Bulletin of the American Physical Society
73rd Annual Gaseous Electronics Virtual Conference
Volume 65, Number 10
Monday–Friday, October 5–9, 2020; Time Zone: Central Daylight Time, USA.
Session UR1: Glows: DC, Pulsed, Microwave, OthersLive
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Chair: Ihor Korolov, Ruhr-University Bochum, Germany |
Thursday, October 8, 2020 1:00PM - 1:15PM Live |
UR1.00001: Generation of stable centimeter-scale glow discharge in presence of external gas flow. Vladislav Gamaleev, Nikolai Britun, Masaru Hori Growing demands in nitric compounds and environmental concerns are leading to requirement of replacement of commonly used Haber-Bosh process by new methods. Nitrogen fixation by plasma looks promising as a ``green'' method for production of nitric compounds; however, some open questions (such as ineffective electric power use) still remain. In this work we propose method of generation of stable centimeter-scale re-pulsing glow discharge in ambient air, which will improve efficiency of electric power use during plasma treatment. Re-pulsing glow discharges were characterized by current and voltage measurements, and optical emission spectrometry. It was found that, at a certain range of parameters, the discharge could be stabilized even in the presence of external gas flow. It was confirmed that by using pulse-width modulation with gas-flow control, rotational and vibrational temperatures could be varied across a wide range. The generation of stable glow discharge in the presence of gas flow with a wide range of parameters that could be precisely controlled by pulse-width modulation looks promising for use in energy-efficient gas conversion. In the presentation, plasma generation process, electrical parameters of the plasma and results of optical diagnostics will be demonstrated. [Preview Abstract] |
Thursday, October 8, 2020 1:15PM - 1:30PM Live |
UR1.00002: Afterglow Measurement of Vibrationally Excited Nitrogen in an Apparent E/N Controlled Plasma by Non-Self-Sustaining DC Discharge Plasma Source Yuki Kunishima, Keisuke Takashima, Toshiro Kaneko A Non-Self-Sustaining DC (NSS DC) discharge plasma source aiming for efficient nitrogen vibrational excitation by apparent reduced electric field (E/N) control has been developed. This plasma source consists of two power sources: a nanosecond pulse plasma generator and a DC power supply. The applied DC voltage controls the apparent E/N suitable for efficient nitrogen vibrational excitation. The temporal evolution of the nitrogen rotational temperature during the discharge is estimated from a nitrogen second positive emission. The decay of nitrogen vibrational distribution after the discharge burst is observed up to v $=$ 4 by laser Raman spectroscopy, which indicates the decay time of a few milliseconds. And the vibrational excitation after the discharge is enhanced with the increase of the apparent reduced electric field increase. Further details will be discussed at the meeting. [Preview Abstract] |
Thursday, October 8, 2020 1:30PM - 1:45PM Live |
UR1.00003: Change in the Heating Mechanism During the Early Stages of Re-Ignition of Pulsed Capacitively Coupled Ar Plasmas. Lawrence Overzet, Keith Hernandez, Matthew Goeckner, Alex Press We have made Phase Resolved Optical Emission Spectroscopy measurements in pulsed Ar plasmas and combined them with measurements of the optical emission intensity (OEI) and electrical characteristics. The OEI exhibits a large overshoot early in the re-ignition at the 100 Hz pulsing rate which is not reflected in any of the electrical characteristics or present at a 10 kHz pulsing rate. This OEI overshoot occurs at a point in time when the RF power, Voltage, DC bias Voltage and electron density are all smaller than they become later in the glow. PROES measurements in combination with time resolved electrical characteristics indicate that the heating mechanism for electrons changes during the overshoot to a combination of stochastic and ohmic heating (from stochastic heating in the steady state). The combination enables a more efficient transfer of the electrical energy to heating electrons. [Preview Abstract] |
Thursday, October 8, 2020 1:45PM - 2:00PM Live |
