Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session TR4: Atmospheric Plasma Jets and Sources II |
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Chair: Sander Nijdam, Eindhoven University Room: 3 |
Thursday, October 13, 2016 4:00PM - 4:15PM |
TR4.00001: Power dissipated in a non-thermal atmospheric pressure plasma jet measured by miniaturized electrical probes Judith Golda, Volker Schulz-von der Gathen Non-thermal atmospheric pressure plasma jets are used in bio-medicine, because they generate reactive species at a low gas temperature. Knowledge and control of plasma parameters is required for stable and reliable operation. Therefore, measuring dissipated power in these plasmas is necessary. However, this is challenging because the delivered sender power is often orders of magnitudes higher than the power dissipated in the discharge itself. To measure this dissipated power, we built miniaturized electrical probes directly attached to the jet device [1]. We observed that the dissipated power is a more comprehensive parameter than the common parameter voltage: For example, gas temperature and emission line intensities rose exponentially with increasing voltage but linearly with increasing power. Our analyses further revealed that a substantial proportion of the dissipated power is transformed into heat. In conclusion, miniaturized electrical probes give a fundamental insight into the energy balance of atmospheric pressure plasmas. In the future, these probes can also be adapted to different types of atmospheric pressure plasmas.\newline [1] Golda, J et al., J. Phys. D: Appl. Phys. 49, 084003 (2016) [Preview Abstract] |
Thursday, October 13, 2016 4:15PM - 4:30PM |
TR4.00002: Influence of Ar/O$_{\mathrm{2}}$/H$_{\mathrm{2}}$O Feedgas AND N$_{\mathrm{2}}$/O$_{\mathrm{2}}$/H$_{\mathrm{2}}$O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers Gottlieb Oehrlein, Pingshan Luan, Andrew Knoll, Santosh Kondeti, Peter Bruggeman An Ar/O$_{\mathrm{2}}$/H$_{\mathrm{2}}$O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H$_{\mathrm{2}}$O in the feed gas and/or present in the N$_{\mathrm{2}}$, O$_{\mathrm{2}}$, or N$_{\mathrm{2}}$/O$_{\mathrm{2}}$ environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O$_{\mathrm{2}}$ or H$_{\mathrm{2}}$O admixture to Ar enhances polymer etching, simultaneous addition of O$_{\mathrm{2}}$ and H$_{\mathrm{2}}$O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO$_{\mathrm{2}}$ in the gas phase. Results where O$_{\mathrm{2}}$ and/or H$_{\mathrm{2}}$O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. [Preview Abstract] |
Thursday, October 13, 2016 4:30PM - 4:45PM |
TR4.00003: Electrode Configurations in Atmospheric Pressure Plasma Jets Amanda M. Lietz, Mark J. Kushner Atmospheric pressure plasma jets (APPJs) are being studied for emerging medical applications including cancer treatment and wound healing. APPJs typically consist of a dielectric tube through which a rare gas flows, sometimes with an O$_{\mathrm{2}}$ or H$_{\mathrm{2}}$O impurity. In this paper, we present results from a computational study of APPJs using \textit{nonPDPSIM}, a 2-D plasma hydrodynamics model, with the goal of providing insights on how the placement of electrodes can influence the production of reactive species. Gas consisting of He/O$_{\mathrm{2}}=$99.5/0.5 is flowed through a capillary tube at 2 slpm into humid air, and a pulsed DC voltage is applied. An APPJ with two external ring electrodes will be compared with one having a powered electrode inside and a ground electrode on the outside. The consequences on ionization wave propagation and the production of reactive oxygen and nitrogen species (RONS) will be discussed. Changing the electrode configuration can concentrate the power deposition in volumes having different gas composition, resulting in different RONS production. An internal electrode can result in increased production of NO$_{\mathrm{x}}$ and HNO$_{\mathrm{x\thinspace }}$by increasing propagation of the ionization wave through the He dominated plume to outside of the tube where humid air is diffusing into the plume. [Preview Abstract] |
Thursday, October 13, 2016 4:45PM - 5:00PM |
