Topic/Type: 1.5 Low-temperature, dusty and nano-plasmas, Poster

3D hybrid computer modelling of Langmuir probes of finite dimensions in low and medium pressure plasmas

V. Hrub?, R. Hrach

Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Prague, Czech Republic

The Langmuir probes are widely used diagnostic technique both in low-temperature and high-temperature plasmas. However, the theoretical analysis of probe interaction with plasma is usually very simplified and restricted to special conditions, low pressures, simple probe geometries, etc. These limits can be overcome by computer simulation. Despite the increasing computer performance, a fully three-dimensional particle model of the finite probe is still extremely ineffective.
In our work there are presented hybrid computational techniques based on a combination of fluid and particle methods. The fluid part of hybrid model increases its efficiency, while the particle part brings detailed information on particle properties. There are examined more types of hybrid models in the simplified one-dimensional geometry in order to choose the optimal method according to our requirements on accuracy, computational time and memory consumption.
The presented fully three-dimensional hybrid model is based on an iterative process alternating the fluid and the particle model. The fluid model is solved by the finite element technique to cope even with complex geometries. In the particle model, trajectories of individual particles are computed using Monte Carlo and molecular dynamics methods. The three-dimensional approach imposes no constraints on the symmetry of the geometry. Therefore the influence of the finite probe dimensions, the charging of dielectric holder and the plasma drift can be considered and included in the model. The low time consumption of the developed hybrid model enabled us to study the interaction of the probe with low-temperature plasmas at wider range of conditions, such as voltage bias, plasma composition and pressure and probe sizes.