Pub Date : 2024-07-10DOI: 10.1088/1361-6595/ad5df8
Chong-Biao Tian, Li Wang, Máté Vass, Xiao-Kun Wang, Wan Dong, Yuan-Hong Song, You-Nian Wang and Julian Schulze
Insights into the spatio-temporally resolved electron power absorption dynamics in capacitively coupled radio-frequency plasmas are essential for understanding the fundamentals of their operation and as a basis for knowledge-based plasma process development. Similar to the γ-mode, an ionization maximum is observed at the sheath edge around the time of maximum sheath voltage in electronegative oxygen discharges at a pressure of 300 Pa. Based on Particle-in-Cell/Monte Carlo Collisions (PIC/MCC) simulations, we demonstrate that this maximum is not only caused by secondary electrons emitted at the electrode and collisionally multiplied inside the sheath. In fact, it also occurs in the complete absence of secondary electrons in the simulation, and is caused by the generation of ions by electron attachment close to the electrode during the local sheath collapse. These negative ions are accelerated towards the plasma bulk by the sheath electric field during sheath expansion. By electron detachment from these negative ions, electrons are generated inside the sheath and are accelerated towards the plasma bulk by the instantaneous sheath electric field—similarly to secondary electrons. Ionization is also observed in the plasma bulk and caused by electrons generated by detachment and accelerated by the high drift-and ambipolar electric fields. This detachment-induced electron power absorption is found to have significant effects on the discharge in the presence and absence of secondary electron emission. Its fundamentals are understood based on an analysis of the spatio-temporal electron and power absorption dynamics as well as the trajectory of selected ions close to the electrode.
了解电容耦合射频等离子体中电子功率吸收的时空分辨动态，对于理解其运行的基本原理以及作为基于知识的等离子体工艺开发的基础至关重要。与 γ 模式类似，在 300 Pa 压力下的负电性氧放电中，在最大鞘电压附近的鞘边缘也观察到了电离最大值。根据粒子在细胞内/蒙特卡罗碰撞（PIC/MCC）模拟，我们证明了这一最大值不仅是由电极发射的二次电子在鞘内碰撞倍增引起的。事实上，在模拟中完全没有二次电子的情况下，也会出现这种最大值，其原因是在局部鞘塌缩过程中，靠近电极的电子附着产生了离子。在鞘膨胀过程中，这些负离子被鞘电场加速向等离子体块移动。电子从这些负离子脱离后，在鞘内产生电子，并在瞬时鞘电场的作用下加速向等离子体块移动--这与次级电子类似。在等离子体体中也能观察到电离现象，电离是由脱离产生的电子在高漂移电场和伏极电场的作用下加速产生的。研究发现，无论是否存在二次电子发射，这种脱离引起的电子功率吸收都会对放电产生重大影响。根据对电子和功率吸收的时空动态以及靠近电极的选定离子轨迹的分析，可以了解其基本原理。
{"title":"The detachment-induced mode in electronegative capacitively coupled radio-frequency plasmas","authors":"Chong-Biao Tian, Li Wang, Máté Vass, Xiao-Kun Wang, Wan Dong, Yuan-Hong Song, You-Nian Wang and Julian Schulze","doi":"10.1088/1361-6595/ad5df8","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5df8","url":null,"abstract":"Insights into the spatio-temporally resolved electron power absorption dynamics in capacitively coupled radio-frequency plasmas are essential for understanding the fundamentals of their operation and as a basis for knowledge-based plasma process development. Similar to the γ-mode, an ionization maximum is observed at the sheath edge around the time of maximum sheath voltage in electronegative oxygen discharges at a pressure of 300 Pa. Based on Particle-in-Cell/Monte Carlo Collisions (PIC/MCC) simulations, we demonstrate that this maximum is not only caused by secondary electrons emitted at the electrode and collisionally multiplied inside the sheath. In fact, it also occurs in the complete absence of secondary electrons in the simulation, and is caused by the generation of ions by electron attachment close to the electrode during the local sheath collapse. These negative ions are accelerated towards the plasma bulk by the sheath electric field during sheath expansion. By electron detachment from these negative ions, electrons are generated inside the sheath and are accelerated towards the plasma bulk by the instantaneous sheath electric field—similarly to secondary electrons. Ionization is also observed in the plasma bulk and caused by electrons generated by detachment and accelerated by the high drift-and ambipolar electric fields. This detachment-induced electron power absorption is found to have significant effects on the discharge in the presence and absence of secondary electron emission. Its fundamentals are understood based on an analysis of the spatio-temporal electron and power absorption dynamics as well as the trajectory of selected ions close to the electrode.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-10DOI: 10.1088/1361-6595/ad5ebc
Chen Zhou, Ismail Rafatov, Ying Wang, Anatoly Kudryavtsev, Chengxun Yuan, Jingfeng Yao and Zhongxiang Zhou
