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Observations of ion velocity distribution functions in two different configurations of a multipolar device with a laser induced fluorescence diagnostic in argon plasma are presented. The first experiment, carried out in the magnetic field closing the two ends of the device, shows the influence of this field on the ion trajectories. In the second experiment performed without the magnetic field closing the two ends of the device, the influence of the electrostatic boundary potential of the plasma is observed. Longitudinal ion velocity distribution functions have been recorded until inside the plasma sheath. The shapes of these distribution functions are in qualitative agreement with the results of a theoretical model and give an experimental justification for the ‘‘flux’’ shape of the ion velocity distribution source function retained in this model. However, to reach this qualitative agreement, it is necessary to adjust the ionic temperature for each distribution function suggesting that, for the authors’ weakly ionized plasma, another heating mechanism is missing in this theory.

Copyright 2000 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas and may be found at http://link.aip.org/link/?PHPAEN/7/4418/1International audienceNegatively charged dust particles are expected to modify the local sheath potential where they are in equilibrium. In the conditions of a hot cathode discharge, sheath profiles are deduced from the measurement of ion drift velocities, with dust particles in suspension and without. In the unperturbed potential profile, the surface potential of an isolated dust particle, its charge, and its potential energy can be estimated as a function of the position in the sheath. In the presence of dust particles, an average increase of the ion drift velocity is measured showing a modification of the local sheath profile. This experimental result suggests that the dust particle charge due to the plasma particle fluxes in the sheath, modifies in turn the local plasma particle distributions