27 results on '"Judith Golda"'
Search Results
2. Gas Flow-Dependent Modification of Plasma Chemistry in μAPP Jet-Generated Cold Atmospheric Plasma and Its Impact on Human Skin Fibroblasts
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Dennis Feibel, Judith Golda, Julian Held, Peter Awakowicz, Volker Schulz-von der Gathen, Christoph V. Suschek, Christian Opländer, and Florian Jansen
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cold atmospheric plasma ,hydrogen peroxide ,nitrite ,nitrate ,nitric oxide ,inhibition of proliferation ,Biology (General) ,QH301-705.5 - Abstract
The micro-scaled Atmospheric Pressure Plasma Jet (µAPPJ) is operated with low carrier gas flows (0.25–1.4 slm), preventing excessive dehydration and osmotic effects in the exposed area. A higher yield of reactive oxygen or nitrogen species (ROS or RNS) in the µAAPJ-generated plasmas (CAP) was achieved, due to atmospheric impurities in the working gas. With CAPs generated at different gas flows, we characterized their impact on physical/chemical changes of buffers and on biological parameters of human skin fibroblasts (hsFB). CAP treatments of buffer at 0.25 slm led to increased concentrations of nitrate (~352 µM), hydrogen peroxide (H2O2; ~124 µM) and nitrite (~161 µM). With 1.40 slm, significantly lower concentrations of nitrate (~10 µM) and nitrite (~44 µM) but a strongly increased H2O2 concentration (~1265 µM) was achieved. CAP-induced toxicity of hsFB cultures correlated with the accumulated H2O2 concentrations (20% at 0.25 slm vs. ~49% at 1.40 slm). Adverse biological consequences of CAP exposure could be reversed by exogenously applied catalase. Due to the possibility of being able to influence the plasma chemistry solely by modulating the gas flow, the therapeutic use of the µAPPJ represents an interesting option for clinical use.
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- 2023
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3. Corrigendum: Characterization of the effluent of a He/O2 micro-scaled atmospheric pressure plasma jet by quantitative molecular beam mass spectrometry (2010 New J. Phys. 12 013021)
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Gert Willems, Judith Golda, Dirk Ellerweg, Jan Benedikt, Achim von Keudell, Nikolas Knake, and Volker Schulz-von der Gathen
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Science ,Physics ,QC1-999 - Published
- 2019
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4. Local enhancement of electron heating and neutral species generation in radio-frequency micro-atmospheric pressure plasma jets: the effects of structured electrode topologies
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Yue Liu, Máté Vass, Gerrit Hübner, David Schulenberg, Torben Hemke, Lena Bischoff, Sascha Chur, David Steuer, Judith Golda, Marc Böke, Julian Schulze, Ihor Korolov, and Thomas Mussenbrock
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Condensed Matter Physics - Abstract
The effects of structured electrode topologies on He/O2 radio frequency micro-atmospheric pressure plasma jets driven at 13.56 MHz are investigated by a combination of 2D fluid simulations and experiments. Good qualitative agreement is found between the computational and experimental results for the 2D spatio-temporally resolved dynamics of energetic electrons measured by phase resolved optical emission spectroscopy, 2D spatially resolved helium metastable densities measured by tunable diode laser absorption spectroscopy and 2D spatially resolved atomic oxygen densities measured by two photon absorption laser induced fluorescence. The presence of rectangular trenches of specific dimensions inside the electrodes is found to cause a local increase of the electron power absorption inside and above/below these surface structures. This method of controlling the electron energy distribution function via tailored surface topologies leads to a local increase of the metastable and atomic oxygen densities. A linear combination of trenches along the direction of the gas flow is found to result in an increase of the atomic oxygen density in the effluent, depending linearly on the number of trenches. These findings are explained by an enhanced Ohmic electric field inside each trench, originating from (a) the low electron density, and, consequently, the low plasma conductivity inside the trenches, and (b) the presence of a current focusing effect as a result of the electrode topology.
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- 2023
5. Spatially and temporally resolved atomic oxygen densities in a micro cavity plasma array
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Volker Schulz-von der Gathen, David Steuer, Henrik Van Impel, Judith Golda, and Marc Böke
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Condensed Matter Physics - Abstract
Micro cavity plasma arrays have numerous applications, such as the treatment of volatile organic compounds or the generation of new species. In recent years, the focus has also shifted to plasma catalysis, in which catalytic surfaces are combined with plasmas. The key to all of these applications is the generation of reactive species such as atomic oxygen within the plasma. Typically, atomic oxygen densities can be measured by laser spectroscopic methods. In the case of a micro plasma array, which consists of thousands of cavities with a diameter between 50 and 200 µm, optical access is limited. For this reason, an optical emission spectroscopy approach, helium state enhanced actinometry, is used. 2D resolved narrow bandwidth measurements are performed by using an ICCD camera in combination with a tunable bandpass filter (550–1000 nm). The discharge is operated in helium with an oxygen admixture of 0.1%. An argon admixture of 0.05% is used as actinometer gas. The triangular excitation voltage is varied between amplitudes of 400 and 800 V at a frequency of 15 kHz. Very high dissociation degrees up to nearly complete dissociation are observed. Time resolved measurements show significant differences in oxygen density between the increasing and the decreasing potential phase.