This work considers the fundamental contradictions in the concept of one of the most well-known and widely used modifications of the fluid model for simulation of a glow discharge (GD), the ‘local mean energy approximation’ (LMEA). In this model, it is proposed to determine the kinetic coefficients in the electron particle and energy balance equations as functions of the electron mean energy (temperature) rather than local electric field, using a one-to-one correspondence between these parameters through the electron Boltzmann equation. It is shown that the scope of applicability of this model, like any other modification of the fluid model, is limited by the local mode of formation of the electron energy distribution function (EEDF). Therefore, as demonstrated by the examples of typical 1D and 2D problems for a GD in argon, its extension to the region of nonlocal EEDF is in no way justified and leads not only to serious errors in the results, but also to a logically intractable situation in attempts to apply the main postulate of the LMEA model to the region of a weak (or even reverse) electric field in a negative glow plasma. At the same time, the apparent reliability of calculations within the framework of the LMEA model for a number of parameters, in our opinion, only slows down progress in modeling of gas discharge plasma.
{"title":"On fundamental inconsistencies in a commonly used modification of a fluid model for glow discharge","authors":"Chen Zhou, Ismail Rafatov, Ying Wang, Anatoly Kudryavtsev, Chengxun Yuan, Jingfeng Yao and Zhongxiang Zhou","doi":"10.1088/1361-6595/ad5ebc","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5ebc","url":null,"abstract":"This work considers the fundamental contradictions in the concept of one of the most well-known and widely used modifications of the fluid model for simulation of a glow discharge (GD), the ‘local mean energy approximation’ (LMEA). In this model, it is proposed to determine the kinetic coefficients in the electron particle and energy balance equations as functions of the electron mean energy (temperature) rather than local electric field, using a one-to-one correspondence between these parameters through the electron Boltzmann equation. It is shown that the scope of applicability of this model, like any other modification of the fluid model, is limited by the local mode of formation of the electron energy distribution function (EEDF). Therefore, as demonstrated by the examples of typical 1D and 2D problems for a GD in argon, its extension to the region of nonlocal EEDF is in no way justified and leads not only to serious errors in the results, but also to a logically intractable situation in attempts to apply the main postulate of the LMEA model to the region of a weak (or even reverse) electric field in a negative glow plasma. At the same time, the apparent reliability of calculations within the framework of the LMEA model for a number of parameters, in our opinion, only slows down progress in modeling of gas discharge plasma.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1088/1361-6595/ad5d13
Pedro A S Randi, Giseli M Moreira and Márcio H F Bettega
Tetramethyltin [Sn(CH3)4] and trimethylgallium [Ga(CH3)3] are important source molecules of Sn and Ga atoms which are used in manufacturing techniques involving low-temperature plasmas. Accurate numerical modeling of plasma environments requires a comprehensive set of electron scattering cross sections by these precursor molecules. Here, we report the elastic integral, differential, and momentum transfer cross sections for electron collisions with Sn(CH3)4 and Ga(CH3)3 for energies ranging from 0 to 30 eV. Our calculations were carried out with the Schwinger multichannel method implemented with pseudopotentials and considered two levels of approximation in our calculations, namely static-exchange and static-exchange plus polarization. We identified three shape resonances for Sn(CH3)4 and one clear low-lying resonance for Ga(CH3)3. The low-energy behavior of the s-wave cross section and eigenphase was investigated and, for both molecules, we found evidence of a Ramsauer–Townsend (RT) minimum and a virtual state. Our results indicate that negative differential conductivity would occur in a gas composed of Sn(CH3)4. On the other hand, this effect would be suppressed in a gas of Ga(CH3)3 due to an overlap between the position of the RT minimum and the shape resonance in the momentum-transfer cross section.
