Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session QR1: Magnetically Enhanced Plasmas |
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Chair: John Foster, University of Michigan Room: Century I |
Thursday, October 31, 2019 1:45PM - 2:15PM |
QR1.00001: Insights into instabilities and electron dynamics in low-temperature magnetized plasma discharges Invited Speaker: Sedina Tsikata Valuable throughout industry, magnetized low-temperature plasma devices are also home to rich and complex physics, including plasma instabilities, anomalous transport, anisotropies and self-organization across different length scales. The ability to understand the physics associated with such features is key for the exploitation of these devices. Planar magnetrons used in plasma-assisted deposition are now increasingly operated in pulsed, dense, high-current plasma states. Access to electron properties and dynamics in these regimes would facilitate an understanding of how plasma behavior affects deposition properties and aid modeling efforts. Similarly, an ability to identify and describe instabilities involved in Hall thruster anomalous transport would provide information required for predictive code development, currently beyond reach. Fortunately, with the recent development and application of advanced laser diagnostics to such plasmas, we are a step closer to mastering the physics of such devices. In this talk, insights from implementations of uniquely-sensitive coherent and incoherent laser Thomson scattering diagnostics are discussed. Coherent Thomson scattering applied to both devices is the source of insights on plasma waves, including time-resolved wave behavior in transient regimes. Incoherent Thomson scattering applied to both devices provides information not only on electron properties, but also electron drifts and anisotropies. These implementations offer a path forward to answering long-standing questions on the physics of such magnetized discharges. [Preview Abstract] |
Thursday, October 31, 2019 2:15PM - 2:30PM |
QR1.00002: Magnetic Asymmetry Effect in Capacitively Coupled RF Discharges Birk Berger, Moritz Oberberg, Dennis Engel, Christian Woelfel, Denis Eremin, Jan Lunze, Ralf Peter Brinkmann, Peter Awakowicz, Julian Schulze The Electrical Asymmetry Effect is known to allow control of plasma parameters such as the discharge symmetry, DC self-bias, and energy distribution functions in capacitively coupled plasmas (CCP). It is based on using consecutive harmonics with adjustable phases. Theoretical studies recently predicted a similar effect by applying a magnetic field which decreases from one electrode to the other. This was introduced as Magnetic Asymmetry Effect (MAE) and is based on the presence of different plasma density regions. In this work, we show results of experimental investigations on the MAE in a single frequency CCP at 13.56 MHz and 1 Pa with a magnetron-like magnetic field configuration at the powered electrode. Increasing the radial magnetic flux density allows to control the DC self-bias, the mean ion energies at the electrodes and the symmetry parameter. Additionally, we show measurements of the RF current in the middle of the grounded electrode as a function of the magnetic field. We find that the generation of high frequency oscillations of the discharge current induced by the self-excitation of the Plasma Series Resonance can be controlled magnetically. [Preview Abstract] |
Thursday, October 31, 2019 2:30PM - 2:45PM |
QR1.00003: Plasma Density Increases in a Low Power ECR Thruster Using Pulsed Power and Frequency Mixing Techniques Benjamin Wachs, Brendan Stassel, Benjamin Jorns The work presented here explores increases in plasma density at the exit plane of a low power Electron Cyclotron Resonance (ECR) magnetic nozzle thruster achieved using custom input power waveforms. The waveforms used in this experiment are generated by a solid-state power amplifier thus allowing for a variety of modulation techniques to be tested. We employ Bayesian optimization to maximize plasma density while keeping total input power constant. Here, multiple frequencies and modulation schemes are combined in different weights to produce new waveforms. We then measure density in real time using a microwave interferometer setup, which gives rapid feedback and thus allows for the exploration of a wide design space. While pulsed power is common in plasma processing and multifrequency heating is often used in high power ion sources, these techniques have not been combined in this manner for real time optimization of plasma parameters. While this experiment is conducted using a prototype thruster, and plasma density serves as a corollary for thrust generation, the techniques developed in this work can easily be applied to plasma processing and other types of plasmas. [Preview Abstract] |
Thursday, October 31, 2019 2:45PM - 3:00PM |
