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 SR2: Dielectric Barrier Discharges and Low Temperature Jets ILive
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Chair: Li Wang, Ruhr-University Bochum, Germany |
Thursday, October 8, 2020 8:00AM - 8:30AM Live |
SR2.00001: Multi-Diagnostic Approach to Energy Transport in Atmospheric Pressure Plasma Discharges Invited Speaker: Judith Golda Many applications in plasma processing science rely on the non-equilibrium properties of cold plasmas. Transport is a consequence of physical non-equilibrium systems as temperature and pressure gradients drive energy and mass transport. The energy that is selectively pumped into the electrons couples via different physical processes to other species present in the plasma on diverging time-scales, e.g. via drift, diffusion, elastic and inelastic collisions. As a consequence, theoretical description of these plasmas is challenging and requires complex models including kinetic description via Boltzmann equation or particle in cell simulations. However, to tailor non-equilibrium plasmas to the desired properties, e.g. for CO$_2$ splitting, a fundamental understanding of these processes is necessary. Here, we present a multi-diagnostic approach to experimentally and quantitatively study the energy transport in an atmospheric pressure plasma discharge. We exemplary investigated an RF-driven helium-oxygen discharge. The electrical energy input was calculated from voltage and current waveform measurements. We used optical emission spectroscopy to measure the atomic oxygen density as a scale for the chemical energy and thermocouple measurements to study the neutral gas temperature as a scale for thermal energy. Using an absolutely calibrated echelle spectrometer, we also measured the radiation energy emitted in the visible wavelength range. We demonstrate that these diagnostics allow to trace the major energy transport mechanisms in the plasma discharge. A parameter study on the control parameters power, frequency, and oxygen admixture revealed only limited control over the final energy distribution in the physical system. [Preview Abstract] |
Thursday, October 8, 2020 8:30AM - 8:45AM Live |
SR2.00002: Hybrid model simulations of He/O$_{\mathrm{2}}$ micro atmospheric pressure plasma jets Yue Liu, Ihor Korolov, Jan Trieschmann, Lena Bischoff, Gerrit Hübner, Julian Schulze, Thomas Mussenbrock We build a hybrid model to investigate the helium micro atmospheric pressure plasma jet with a small amount of oxygen admixture. The model treats electrons kinetically based on the Particle-in-cell/ Monte Carlo Collision (PIC/MCC) algorithm, while various heavy species based on the fluid equations. The simulation results show good agreements with multiple experimental diagnostics, including the electron heating dynamics, the helium metastable density, and the atomic oxygen density. We demonstrate that voltage waveform tailoring allows us to control and enhance the generation of reactive species, which are highly relevant for a variety of biological and technological applications. [Preview Abstract] |
Thursday, October 8, 2020 8:45AM - 9:00AM Live |
SR2.00003: Characterization of plasma jets interacting with dielectric and metallic targets: comparison between simulations and experiments Anne Bourdon, Pedro Viegas, Elmar Slikboer, Marlous Hofmans, Olivier van Rooij, Adam Obrusnik, Bart Klarenaar, Zdenek Bonaventura, Enric Garcia-Caurel, Olivier Guatiella, Ana Sobota We study through quantitative comparisons between fluid modeling and experiments, the interaction of a kHz $\mu$s-pulsed atmospheric pressure plasma jet with different target surfaces: floating dielectric and metallic and grounded metallic. It is shown that when the discharge impacts on a dielectric target, it charges locally in a few ns. Conversely, the electric potential of the floating target is close to grounded in the instants after the impact of the discharge, but rises to a high voltage, potentially more than half of the applied voltage, at the end of the 1 $\mu$s pulse. As a result, a return stroke takes place after the discharge impact with both grounded and floating metallic targets, as a redistribution between the high voltage electrode and the low voltage target. Electric field, electron temperature and electron density in the plasma plume are higher during the pulse with grounded target than with the floating targets, as gradients of electric potential progressively dissipate in the latter cases. Finally, at the fall of the pulse, another electrical redistribution takes place, with higher intensity with the floating dielectric and metallic targets than with the grounded target. [Preview Abstract] |