UR1.00004: Contraction and stability of the positive column of a self-sustained glow discharge in a reactive mixture Hongtao Zhong, Mikhail Shneider, Yiguang Ju Weakly ionized plasma in a glow discharge is known to contract from a homogeneous volumetric state into a filamentary channel when the energy input exceeds some threshold. This contraction is critical for various plasma applications. In this work, the stability analysis is performed for the positive column of a self-sustained glow discharge in a reactive mixture. A zero-dimensional plasma model is first formulated by including equations for the electron/ion number densities, molecular species densities, gas translational temperature and vibrational energy. By perturbing the plasma model with plane waves, dispersion relations involving cyclic frequency and physical parameters could be analytically derived and numerically solved. The critical points physically correspond to the transition from homogeneous stable state to the contracted unstable state. This transition is shown to be not only affected by the well-known ionization-thermal mechanism, but also chemical heat release/absorption and chemical kinetics. The stability analysis will advance the understanding of interactions between weakly-ionized plasma and chemical kinetics, which is of practical interest for plasma assisted chemical synthesis and material processing. [Preview Abstract] |
Thursday, October 8, 2020 2:00PM - 2:15PM Live |
UR1.00005: A miniaturized plasma-based sheet electron beam source suitable for high power sub-THz generation Nikita Gurjar, Sahil Jain, Niraj Kumar Plasma cathode electron (PCE) gun has been used for the generation of a high-power microwave and terahertz signal. PCE guns are capable of generating cylindrical as well as sheet electron beams. Sheet electron beam offers high current density than the cylindrical electron beam for the same aperture area. It is preferred over cylindrical electron beam especially in sub-THz regime. Sheet electron beams are suitable for planar interaction structures which are easier to fabricate in sub-THz regime. In this work, a miniaturized plasma based sheet electron beam source has been designed and developed. The sheet electron beam has been propagated for more than 50mm inside the plasma assisted drift space without any assistance of external magnetic field. The propagated distance by sheet electron beam is sufficient to design the interaction structure of sub-THz oscillator. The beam aspect ratio has also been optimized to keep the fill factor around 70 \%. The gun has been operated for the self-breakdown condition by applying the input voltage of 10-30 kV to generate the high current density ($>$50 A/cm$^{2}$) sheet electron beam. This will help in the generation of high power sub-THz radiation. [Preview Abstract] |
Thursday, October 8, 2020 2:15PM - 2:45PM Live |
UR1.00006: Ion implantation technology architecture and modelling challenges Invited Speaker: Svetlana Radovanov Ribbon ion beams were introduced in the mid 90's. A broad beam ion implanter employs a high current density plasma source, a bending magnet to steer the beam, a collimator magnet to straighten trajectories and multipoles and rods across the beam path to tailor a precise one-dimensional beam current distribution. Furthermore, energy filters are used to decelerate ions and filter high energy neutrals [1,2]. One of the features that made these tools so successful in device fabrication is the precise control of the dopant concentration depth profiles at low energies. Examples of ion depth profiles and ion dynamic calculations using TRIM and TRI3DSTP will be shown [3]. The evolution of multiple other technologies, like plasma doping, directional doping, unique processing capabilities using large area RF plasma sources and ribbon beams will be described. For example, the plasma doping system enables source and drain shallow doping for fins and non-line of sight doping at high doses \textasciitilde 5x10$^{\mathrm{16}}$ /cm$^{\mathrm{2}}$. Unlike the beam line tools, ions are not mass analyzed, but instead the wafer is processed within the plasma chamber or in an adjacent vacuum chamber. Pulsed DC bias ranging from 0.1- 10 kV at frequency f\textasciitilde 5- 400 kHz is applied to the wafer. The RF plasma is generated by an inductively coupled coil. This talk is focused on the beam generation from a plasma source, magnetic and electrostatic focusing, filtering and steering of an ion beam, as well as space charge simulations of low energy transport. In addition, we discuss modeling tools that are used to compute trajectories, space charge densities, electrostatic and magneto static potentials in 2D/3D space. \begin{enumerate} \item A. Renau, Review Scientific Instruments, 81, 02B907 (2010). \item P. Kellerman et al. US 7,888,653 (2011). \item J. England and W. Moller, Nucl. Inst. Methods, 365, 105 (2015). \end{enumerate} [Preview Abstract] |
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