Formation of a cylindrical dust void in a plasma crystal due to a potential bump.

Formation of a cylindrical dust void in dust plasma crystals is simulated using the molecular dynamics method in a three-dimensional fluid sheath model with axisymmetry. The dust trajectories are integrated under a self-consistent field composed of the interactions with the electrostatic sheath field, gravity, drags, wakes, and nonlinear screened Coulomb forces. The simulation successfully explains how a uniform dust cloud transforms into a dust void as the dust particles grow to a sufficient size [D. Samsonov, Phys. Rev. E 59, 1047 (1999)] or the power supply and/or gas pressure increases to certain levels [R. P. Dahiya, Phys. Rev. Lett. 89, 125001 (2002)]. It is found that instead of the ion drag or thermophoretic force effect, the formation of the dust void in the axisymmetric three-dimensional sheath is due to a gentle potential bump in the central region of the electrode caused by the cylindrical geometry.