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- 2023
6. RF-driven atmospheric-pressure capillary plasma jet in a He/O2 gas mixture: Multi-diagnostic approach to energy transport
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Ruhr-Universit Bochum Schüttler, Tristan Winzer, Natascha Blosczyk, David Steuer, Judith Golda, and Jan Benedikt
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General Physics and Astronomy - Abstract
Atmospheric-pressure plasma jets operated in noble gases with an oxygen admixture have high application potential in industry and medicine. In this paper, we report on an extension of the well-studied RF-driven plasma jet from the European Cooperation in Science and Technology (COST-Jet), which has shown to deliver stable and reproducible discharge conditions but is limited to the [Formula: see text]-discharge mode at low input powers. The so-called capillary-jet features the same discharge geometry as the COST-Jet, but the plasma is ignited inside a capillary with a square cross section acting as a dielectric in front of the electrodes. This prevents a glow-to-arc-transition at high input powers and allows stable operation in the [Formula: see text]-mode. We performed a set of measurements on the capillary-jet in the [Formula: see text]- and [Formula: see text]-mode and compared the [Formula: see text]-mode results to data obtained for the COST-Jet showing that the discharges are indeed similar and that the capillary-jet extends the accessible parameter range to high input powers. The presented results include power characteristics, temperature measurements, atomic oxygen densities from helium state enhanced actinometry, and molecular beam mass spectrometry (MBMS) as well as ozone densities from MBMS as functions of input power and molecular oxygen admixture. The results are summarized into an energy balance with most of the power dissipated into heating of the plasma feed gas.
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- 2022
7. State enhanced actinometry in the COST microplasma jet
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Andrew Gibson, Volker Schulz-von der Gathen, David Steuer, Henrik Van Impel, Judith Golda, and Marc Böke
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Condensed Matter Physics - Abstract
A new actinometry approach, helium state enhanced actinometry (SEA), is presented. This diagnostic uses the emission of the atomic states O(3p3P) (λ = 844.6 nm), Ar(2p1) (λ = 750.4 nm) and He(33S) (λ = 706.5 nm) and allows the atomic oxygen density and the mean electron energy to be determined simultaneously from the spectral line intensity ratios. Here, the atomic states are selected in a way that they cover a wide range of the electron energy distribution function (EEDF). The method is compared to the classical actinometry approach and energy resolved actinometry (ERA) based on measurements on the COST microplasma jet. In addition, a benchmark against two-photon absorption laser induced fluorescence measurements is performed. Both atomic oxygen densities and mean electron energies are in good agreement with the literature. Furthermore, SEA offers a number of advantages over known approaches. Firstly, the experimental complexity is significantly reduced by using time-integrated spectra instead of phase-resolved measurements, as used in the original ERA approach. Secondly, the precision of the electron energy measurement can be significantly improved by the use of the helium state. In addition, known uncertainties e.g. due to excitation of oxygen excited levels via metastable oxygen states can be reduced.
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- 2022
8. Applications of the COST Plasma Jet: More than a Reference Standard
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Volker Schulz-von der Gathen, Annemie Bogaerts, Yury Gorbanev, and Judith Golda
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Jet (fluid) ,Computer science ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Comparison standard ,Plasma jet ,Plasma ,respiratory system ,equipment and supplies ,complex mixtures ,Chemistry ,Physics::Plasma Physics ,Physics::Space Physics ,Plasma chemistry ,Aerospace engineering ,business ,human activities ,Biology ,Reference standards ,circulatory and respiratory physiology - Abstract
The rapid advances in the field of cold plasma research led to the development of many plasma jets for various purposes. The COST plasma jet was created to set a comparison standard between different groups in Europe and the world. Its physical and chemical properties are well studied, and diagnostics procedures are developed and benchmarked using this jet. In recent years, it has been used for various research purposes. Here, we present a brief overview of the reported applications of the COST plasma jet. Additionally, we discuss the chemistry of the plasma-liquid systems with this plasma jet, and the properties that make it an indispensable system for plasma research.
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- 2019
9. Electric field strengths within a micro cavity plasma array measured by Stark shift and splitting of a helium line pair
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Sebastian Dzikowski, David Steuer, Sylvain Iséni, Judith Golda, Marc Böke, and Volker Schulz-von der Gathen
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Condensed Matter Physics - Abstract
The electric field is a fundamental parameter for plasma sources and devices. Its knowledge is a dominant setscrew for many processes such as controllable fluxes and energies of charged particles onto surfaces and for the electron energy distribution function. However, experimental data of electric field strengths in micro-structured surface dielectric barrier discharges are rare. Due to geometric configurations and dimensions in micrometer scale, probe-based investigations are challenging. To tackle these issues, we exploit the optical access into micro cavities of a plasma array operated with pure helium to use the Stark effect of the allowed 492.19 nm ( D 1 ↦ P 0 1 ) and forbidden 492.06 nm helium line ( F 0 1 ↦ P 0 1 ) . Based on it, we present spatially-integrated and time-resolved electric field strengths in a range between 20 kV cm−1 and 60 kV cm−1 depending on various parameters such as cavity diameters in 100 μm range and excitation properties. The obtained electric fields can be controlled just by bipolarity of applied voltage and show a good agreement to previous simulated field strengths in pore and silicon-based devices. As expected from simulation dealing with discharges in pores, a smaller cavity dimension yields higher electric field strengths. Due to these high electric fields and the option of this plasma source to easily integrate a catalyst in the discharge volume, this micro cavity plasma array promises further insights into plasma-enhanced catalysis.
