Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session KW74: Basic Plasma Physics Phenomena in Low-temperature Plasmas I |
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Chair: Alex Likhanskii, Applied Materials, Inc. Room: Virtual GEC platform |
Wednesday, October 6, 2021 3:45PM - 4:15PM |
KW74.00001: The impact of plasma pattern formation on particle growth in strongly magnetized, low temperature plasmas Invited Speaker: Edward E Thomas Over the last three decades, plasma scientists have learned how to control a new type of plasma system known as a “complex” or “dusty” plasma. These are four-component plasma systems that consist of electrons, ions, neutral atoms, and charged, solid, nanometer- to micrometer-sized particles. The vast majority of dusty/complex plasma experiments have involved the suspension of charged, micron-sized particles in plasmas. The particles are suspended due to an exquisite balance between gravitational, electrostatic, and drag forces. With the addition of a magnetic field, the properties of the background plasma and the dust are modified as the dynamics of the electrons, then the ions, and finally the charged dust grains become dominated by the magnetic field. |
Wednesday, October 6, 2021 4:15PM - 4:30PM |
KW74.00002: A Kinetic Model of Friction in Strongly Coupled Strongly Magnetized Plasmas Louis Jose, Scott D Baalrud Novel transport properties exhibited by plasmas that are strongly magnetized in the sense that the gyrofrequency exceeds the plasma frequency are not well understood. Recent works studying the weakly coupled plasmas have shown that strong magnetization leads to a transverse component of the friction force that is perpendicular to both the Lorentz force and velocity of the test charge; in addition to the stopping power component. Recent molecular dynamics simulations have also shown that strong Coulomb coupling in addition to strong magnetization gives rise to a third ``gyrofriction'' component of the friction force in the direction of the Lorentz force. Here, we compute the friction force acting on a massive test charge moving through a strongly coupled and strongly magnetized one-component plasma using a generalized Boltzmann kinetic theory. The theory captures these effects and generally agrees well with the molecular dynamics simulations over a broad range of magnetization strength and Coulomb coupling regimes. The gyrofriction component arises due to asymmetries associated with gyromotion during short-range collisions. The transverse force is found to strongly influence the average motion of a test charge by changing the gyroradius and the gyrofriction force is found to slightly change the gyrofrequncy of the test charge resulting in a phase shift. |
Wednesday, October 6, 2021 4:30PM - 4:45PM |
KW74.00003: Analysis of the efficiency of MHD cycle supported by ns pulsed discharge pre-ionization Andrey Starikovskiy, Mikhail Shneider, Nickolay Aleksandrov Numerical characterization of nanosecond pulsed discharges has been conducted in a strong magnetic field environment. Streamer discharge development and plasma generation in pure CO2 was analyzed when magnetic field was directed along the axis of the discharge cell. Numerical simulations were based of a two-dimensional fluid model. It is shown that strong magnetic field affect dramatically on the plasma formation. We simulate the NS-DBD plasma conductivity in a wide range of the external magnetic field amplitudes. Comparison with the experimental results shows an excellent agreement between calculated and measured plasma distribution. The energy spent on ionization of the gap and Joule heating of the gas is Qion ~ 0.3 mJ during 6 ns of the discharge for MHD generator volume of 50×50×100 mm3. The total energy extracted from the "hot" flow at U = 1571 m/s during 10 ms after the pre-ionizing pulse is 28.3 J/m3, which gives QMHD = 7.1 mJ from the same volume. Thus, in an ideal Faraday MHD generator with segmented electrodes, the energy extracted by MHD generator in a high-speed flow could be much higher than the energy required for gas ionization: QMHD/Qion ~ 24. |
Wednesday, October 6, 2021 4:45PM - 5:00PM |
KW74.00004: Drift-driven microturbulence in planar magnetrons Sedina Tsikata, Tiberiu M Minea, Adrien Revel E x B discharges play a well-known role in plasma-assisted deposition. Planar magnetrons operated in high-current, pulsed regimes are used for tailored thin film deposition with improved properties. In spite of this, an understanding of the physics of such regimes and how to model their particle dynamics is still far from complete. As with other E x B discharges, in addition to large-scale self-organization [1], the presence of microinstabilities has been demonstrated [2], with implications for performance and modeling. Coherent Thomson scattering studies of electron density fluctuations reveal a rapid evolution in amplitude and frequency of the azimuthal electron cyclotron drift instability during pulsing. Counterpropagating ion-ion two-stream instabilities, in the presence of a complex electric field structure and multiple ionization states, are also created. 2D PIC MCC simulations [3] also reveal modulations in the electron density consistent with short-scale wave activity. These recent findings on magnetron microturbulence are discussed. |
Wednesday, October 6, 2021 5:00PM - 5:15PM |
KW74.00005: External plate biasing and diverging magnetic field effects on radial characteristics of back diffused expanding plasma column SATADAL DAS, Shantanu Karkari Independent control of the plasma parameters distribution inside a discharge is significantly desirable to achieve plasma uniformity for microelectronic industry or in front of an ion extraction grid inside ion sources to minimize the beam divergence occurring due to spatial distribution of plasma in fusion devices. Electrode biasing is one of the popular techniques that is widely used for controlling the edge plasma density and temperature profile in magnetized plasma devices like, tokamak or linear device. Likewise, the spatial divergence in magnetic field also affects the charged particle dynamics in magnetized plasma. Therefore, the separate effect of electrode biasing and diverging magnetic field on spatial plasma properties are well known, but the combined effects of these two have not been well understood. |
Wednesday, October 6, 2021 5:15PM - 5:30PM Not Participating |
KW74.00006: Experimental investigations of radial physics in Hall thrusters Thibault Dubois, Sedina Tsikata, Guillaume Largeau Hall plasma thrusters and other devices with crossed electric and magnetic field geometries feature complex three-dimensional physics. The development of instabilities in such geometries is the subject of active study. In recent years, results from numerical simulations have provided some insight regarding radial features (observed parallel to the magnetic field), such as the complex coupling between wall emission and drift driven instabilities [1, 2]. However, few direct measurements of plasma properties and dynamics in the radial direction are available. In this work, radial investigations of electron properties in the exit plane of a Hall thruster have been performed using incoherent Thomson scattering. For the conditions investigated, large electron temperature gradients are measured between the inner and outer walls of the annular discharge, while a radial density gradient consistent with non-uniform ionization is observed. These measurements of electron properties (non-invasive and highly spatially-resolved) provide a means to develop an understanding of the radial features of Hall thrusters and contribute to the ongoing development of 3D codes.
[1] A. Héron and J-C. Adam. Phys Plasmas 20, 082313 (2013) [2] A. Tavant et al., Plasma Sources Sci. Technol. 27, 124001 (2018) |
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