Hypervelocity Impacts and Dusty Plasma Lab (HIDPL)

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Digital Imaging and Analysis of Dusty Plasmas
(Advances in Space Research, 2004) Boesse, Carolyn M.; Henry, Michael; Hyde, Truell Wayne.; Matthews, Lorin Swint.
Dust particles immersed within a plasma environment, such as those found in planetary rings or cometary environments, will acquire an electric charge. If the ratio of interparticle potential energy to average kinetic energy is high enough the particles will form either a ‘liquid’ structure with short-range ordering or a crystalline structure with long-range ordering. Since their discovery in laboratory environments in 1994, such crystals have been the subject of a variety of experimental, theoretical, and numerical investigations. Laboratory experiments analyzing the behavior of dust grains in a plasma rely on optical diagnostics to provide data about the system in a non-perturbative manner. In the past, capturing, imaging, and analyzing crystalline structure in dusty plasmas has been a non-trivial problem. Utilizing digital imaging and analysis systems, data capture, image formatting, and analysis can be done quickly. Following data capture, image analysis is conducted using modified Particle Image Velocimetry and Particle Tracking Velocimetry algorithms. The data extracted is then used to construct Voronoi diagrams, calculate particle density, inter-particle spacing, pair correlation functions, and thermal energy. From this data other dust plasma parameters can be inferred such as inter-particle forces and grain charges.
Dusty Plasma Correlation Function Experiment
(Advances in Space Research, 2004) Smith, Bernard (Bernie).; Vasut, John; Matthews, Lorin Swint.; Hyde, Truell Wayne.; Reay, Jerry; Cook, Mike; Schmoke, Jimmy
Dust particles immersed within a plasma environment, such as those in protostellar clouds, planetary rings or cometary environments, will acquire an electric charge. If the ratio of the inter-particle potential energy to the average kinetic energy is high enough the particles will form either a “liquid” structure with short-range ordering or a crystalline structure with long range ordering. Many experiments have been conducted over the past several years on such colloidal plasmas to discover the nature of the crystals formed, but more work is needed to fully understand these complex colloidal systems. Most previous experiments have employed monodisperse spheres to form Coulomb crystals. However, in nature (as well as in most plasma processing environments) the distribution of particle sizes is more randomized and disperse. This paper reports experiments which were carried out in a GEC radio frequency reference cell modified for use as a dusty plasma system, using varying sizes of particles to determine the manner in which the correlation function depends upon the overall dust grain size distribution. (The correlation function determines the overall crystalline structure of the lattice.) Two-dimensional plasma crystals were formed of assorted glass spheres with specific size distributions in an argon plasma. Using various optical techniques, the pair correlation function was determined and compared to those calculated numerically.
Effect of Multi-Sized Dust Distribution on Local Plasma Sheath Potentials
(Advances in Space Research, 2006) Sun, Meihong; Matthews, Lorin Swint.; Hyde, Truell Wayne.
This work investigates the modification of a plasma sheath in a complex plasma due to the presence of dust particles with a specified size distribution. A self-consistent model for the plasma sheath is combined with a self-consistent dynamical code in order to determine the interaction of the dust particles with the local sheath potential and the subsequent effect on the dynamics of the particles. It is shown that the ion density in the region of levitated particles is decreased. The sheath potential in the region of levitated dust particles is also more negative which is qualitatively consistent with the experimental results of Arnas et al. [Arnas, C., Mikikian, M., Bachet, G., Doveil, F. Sheath modification in the presence of dust particles. Phys. Plasmas 7(11), 4418–4422, 2000.].
Phase Transitions in a Dusty Plasma with Two Distinct Particle Sizes
(Advances in Space Research, 2008) Smith, Bernard (Bernie).; Hyde, Truell Wayne.; Matthews, Lorin Swint.; Reay, Jerry; Cook, Mike; Schmoke, Jimmy
In semiconductor manufacturing, contamination due to particulates significantly decreases the yield and quality of device fabrication, therefore increasing the cost of production. Dust particle clouds can be found in almost all plasma processing environments including both plasma etching devices and in plasma deposition processes. Dust particles suspended within such plasmas will acquire an electric charge from collisions with electrons and ions in the plasma. If the ratio of inter-particle potential energy to the average kinetic energy is sufficient, the particles will form either a “liquid” structure with short-range ordering or a crystalline structure with long-range ordering. Many experiments have been conducted over the past decade on such colloidal plasmas to discover the character of the systems formed, but more work is needed to fully understand these structures. The preponderance of previous experiments used monodisperse spheres to form complex plasma systems. However, most plasma processing environments contain more arbitrary distributions of particle size. In order to examine in more detail the effects of a size distribution, experiments were carried out in a GEC rf reference cell modified for use as a dusty plasma system. Using two monodisperse particle sizes, experiments were conducted to determine the manner in which phase transitions and other thermodynamic properties depended upon the overall dust grain size distribution. Plasma crystals were formed from different mixtures of 8.89 and 6.50 μm monodisperse particles in argon plasma. With the use of various optical techniques, the pair correlation function was determined at different pressures and powers and then compared to measurements obtained for monodisperse spheres.