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- 2022
10. Treating Surfaces with a Cold Atmospheric Pressure Plasma using the COST-Jet
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Jan Benedikt, Volker Schulz-von der Gathen, J Held, Kerstin Sgonina, and Judith Golda
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Protocol (science) ,Jet (fluid) ,Materials science ,Atmospheric pressure ,General Immunology and Microbiology ,Plasma Gases ,business.industry ,Microplasma ,Surface Properties ,General Chemical Engineering ,General Neuroscience ,Reproducibility of Results ,Water ,Atmospheric-pressure plasma ,Plasma treatment ,Starch ,Plasma ,General Biochemistry, Genetics and Molecular Biology ,Atmospheric Pressure ,Imaging, Three-Dimensional ,Electricity ,Plasma medicine ,Process engineering ,business - Abstract
In recent years, non-thermal atmospheric pressure plasmas have been used extensively for surface treatments, in particular, due to their potential in biological applications. However, the scientific results often suffer from reproducibility problems due to unreliable plasma conditions as well as complex treatment procedures. To address this issue and provide a stable and reproducible plasma source, the COST-Jet reference source was developed. In this work, we propose a detailed protocol to perform reliable and reproducible surface treatments using the COST reference microplasma jet (COST-Jet). Common issues and pitfalls are discussed, as well as the peculiarities of the COST-Jet compared to other devices and its advantageous remote character. A detailed description of both solid and liquid surface treatment is provided. The described methods are versatile and can be adapted for other types of atmospheric pressure plasma devices.
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- 2020
11. Reproducibility of 'COST Reference Microplasma Jets'
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Deborah O'Connell, Judith Golda, V Schulz-von der Gathen, Timo Gans, J Held, Jerome Bredin, F. Riedel, Kari Niemi, M. W. van der Woude, and H. Davies
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Paper ,Ozone ,Materials science ,Field (physics) ,FOS: Physical sciences ,01 natural sciences ,7. Clean energy ,Temperature measurement ,010305 fluids & plasmas ,chemistry.chemical_compound ,atmospheric pressure plasma jet ,0103 physical sciences ,power measurements ,capacitively coupled radio frequency discharge ,COST reference microplasma jet ,010302 applied physics ,Reproducibility ,Atmospheric pressure ,Microplasma ,Plasma ,plasma medicine ,Condensed Matter Physics ,Physics - Plasma Physics ,Computational physics ,Plasma Physics (physics.plasm-ph) ,biomedical applications of plasmas ,chemistry ,Plasma medicine - Abstract
Atmospheric pressure plasmas have been ground-breaking for plasma science and technologies, due to their significant application potential in many fields, including medicinal, biological, and environmental applications. This is predominantly due to their efficient production and delivery of chemically reactive species under ambient conditions. One of the challenges in progressing the field is comparing plasma sources and results across the community and the literature. To address this a reference plasma source was established during the ‘biomedical applications of atmospheric pressure plasmas’ EU COST Action MP1101. It is crucial that reference sources are reproducible. Here, we present the reproducibility and variance across multiple sources through examining various characteristics, including: absolute atomic oxygen densities, absolute ozone densities, electrical characteristics, optical emission spectroscopy, temperature measurements, and bactericidal activity. The measurements demonstrate that the tested COST jets are mainly reproducible within the intrinsic uncertainty of each measurement technique.
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- 2020
12. 2D spatially resolved O atom density profiles in an atmospheric pressure plasma jet: from the active plasma volume to the effluent
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David Steuer, Judith Golda, Ihor Korolov, Marc Böke, Volker Schulz-von der Gathen, Sascha Chur, and Julian Schulze
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Jet (fluid) ,Materials science ,Acoustics and Ultrasonics ,Spatially resolved ,Atom ,Atmospheric-pressure plasma ,Atomic physics ,Condensed Matter Physics ,Plasma volume ,Effluent ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
Two-dimensional spatially resolved absolute atomic oxygen densities are measured within an atmospheric pressure micro plasma jet and in its effluent. The plasma is operated in helium with an admixture of 0.5% of oxygen at 13.56 MHz and with a power of 1 W. Absolute atomic oxygen densities are obtained using two photon absorption laser induced fluorescence spectroscopy. The results are interpreted based on measurements of the electron dynamics by phase resolved optical emission spectroscopy in combination with a simple model that balances the production of atomic oxygen with its losses due to chemical reactions and diffusion. Within the discharge, the atomic oxygen density builds up with a rise time of 600 µs along the gas flow and reaches a plateau of 8 × 1015 cm−3. In the effluent, the density decays exponentially with a decay time of 180 µs (corresponding to a decay length of 3 mm at a gas flow of 1.0 slm). It is found that both, the species formation behavior and the maximum distance between the jet nozzle and substrates for possible oxygen treatments of surfaces can be controlled by adjusting the gas flow.
