Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session LW2: Plasma Jets |
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Chair: Uwe Czarnetzki, Ruhr University Bochum Room: 151 |
Wednesday, October 6, 2010 4:00PM - 4:30PM |
LW2.00001: Interactions of multiple atmospheric pressure plasma jets and DNA Invited Speaker: Cold atmospheric pressure plasmas offer a unique environment for treatment of soft materials, including bio-materials and living tissue. Single plasma devices can be as small as micro-meters allowing very precise treatments reducing damage to surrounding healthy living cells. While multiple devices arranged in arrays also allow large area and even 3-dimensional treatment. When two or more cold plasmas are brought close enough together the interaction zone itself can enter a new regime of operation offering the possibility of improved control and manipulation of the plasma chemical environment for applications. The interaction dynamics between two plasma jets is investigated. Individual plasma jets operated between 2 kHz and 40 MHz, in He/O$_{2}$ gas mixtures, are allowed to interact with each other. Depending on the electric field configuration of the individual plasmas the interaction itself is dominated by different plasma energy carriers -- either charged, neutral species or radiation. For biological treatment reactive oxygen species have been identified as important. Absolute densities of various important neutral species are measured: atomic oxygen, ozone, molecular singlet delta oxygen. For biological applications it is imperative to determine and assess potential damage and risk. Plasmid DNA is exposed to the plasma interaction environment and we quantitatively determine the rate of single (SSB) and double strand breaks (DSB) as a function of various plasma parameters. In order to determine the relevance of these species SSB and DSB rates are directly correlated to absolute species densities. Control strategies are also developed for manipulating these species. [Preview Abstract] |
Wednesday, October 6, 2010 4:30PM - 4:45PM |
LW2.00002: Understanding the physics of atmospheric pressure low temperature plasma jets Erdinc Karakas, Mounir Laroussi In this paper, we present the current state of the art of our APLTPJs sources, namely the ``Plasma Pencil'' and the ``Tube Reactor.'' Recent experimental results show that an ionization wave exists and propagates along the plasma jet. The plasma jet created by this ionization wave is not a continuous medium but rather consists of a bullet-like-structures known as ``Plasma Bullets.'' More interestingly, these plasma bullets actually have a donut-shaped makeup. Our latest plasma jet experiments reveal that the propagation characteristics of the ionization wave can be explained using a streamer theory model. This is especially important for adequate explanations of the plasma bullet propagation. It is also found that the secondary discharge, ignited by the charge accumulation on the dielectric electrode surfaces at the end of the applied voltage, interrupts the plasma bullet propagation due to an opposing current along the ionization channel. In addition, the plasma bullet also comes to an end when the helium mole fraction along the ionization channel, or applied voltage, or both, are less than some critical values. The APLTPJs' chemical composition includes short-lived and long-lived reactive species. Especially, helium metastables play an important role promoting an enhanced chemistry along the plasma jet. [Preview Abstract] |
Wednesday, October 6, 2010 4:45PM - 5:00PM |
LW2.00003: A generalized electro-acoustic model for laboratory scale and industrial scale atmospheric pressure plasma jets Victor Law, Stepen Daniels, Denis Dowling The use of acoustic measurement provides a low cost and effective diagnostic measurement of atmospheric plasmas. This paper reports upon the application of an electro-acoustic model to atmospheric pressure plasma (APP) jets. The model is based upon a closed-end air and/or helium column model to predict the fundamental sound pressure and its overtones, where even harmonic overtones are absent [1]. A simple 5 element electrical equivalent transmission-line model is shown to predict the sound pressure response of the plasma plume as it interacts with a target surface, including the plasma-to-surface gap distance. The model is evaluated on three jet systems: a laboratory scale dielectric barrier plasma jet with a helium flow of 1-3 slm; and two industrial scale APP jets, these are the Dow Corning PlasmaStream that operates with a helium flow 10 l/m and the Plasmatreat PFW10 jet which operates with an air flow of 40 l/m. We found a good correlation between model predictions and acoustic data acquired from all three systems.\\[4pt] [1] Acoustic emission within an atmospheric helium corona discharge Jet. V J Law, C E Nwankire, D P Dowling and S Daniels. Chaos2010, 1-5th June. Chania, Crete, Greece 2010. [Preview Abstract] |
Wednesday, October 6, 2010 5:00PM - 5:15PM |
