Mode Transition Induced by Gas Heating Along the Discharge Channel in Capacitively Coupled Atmospheric Pressure Micro Plasma Jets

IF 2.6 3区物理与天体物理 Q3 ENGINEERING, CHEMICAL Plasma Chemistry and Plasma Processing Pub Date : 2024-01-12 DOI:10.1007/s11090-023-10444-6

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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.

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电容耦合大气压微等离子体射流中沿放电通道的气体加热诱发的模式转换

摘要通过实验和模拟，研究了沿平行板微大气压等离子体射流（COST-jet）放电通道内气体流动方向的中性气体加热对高能电子时空动力学的影响。等离子体源由 13.56 MHz 的单频正弦电压波形驱动，在氦气中掺入（0.05-0.2%）氮气。光学发射光谱测量用于确定从基态进入 He I (3s) \(^3\) S \(_1\)态的时空分辨电子碰撞激发动力学，以及氮分子在 30 毫米长放电通道内沿气流方向不同位置的旋转温度。假定气体温度等于 N （_2）旋转温度，发现气体温度会沿着放电通道上升。随着气体混合物中氮气浓度的增加，这种效应逐渐减弱，最终形成恒定的温度曲线。实验数据还揭示了沿放电通道从\(\Omega\) - 到潘宁模式的等离子体工作模式转变，并与 1d3v 动力学模拟结果显示出良好的一致性，该模拟对电极间空间进行了空间解析，并使用气体温度作为输入值。模拟结果表明，气体温度的升高会导致观察到的模式转换。结果表明，可以使用氮气混合物和进料气体温度作为额外的控制参数，(i) 沿气体流动方向调整等离子体运行模式，从而优化特定自由基的产生；(ii) 控制流出物的最终气体温度。后者对生物应用特别有意义，因为在生物应用中，气体温度的上限是由被处理材料相当低的热损伤阈值决定的。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Plasma Chemistry and Plasma Processing 工程技术-工程：化工

CiteScore

5.90

自引率

8.30%

发文量

审稿时长

6-12 weeks

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.