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- 2021
13. Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets
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Jan Benedikt, Tristan Winzer, Vincent Layes, Judith Golda, and Beatrix Biskup
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Materials science ,Polymers and Plastics ,Plasma chemistry ,Analytical chemistry ,Atmospheric-pressure plasma ,Vacuum ultraviolet spectroscopy ,Condensed Matter Physics ,Excimer - Published
- 2020
14. Cross-correlating discharge physics, excitation mechanisms and plasma chemistry to describe the stability of an RF-excited atmospheric pressure argon plasma jet
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Judith Golda
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Vakuum-UV-Spektroskopie ,ddc:530 ,Hochfrequenzentladung ,Argon ,Atmosphärendruckplasma ,Plasmainstabilität - Abstract
Aufgrund von Nicht-Gleichgewichtseigenschaften erzeugen kalte Atmosphärendruckplasmen eine reichhaltige Plasmachemie. Daher werden diese Plasmen bereits sehr erfolgreich für biomedizinische Anwendungen eingesetzt. Aufgrund einer Vielzahl an unterschiedlichen Entladungsgeometrien ist der direkte Vergleich von Messergebnissen allerdings erschwert, sodass der wissenschaftliche Fortschritt behindert wird. In dieser Arbeit wird die Entwicklung einer reproduzierbaren, stabilen Entladungsgeometrie beschrieben. Es wird gezeigt, dass die gemessene, elektrische Leistung ein geeigneter übertragbarer Kontrollparameter ist. Darauf aufbauend wird die Stabilität des Plasmas ausgenutzt, um Plasmaprozesse und Instabilitäten in einer Argonentladung zu analysieren. Mit verschiedenen Diagnostiken und durch den direkten Vergleich mit der bereits gut untersuchten Heliumentladung werden makroskopische Beobachtungen auf fundamentale, mikroskopische Eigenschaften des jeweiligen Entladungsgases zurückgeführt. Due to their non-equilibrium characteristics, cold atmospheric pressure plasmas (CAPs) produce a rich plasma chemistry. Consequently, CAPs are already being used successfully for bio-medical applications. However, due to the large number of different discharge geometries, direct comparison of measurement results is challenging and scientific progress is hampered. This thesis illustrates the development of a reproducible, stable discharge geometry. It is shown that the measured electrical power is a suitable transferable control parameter. Based on this, the stability of the plasma is harnessed to analyze the plasma processes and instabilities in an argon discharge. The macroscopic observations are traced back to fundamental, microscopic properties of the feed gas by means of various diagnostics and direct comparison with the already well-investigated helium discharge.
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- 2018
15. Chemical fingerprints of cold physical plasmas – an experimental and computational study using cysteine as tracer compound
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Sander Bekeschus, Judith Golda, J Held, Friederike Kogelheide, Katharina Stapelmann, Kristian Wende, Christof C. W. Verlackt, V Schulz-von der Gathen, Jan-Wilm Lackmann, Johann Volzke, and Annemie Bogaerts
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0301 basic medicine ,Radical ,Science ,Cystine ,Mass spectrometry ,Article ,Plasma physics ,03 medical and health sciences ,chemistry.chemical_compound ,Molecular dynamics ,Computational chemistry ,Metabolomics ,chemistry.chemical_classification ,Multidisciplinary ,Chemistry ,Singlet oxygen ,030104 developmental biology ,Covalent bond ,Thiol ,Medicine ,Engineering sciences. Technology ,Cysteine - Abstract
Reactive oxygen and nitrogen species released by cold physical plasma are being proposed as effectors in various clinical conditions connected to inflammatory processes. As these plasmas can be tailored in a wide range, models to compare and control their biochemical footprint are desired to infer on the molecular mechanisms underlying the observed effects and to enable the discrimination between different plasma sources. Here, an improved model to trace short-lived reactive species is presented. Using FTIR, high-resolution mass spectrometry, and molecular dynamics computational simulation, covalent modifications of cysteine treated with different plasmas were deciphered and the respective product pattern used to generate a fingerprint of each plasma source. Such, our experimental model allows a fast and reliable grading of the chemical potential of plasmas used for medical purposes. Major reaction products were identified to be cysteine sulfonic acid, cystine, and cysteine fragments. Less-abundant products, such as oxidized cystine derivatives or S-nitrosylated cysteines, were unique to different plasma sources or operating conditions. The data collected point at hydroxyl radicals, atomic O, and singlet oxygen as major contributing species that enable an impact on cellular thiol groups when applying cold plasma in vitro or in vivo.
