Bulletin of the American Physical Society
75th Annual Gaseous Electronics Conference
Volume 67, Number 9
Monday–Friday, October 3–7, 2022;
Sendai International Center, Sendai, Japan
The session times in this program are intended for Japan Standard Time zone in Tokyo, Japan (GMT+9)
Session DR5: Optical Diagnostics |
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Chair: Holger Kersten, Kiel University, Germany Room: Sendai International Center Tachibana |
Thursday, October 6, 2022 4:00PM - 4:15PM |
DR5.00001: Coupled Electrical and Optical Characterization of Electrostatic Discharges Claudia A Schrama, Sarah Hinnegan, Jonathan Barolak, Daniel Adams, Alex Wilhelm, Charles G Durfee Electrostatic discharge (ESD) can harm electronics and sensitive materials. ESDs that are limited by stored charge on objects of moderate size are closer to threshold than arc switches. We are studying the energy transfer and plasma dynamics in ESDs. We develop numerical models and make electrical and optical measurements to understand the time dependent resistance and electron and neutral density evolution in ESDs. |
Thursday, October 6, 2022 4:15PM - 4:30PM |
DR5.00002: Locally-resolved temperature and electron number density measurements in the VKI inductively-coupled plasma wind tunnel Andrea Fagnani, Diana Luis, Damien Le Quang, Alan Viladegut, Bernd Helber, Olivier Chazot We perform locally resolved Optical Emission Spectroscopy (OES) from the UV to the NIR wavelengths in the air plasma jet produced by the 160 mm diameter VKI Plasmatron ICP torch, at a pressure of 100 mbar. A 750 mm focal length Czerny-Turner spectrograph, featuring a 1200 grooves/mm grating and an intensified CCD camera is coupled to a double mirror imaging system to provide spatially resolved measurements across the jet axis. Absolute calibration and Abel inversion allow to retrieve locally resolved emission intensities. Temperatures are determined either from LTE absolute line fitting, Boltzmann plot method or by rotational/vibrational fitting of molecular transitions. Oxygen and nitrogen lines provide consistent temperature measurements up to 50 mm from the jet-axis, while spectral fitting shows a fair agreement with LTE spectra. A mixture of synthetic air and 2% H2 is used to provide enough line strength of the H-beta line at 486 nm. Electron density profiles are being determined from the line shape fitting, accounting for the broadening mechanisms. OES analysis provides useful information on the thermodynamic state of the plasma, such as enthalpy profiles and local thermodynamic equilibrium, for ground test facilities aiming at replication of atmospheric entry conditions. |
Thursday, October 6, 2022 4:30PM - 5:00PM |
DR5.00003: Optical Emission Spectroscopy Measurement for Plasma Parameter Identification — from Kinetic Modeling to Data Science Invited Speaker: Hiroshi Akatsuka Recent progresses in studies of optical emission spectroscopy (OES) measurement of low-temperature plasmas are presented. Two methods are presented; the first one is line-spectrum measurement assisted with excitation kinetic model like collisional-radiative (CR) model. The second one is continuum-spectrum measurement due to bremsstrahlung of free electrons in low-temperature plasma, which can be applied only to atmospheric-pressure plasmas. |
Thursday, October 6, 2022 5:00PM - 5:15PM |
DR5.00004: Spatially and temporally resolved Optical Emission Spectroscopy of a nanosecond Atmospheric Pressure Plasma Jet Nikita D Lepikhin, Jan Kuhfeld, Zoltán Donkó, Dirk Luggenhölscher, Uwe Czarnetzki Nanosecond Atmospheric Pressure Plasma Jet (ns-APPJ) consists of two distinct phases, fast breakdown at high electric fields and a quasi-DC phase at lower permanent electric field and high electron density, as was shown recently by Picosecond Electric-Field Induced Second Harmonic (EFISH) measurements [1,2]. These phases can be controlled independently in order to optimize the production of excited species [2, 3]. |
Thursday, October 6, 2022 5:15PM - 5:30PM |
