Browsing by Author "Sobota, A."

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    Concepts and characteristics of the ‘COST Reference Microplasma Jet’
    (Bristol : IOP Publ., 2016) Golda, J.; Held, J.; Redeker, B.; Konkowski, M.; Beijer, P.; Sobota, A.; Kroesen, G.; Braithwaite, N.S.J.; Reuter, S.; Turner, M.M.; Gans, T.; O’Connell, D.; Schulz-von der Gathen, V.
    Biomedical applications of non-equilibrium atmospheric pressure plasmas have attracted intense interest in the past few years. Many plasma sources of diverse design have been proposed for these applications, but the relationship between source characteristics and application performance is not well-understood, and indeed many sources are poorly characterized. This circumstance is an impediment to progress in application development. A reference source with well-understood and highly reproducible characteristics may be an important tool in this context. Researchers around the world should be able to compare the characteristics of their own sources and also their results with this device. In this paper, we describe such a reference source, developed from the simple and robust micro-scaled atmospheric pressure plasma jet (μ-APPJ) concept. This development occurred under the auspices of COST Action MP1101 'Biomedical Applications of Atmospheric Pressure Plasmas'. Gas contamination and power measurement are shown to be major causes of irreproducible results in earlier source designs. These problems are resolved in the reference source by refinement of the mechanical and electrical design and by specifying an operating protocol. These measures are shown to be absolutely necessary for reproducible operation. They include the integration of current and voltage probes into the jet. The usual combination of matching unit and power supply is replaced by an integrated LC power coupling circuit and a 5 W single frequency generator. The design specification and operating protocol for the reference source are being made freely available.
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    Corrigendum: Concepts and characteristics of the 'COST Reference Microplasma Jet' (Journal of Physics D: Applied Physics (2016) 49 (084003) DOI: 10.1088/0022-3727/49/8/084003)
    (Bristol : IOP Publ., 2019) Golda, J.; Held, J.; Redeker, B.; Konkowski, M.; Beijer, P.; Sobota, A.; Kroesen, G.; Braithwaite, N.St.J.; Reuter, S.; Turner, M.M.; Gans, T.; O’Connell, D.; Schulz-von der Gathen, V.
    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. © 2018 IOP Publishing Ltd.
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    Effect of a high-voltage mesh electrode on the volume and surface characteristics of pulsed dielectric barrier discharges
    (Melville, NY : American Inst. of Physics, 2020) Kettlitz, M.; van Rooij, O.; Höft, H.; Brandenburg, R.; Sobota, A.
    Electrical breakdown in a pulsed asymmetric dielectric barrier discharge between a glass-covered mesh electrode and a grounded metal electrode in the air at atmospheric pressure is investigated. Volume discharge forms between the metal tip and the dielectric surface and spreads over the dielectric surface. Breakdown and discharge behaviors depend on the polarity of the charged electrode covered with glass compared to the metal rod electrode. In the case of the dielectric cathode (covered mesh), volume discharge features a stronger and longer-lasting emission. Volume discharge is weaker with outstretched surface discharge developing on the opposite glass electrode sustained by the embedded mesh when the metal rod functions as a cathode. The development and spatial distribution of the surface discharge depend on the relative polarity of the dielectrics caused by the charge deposition of the preceding discharge and is independent of the polarity of the applied high voltage. The discharge emission is brighter for the metal cathode and dielectric anode than for the metal anode, with a branching discharge developing and spreading in a star-like structure along the embedded grid, while a ring-like structure was observed for the metal anode and dielectric cathode. The duty cycle influences the discharge development and properties through the effects of the gas phase and surface pre-ionization.