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- 2018
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16. Dissipated electrical power and electron density in an RF atmospheric pressure helium plasma jet
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Friederike Kogelheide, V Schulz-von der Gathen, Judith Golda, and Peter Awakowicz
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Plasma impedance ,Jet (fluid) ,Electron density ,Materials science ,Atmospheric pressure ,Atmospheric-pressure plasma ,Electric power ,Atomic physics ,Condensed Matter Physics ,Helium plasma - Abstract
Atmospheric pressure plasmas have great potential, especially for biomedical applications, due to the large number of reactive species produced. In particular with regard to these applications, the comparability of processes through appropriate control of plasma parameters is essential for treatment safety. Here we present a method for the operando determination of absolute absorbed power in an RF atmospheric pressure helium plasma discharge using miniaturized probes. A detailed error analysis demonstrates the reliability of the measured power values. With the help of a global model, the sheath width and electron density (4 × 1016–11 × 1016 m−3) are derived from these power measurements and compared to literature. The results and thus the validity of the electrical model are confirmed by a second, independent characterization method using optical emission spectroscopy and time-averaged imaging.
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- 2019
17. Corrigendum: Characterization of the effluent of a He/O2 micro-scaled atmospheric pressure plasma jet by quantitative molecular beam mass spectrometry (2010 New J. Phys. 12 013021)
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Volker Schulz-von der Gathen, Gert Willems, Judith Golda, Achim von Keudell, Dirk Ellerweg, N. Knake, and Jan Benedikt
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Physics ,Jet (fluid) ,Analytical chemistry ,General Physics and Astronomy ,Atmospheric-pressure plasma ,Mass spectrometry ,Effluent ,Molecular beam ,Characterization (materials science) - Published
- 2019
18. Corrigendum: Concepts and characteristics of the ‘COST Reference Microplasma Jet’ (2016 J. Phys. D: Appl. Phys. 49 084003)
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V Schulz-von der Gathen, M. Konkowski, Deborah O'Connell, A Ana Sobota, B. Redeker, N. St. J. Braithwaite, J Held, Miles M. Turner, Paul Arnold Christiaan Beijer, Timo Gans, Gmw Gerrit Kroesen, Judith Golda, and Stephan Reuter
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010302 applied physics ,Physics ,Jet (fluid) ,Acoustics and Ultrasonics ,Applied physics ,Microplasma ,Mathematical analysis ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,law ,0103 physical sciences ,Oscilloscope ,Resistor ,Voltage drop ,Voltage ,Probe calibration - Abstract
There is an incorrect representation of the expression for resistances in parallel in equation (1) in section 4.1 'Voltage probe calibration' on page 6. The numerator and denominator in the equation are reversed and should read: I = Uc Rm + Rt/RmRt. Rm is the measuring resistor, Rt the terminating resistor at the oscilloscope and Uc is the voltage drop across Rm induced by the current I. None of the calculations and conclusions of the paper are affected. The authors apologise for any confusion that this transcription error may have caused.
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- 2018
19. Pressure broadening of atomic oxygen two-photon absorption laser induced fluorescence
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Oyn Olivier Guaitella, Jean-Paul Booth, Christophe Blondel, Blm Bart Klarenaar, Rah Richard Engeln, Daniil Marinov, Judith Golda, Volker Schulz-von der Gathen, Cyril Drag, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire Aimé Cotton (LAC), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École normale supérieure - Cachan (ENS Cachan), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Cachan (ENS Cachan)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Plasma & Materials Processing, and Plasma-based gas conversion
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010302 applied physics ,sub-Doppler spectroscopy ,chemistry.chemical_element ,Condensed Matter Physics ,01 natural sciences ,Oxygen ,Two-photon absorption ,010305 fluids & plasmas ,Doppler-free ,chemistry ,oxygen atoms ,13. Climate action ,pressure broadening ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,Excited state ,0103 physical sciences ,Absorption (chemistry) ,Atomic physics ,Laser-induced fluorescence ,Bar (unit) ,Ambient pressure ,Doppler broadening ,TALIF - Abstract
International audience; Atomic oxygen, considered to be a determining reactant in plasma applications at ambient pressure, is routinely detected by two-photon absorption laser induced fluorescence (TALIF). Here, pressure broadening of the (2 p 4 3 P 2 ?????3 p 3 P J =0,1,2 ) two-photon transition in oxygen atoms was investigated using a high-resolution TALIF technique in normal and Doppler-free configurations. The pressure broadening coefficients determined were ##IMG## [http://ej.iop.org/images/0963-0252/25/6/06LT03/psstaa4481ieqn001.gif] γ_\textO_2 ??=??0.40??±??0.08? cm ?1 /bar for oxygen molecules and ##IMG## [http://ej.iop.org/images/0963-0252/25/6/06LT03/psstaa4481ieqn002.gif] γ_\textHe ??=??0.46??±??0.03?cm ?1 /bar for helium atoms. These correspond to pressure broadening rate constants ##IMG## [http://ej.iop.org/images/0963-0252/25/6/06LT03/psstaa4481ieqn003.gif] k_\textPB^\textO_2 ??=??9 · 10 ?9 cm 3 s ?1 and ##IMG## [http://ej.iop.org/images/0963-0252/25/6/06LT03/psstaa4481ieqn004.gif] k_\textPB^\textHe ??=??4 · 10 ?9 cm 3 s ?1 , respectively. The well-known quenching rate constants of O(3 p 3 P J ) by O 2 and He are at least one order of magnitude smaller, which signifies that non-quenching collisions constitute the main line-broadening mechanism. In addition to providing new insights into collisional processes of oxygen atoms in electronically excited 3 p 3 P J state, reported pressure broadening parameters are important for quantification of oxygen TALIF line profiles when both collisional and Doppler broadening mechanisms are important. Thus, the Doppler component (and hence the temperature of oxygen atoms) can be accurately determined from high resolution TALIF measurements in a broad range of conditions.