DR5.00005: Diagnostics of Electron Density and Temperature of Atmospheric Pressure Helium Plasma with Revise Collisional-Radiative Model Includes Atomic Collision Processes Keren Lin, Atsushi Nezu, Hiroshi Akatsuka The helium collisional-radiative model (CR model) is revised. Part of the optically allowed electron collision excitation and deexcitation processes and the electron collision ionization processes are recalculated from the cross-sections. The atomic impact processes, which include excitation, deexcitation, ionization, and three-body recombination are integrated into the model as well. This expands the valid pressure of the helium CR model to atmospheric pressure. An algorithm that possesses the function of diagnosing electron density and temperature of helium plasma at atmospheric pressure coupled with the revised CR model is developed. It uses the number density of excited levels (31S, 33S, 31P, 33P, 31D, 33D, 41D, and 43D) which can be obtained by optical emission spectroscopy (OES) measurements in visible wavelength range as input to fit the number density of two metastable states (21S and 23S), electron density, and electron temperature. The algorithm was verified theoretically and experimentally. The results showed the theoretical error of the algorithm was small enough, and the diagnosed electron density and temperature in low-pressure microwave induced helium plasma were in good agreement with the results of probe method. |
Thursday, October 6, 2022 5:30PM - 5:45PM |
DR5.00006: Spectroscopic characterization of a He/N₂ dielectric barrier discharge for determination of plasma parameters and estimation of impurity content Niklas Nawrath, Gregor Welling, Nikita Bibinov, Peter Awakowicz, Andrew R Gibson Optical emission spectroscopy (OES) is among the most convenient methods for plasma diagnostics, as it allows to investigate a plasma without physical intervention. In this study, absolutely calibrated optical emission spectroscopy is used together with a collisional radiative model to determine the electron density, reduced electric field and gas temperature in a low temperature volume dielectric barrier discharge (vDBD) in helium with small admixtures of nitrogen. The vDBD is operated in an enclosed chamber at atmospheric pressure to control all necessary environmental conditions. Nevertheless, nitrogen emission is observed even without intentional addition to the chamber. To better understand the discharge properties, OES is also used to estimate the air impurity content in the chamber. A fitting procedure is used to separate overlapping emission bands and estimate the gas temperature. The ratio of the fitted N₂(C-B) and N₂⁺(B-X) emission is then used to calculate the reduced electric field. Using the absolute emission intensity, the electron density is then calculated. Calculated electron densities and the impurity of the setup are found to be in the range of 1x10⁹ - 1x10¹⁰ cm⁻³ and ~750ppm, respectively. |
Thursday, October 6, 2022 5:45PM - 6:00PM |
DR5.00007: Imaging of Hydrogen Peroxide and Methyl in Nanosecond Pulsed Plasmas by Photofragmentation Laser-Induced Fluorescence Dirk van den Bekerom, Caleb Richards, Malik M Tahiyat, Erxiong Huang, Igor V Adamovich, Tanvir I Farouk, Jonathan H Frank Hydrogen peroxide (H2O2) and the methyl (CH3) are key reactive species in plasma assisted processes such as surface decontamination, biomedical treatments, catalysis, and combustion. Imaging of H2O2 and CH3 is challenging because they cannot be detected directly by laser-induced fluorescence. We present a technique for imaging 2D distributions of these species in plasmas using photofragmentation laser-induced fluorescence (PF-LIF). The target molecule, H2O2 or CH3, is photodissociated by a UV pump laser to produce OH or CH fragments, respectively. These photofragments are then detected with LIF imaging using an overlapping probe laser beam for LIF excitation. For H2O2 PF-LIF measurements, the probe laser excites transitions in the A-X(1,0) band of OH, and fluorescence is detected from A-X(1,1) and (0,0) bands. For CH3 PF-LIF measurements, transitions in the B-X band of CH are excited, and fluorescence from the overlapping A-X(0,0), A-X(1,1), and B-X(0,1) bands is detected with the A-state populated by collisional B-A electronic energy transfer. These non-resonant detection schemes enable interrogation near surfaces. We demonstrate PF-LIF imaging measurements of H2O2 and CH3 mole fractions in nanosecond pulsed DBD plasmas with mixtures of He-H2O-O2 and CH4-CO2-He, respectively. |
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