Dust particle charge in plasma with ion flow and electron depletion near plasma boundaries

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

Dust particle charge in plasma with ion flow and electron depletion

The charge of micrometer-sized dust particles suspended in plasma above the powered electrode of radio-frequency (RF) 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 towards 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

Glow and dust in plasma boundaries

The sheath region is probed in different complex plasma experiments using dust particles in addition to measurement of the optical emission originating from the plasma. The local maximum in 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

Hantavirus Outbreaks in Deer Mice in Montana May Be Predictable Based on Mouse Population Dynamics

Sin Nombre hantavirus (SNV) is a rodent-borne virus that causes hantavirus pulmonary syndrome in humans, which has a 37% mortality rate. There is no vaccine or cure, therefore the best strategy is to prevent spillover from rodent hosts. Understanding the ecological drivers of infection in rodent populations can lead to better predictive models of disease dynamics in the reservoir and consequent risk to humans. Using an epidemiological model parameterized and cross-validated using a long term dataset from Montana, I show how environmental variation and fluctuating mouse density affects hantavirus prevalence. I provide evidence for a critical host density necessary to sustain transmission and show how there can be long delays between peaks in density and subsequent peaks in infection prevalence. The lengths of these delays vary with density but are predictable. This means that outbreaks may sometimes be predictable many months in advance. These same principles should also apply to many other disease systems in wildlife with fluctuating populations, and may help predict and mitigate wildlife disease

Optimizing a Passive Tracking Solar Panel System

For a solar panel to function efficiently, it must turn to face the sun throughout the day. Usually, an electronic device rotates a solar panel. In this experiment, hourly rotation of the panel was achieved through contraction of a shape memory alloy (SMA) and a gear system. A Fresnel lens directed the sun\u27s rays onto the SMA causing it to contract. A delayed reset system was built to turn the panel from west to east at the end of the day. In addition, this project investigated different materials to properly heat and cool the SMA within the plexiglass housing apparatus. The overall goal for the project was to automatically power an appliance on campus with solar energy

Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a RF 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 selfconsistent 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

One-dimensional vertical dust strings in a glass box

The oscillation spectrum of a one-dimensional vertical dust string formed inside a glass box on top of the lower electrode in a GEC reference cell was studied. A mechanism for creating a single vertical dust string is described. It is shown that the oscillation amplitudes, resonance frequencies, damping coefficients, and oscillation phases of the dust particles separate into two distinct groups. One group exhibits low damping coefficients, increasing amplitudes and decreasing resonance frequencies for dust particles closer to the lower electrode. The other group shows high damping coefficients but anomalous resonance frequencies and amplitudes. At low oscillation frequencies, the two groups are also separated by a {\pi}-phase difference. One possible cause for the difference in behavior between the two groups is discussed

Crystallization dynamics of a single layer complex plasma

We report a series of complex (dusty) plasma experiments, aimed at the study of the detailed time evolution of the re-crystallisation 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 inter-particle interaction. Both experiment and simulation show a $\propto t^\alpha$ (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 $\alpha=0.93\pm0.1$. At longer time-scales, small crystallites undergo collective rearrangement, merging into bigger ones, resulting in a smaller exponent $\alpha=0.38\pm0.06$.Comment: 4 pages, 3 figures. Submitted to PR