Thursday, October 8, 2020 9:00AM - 9:15AM Live |
SR2.00004: Hydroxyl and hydrogen radicals in the active plasma and plasma effluent of an atmospheric pressure plasma jet Yuanfu Yue, Jingkai Jiang, Santosh Kondeti, Peter Bruggeman Non-equilibrium atmospheric pressure plasma jets (N-APPJs) have received a lot of attentions in the last decade due to promising biomedical applications. Reactive species (such as OH and H) generated by plasmas play essential roles in these applications. In this work, we studied both H and OH density profiles temporally along the axis of symmetry of a N-APPJ from the ionizing plasma inside the jet to the jet effluent by laser induced fluorescence (LIF). The plasma jet is driven by a nanosecond pulser with helium and H$_{\mathrm{2}}$O mixture. We found that the dominant generation of H/OH locates between the electrodes inside the jet tube rather than by the guided streamer in the effluent. In the afterglow period, H/OH is convectively transported to the downstream while recombining. The effect of the pulse repetition rate on the generation of H/OH shows a significant memory effect, different for H and OH. This is attributed to different production mechanisms of H and OH. The work also suggests that the plasma kinetics inside the jet, often not considered in many experimental studies, may ultimately determine the reactivity in the jet effluent. [Preview Abstract] |
Thursday, October 8, 2020 9:15AM - 9:30AM Live |
SR2.00005: Continuous gas temperature measurement of cold plasma jets containing microdroplets, using a focussed spot IR sensor Nourhan Hendawy, Harold McQuaid, Davide Mariotti, Paul Maguire Controlling gas temperature in real time via continuous monitoring is essential in various plasma applications especially for biomedical treatments and nanomaterial synthesis. Traditional techniques have limitations due to low accuracy, high cost or experimental complexity. Adding droplets to plasmas offers the possibility of enhanced delivery of plasma activated water but has the potential to destabilise the plasma and increase gas temperature. We demonstrate continuous high-accuracy gas temperature measurements of droplet-laden low-temperature plasma jets using a small focal spot infrared sensor directed at the outer quartz wall of the plasma. Heat transfer across the capillary tube was determined using calibration measurements of the inner wall temperature. Measured gas temperatures, without droplets, varied from 25 $^{\mathrm{o}}$C -- 50 $^{\mathrm{o}}$C, increasing with absorbed power and decreased gas flow. The introduction into the plasma of a stream of microdroplets (\textasciitilde 12 um diameter) led to a reduction in gas temperature of \textasciitilde 10 $^{\mathrm{o}}$C, for the same absorbed power. This is an important parameter in determining droplet evaporation and its impact on plasma chemistry. [Preview Abstract] |
Thursday, October 8, 2020 9:30AM - 9:45AM Live |
SR2.00006: Energetics of reactions in a dielectric barrier discharge with argon carrier gas: Halocarbons Sean Watson, Bernard Nisol, Stephan Reuter, Michael R. Wertheimer The novel method we developed for understanding energy exchanges between argon (Ar) carrier gas and precursor molecules in a large-area $216\, cm^2$ dielectric barrier discharge (DBD) reactor has resulted in a series of articles, each relating to a different family of organic compounds. This communication focuses on two new groups, perfluorocarbons, $C_xF_y$ and perchlorocarbons, $C_xCl_y$, and compares results with earlier ones for hydrocarbons, $C_xH_y$[1] and hydrofluoromethanes, $CH_xF_y$[2]. The precursors (in $^o/_{oo}$ concentrations) were mixed with Ar in a 20 kHz, 8 kV (peak to peak) DBD. For each separate compound $E_m$, the energy (in eV) absorbed per molecule, was determined from measurements of the time resolved discharge current, $I_d$, and the gap voltage, $V_{gap}$. Optical emission spectra were recorded and $E_m$ was plotted as a function of precursor flow rate, $F_d$. The process generally led to thin “plasma polymer” (PP) deposits (e.g. on Si wafer substrates). Their characteristics, like their C/F or C/Cl composition ratios from XPS measurements, strongly correlated with $E_m$ and $F_d$, as did PP deposition rates and water contact angles. [1] B. Nisol et al., Plasma Process Polym, 2016;14:e201600191 [2] S. Watson et al., Plasma Process Polym, 2020;17:e201900125. [Preview Abstract] |
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