{"title":"Elastic cross section data for precursor molecules used in low-temperature plasmas: Sn(CH3)4 and Ga(CH3)3","authors":"Pedro A S Randi, Giseli M Moreira and Márcio H F Bettega","doi":"10.1088/1361-6595/ad5d13","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5d13","url":null,"abstract":"Tetramethyltin [Sn(CH3)4] and trimethylgallium [Ga(CH3)3] are important source molecules of Sn and Ga atoms which are used in manufacturing techniques involving low-temperature plasmas. Accurate numerical modeling of plasma environments requires a comprehensive set of electron scattering cross sections by these precursor molecules. Here, we report the elastic integral, differential, and momentum transfer cross sections for electron collisions with Sn(CH3)4 and Ga(CH3)3 for energies ranging from 0 to 30 eV. Our calculations were carried out with the Schwinger multichannel method implemented with pseudopotentials and considered two levels of approximation in our calculations, namely static-exchange and static-exchange plus polarization. We identified three shape resonances for Sn(CH3)4 and one clear low-lying resonance for Ga(CH3)3. The low-energy behavior of the s-wave cross section and eigenphase was investigated and, for both molecules, we found evidence of a Ramsauer–Townsend (RT) minimum and a virtual state. Our results indicate that negative differential conductivity would occur in a gas composed of Sn(CH3)4. On the other hand, this effect would be suppressed in a gas of Ga(CH3)3 due to an overlap between the position of the RT minimum and the shape resonance in the momentum-transfer cross section.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1088/1361-6595/ad5df7
Shimin Yu, Hao Wu, Shali Yang, Lu Wang, Zhipeng Chen, Zhijiang Wang, Wei Jiang, Julian Schulze and Ya Zhang
Impedance matching is crucial for optimizing plasma generation and reducing power reflection in capacitively coupled plasmas (CCP). Designing these matchings is challenging due to the varying and typically unknown impedance of the plasma, especially in the presence of multiple driving frequencies. Here, a computational design method for impedance matching networks (IMNs) for CCPs is proposed and applied to discharges driven by tailored voltage waveforms (TVW). This method is based on a self-consistent combination of particle in cell/Monte Carlo collision simulations of the plasma with Kirchhoff’s equations to describe the external electrical circuit. Two Foster second-form networks with the same structure are used to constitute an L-type matching network, and the matching capability is optimized by iteratively updating the values of variable capacitors inside the IMN. The results show that the plasma density and the power absorbed by the plasma continuously increase in the frame of this iterative process of adjusting the matching parameters until an excellent impedance matching capability is finally achieved. Impedance matching is found to affect the DC self-bias voltage, whose absolute value is maximized when the best matching is achieved. Additionally, a change in the quality of the impedance matching is found to cause an electron heating mode transition. Poor impedance matching results in a heating mode where electron power absorption in the plasma bulk by drift electric fields plays an important role, while good matching results in the classical α-mode operation, where electron power absorption by ambipolar electric fields at the sheath edges dominates. The method proposed in this work is expected to be of great significance in promoting TVW plasma sources from theory to industrial application, since it allows designing the required complex multi-frequency IMNs.
