https://doi.org/10.1140/epjd/e2011-20077-4
Regular Article
Determination of sheath parameters by test particles upon local electrode bias and plasma switching
1
Institut für Physik, Ernst-Moritz-Arndt-Universität
Greifswald, Germany
2
Regionales Rechenzentrum Erlangen, Friedrich-Alexander-Universität
Erlangen-Nürnberg, Germany
3
Leibniz-Institute for Plasma Research and Technology (INP)
Greifswald,
Germany
4
Institute for Experimental and Applied Physics, University of
Kiel, Germany
a e-mail: kersten@physik.uni-kiel.de
Received:
31
January
2011
Received in final form:
5
May
2011
Published online:
28
June
2011
Equilibrating gravitation by electric forces, microparticles can be confined in the plasma sheath above suitably biased local electrodes. Their position depends on the detailed structure of the plasma sheath and on the charge that the particles acquire in the surrounding plasma, that is by the electron and ion currents towards it. Bias switching experiments reveal how the charge and equilibrium position of the microparticle change upon altered sheath conditions. Above a critical bias, the particle is subject to an additional downward acceleration that cannot be explained solely by gravity and ion drag. This acceleration can be attributed to a positive charging of the particle induced by extreme out-of-equilibrium conditions of the plasma sheath in its surroundings: locally the plasma sheath can be completely deprived of electrons by means of the bias. We observe similar particle behaviors also in the afterglow of the discharge for a persisting bias voltage on the electrode: damped oscillation into a new equilibrium or (accelerated) fall according to the bias. The observed particle dynamics in locally tailored plasma sheath environments directly monitors changes in electric field structures and plasma density profiles.
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2011
