Dust grain charging and levitation in a weakly collisional sheath

An experiment is described in which monodisperse dust grains are levitated within a dc sheath above a conducting plate in argon plasma. For plate bias voltages that are not too negative (⩾−10 electron temperatures), the observed dust levitation heights are near to values calculated from a model combining equations for the sheath with those for grain charging. When the plate is more negatively biased, the theoretical levitation heights are higher than the observed heights as a consequence of the measured sheath thickness being smaller than values obtained from the models.