Hypervelocity Impacts and Dusty Plasma Lab (HIDPL)
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Browsing Hypervelocity Impacts and Dusty Plasma Lab (HIDPL) by Author "Douglass, Angela Michelle."
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Item Crystallization Dynamics of a Single Layer Complex Plasma(Physical Review Letters, 2010-09) Hartmann, Peter; Douglass, Angela Michelle.; Carmona-Reyes, Jorge; Matthews, Lorin Swint.; Hyde, Truell Wayne.; Kovacs, Aniko Zs.; Donko, ZoltanWe report a series of complex (dusty) plasma experiments, aimed at the study of the detailed time evolution of the recrystallization process following a rapid quench of a two-dimensional dust liquid. The experiments were accompanied by large-scale (million-particle) molecular dynamics simulations, assuming Yukawa-type interparticle interaction. Both experiment and simulation show a t ^/alpha (power-law) dependence of the linear crystallite domain size as measured by the bond-order correlation length, translational correlation length, dislocation (defect) density, and a direct size measurement algorithm. The results show two stages of order formation. On short time scales, individual particle motion dominates; this is a fast process characterized by alpha = 0.93 +/- 0.1. At longer time scales, small crystallites undergo collective rearrangement, merging into bigger ones, resulting in a smaller exponent /alpha = 0.38 +/- 0.06.Item Determination of the levitation limits of dust particles within the sheath in complex plasma experiments(Physics of Plasmas, 2012-01-23) Douglass, Angela Michelle.; Land, Victor; Qiao, Ke; Matthews, Lorin Swint.; Hyde, Truell Wayne.Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a radio frequency plasma discharge by changing the discharge power. The trajectories of particles dropped from the top of the discharge chamber are used to reconstruct the vertical electric force acting on the particles. The resulting data, together with the results from a self-consistent fluid model, are used to determine the lower levitation limit for dust particles in the discharge and the approximate height above the lower electrode where quasineutrality is attained, locating the sheath edge. These results are then compared with current sheath models. It is also shown that particles levitated within a few electron Debye lengths of the sheath edge are located outside the linearly increasing portion of the electric field.Item Dust particle charge in plasma with ion flow and electron depletion near plasma boundaries(Physics of Plasmas, 2011-08-01) Douglass, Angela Michelle.; Land, Victor; Matthews, Lorin Swint.; Hyde, Truell Wayne.The charge on micrometer-sized dust particles suspended in plasma above the powered electrode of radio-frequency discharges is studied. Using a self-consistent fluid model, the plasma profiles above the electrode are calculated and the electron depletion towards the electrode, as well as the increasing flow speed of ions toward the electrode are considered in the calculation of the dust particle floating potential. The results are compared with those reported in literature and the importance of the spatial dust charge variation is investigated.Item The effect of dust charge variation, due to ion flow and electron depletion, on dust levitation(AIP Conference Proceedings, 2011) Land, Victor; Douglass, Angela Michelle.; Qiao, Ke; Matthews, Lorin Swint.; Hyde, Truell Wayne.Using a fluid model, the plasma densities, electron temperature and ion Mach number in front of a powered electrode in different plasma discharges is computed. The dust charge is computed using OML theory for Maxwellian electrons and ions distributed according to a shifted-Maxwellian. By assuming force balance between gravity and the electrostatic force, the dust levitation height is obtained. The importance of the dust charge variation is investigated.Item Glow and Dust in Plasma Boundaries(IEEE Transactions on Plasma Science, 2013-04) Land, Victor; Douglass, Angela Michelle.; Qiao, Ke; Zhang, Zhuanhao.; Matthews, Lorin Swint.; Hyde, Truell Wayne.The sheath region is probed in different complex plasma experiments using dust particles in addition to the measurement of the optical emission originating from the plasma. The local maximum in the optical emission coincides with the breaking of quasi-neutrality at the sheath boundary, as indicated by the vertical-force profile reconstructed from dust-particle trajectories as well as by the local onset of dust-density waves in high-density dust clouds suspended in a dielectric box.Item Slow Plastic Deformation (Creep) of 2D Dusty Plasma Solids(Physical Review Letters, 2014-07-09) Hartmann, Peter; Kovacs, Aniko Zs.; Douglass, Angela Michelle.; Carmona-Reyes, Jorge; Matthews, Lorin Swint.; Hyde, Truell Wayne.We report complex plasma experiments, assisted by numerical simulations, providing an alternative qualitative link between the macroscopic response of polycrystalline solid matter to small shearing forces and the possible underlying microscopic processes. In the stationary creep regime we have determined the exponents of the shear rate dependence of the shear stress and defect density, being α=1.15±0.1 and β=2.4±0.4, respectively. We show that the formation and rapid glide motion of dislocation pairs in the lattice are dominant processesItem Vertical Interaction Between Dust Particles Confined in a Glass Box in a Complex Plasma(IEEE Transactions on Plasma Science, 2013-04) Kong, Jie; Qiao, Ke; Carmona-Reyes, Jorge; Douglass, Angela Michelle.; Zhang, Zhuanhao.; Matthews, Lorin Swint.; Hyde, Truell Wayne.In this experiment, falling particle trajectories within and without a glass box placed on the lower electrode in a Gaseous Electronics Conference reference cell are recorded and analyzed, and the electrostatic forces exerted on the dust particles are measured and compared. Experimental results show that, for particles falling in a complex plasma with no glass box, only a single force balance point (i.e., the position where the gravitational force is balanced by the electrostatic force) exists in the vertical direction while, for particles falling inside a glass box, this force balance spans an extended vertical range.