Dust particle alignments and confinement in a radio frequency sheath

Stability of vertical and horizontal confinement of dust particles levitating in a rf sheath was studied experimentally. The experiments were carried out in an argon plasma discharge with micron-sized dust particles. Disruptions of particle arrangements were triggered by changing the discharge controlling parameters (pressure and peak-to-peak voltage) as well as by applying an additional bias to the confining electrode. Where the transition was triggered by changes of the discharge parameters, the transition from the horizontal to the vertical alignment has been found to be more pronounced than the reverse one. Clear hysteretic phenomena were observed for the transition triggered by changes of the confining voltage.