Berlin 2014 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 16: Helmholtz Graduate School for Plasma Physics I

P 16.3: Fachvortrag

Mittwoch, 19. März 2014, 14:50–15:15, SPA HS202

Non-equidistant Particle-In-Cell for Ion Thruster Plume simulation — •Julia Duras — Ernst-Moritz-Arndt Universität Greifswald, D-17489, Germany

The interaction of ion thrusters and satellites is determined by the plume plasmas. Since the mean free paths are such that the probability for collisions relaxing the distribution functions to Maxwellians is quite low, a correct model of the plume plasma has to be kinetic. Unfortunately, the well-established Particle-In-Cell (PIC) method is only momentum conserving and free of artificial self forces in the case of equidistant meshes. This allows only small domains for the plume due to computational time restrictions. Those simulations suffer from the strong influence of the solution from the boundary conditions at the end of the plume domain.

In the outer plume the densities of electrons and ions decrease by 4-8 magnitudes compared with the thruster channel. This leads to an increasing Debye length, which gives the possibility to enlarge the domain by using a non-equidistant grid. Therefore, momentum and energy conservation in 1D electrostatic PIC codes using non-equidistant grids are studied. A modified two point central difference scheme for non-equidistant grids is suggested, which can be proven analytically and numerically to give the exact solution for the electrical field. In addition a 2D axis-symmetric Poisson solver for non-equidistant grids using the Finite Volume Method is presented.