计算,用蒙特卡罗截面法处理碰撞过程,可以减小一些人为的误差,所以我们的模拟结果比理论分析更接近于实验研究的结果。更多还原

【Abstract】 The Langmuir probe is a well-established diagnostic tool for low-pressure, stationary plasma. As a plasma diagnostic method and tool which occurred in the 1920s, Langmuir probe is simple equipment, easy-to-use features, and its diagnostic capability is also relatively strong, and one can get rich information from the diagnosis, and the scope of its application mainly in the field of low-temperature low-pressure plasma is gradually expanding. There are drawbacks coming after the benefits of the simple equipment of the Langmuir probe, such as poor in interference and vulnerable to interference in the process of collecting data. The emergence of computers in the world brought on a science and technology revolution, and the use of computer technology for solving complex data has become a trend, so using computer programming method in the data processing of the Langmuir probe diagnosis can greatly improve efficiency and increase accuracy. The importance of numerical simulation for study is well known, and numerical simulations of Langmuir probe were developed.Our PIC-MCC model was based on cylindrical Langmuir probes, and in Ar plasma. The "buffer zone" between the plasma bulk and presheath zone is not considered and a more precise algorithm for the species’orbiting motion in the sheath and absorption on the probe surface is applied. Moreover, in order to verify the model, the results concerning low-pressure Ar plasma are compared here with the experimental and other theoretical results of Sternovsky et al. Also, the assumptions about the ratio of electron to ion thermal (temperature) energy and Boltzmann electron profile are discussed.At present, hybrid model and the Monte-Carlo method are used in most cases, but with them there are a lot of errors in the results. So, we used PIC method to solve the equations exactly, and used MCC method and the knowledge of collision cross sections for all possible collisions. The agreements between our results with the experimental results are better than the extended OML theoretical results.更多还原