{"title":"Kinetic simulations of capacitively coupled plasmas driven by tailored voltage waveforms with multi-frequency matching","authors":"Shimin Yu, Hao Wu, Shali Yang, Lu Wang, Zhipeng Chen, Zhijiang Wang, Wei Jiang, Julian Schulze and Ya Zhang","doi":"10.1088/1361-6595/ad5df7","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5df7","url":null,"abstract":"Impedance matching is crucial for optimizing plasma generation and reducing power reflection in capacitively coupled plasmas (CCP). Designing these matchings is challenging due to the varying and typically unknown impedance of the plasma, especially in the presence of multiple driving frequencies. Here, a computational design method for impedance matching networks (IMNs) for CCPs is proposed and applied to discharges driven by tailored voltage waveforms (TVW). This method is based on a self-consistent combination of particle in cell/Monte Carlo collision simulations of the plasma with Kirchhoff’s equations to describe the external electrical circuit. Two Foster second-form networks with the same structure are used to constitute an L-type matching network, and the matching capability is optimized by iteratively updating the values of variable capacitors inside the IMN. The results show that the plasma density and the power absorbed by the plasma continuously increase in the frame of this iterative process of adjusting the matching parameters until an excellent impedance matching capability is finally achieved. Impedance matching is found to affect the DC self-bias voltage, whose absolute value is maximized when the best matching is achieved. Additionally, a change in the quality of the impedance matching is found to cause an electron heating mode transition. Poor impedance matching results in a heating mode where electron power absorption in the plasma bulk by drift electric fields plays an important role, while good matching results in the classical α-mode operation, where electron power absorption by ambipolar electric fields at the sheath edges dominates. The method proposed in this work is expected to be of great significance in promoting TVW plasma sources from theory to industrial application, since it allows designing the required complex multi-frequency IMNs.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1088/1361-6595/ad5df5
Filippo Manaigo, Abhyuday Chatterjee, Annemie Bogaerts and Rony Snyders
A gliding arc (GA) plasma, operating at atmospheric pressure in a gas mixture of 50% N2 and 50% O2, is studied using laser-induced fluorescence spectroscopy. The main goal is to determine the two-dimensional distribution of both the gas temperature and the NO ground state density in the afterglow. As GA plasma discharges at atmospheric pressure normally produce rather high NOx densities, the high concentration of relevant absorbers, such as NO, may impose essential restrictions for the use of ‘classical’ laser-induced fluorescence methods (dealing with excitation in the bandhead vicinity), as the laser beam would be strongly absorbed along its propagation in the afterglow. Since this was indeed the case for the studied discharge, an approach dealing with laser-based excitation of separate rotational lines is proposed. In this case, due to a non-saturated absorption regime, simultaneous and reliable measurements of both the NO density and the gas temperature (using a reference fitting spectrum) are possible. The proposed method is applied to provide a two-dimensional map for both the NO density and the gas temperature at different plasma conditions. The results show that the input gas flow rate strongly alters the plasma shape, which appears as an elongated column at low input gas flow rate and spreads laterally as the flow rate increases. Finally, based on temperature map analysis, a clear correlation between the gas temperature and NO concentration is found. The proposed method may be interesting for the plasma-chemical analysis of discharges with high molecular production yields, where knowledge of both molecular concentration and gas temperature is required.