LW2.00004: Electrical and optical characterization of plasma jet driven by kilohertz frequency ac voltage at atmospheric pressure Jung-Woo Ok, Dong-Hyun Kim, Hae June Lee, Ho-Jun Lee, Chung-Hoo Park At atmospheric pressure, plasma jet source driven by low frequency continuous wave of several tens kHz ac voltage was characterized. The plasma jet source consists of stainless-steel tube (inner electrode) through which helium flow in the middle of glass tube and a ground electrode (outer electrode) roundly surrounds in the vicinity of glass tube end. The electrical and optical properties of the plasma jet source, such as lissajous of current-voltage, optical emission spectrum, and rotational temperature were investigated. With various applied voltage, gas flow rate (1 $\sim $ 5 liter per min), and driven frequency (60 $\sim $ 90 kHz) parameters changed, plasma jet showed different discharge characteristics. Through an analysis of lissajous of voltage-current, plasma jet source has various glow discharge modes. The plume of plasma jet is up to 4 cm and rotational temperature of plasma jet is within 450 $\sim $ 800 K. [Preview Abstract] |
Wednesday, October 6, 2010 5:15PM - 5:30PM |
LW2.00005: Effect of Ar admixture on production of Ar 1s$_5$ metastable in a streamer-like He/Ar atmospheric pressure plasma jet Brian Sands, Robert Leiweke, Biswa Ganguly Dielectric-capillary atmospheric pressure plasma jet devices, initiated by a streamer-like ionization front, have typically been studied with He or Ar as the carrier gas. Our configuration uses He with a small admixture of Ar. With apparent exception to the pure gas cases, we have found that in the He/Ar plasma jet, production is renewed behind the leading ionization front in the residual streamer channel. Production of the metastable Ar 1s$_5 $ (Ar$^{\rm m}$) state is dominated by this residual production near the capillary tip. The density can remain $>$10$^{11}$ cm$^ {-2}$ for up to 10 $\mu$s after discharge ignition, significantly extending the timescale for afterglow plasma chemistry. We extend this work by varying the Ar composition from 0-30\% and use a combination of optical and laser spectroscopic methods and inductive loop current measurements to characterize the discharge in a 2 mm ID glass capillary with a 20 ns risetime unipolar voltage pulse. The Ar$^{\rm m}$ production rate in the residual streamer channel rises steeply up to 2\% Ar; for larger concentrations, the level of overvolting is more significant in determining the optimum Ar percentage. The effect of Ar admixture on other discharge parameters and possible mechanisms for the residual channel production will be discussed. [Preview Abstract] |
Wednesday, October 6, 2010 5:30PM - 5:45PM |
LW2.00006: Built-up of reactive oxygen species concentrations in a Micro-scaled Atmospheric Pressure Plasma Jet Volker Schulz-von der Gathen, Hendrik Bahre, Daniel Schr\"{o}der, Nikolas Knake Reactive oxygen species (ROS) such as atomic oxygen or ozone are detected in the post discharge effluent of a micro-scaled Atmospheric Pressure Plasma Jet ($\mu$APPJ) operated with a helium/ oxygen gas flow. These species are supposed to be of major importance for bio-medical tissue treatment and for surface modifications. Models and numerical simulations proposed to understand the plasma-chemical processes still have to be cross-checked. We report on measurements of the spatial distribution and its development of ROS from the gas inlet to the free effluent of the discharge. Investigations were carried under variation of gas mixture, gas velocity and applied power. Atomic oxygen was determined by means of two-photon laser induced fluorescence spectroscopy; Ozone has been investigated by UV absorption spectroscopy. For both species densities built up to several 10$^{15}$ cm$^{-3}$ typically within the discharge's first few millimetres corresponding to a reaction time of $\sim$50 $\mu$s varying with the operation parameters. Experiments have been carried out in the frame of the DFG research group FOR1123 ``Physics of Microplasmas.'' [Preview Abstract] |
Wednesday, October 6, 2010 5:45PM - 6:00PM |
LW2.00007: Spectroscopic investigations of an atmospheric pressure microplasma source of singlet delta oxygen J.S. Sousa, G. Bauville, B. Lacour, P. Jeanney, L. Magne, V. Puech The atmospheric pressure generation of singlet delta oxygen (SDO) by microplasmas has been experimentally studied. The remarkable stability of microcathode sustained discharges (MCSD) has allowed us to operate DC glow discharges, free from the glow-to-arc transition, in He/O$_{2}$/NO mixtures at atmospheric pressure. From optical diagnostics measurements we deduced the gas temperature (Tgas), the atomic oxygen (O) density profiles, the ozone (O$_{3})$ spatial distribution, and the yield of SDO. We observed that MCSD are similar to positive columns, with low values of E/N (5-10Td) and of Tgas (300-375K). In addition, our results show that the O is confined to the discharge chamber. Therefore, MCSD can efficiently generate large amounts of SDO. In fact, by operating arrays of several MCSD, SDO densities higher than 1.0 10$^{17}$cm$^{-3}$ have been effectively produced and transported over distances longer than 50cm. This opens opportunities for a large spectrum of new applications, making notably this plasma source very useful for many biological applications [1]. Furthermore, O$_{3}$ densities up to 10$^{16}$cm$^{-3}$ have also been obtained. The effect of different parameters, such as gas flows and mixtures, and discharge current, are discussed in the study. [1] J. S. Sousa et al., these proceedings [Preview Abstract] |
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