Stuttgart 2012 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 21: Poster: Staubige Plasmen

P 21.13: Poster

Donnerstag, 15. März 2012, 16:30–19:00, Poster.III

The Triple Correlation function as a tool for structural analysis — •Hauke Thomsen, Patrick Ludwig, and Michael Bonitz — ITAP, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 15, 24098 Kiel

Dust particles in a plasma allow an analysis of strong correlations effects. The particles usually accumulate high negative charge inside a plasma which results in a strong repulsive interactions. In a parabolic trap, these particles form spherical clusters with a characteristic shell structure. Finite size effects play a major role here.

When analyzing the cluster structure and its temperature behavior, it appears the radial distribution ρ(r) and radial pair distribution g₂(|r_ij^→|) are often insufficient to describe the melting process. Therefore, we analyze the Triple Correlation Function (TCF), for which we sample all pairs of three particles and record two distances and one angle. This allows for an analysis beyond the pair distribution[1,2]. In a second variant specifically adapted to the spherical shape of trapped dust clusters, we sample particle pairs and use the trap center as a reference points.This quantity resolves both correlation within one shell and angular correlations between different shells and it is invariant under rotation of the cluster as a whole.

Using the TCF, furthermore, we study how the intra shell structure vanishes at a lower temperature than the radial structure and the dependence of intra and inter shell correlation on the screening length.

[1] P. Ludwig et al., Plasma Phys. Control. Fusion 52, 124013 (2010) [2] A. Schella et al., Phys. Rev. E., accepted for publication (2011)