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 ET41: Atmospheric and High Pressure Plasmas: Jets and Gliding Arcs I |
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Chair: David Go, University of Notre Dame Room: Virtual GEC platform |
Tuesday, October 5, 2021 2:00PM - 2:15PM |
ET41.00001: Student Excellence Award Finalist: Ion Dynamics and Pre-Ionization Effects in an Ar-O2 Modulated RF-Driven Atmospheric Pressure Plasma Jet Jingkai Jiang, Peter Bruggeman In this work, we report a characterization of ion fluxes impinging on substrates as produced by a modulated RF-driven atmospheric pressure plasma jet operating in a homogenous gas environment (Ar+1% O2) using molecular beam mass spectrometry (MBMS). The influence of the RF modulation frequency (100 Hz-20 kHz) upon the ion fluxes was investigated by time-resolved measurements, and lifetimes of the dominant ions, O2+, NO+, O-, O2- and O3-, were found to be 28±2 μs, 117±8 μs, 7.3±0.4 μs, 17±1 μs, and 23±2 μs, respectively. The absolute ion densities in the near afterglow region were found to be on the order of 1011 cm-3. Significant differences in the dynamics of the positive and negative ions were found and explained by large electron densities in the afterglow produced by electron detachment reactions from negative ions due to the large concentrations of atomic oxygen and singlet delta oxygen. Transitions in ion flux dynamics for different modulation frequencies and at the startup of the plasma were analyzed together with ICCD images recording the plasma propagation, to assess the dynamics of plasma plume propagation and how it is impacted by “memory effects”. Quantitative measurements of the ion densities causing these memory effects are reported. The results highlight the tremendous impact of memory effects on plasma propagation and their corresponding pre-ionization densities. |
Tuesday, October 5, 2021 2:15PM - 2:30PM |
ET41.00002: Student Excellence Award Finalist: Electric field measurements of piezoelectric direct discharge plasmas using electric-field induced second harmonic (E-FISH) generation Jinyu Yang, Edward V Barnat, Seong-kyun Im, David B Go Piezoelectric direct discharge (PDD) plasmas are generated by the high voltage output of a piezoelectric transformer (PT). When a PT is actuated at its second harmonic frequency by a low input voltage of ~ 10 Vrms, the generated electric field at the distal end can be sufficient to breakdown the surrounding gas, making it an attractive power source for non-equilibrium plasma generation. Understanding the surface potential and electric field distribution around the distal end is important for effectively using PTs for plasma generation. In this work, the spatiotemporally-resolved characteristics of the electric field generated by a PT operating in open air have been investigated using the electric-field induced second harmonic (E-FISH) generation method. Absolute calibration of the E-FISH signal was obtained by measuring a known uniform electric field generated within the gap of parallel plates. Electric field components were determined by simultaneously conducting E-FISH measurements with the incident laser polarized in two orthogonal directions. Results show the spatial distribution of the electric field around the PT’s output distal end and how it evolves in time. Notably, the strongest electric field appears on the face of the PT’s distal end and when operated just below the breakdown threshold, is 30.4 kV/cm, consistent with the breakdown field of air. |
Tuesday, October 5, 2021 2:30PM - 3:00PM |
ET41.00003: Numerical simulations of radio frequency capacitively coupled atmospheric pressure micro plasma jets: from fluid to kinetic models Invited Speaker: Yue Liu Based on the COST-reference micro plasma jet, radio frequency capacitively coupled atmospheric pressure discharges operated in He/O2 mixtures are investigated by numerical simulations, including a fluid dynamics model and a kinetic hybrid model. The simulation results are compared with various experimental measurements. The fluid model is performed by nonPDPSIM. It is shown that the fluid model is capable of capturing the electron heating mode transitions. The electron heating dynamics and reactive neutral species generations are enhanced in the trenches by using a structured electrode topology. In the kinetic hybrid model, electrons are traced by the Particle-in-cell/Monte Carlo Collision algorithm, while ions and neutral species are handled by fluid equations. The simulated results obtained from the hybrid model, show quantitative agreement with experimental results, including the electron impact excitation rates, the helium metastable density and the atomic oxygen density. The electron energy probability function is found to be spatio-temporally controlled by the voltage waveform tailoring. The simulation results from both models demonstrate that desired neutral species generations in a micro atmospheric pressure plasma jet can be enhanced and controlled via adjusting external discharge parameters, such as the shape of the voltage waveform, and the electrode structure. |
Tuesday, October 5, 2021 3:00PM - 3:15PM |
ET41.00004: OH in the effluent of the COST-Jet in humid environment by laser-induced fluorescence Sebastian Burhenn, Pia-Victoria Pottkämper, Robin Labenski, Volker Schulz-von der Gathen, Judith Golda The surrounding atmosphere of atmospheric pressure plasma jets has crucial impact on the reactive species in the effluent region. In particular, the diffusion of humid ambient air into the effluent may significantly change its plasma chemical properties. Moreover, humidity is also added by water impurities in the feed gas of the jet. By measuring the distribution of the tracer molecule OH in the jet effluent under controlled atmosphere, conclusions about the production channels of OH can be drawn. This was done by laser-induced fluorescence (LIF) in the exit region of a COST-Jet. To ensure a controlled humid environment, the COST-Jet was installed in a closed vessel, which allows to control the composition of the surrounding atmosphere. To investigate the influence of humid environment on the OH density, the humidity inside the vessel was systematically varied. In addition to the spatial distribution of OH, the measured lifetimes also provide valuable information about the ongoing processes in the jet effluent. |
Tuesday, October 5, 2021 3:15PM - 3:30PM |
ET41.00005: Atomic oxygen distribution in the interaction zone of a micro atmospheric pressure plasma jet and a surface. Sascha Chur, David Steuer, Volker Schulz-von der Gathen, Judith Golda, Marc Böke As a reactive species atomic O finds successful use for surface treatments or in medical applications. To examine the distribution along treated substrates, two-dimensional two photon absorption laser induced fluorescence spectroscopy (TALIF) was used. Measurements of the atomic O density were performed in the effluent of a rf coupled micro atmospheric pressure plasma jet (COST-(μAPPJ) ) in the interaction zone of a metallic (Cu) surface with a He/O gasflow. To this end, the width of the atomic O profile in the effluent, the atomic O peak density in the maximum of the effluent and the atomic O density integrated over the laser axis across the effluent profile were examined. For the width a flow dependent broadening of the profile was asserted, where smaller flows resulted in a wider broadening in front of the surface. The investigation of the peak density yielded a longer life span of atomic O in comparison to the integrated density because of a smaller quenching influence from air inflow in the effluent center. Additionally, the integrated density made an increase in atomic O in front of a surface visible, at which smaller flows caused a higher percentage density increase. Furthermore, two-dimensional atomic O density distributions along the surface were shown. Schlieren imaging confirmed that atomic oxygen follows the Helium flow and laid the basis for transferring the TALIF results to other jet-surface-configurations. |
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