Hypervelocity Impacts and Dusty Plasma Lab (HIDPL)

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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.
Analysis of Magnetic Field Plasma Interactions Using Micro Particles as Probes
(American Physics Society/ Physical Review E, 2015-08-26) Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin Swint; Hyde, T. W.
The interaction between a magnetic field and plasma close to a nonconductive surface is of interest for both science and technology. In space, crustal magnetic fields on celestial bodies without atmosphere can interact with the solar wind. In advanced technologies such as those used in fusion or spaceflight, magnetic fields can be used to either control a plasma or protect surfaces exposed to the high heat loads produced by plasma. In this paper, a method will be discussed for investigating magnetic field plasma interactions close to a nonconductive surface inside a Gaseous Electronics Conference reference cell employing dust particles as probes. To accomplish this, a magnet covered by a glass plate was exposed to a low power argon plasma. The magnetic field was strong enough to magnetize the electrons, while not directly impacting the dynamics of the ions or the dust particles used for diagnostics. In order to investigate the interaction of the plasma with the magnetic field and the nonconductive surface, micron-sized dust particles were introduced into the plasma and their trajectories were recorded with a high-speed camera. Based on the resulting particle trajectories, the accelerations of the dust particles were determined and acceleration maps over the field of view were generated which are representative of the forces acting on the particles. The results show that the magnetic field is responsible for the development of strong electric fields in the plasma, in both horizontal and vertical directions, leading to complex motion of the dust particles.
Comparison of Plasma Magnetic Field Interactions in a Static and Dynamic Plasma Facility
(Transactions of the Japan Society for Aeronautical and Space Sciences, Aerospace Technology Japan, 2016) Dropmann, Michael; Knapp, A.; Eichhorn, C.; Loehle, S.; Laufer, Rene; Herdrich, Georg; Matthews, Lorin Swint.; Hyde, Truell Wayne.; Fasoulas, Stefanos; Roeser, Hans-Peter
Magnetic fields are a principal/widespread/promising tool/instrument in space technology design for the use in advanced propulsion concepts, shielding from radiation or to aid thermal protection during the atmospheric entry of spacecraft. Two experiments have been conducted to investigate the feasibility of using magnetic fields to reduce the heat flux onto a thermal protection system during atmospheric entry. For this purpose a modified heat flux probe with embedded permanent magnets has been exposed to a plasma jet and the structure of the bow shock in front of the probe has been observed using an emission spectroscopy setup. The intensity ratio of ionized argon lines for the experiment with and without magnets has been determined and used to analyze the magnetic field`s impact on the flow. Complementary experiments in a low power capacitively driven plasma have been conducted using micron sized particles as probes to map electric fields in a magnetically perturbed plasma. The results from both experiments are presented and analogies are drawn from both approaches. The experiments have shown that the interactions of the magnetic field with the plasma can create strong electric fields which strongly influence the ions even though the field is too weak to magnetize the ions.
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.
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.
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.
Dust as probe for horizontal field distribution in low pressure gas discharges
(Plasma Sources Science and Technology, 2014-06-23) Hartmann, Peter; Kovacs, Aniko Zs.; Carmona-Reyes, Jorge; Matthews, Lorin Swint.; Hyde, Truell Wayne.
Using dust grains as probes in gas discharge plasma is a very promising, but at the same time very challenging method, as the individual external control of dust grains has to be solved. We propose and demonstrate the applicability of the RotoDust experiment, where the well controlled centrifugal force is balanced by the horizontal confinement field in plane electrode argon radio frequency gas discharges. We have reached a resolution of 0.1 V cm−1 for the electric field. This technique is used to verify numerical simulations and to map symmetry properties of the confinement in dusty plasma experiments using a glass box.
Dust as probes: Determining confinement and interaction forces
(IOP Publishing, 2020-10) Hartmann, Peter; Rosenberg, Marlene; Juhasz, Z.; Matthews, Lorin; Sanford, Dustin; Vermillion, Katrina; Reyes, Jorge; Hyde, Truell
The PK-4 system is a micro-gravity dusty plasma experiment currently in operation on-board the International Space Station. The experiment utilizes a long DC discharge in neon or argon gases. We apply our 2D particle-in-cell with Monte Carlo collisions discharge simulation to compute local plasma parameters that serve as input data for future dust dynamics models. The simulation includes electrons, Ne+ ions, and Ne^m metastable atoms in neon gas and their collisions at solid surfaces including secondary electron emission and glass wall charging. On the time scale of the on-board optical imaging, the positive column appears stable and homogeneous. On the other hand, our simulations show that on microsecond time scales the positive column is highly inhomogeneous: ionization waves with phase velocities in the range between 500 m s−1 and 1200 m s−1 dominate the structure. In these waves, the electric field and charged particle densities can reach amplitudes up to 10 times of their average value. Our experiments on ground-based PK-4 replica systems fully support the numerical findings. In the experiment, the direction of the DC current can be alternated, which has been found to favor dust particle chain formation. We discuss possible mechanisms for how the highly oscillatory plasma environment contributes to the dust particle chain formation.