QR1.00004: Plasma instabilities and cross-field electron transport in low-temperature magnetized plasmas Kentaro Hara, Sedina Tsikata Anomalous electron transport across magnetic field lines remains poorly understood in low-temperature magnetized plasmas. Recent advancements in experimental capabilities, such as Thomson scattering, strongly indicate the presence of plasma waves, which are likely driven by plasma instabilities. The electron confinement is reduced by the fluctuations, particularly in the E$\times $B direction, resulting in anomalous cross-field electron transport. In this talk, we will review various plasma instabilities relevant to low-temperature magnetized plasmas, including electron cyclotron drift instability, modified two-stream instability, ion acoustic instability, and gradient drift instability. Recent progress in Thomson scattering and kinetic theory will be discussed. [Preview Abstract] |
Thursday, October 31, 2019 3:00PM - 3:15PM |
QR1.00005: Particle-in-cell simulations for the effect of target erosions on the sputtering yield of a DC magnetron sputtering system Young Hyun Jo, Heesung Park, Min Young Hur, Hae June Lee The DC magnetron sputtering is a standard sputtering method which has good deposition film quality in various coating processes for conductor targets even at low temperature. The deposition profile of the DC magnetron sputtering system depends on the sputtering yield profile which is directly related to the ion incidence from plasmas. Therefore, the way to control the energy and angle distributions of incident ions (IEAD or IEADF) is a key issue to get a better deposition profile. It was revealed in the previous study [1] that gas pressure dominantly affects the IEADF. However, there are no information of the effect of target erosions, though it is important to know the lifetime of the target during the deposition process. In this presentation, the change of the properties in the deposition process is discussed based on the analysis of variation of IEADF and plasma characteristics using particle-in-cell simulations. [1] M. Y. Hur, S. Oh, H. J. Kim, and H. J. Lee, Appl. Sci. Converg. Technol. \textbf{27}, 19-22 (2018) [Preview Abstract] |
Thursday, October 31, 2019 3:15PM - 3:30PM |
QR1.00006: Interaction of Double and Triple Alfvenic Solitons in Non Maxwellian Space Plasmas Kuldeep Singh, Nareshpal Singh Saini Over the past many years the variety of nonlinear structures, Alfven waves and the magnetoacoustic waves (slow and fast) are the basic wave modes in the magnetohydrodynamic (MHD) systems in which Alfv\'{e}n waves are the low frequency waves which play a central role in many laboratory, cosmic as well as fusion plasmas where the plasma $\beta $is typically much smaller than the electron to ion mass ratio. The propagation and interaction of multi-solitons are important phenomena in plasma physics. They interact elastically and owing to this reason, the amplitudes of solitons do not change; however each soliton gets a phase shift. In the present work, we have investigated the propagation of ion acoustic kinetic Alfven waves in a low $\beta $ plasma. In this regard, Korteweg de Vries equation is derived and discussed using the plasma parameters that are typically found in solar corona. The interaction of fast IAKAWs is explored by using the Hirota bilinear formalism, which admits multi-soliton solutions. It is observed that the values of the propagation vectors determine the interaction of solitary waves. It is pertinent to mention here that this solution describes two solitons travelling in the same direction and the soliton interaction takes place when the faster solitary wave overtakes the slower solitary wave. It is further noted that the amplitude of the respective solitary waves remain unchanged after the interaction, however, they do experience a phase shift. This study may also be helpful in understanding various non-linear coherent structures in space and astrophysical plasma environments. [Preview Abstract] |
Thursday, October 31, 2019 3:30PM - 3:45PM |
QR1.00007: Experimental Study of a Low Noise Tunable Plasma Antenna Sustained by CW and Pulsed RF Power Vladlen Podolsky, Abbas Semnani, Sergey Macheret Plasma antennas based on electric discharges are attractive because they can withstand high power, and their resonant frequency and bandwidth are tunable by changing the plasma parameters. However, continuous-operation plasma antennas have a very high Johnson-Nyquist thermal noise due to the high electron temperatures, precluding their use as receiving antennas. In this talk, we present results of a tunable antenna consisting of an argon plasma enclosed in a Pyrex tube sustained by a surface wave discharge. We demonstrate the effects of increasing power, changing gas pressure, and varying glass tube diameter on the center resonance frequency and the bandwidth. A comparison of the noise figure for CW antenna to that of a plasma amtenna sustained by RF pulses reveals that on average, the repetitively pulsed plasma has lower levels of thermal noise. Indeed, in the afterglow between the pulses the electron temperature decays much faster than the electron density, substantially reducing the noise. Such characteristics are beneficial to the creation of a plasma antenna that can act as a transmitter of the driving frequency when the pulse is applied and an efficient receiver between the pulses. [Preview Abstract] |
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