Experimental and computational characterization of a modified GEC cell for dusty plasma experiments
(New Journal of Physics, 2009-06-12) Land, Victor; Shen, Erica; Smith, Bernard (Bernie).; Matthews, Lorin Swint.; Hyde, Truell Wayne.
A self-consistent fluid model developed for simulations of microgravity dusty plasma experiments has for the first time been used to model asymmetric dusty plasma experiments in a modified Gaseous Electronics Conference (GEC) reference cell with gravity. The numerical results are directly compared with experimental data and the experimentally determined dependence of global discharge parameters on the applied driving potential and neutral gas pressure is found to be well matched by the model. The local profiles important for dust particle transport are studied and compared with experimentally determined profiles. The radial forces in the midplane are presented for the different discharge settings. The differences between the results obtained in the modified GEC cell and the results first reported for the original GEC reference cell are pointed out.
Nonlinear mode coupling and internal resonance observed in a dusty plasma
(New Journal of Physics, 2009-10) Ding, Zhiyue; Qiao, Ke; Ernst, N.; Kong, Jie; Chen, M.; Matthews, L.S.; Hyde, T. W.
In this paper, we report the first experimental observation of internal resonance in a dusty plasma, which shows the intrinsic nonlinearities of dust interactions in plasmas. When driving a system of vertically aligned dust particle pairs in the vertical direction, the horizontal motion is found to be excited during onset of internal resonance when the higher-frequency horizontal sloshing mode is nonlinearly coupled to the vertical breathing mode through the 1:2 commensurable relation. A theoretical model of the nonlinear interaction of dust particles in plasma is also provided and the results of the theoretical model are shown to match experimental observations.
Probing the sheath electric field using thermophoresis in dusty plasma
(IEEE Transactions on Plasma Science, 2010-04) Land, Victor; Smith, Bernard (Bernie).; Matthews, Lorin Swint.; Hyde, Truell Wayne.
A self-consistent dusty plasma fluid model has been extended to incorporate all the oble gases as the carrier gas. An analysis of void closure in complex plasma composed of these gases over a wide range of experimental parameters is presented. Driving potential-pressure maps are constructed, which show the range in parameter space where isotropic void-free dust crystals can be expected, where a void is to be expected and where the discharge is expected to extinguish.
Fluid modeling of void closure in microgravity noble gas complex plasmas
(Physics Review E, 2010-05-12) Land, Victor; Matthews, Lorin Swint.; Hyde, Truell Wayne.; Bolser, Diana
A self-consistent dusty plasma fluid model has been extended to incorporate all the noble gases as the carrier gas. An analysis of void closure in complex plasma composed of these gases over a wide range of experimental parameters is presented. Driving potential-pressure maps are constructed, which show the range in parameter space where isotropic void-free dust crystals can be expected, where a void is to be expected and where the discharge is expected to extinguish.
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, Zoltan
We 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.
Simple method to measure the interaction potential of dielectric grains in a dusty plasma
(Physics Review E, 2010-09) Zhang, Zhuanhao.; Qiao, Ke; Kong, Jie; Matthews, Lorin Swint.; Hyde, Truell Wayne.
A simple minimally perturbative method is introduced which provides the ability to experimentally measure both the radial confining potential and the interaction potential between two individual dust particles, levitated in the sheath of a radio-frequency (RF) argon discharge. In this technique, a single dust particle is dropped into the plasma sheath to interact with a second individual dust particle already situated at the system’s equilibrium point, without introducing any external perturbation. The resulting data are analyzed using a method employing a polynomial fit to the particle displacement(s), X(t), to reduce uncertainty in calculation. Employing this technique, the horizontal confinement is shown to be parabolic over a wide range of pressures and displacements from the equilibrium point. The interaction potential is also measured and shown to be well described by a screened Coulomb potential and to decrease with increasing pressure. Finally, the charge on the particle and the effective dust screening distance are calculated. It is shown for the first time experimentally that the charge on a particle in the sheath of an RF plasma decreases with increasing pressure, in agreement with theoretical predictions. The screening distance also decreases with increasing pressure as expected. This technique can be used for rapid determination of particle parameters in dusty plasma.