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.
Dust particle pair correlation functions and the non-linear effect of interaction potentials
(IEEE Transactions on Plasma Science, 2019-07) Kong, Jie; Qiao, Ke; Matthews, Lorin Swint.; Hyde, Truell Wayne.
Dust kinetic temperature is a measure of the energy of the stochastic motion of a dust particle and is a result of the combination of the Brownian motion and the fluctuations in the dust charge and confining electric field. A method using the equilibrium value of the mean square displacement was recently introduced to obtain the dust kinetic temperature experimentally. As a follow up, this paper investigates the relationship between the dust kinetic energy derived from the mean square displacement technique and a technique using the probability distribution of the displacements obtained from random fluctuations of the dust particle. The experimental results indicate that the harmonic confinement potential acting on the dust particle can be obtained by combining the two methods, allowing the nonlinear effect of the confining force to be investigated. The thermal expansion in a 1-D vertical chain is discussed as a representative application as it is related to the nonlinear confinement force, or the asymmetric confinement potential.
Dust particle pair correlation functions and the non-linear effect of interaction potentials
(IEEE Transactions on Plasma Science, 2019-07) Kong, Jie; Qiao, Ke; Matthews, L.S.; Hyde, T.W.
Dust temperature is a measure of the energy of the stochastic motion of a dust particle, and is a result of the combination of the Brownian motion and the fluctuations in the dust charge and confining electric field. A method using the equilibrium value of the mean square displacement was recently introduced to obtain the dust temperature experimentally. As a follow up, this paper investigates the relationship between the temperature derived from the mean square displacement technique and a technique using the probability distribution of the displacements obtained from random fluctuations of the dust particle. Experimental results indicate that the harmonic confinement potential acting on the dust particle can be obtained by combining the two methods, allowing the non-linear effect of the confining force to be investigated. The thermal expansion in a one-dimensional vertical chain is discussed as a representative application as it is related to the non-linear confinement force, or the asymmetric confinement potential.
Dusty plasma cavities: Probe-induced and natural
(American Physical Society, 2015-06-22) Harris, Brandon Joseph.; Matthews, Lorin Swint.; Hyde, Truell Wayne.
A comprehensive exploration of regional dust evacuation in complex plasma crystals is presented.Voids created in three-dimensional crystals on the International Space Station have provided a rich foundation for experiments, but cavities in dust crystals formed in ground-based experiments have not received as much attention. Inside a modified Gaseous Electronics Conference rf cell, a powered vertical probe was used to clear the central area of a dust crystal, producing a cavity with high cylindrical symmetry. Cavities generated by three mechanisms are examined. First, repulsion of micrometer-sized particles by a negatively charged probe is investigated. A model of this effect developed for a dc plasma is modified and applied to explain experimental data in rf plasma. Second, the formation of natural cavities is surveyed; a radial ion drag proposed to occur due to a curved sheath is considered in conjunction with thermophoresis and a flattened confinement potential above the center of the electrode. Finally, cavity formation upon increasing the probe potential above the plasma floating potential is justified by a combination of ion drag and sheath edge modification. The cavities produced by these methods appear similar, but each is shown to be facilitated by fundamentally different processes.
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.
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.
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.
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.].
Electrical Conductivity of the Thermal Dusty Plasma under the Conditions of a Hybrid Plasma Environment Simulation Facility
(New Journal of Physcis, 2015-05-27) Zhukhovitskii, D.; Petrov, O.; Hyde, Truell Wayne.; Herdrich, Georg; Laufer, Rene; Dropmann, Michael; Matthews, Lorin Swint.
We discuss the inductively heated plasma generator (IPG) facility in application to the generation of the thermal dusty plasma formed by the positively charged dust particles and the electrons emitted by them. We develop a theoretical model for the calculation of plasma electrical conductivity under typical conditions of the IPG. We show that the electrical conductivity of dusty plasma is defined by collisions with the neutral gas molecules and by the electron number density. The latter is calculated in the approximations of an ideal and strongly coupled particle system and in the regime of weak and strong screening of the particle charge. The maximum attainable electron number density and corresponding maximum plasma electrical conductivity prove to be independent of the particle emissivity. Analysis of available experiments is performed, in particular, of our recent experiment with plasma formed by the combustion products of a propane–air mixture and the CeO2 particles injected into it. A good correlation between the theory and experimental data points to the adequacy of our approach. Our main conclusion is that a level of the electrical conductivity due to the thermal ionization of the dust particles is sufficiently high to compete with that of the potassium-doped plasmas.
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.
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.
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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