利用激光诱导荧光光谱法研究了在大气压力下，在 50% N2 和 50% O2 混合气体中运行的滑弧等离子体（GA）。主要目的是确定余辉中气体温度和 NO 基态密度的二维分布。由于 GA 等离子体在大气压力下放电通常会产生相当高的氮氧化物密度，因此高浓度的相关吸收剂（如 NO）可能会对使用 "经典 "激光诱导荧光方法（处理带头附近的激发）造成重要限制，因为激光束在余辉中传播时会被强烈吸收。鉴于所研究的放电现象确实如此，我们提出了一种基于激光的单独旋转线激发方法。在这种情况下，由于非饱和吸收机制，可以同时可靠地测量 NO 密度和气体温度（使用参考拟合光谱）。所提出的方法可用于提供不同等离子体条件下 NO 密度和气体温度的二维地图。结果表明，输入气体的流速会极大地改变等离子体的形状，在输入气体流速较低时，等离子体呈拉长的柱状，而随着流速的增加，等离子体会向横向扩散。最后，根据温度图分析，发现气体温度与 NO 浓度之间存在明显的相关性。在需要同时了解分子浓度和气体温度的情况下，所提出的方法可能对分子产量较高的放电等离子体化学分析很有意义。
{"title":"Insight in NO synthesis in a gliding arc plasma via gas temperature and density mapping by laser-induced fluorescence","authors":"Filippo Manaigo, Abhyuday Chatterjee, Annemie Bogaerts and Rony Snyders","doi":"10.1088/1361-6595/ad5df5","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5df5","url":null,"abstract":"A gliding arc (GA) plasma, operating at atmospheric pressure in a gas mixture of 50% N2 and 50% O2, is studied using laser-induced fluorescence spectroscopy. The main goal is to determine the two-dimensional distribution of both the gas temperature and the NO ground state density in the afterglow. As GA plasma discharges at atmospheric pressure normally produce rather high NOx densities, the high concentration of relevant absorbers, such as NO, may impose essential restrictions for the use of ‘classical’ laser-induced fluorescence methods (dealing with excitation in the bandhead vicinity), as the laser beam would be strongly absorbed along its propagation in the afterglow. Since this was indeed the case for the studied discharge, an approach dealing with laser-based excitation of separate rotational lines is proposed. In this case, due to a non-saturated absorption regime, simultaneous and reliable measurements of both the NO density and the gas temperature (using a reference fitting spectrum) are possible. The proposed method is applied to provide a two-dimensional map for both the NO density and the gas temperature at different plasma conditions. The results show that the input gas flow rate strongly alters the plasma shape, which appears as an elongated column at low input gas flow rate and spreads laterally as the flow rate increases. Finally, based on temperature map analysis, a clear correlation between the gas temperature and NO concentration is found. The proposed method may be interesting for the plasma-chemical analysis of discharges with high molecular production yields, where knowledge of both molecular concentration and gas temperature is required.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6595/ad5abd
Kevin Köhn, Dennis Krüger, Denis Eremin, Liang Xu and Ralf Peter Brinkmann
A recent publication by Köhn et al (2023 Plasma Sources Sci. Technol.32 055012) studied the quasi-equilibria of high power magnetron discharges through thermodynamic principles. A generalized, magnetic-field aware Poisson–Boltzmann relation for the electric potential and the electron density was established using a non-standard (multi-objective) variational principle. This addendum demonstrates that, assuming slow or quasistatic evolution, the same result can be realized via a standard (single-objective) variational principle, thereby streamlining the theoretical framework while preserving the robustness of the finding.