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.
Agglomeration of Dust Particles in the Lab
(AIP Conference Proceedings, 2011) Matthews, Lorin Swint.; Carmona-Reyes, Jorge; Land, Victor; Hyde, Truell Wayne.
Dust aggregates are formed in a laboratory plasma as monodisperse spheres are accelerated in a self-excited dust density wave. The asymmetric charge on the aggregates causes them to rotate as they interact with the sheath electric field or other aggregates The charge and dipole moment can be estimated and compared to numerical models. “Dust molecules”, where two particles are electrostatically bound but not physically touching, are also observed.
The effect of electrode heating on the discharge parameters in complex plasma experiments
(IOP Publishing, 2011-01-25) Land, Victor; Carmona-Reyes, Jorge; Creel, James Ruell.; Schmoke, Jimmy; Cook, Mike; Matthews, Lorin Swint.; Hyde, Truell Wayne.
Thermophoresis is a tool often applied in complex plasma experiments. One of the usual stated benefits over other experimental tools is that electrode temperature changes required to induce thermophoresis do not directly influence the plasma parameters. From electronic data, plasma emission profiles in the sheath, and Langmuir probe data in the plasma bulk, we conclude that this assumption does not hold. An important effect on the levitation of dust particles in argon plasma is observed as well. The reason behind the changes in plasma parameters seems to be the change in neutral atom density accompanying the increased gas temperature while running at constant pressure.
One-dimensional vertical dust strings in a glass box
(Physical Review E, 2011-07-28) Kong, Jie; Hyde, Truell Wayne.; Matthews, Lorin Swint.; Qiao, Ke; Zhang, Zhuanhao.
The oscillation spectrum of a one-dimensional vertical dust string formed inside a glass box on top of the lower electrode in a gaseous electronics conference (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 π phase difference. One possible cause for the difference in behavior between the two groups is discussed.
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.
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.
Mode Couplings and Conversions for Horizontal Dust Particle Pairs in Complex Plasmas
(IEEE Transactions on Plasma Science, 2013-04) Qiao, Ke; Kong, Jie; Zhang, Zhuanhao.; Matthews, Lorin Swint.; Hyde, Truell Wayne.
The normal modes for horizontal dust particle pairs in a complex plasma are investigated using two methods, a numerical calculation and a molecular dynamics simulation. The ion wakefield downstream of each particle and the variation of charge with particle levitation height are taken into account independently. It is shown that both mechanisms can create mode couplings or hybrid modes. As the modes hybridize, their frequencies are altered. Mode conversions and resonance instabilities are also observed and examined near the resonance points. The resulting power spectrum clearly resembles the experimentally observed high energy density signature for large crystals. The criteria for the occurrence of both the mode conversion and resonance instability are found to be accurately calculated by the double derivative of the interparticle potential, for both the ion wakefield and charge variation cases.
A New Inductively Driven Plasma Generator (IPG6)—Setup and Initial Experiments
(IEEE Transactions on Plasma Science, 2013-04) Dropmann, Michael; Herdrich, Georg; Laufer, Rene; Puckert, Dominik; Fulge, Hannes; Fasoulas, Stefanos; Schmoke, Jimmy; Cook, Mike; Hyde, Truell Wayne.
As part of the partnership between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University and the Institute of Space Systems (IRS) at the University of Stuttgart, a new design for a modular inductively driven plasma generator (IPG) is being developed and tested within CASPER and the IRS. The current IPG design is built on a well-established heritage of modular IPGs designed and operated at IRS. This latest IPG source enables the electrodeless generation of high-enthalpy plasmas and will provide CASPER researchers with the ability to operate with various gases at plasma powers of approximately 15 kW. It will also provide minimized field losses and operation over a wide scope of parameters not possible using existing designs requiring flow-controlled stabilization. The setup of the two facilities in Stuttgart (IPG6-S) and at Baylor (IPG6-B) is described, and results from the first characterization with air plasma are presented. Furthermore, the objectives of the test facilities will be described shortly.
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.
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.

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