- Published
- 2016
20. Width dependent interaction of trench-like microdischarges arranged in sub-arrays on a single silicon based chip
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Mukesh Kulsreshath, Remi Dussart, V Schulz-von der Gathen, Judith Golda, Groupe de recherches sur l'énergétique des milieux ionisés (GREMI), Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Institute for Applied Plasma Physics, Ruhr-Universität Bochum [Bochum], and Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)
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010302 applied physics ,Argon ,Materials science ,Silicon ,Atmospheric pressure ,business.industry ,Analytical chemistry ,chemistry.chemical_element ,Condensed Matter Physics ,Chip ,01 natural sciences ,7. Clean energy ,010305 fluids & plasmas ,chemistry ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,0103 physical sciences ,Trench ,Optoelectronics ,Electrical measurements ,business ,Excitation ,ComputingMilieux_MISCELLANEOUS ,Voltage - Abstract
Multiple trench microdischarge reactor arrays based on a silicon (Si) platform were investigated as a concept to overcome production-based errors. The devices incorporated four sub-arrays of trench-like anisotropically etched cavities on a single 2 cm × 2 cm Si chip. Each sub-array consisted of an equal number of structures of equal length, depth and separation only varying in trench width. Experiments were performed in argon (Ar) close to atmospheric pressure at ac frequencies of the order of 10 kHz. The arrays were characterized by means of electrical measurements and by (phase-resolved) optical emission. It is shown that the whole device as well as the independent sub-arrays and the individual cavities behave in a similar way as the inverted-pyramid structures investigated beforehand. Under identical conditions, the voltage required for a first ignition increases with the width of the cavities. For maximum voltages high enough for operation of all sub-arrays, the individual arrays ignite within the excitation period in reverse order. For different excitation frequencies, self-pulsing and emission waves propagating independently across the sub-arrays were observed. Both phenomena show distinct characteristics for the individual sub-arrays being more prominent for the smaller cavities. The observations are interpreted within the frame of a simple physical picture, as a field and a surface-dependent process and the influence of long-living species such as metastables.
- Published
- 2014
21. Circular Emission and Destruction Patterns on a Silicon-Based Microdischarge Array
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Valentin Felix, Mukesh Kulsreshath, Volker Schulz-von der Gathen, Judith Golda, Remi Dussart, Henrik Boettner, Institute for Applied Plasma Physics, Ruhr-Universität Bochum [Bochum], Groupe de recherches sur l'énergétique des milieux ionisés (GREMI), and Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
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010302 applied physics ,Nuclear and High Energy Physics ,Materials science ,High interest ,Silicon ,Atmospheric pressure ,business.industry ,chemistry.chemical_element ,Plasma ,Condensed Matter Physics ,7. Clean energy ,01 natural sciences ,Dielectric surface ,010305 fluids & plasmas ,Silicon based ,Highly sensitive ,Operation mode ,chemistry ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,0103 physical sciences ,Optoelectronics ,Atomic physics ,business - Abstract
International audience; Silicon-based microdischarge arrays are of high interest as they enable nonthermal plasmas at atmospheric pressure. However, due to their small dimensions, they are highly sensitive to instabilities that can lead to the destruction of the confining structures. The damage, in particular of the top dielectric surface of these devices, can be directly correlated with a destructive operation mode. Images present the emission and destruction structures, which both show a circular pattern along the edges of the cavities.