{"title":"Addendum: Thermodynamic quasi-equilibria in high power magnetron discharges: a generalized Poisson–Boltzmann relation (2023 Plasma Sources Sci. Technol. 32 055012)","authors":"Kevin Köhn, Dennis Krüger, Denis Eremin, Liang Xu and Ralf Peter Brinkmann","doi":"10.1088/1361-6595/ad5abd","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5abd","url":null,"abstract":"A recent publication by Köhn et al (2023 Plasma Sources Sci. Technol.32 055012) studied the quasi-equilibria of high power magnetron discharges through thermodynamic principles. A generalized, magnetic-field aware Poisson–Boltzmann relation for the electric potential and the electron density was established using a non-standard (multi-objective) variational principle. This addendum demonstrates that, assuming slow or quasistatic evolution, the same result can be realized via a standard (single-objective) variational principle, thereby streamlining the theoretical framework while preserving the robustness of the finding.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141547332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1088/1361-6595/ad590b
Jiří Fujera, Tomáš Homola, Vít Jirásek, Jakub Ondráček, Barbora Tarabová, Václav Prukner and Milan Šimek
Nonthermal plasma reactors, which enable electrical discharges to be generated in various gases and both liquid and gaseous water, have attracted considerable attention as an alternative method for producing ammonia and fixing nitrogen. In this work, we investigated the basic performance of multihollow surface dielectric barrier discharge (MSDBD) to generate plasma in synthetic air and nitrogen-containing admixtures of water aerosols. The MSDBD in combination with the aerosol stream represents a rather complex geometry for generating the discharge; the plasma is significantly affected by the physicochemical properties of water aerosols on the one hand, on the other hand, this system facilitates the solvation of gaseous plasma products in water and the production of plasma-activated nitrogen-rich water (PAW). The plasma interaction with the water aerosols was studied using optical emission spectroscopy and a scanning mobility particle sizer to provide information about the size and distribution of the water particles entering and exiting the plasma reactor. The gas exiting the plasma reactor was analyzed using Fourier-transform infrared spectroscopy, and the PAW collected in an ice-cooled vessel was analyzed for nitrates (NO2−), nitrites (NO3−), and ammonia (NH3). MSDBD shows promise as a catalyst- and H2-free method for fixing nitrogen in water. Additionally, given the low energy consumption (<5 W) of MSDBD and the straightforward construction of the plasma unit, the suggested approach for PAW production offers a viable route for advancing a decentralized sustainable economy.
{"title":"Aerosol-based multihollow surface DBD: a promising approach for nitrogen fixation","authors":"Jiří Fujera, Tomáš Homola, Vít Jirásek, Jakub Ondráček, Barbora Tarabová, Václav Prukner and Milan Šimek","doi":"10.1088/1361-6595/ad590b","DOIUrl":"https://doi.org/10.1088/1361-6595/ad590b","url":null,"abstract":"Nonthermal plasma reactors, which enable electrical discharges to be generated in various gases and both liquid and gaseous water, have attracted considerable attention as an alternative method for producing ammonia and fixing nitrogen. In this work, we investigated the basic performance of multihollow surface dielectric barrier discharge (MSDBD) to generate plasma in synthetic air and nitrogen-containing admixtures of water aerosols. The MSDBD in combination with the aerosol stream represents a rather complex geometry for generating the discharge; the plasma is significantly affected by the physicochemical properties of water aerosols on the one hand, on the other hand, this system facilitates the solvation of gaseous plasma products in water and the production of plasma-activated nitrogen-rich water (PAW). The plasma interaction with the water aerosols was studied using optical emission spectroscopy and a scanning mobility particle sizer to provide information about the size and distribution of the water particles entering and exiting the plasma reactor. The gas exiting the plasma reactor was analyzed using Fourier-transform infrared spectroscopy, and the PAW collected in an ice-cooled vessel was analyzed for nitrates (NO2−), nitrites (NO3−), and ammonia (NH3). MSDBD shows promise as a catalyst- and H2-free method for fixing nitrogen in water. Additionally, given the low energy consumption (<5 W) of MSDBD and the straightforward construction of the plasma unit, the suggested approach for PAW production offers a viable route for advancing a decentralized sustainable economy.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"79 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1088/1361-6595/ad5932
Zhenyu Wei, Ryo Ono and Atsushi Komuro
In this study, we investigated the effect of various concentrations, from 20% to 90%, in nitrogen–oxygen ( ) mixtures on the characteristics of secondary streamers. As oxygen molecules have different molecular characteristics from nitrogen molecules in terms of ionisation threshold and electron attachment property, streamer discharges generated under various nitrogen–oxygen ratios may exhibit differing characteristics such as electron density, electric field, and radical formation. We focused on the changes in these parameters in secondary streamers using simulations. Simulations were first performed under the same conditions as those in previous experiments to compare the results of the ozone production, discharge current, and discharge emission characteristics. To compare the ozone production characteristics, simulated O radicals–the precursor of ozone–were used in the simulation for simplicity. This comparison showed that, although the absolute values of each parameter were different, the simulation exhibited a similar trend in the case of the experimentally obtained oxygen concentration dependence. After the validity of the simulation was verified to some extent via a comparison with the experiment, the results obtained from the simulation were analysed in detail. The results showed that, although the electric field strength in the secondary streamer did not change much as the oxygen concentration increased, the decrease rate of the electron density was greatly accelerated by the electron attachment reaction of oxygen. As a result, many of the electrons had already dissipate during the development of the primary streamer, and few electrons remained when the secondary streamer was formed. This effect suggests that the ratio of the amount of O radicals produced in the primary streamer to that produced in the secondary streamer changes as the oxygen concentration changes.
