24 research outputs found
Glow discharge in low pressure plasma PVD: mathematical model and numerical simulations
In this paper we analyze the problem of glow discharge in low pressure plasma
in industrial plant, for chambers of different shapes and various working
parameters, like pressure and electric potential. The model described is based
upon a static approximation of the AC configuration with two electrodes and a
drift diffusion approximation for the current density of positive ions and
electrons. A detailed discussion of the boundary conditions imposed is given,
as well as the full description of the mathematical model. Numerical
simulations were performed for a simple 1D model and two different 2D models,
corresponding to two different settings of the industrial plant. The simpler
case consists of a radially symmetric chamber, with one central electrode
(cathode), based upon a DC generator. In this case, the steel chamber acts as
the anode. The second model concerns a two dimensional horizontal cut of the
most common plant configuration, with two electrodes connected to an AC
generator. The case is treated in a "quasi-static" approximation. The three
models show some common behaviours, particularly including the main expected
features, such as dark spaces, glow regions and a wide "plasma region".
Furthermore, the three shown models show some similarities with previously
published results concerning 1D and simplified 2D models, as well as with some
preliminary results of the full 3D case.Comment: 16 pages, 11 figures, in pres
Surface electrons at plasma walls
In this chapter we introduce a microscopic modelling of the surplus electrons
on the plasma wall which complements the classical description of the plasma
sheath. First we introduce a model for the electron surface layer to study the
quasistationary electron distribution and the potential at an unbiased plasma
wall. Then we calculate sticking coefficients and desorption times for electron
trapping in the image states. Finally we study how surplus electrons affect
light scattering and how charge signatures offer the possibility of a novel
charge measurement for dust grains.Comment: To appear in Complex Plasmas: Scientific Challenges and Technological
Opportunities, Editors: M. Bonitz, K. Becker, J. Lopez and H. Thomse
Verification of the global gyrokinetic stellarator code XGC-S for linear ion temperature gradient driven modes
XGC (X-point Gyrokinetic Code) is a whole-volume, total-f gyrokinetic particle-in-cell code developed for modelling tokamaks.In recent work, XGC has been extended to model more general 3D toroidal magnetic configurations, such as stellarators.These improvements have resulted in the XGC-S version.In this paper, XGC-S is benchmarked in the reduced delta-f limit for linear electrostatic ion temperature gradient-driven microinstabilities, which can underlie turbulent transport in stellarators.An initial benchmark of XGC-S in tokamak geometry shows good agreement with the XGC1, ORB5, and global GENE codes.A benchmark between XGC-S and the EUTERPE global gyrokinetic code for stellarators has also been performed, this time in geometry of the optimised stellarator Wendelstein 7-X.Good agreement has been found for the mode number spectrum, mode structure, and growth rate.readme and digital data file