- Published
- 2014
22. Origin of microplasma instabilities during DC operation of silicon based microhollow cathode devices
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Valentin Felix, Remi Dussart, Lawrence J. Overzet, Olivier Aubry, Volker Schulz-von der Gathen, Judith Golda, Philippe Lefaucheux, Groupe de recherches sur l'énergétique des milieux ionisés (GREMI), Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Institute for Applied Plasma Physics, Ruhr-Universität Bochum [Bochum], Plasma Application Laboratory (PAL), University of Texas at Dallas [Richardson] (UT Dallas), and PROCOPE cooperation (Project number 33340PC)
- Subjects
Materials science ,Silicon ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,law.invention ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,law ,Etching (microfabrication) ,0103 physical sciences ,medicine ,microplasma ,implantation ,010302 applied physics ,business.industry ,Microplasma ,silicon ,Blisters ,Plasma ,Nanosecond ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Cathode ,Anode ,instability ,MHCD ,chemistry ,Optoelectronics ,medicine.symptom ,microdischarge ,0210 nano-technology ,business - Abstract
International audience; The failure mechanisms of micro hollow cathode discharges (MHCD) in silicon have been investigated using their I-V characteristics, high speed photography and scanning electron microscopy. Experiments were carried out in helium. We observed I–V instabilities in the form of rapid voltage decreases associated with current spikes. The current spikes can reach values more than 100 times greater than the average MHCD current. (The peaks can be more than 1 Ampere for a few 10’s of nanoseconds.) These current spikes are correlated in time with 3–10 μm diameter optical flashes that occur inside the cavities. The SEM characterizations indicated that blister-like structures form on the Si surface during plasma operation. Thin Si layers detach from the surface in localized regions. We theorize that shallow helium implantation occurs and forms the ‘blisters’ whenever the Si is biased as the cathode. These blisters ‘explode’ when the helium pressure inside them becomes too large leading to the transient micro-arcs seen in both the optical emission and the I–V characteristics. We noted that blisters were never found on the metal counter electrode, even when it was biased as the cathode (and the Si as the anode). This observation led to a few suggestions for delaying the failure of Si MHCDs. One may coat the Si cathode (cavities) with blister resistant material; design the MHCD array to operate with the Si as the anode rather than as the cathode; or use a gas additive to prevent surface damage. Regarding the latter, tests using SF6 as the gas additive successfully prevented blister formation through rapid etching. The result was an enhanced MHCD lifetime.
- Published
- 2016
23. Summarizing results on the performance of a selective set of atmospheric plasma jets for separation of photons and reactive particles
- Author
-
Judith Golda, Volker Schulz-von der Gathen, Julia E. Bandow, Jan-Wilm Lackmann, Vincent Layes, Simon Schneider, Jan Benedikt, and Fabian Jarzina
- Subjects
Jet (fluid) ,Photon ,Acoustics and Ultrasonics ,Chemistry ,Astrophysics::High Energy Astrophysical Phenomena ,Atmospheric-pressure plasma ,respiratory system ,equipment and supplies ,Condensed Matter Physics ,Mass spectrometry ,complex mixtures ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Wavelength ,Remote plasma ,Particle ,Atomic physics ,human activities ,Microscale chemistry ,circulatory and respiratory physiology - Abstract
A microscale atmospheric-pressure plasma jet is a remote plasma jet, where plasma-generated reactive particles and photons are involved in substrate treatment. Here, we summarize our efforts to develop and characterize a particle- or photon-selective set of otherwise identical jets. In that way, the reactive species or photons can be used separately or in combination to study their isolated or combined effects to test whether the effects are additive or synergistic. The final version of the set of three jets—particle-jet, photon-jet and combined jet—is introduced. This final set realizes the highest reproducibility of the photon and particle fluxes, avoids turbulent gas flow, and the fluxes of the selected plasma-emitted components are almost identical in the case of all jets, while the other component is effectively blocked, which was verified by optical emission spectroscopy and mass spectrometry. Schlieren-imaging and a fluid dynamics simulation show the stability of the gas flow. The performance of these selective jets is demonstrated with the example of the treatment of E. coli bacteria with the different components emitted by a He-only, a He/N2 and a He/O2 plasma. Additionally, measurements of the vacuum UV photon spectra down to the wavelength of 50 nm can be made with the photon-jet and the relative comparison of spectral intensities among different gas mixtures is reported here. The results will show that the vacuum UV photons can lead to the inactivation of the E.coli bacteria.
- Published
- 2015
24. Gas and heat dynamics of a micro-scaled atmospheric pressure plasma reference jet
- Author
-
Sean Kelly, Judith Golda, Volker Schulz-von der Gathen, and Miles M. Turner
- Subjects
Jet (fluid) ,Acoustics and Ultrasonics ,Microplasma ,Chemistry ,chemistry.chemical_element ,Thermodynamics ,Atmospheric-pressure plasma ,Mechanics ,Condensed Matter Physics ,Schlieren imaging ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Exponential function ,Thermocouple ,Quartz ,Helium - Abstract
Gas and heat dynamics of the 'Cooperation on Science and Technology (COST) Reference Microplasma Jet' (COST-jet), a European lead reference device for low temperature atmospheric pressure plasma application, are investigated. Of particular interest to many biomedical application scenarios, the temperature characteristics of a surface impacted by the jet are revealed. Schlieren imaging, thermocouple measurements, infrared thermal imaging and numerical modelling are employed. Temperature spatial profiles in the gas domain reveal heating primarily of the helium fraction of the gas mixture. Thermocouple and model temporal data show a bounded exponential temperature growth described by a single characteristic time parameter to reach ~63% or (1-1/e) fraction of the temperature increase. Peak temperatures occurred in the gas domain where the carrier jet exits the COST-jet, with values ranging from ambient temperatures to in excess of 100 °C in 'α-mode' operation. In a horizontal orientation of the COST-jet a curved trajectory of the helium effluent at low gas flows results from buoyant forces. Gas mixture profiles reveal significant containment of the helium concentrations for a surface placed in close proximity to the COST-jet. Surface heating of a quartz plate follows a similar bounded exponential temporal temperature growth as device heating. Spatial profiles of surface heating are found to correlate strongly to the impacting effluent where peak temperatures occur in regions of maximum surface helium concentration.
