Computational analysis of finite Langmuir probe characteristics

The Langmuir probes belong to the oldest and widely used diagnostic methods of both low-temperature and high-temperature plasmas. The practical experience with Langmuir probes used in our laboratory proved that a deeper knowledge of the interaction between the probe and the plasma would increase the accuracy and usefulness of this technique. The increasing computer performance allows the introduction of new methods based on computational simulations of the plasma-probe interaction. The computational technique presented in our contribution is based on a combination of fluid and particle methods to gain advantage from both of them. The fluid part of the model is capable to cope with complex three-dimensional geometries, while the particle part brings detailed information on the motion of individual particles. The two parts of the model are iteratively coupled to obtain a steady state solution. we have made a comparison of Langmuir probe measurements with computational simulations and a theoretical approach. According to our results, the finite dimensions of the probe and the presence of the dielectric holder strongly influence the probe characteristics, while the influence of collisions in the sheath is minor. The main advantage of the hybrid model is its high efficiency in three-dimensional simulations, which allows to study problems without restrictions on simplified geometries