{"title":"Mode Transition Induced by Gas Heating Along the Discharge Channel in Capacitively Coupled Atmospheric Pressure Micro Plasma Jets","authors":"","doi":"10.1007/s11090-023-10444-6","DOIUrl":null,"url":null,"abstract":"<h3>Abstract</h3> <p>The effects of neutral gas heating along the direction of the gas flow inside the discharge channel of a parallel plate micro atmospheric pressure plasma jet, the COST-jet, on the spatio-temporal dynamics of energetic electrons are investigated by experiments and simulations. The plasma source is driven by a single frequency sinusoidal voltage waveform at 13.56 MHz in helium with an admixture (0.05–0.2%) of nitrogen. Optical emission spectroscopy measurements are applied to determine the spatio-temporally resolved electron impact excitation dynamics from the ground state into the He I (3s)<span> <span>\\(^3\\)</span> </span>S<span> <span>\\(_1\\)</span> </span> state and the rotational temperature of nitrogen molecules at different positions along the direction of the gas flow inside the 30 mm long discharge channel. The gas temperature, which is assumed to be equal to the N<span> <span>\\(_2\\)</span> </span> rotational temperature, is found to increase along the discharge channel. This effect is attenuated as the nitrogen concentration is increased in the gas mixture, leading to an eventually constant temperature profile. The experimental data also reveal a plasma operating mode transition along the discharge channel from the <span> <span>\\(\\Omega\\)</span> </span>- to the Penning-mode and show good agreement with the results of 1d3v kinetic simulations, which spatially resolve the inter-electrode space and use the gas temperature as an input value. The simulations demonstrate that the increase of the gas temperature leads to the observed mode transition. The results suggest the possibility of using the nitrogen admixture and the feed gas temperature as additional control parameters, (i) to tailor the plasma operating mode along the direction of the gas flow so that the production of specific radicals is optimized; and (ii) to control the final gas temperature of the effluent. The latter could be particularly interesting for biological applications, where the upper gas temperature limit is dictated by the rather low thermal damage threshold of the treated material.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Plasma Chemistry and Plasma Processing","FirstCategoryId":"5","ListUrlMain":"https://doi.org/10.1007/s11090-023-10444-6","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}
引用次数: 0
Abstract
The effects of neutral gas heating along the direction of the gas flow inside the discharge channel of a parallel plate micro atmospheric pressure plasma jet, the COST-jet, on the spatio-temporal dynamics of energetic electrons are investigated by experiments and simulations. The plasma source is driven by a single frequency sinusoidal voltage waveform at 13.56 MHz in helium with an admixture (0.05–0.2%) of nitrogen. Optical emission spectroscopy measurements are applied to determine the spatio-temporally resolved electron impact excitation dynamics from the ground state into the He I (3s)\(^3\)S\(_1\) state and the rotational temperature of nitrogen molecules at different positions along the direction of the gas flow inside the 30 mm long discharge channel. The gas temperature, which is assumed to be equal to the N\(_2\) rotational temperature, is found to increase along the discharge channel. This effect is attenuated as the nitrogen concentration is increased in the gas mixture, leading to an eventually constant temperature profile. The experimental data also reveal a plasma operating mode transition along the discharge channel from the \(\Omega\)- to the Penning-mode and show good agreement with the results of 1d3v kinetic simulations, which spatially resolve the inter-electrode space and use the gas temperature as an input value. The simulations demonstrate that the increase of the gas temperature leads to the observed mode transition. The results suggest the possibility of using the nitrogen admixture and the feed gas temperature as additional control parameters, (i) to tailor the plasma operating mode along the direction of the gas flow so that the production of specific radicals is optimized; and (ii) to control the final gas temperature of the effluent. The latter could be particularly interesting for biological applications, where the upper gas temperature limit is dictated by the rather low thermal damage threshold of the treated material.
期刊介绍：
Publishing original papers on fundamental and applied research in plasma chemistry and plasma processing, the scope of this journal includes processing plasmas ranging from non-thermal plasmas to thermal plasmas, and fundamental plasma studies as well as studies of specific plasma applications. Such applications include but are not limited to plasma catalysis, environmental processing including treatment of liquids and gases, biological applications of plasmas including plasma medicine and agriculture, surface modification and deposition, powder and nanostructure synthesis, energy applications including plasma combustion and reforming, resource recovery, coupling of plasmas and electrochemistry, and plasma etching. Studies of chemical kinetics in plasmas, and the interactions of plasmas with surfaces are also solicited. It is essential that submissions include substantial consideration of the role of the plasma, for example, the relevant plasma chemistry, plasma physics or plasma–surface interactions; manuscripts that consider solely the properties of materials or substances processed using a plasma are not within the journal’s scope.
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