Particle-in-cell Monte Carlo Simulation Of Cylindrical Langmuir Probes Sheaths

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.