- Published
- 2015
25. Ignition dynamics of dry-etched vertical cavity single-hole microdischarge reactors in ac regime operating in noble gases
- Author
-
Mukesh Kulsreshath, Remi Dussart, V Schulz-von der Gathen, Valentin Felix, and Judith Golda
- Subjects
Acoustics and Ultrasonics ,Atmospheric pressure ,Silicon ,business.industry ,Dynamics (mechanics) ,Analytical chemistry ,chemistry.chemical_element ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Ignition system ,chemistry ,law ,Single hole ,Optoelectronics ,business ,Polarity (mutual inductance) ,Intensity (heat transfer) ,Voltage - Abstract
Silicon-based multi-cavity microdischarge reactors allow the generation of large-area uniform glow discharges over a wide pressure range up to atmospheric pressure. These devices, fabricated using micro electro-mechanical system technology, have shown complex interactions between the individual cavities. To discriminate these interactions, devices with only one shallow vertical cavity are studied here. Operation characteristics are investigated using electrical and optical analysing techniques. The spatial and temporal dynamics of the discharge are investigated for positive and negative voltage polarity of the applied ac voltage ramp by phase-resolved imaging. Within each voltage half-period, emission from the single cavity shows repetitive pulsing features and distinct spatial distributions. In the positive half-period, ring-shaped structures develop, while the negative half-period is distinguished by a bell-shaped intensity distribution. Effects of pressure and operation frequency on the spatial and temporal intensity profiles are discussed.
- Published
- 2014
26. Pressure broadening of atomic oxygen two-photon absorption laser induced fluorescence.
- Author
-
Daniil Marinov, Cyril Drag, Christophe Blondel, Olivier Guaitella, Judith Golda, Bart Klarenaar, Richard Engeln, Volker Schulz-von der Gathen, and Jean-Paul Booth
- Subjects
PRESSURE broadening ,LIGHT absorption ,LASER-induced fluorescence ,DOPPLER broadening ,QUENCHING (Chemistry) ,GLOW discharges - Abstract
Atomic oxygen, considered to be a determining reactant in plasma applications at ambient pressure, is routinely detected by two-photon absorption laser induced fluorescence (TALIF). Here, pressure broadening of the (2p
4 3 P2 → 3p3 PJ=0,1,2 ) two-photon transition in oxygen atoms was investigated using a high-resolution TALIF technique in normal and Doppler-free configurations. The pressure broadening coefficients determined were = 0.40 ± 0.08 cm−1 /bar for oxygen molecules and = 0.46 ± 0.03 cm−1 /bar for helium atoms. These correspond to pressure broadening rate constants = 9 · 10–9 cm3 s−1 and = 4 · 10−9 cm3 s−1 , respectively. The well-known quenching rate constants of O(3p3 PJ ) by O2 and He are at least one order of magnitude smaller, which signifies that non-quenching collisions constitute the main line-broadening mechanism. In addition to providing new insights into collisional processes of oxygen atoms in electronically excited 3p3 PJ state, reported pressure broadening parameters are important for quantification of oxygen TALIF line profiles when both collisional and Doppler broadening mechanisms are important. Thus, the Doppler component (and hence the temperature of oxygen atoms) can be accurately determined from high resolution TALIF measurements in a broad range of conditions. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
27. Summarizing results on the performance of a selective set of atmospheric plasma jets for separation of photons and reactive particles.
- Author
-
Simon Schneider, Vincent Layes, Jan Benedikt, Julia Elisabeth Bandow, Fabian Jarzina, Jan-Wilm Lackmann, Judith Golda, and Volker Schulz-von der Gathen
- Subjects
PLASMA jets ,REACTIVE oxygen species ,MOLECULAR beams ,MASS spectrometry ,PHYSICS research - Abstract
A microscale atmospheric-pressure plasma jet is a remote plasma jet, where plasma-generated reactive particles and photons are involved in substrate treatment. Here, we summarize our efforts to develop and characterize a particle- or photon-selective set of otherwise identical jets. In that way, the reactive species or photons can be used separately or in combination to study their isolated or combined effects to test whether the effects are additive or synergistic. The final version of the set of three jets—particle-jet, photon-jet and combined jet—is introduced. This final set realizes the highest reproducibility of the photon and particle fluxes, avoids turbulent gas flow, and the fluxes of the selected plasma-emitted components are almost identical in the case of all jets, while the other component is effectively blocked, which was verified by optical emission spectroscopy and mass spectrometry. Schlieren-imaging and a fluid dynamics simulation show the stability of the gas flow. The performance of these selective jets is demonstrated with the example of the treatment of E. coli bacteria with the different components emitted by a He-only, a He/N
2 and a He/O2 plasma. Additionally, measurements of the vacuum UV photon spectra down to the wavelength of 50 nm can be made with the photon-jet and the relative comparison of spectral intensities among different gas mixtures is reported here. The results will show that the vacuum UV photons can lead to the inactivation of the E.coli bacteria. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
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