TR4.00004: Numerical and experimental study on the dynamics of a $\mu$s helium plasma gun with various amounts of O$_2$ admixture Pedro Viegas, Xavier Damany, Sylvain Iseni, Jean-Michel Pouvesle, Eric Robert, Anne Bourdon The use of admixtures (mostly O$_2$ and N$_2$) to a helium buffer has been studied recently to tailor the generation of reactive species in plasma jets for biomedical applications. So far, most experiments have been dedicated to the study of the plasma plume. For endoscopic treatments, it is also important to better understand and optimize the propagation of discharges in long dielectric tubes as catheters. In this work, we present an experimental and numerical study on the dynamics of a $\mu$s helium plasma discharge with O$_2$ admixture in a long dielectric tube. In simulations, a 2D fluid model is used. For comparison purposes, the geometries of the set-ups used for simulations and experiments are as close as possible. We compare experiments and simulations for different amounts of O$_2$ admixture added to the buffer gas and present results on the velocity of the discharge front for the various amounts of O$_2$ and different applied voltages. In order to study the influence of different amounts of O$_2$ admixture on the helium discharge dynamics, detailed kinetic schemes have been used. The influence of Penning and charge exchange reactions on the discharge structure and dynamics are studied, as well as the role of negative ions. [Preview Abstract] |
Thursday, October 13, 2016 5:00PM - 5:15PM |
TR4.00005: Atomic oxygen behavior at downstream of AC excited atmospheric pressure He plasma jet Keigo Takeda, Kenji Ishikawa, Hiromasa Tanaka, Makoto Sekine, Masaru Hori Applications of atmospheric pressure plasma jets (APPJ) have been investigated in the plasma medical fields such as cancer therapy, blood coagulation, etc. Reactive species generated by the plasma jet interacts with the biological surface. Therefore, the issue attracts much attentions to investigate the plasma effects on targets. In our group, a spot-size AC excited He APPJ have been used for the plasma medicine. From diagnostics of the APPJ using optical emission spectroscopy, the gas temperature and the electron density was estimated to be 299 K and 3.4$\times $10$^{\mathrm{15}}$ cm$^{\mathrm{-3}}$. The AC excited He APPJ which affords high density plasma at room temperature is considered to be a powerful tool for the medical applications. In this study, by using vacuum ultraviolet absorption spectroscopy, the density of atomic oxygen on a floating copper as a target irradiated by the He APPJ was measured as a function of the distance between the plasma source and the copper wire. The measured density became a maximum value around 8$\times $10$^{\mathrm{13}}$ cm$^{\mathrm{-3}}$ at 12 mm distance, and then decreased over the distance. It is considered that the behavior was due to the changes in the plasma density on the copper wire and influence of ambient air. [Preview Abstract] |
(Author Not Attending)
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TR4.00006: Photochemical/Microchannel Plasma Reactors Driven By High Power Vacuum Ultraviolet Lamps Chul Shin, Sung-jin Park, Gary Eden Experiments are being conducted in which molecular dissociation or other chemical reactions in microchannel plasmas are accelerated by the introduction of vacuum ultraviolet photons. Initial emphasis is being placed on recently-developed Xe$_{\mathrm{2}}$ lamps that are efficient sources of 172 nm (h$\nu \approx $ 7.2 eV) photons. Thin, flat lamps, fabricated from fused silica and having microcavity arrays internal to the lamp, have been developed by the University of Illinois and Eden Park Illumination and produce intensities above 200 mW/cm$^{\mathrm{2}}$. Integrating such lamps into a microcavity plasma reactor yields a hybrid photochemical/plasma system in which product yield and power consumption can be optimized. The selectivity of photodissociation in generating radicals and atomic fragments offers new synergies in plasma processing. Data concerning CO$_{\mathrm{2}}$ dissociation in arrays of microchannel plasmas, and the modification of this process by external 172 nm radiation, will be presented. [Preview Abstract] |
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