在这项研究中，我们研究了氮氧（ ）混合物中从 20% 到 90% 的不同浓度对二次流束特性的影响。由于氧分子在电离阈值和电子附着特性方面与氮分子具有不同的分子特性，因此在不同的氮氧比例下产生的流束放电可能表现出不同的特性，如电子密度、电场和自由基的形成。我们通过模拟重点研究了二级流束中这些参数的变化。首先在与之前实验相同的条件下进行模拟，以比较臭氧产生、放电电流和放电发射特性的结果。为了比较臭氧产生特性，模拟中使用了模拟 O 自由基（臭氧的前体），以简化操作。比较结果表明，虽然各参数的绝对值不同，但模拟结果与实验得出的氧气浓度依赖性趋势相似。通过与实验进行比较，在一定程度上验证了模拟的有效性之后，对模拟得到的结果进行了详细分析。结果表明，虽然随着氧气浓度的增加，二级流束中的电场强度变化不大，但由于氧气的电子附着反应，电子密度的下降速度大大加快。因此，许多电子在一级流线体的发展过程中就已经消散，当二级流线体形成时，剩下的电子就很少了。这种效应表明，随着氧气浓度的变化，初级流束中产生的 O 自由基数量与次级流束中产生的 O 自由基数量之比会发生变化。
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Pub Date : 2024-06-19DOI: 10.1088/1361-6595/ad56c7
M Farahani, T Kozák, A D Pajdarová and J Čapek
The reverse discharge (RD) phenomenon in bipolar HiPIMS has been observed when a sufficiently long positive pulse is applied to the magnetron. Due to the magnetic field, electrons accumulated behind the magnetic trap are prevented from reaching the positive target. Consequently, a space charge double layer (DL) is formed between the positive target and the plasma behind the magnetic trap, leading to electron acceleration across the DL and RD ignition. This study reveals the significant impact of the magnetic field configuration on RD ignition. Experiments are performed using a Ti target involving magnetic field variation, wire probe measurements of floating potential, and optical emission spectroscopy imaging. It is found that adjusting the magnetic field to a more balanced configuration leads to earlier RD ignition, while a more unbalanced one delays or even prevents it. Specifically, the time of RD ignition decreases with an increase in the magnetic null point distance from the target. Moreover, the size and shape of optical emission in the RD varies with nearby probe placement, suggesting sensitivity to external electrodes.
{"title":"Effect of magnetic field configuration on double layer formation and reverse discharge ignition in bipolar HiPIMS","authors":"M Farahani, T Kozák, A D Pajdarová and J Čapek","doi":"10.1088/1361-6595/ad56c7","DOIUrl":"https://doi.org/10.1088/1361-6595/ad56c7","url":null,"abstract":"The reverse discharge (RD) phenomenon in bipolar HiPIMS has been observed when a sufficiently long positive pulse is applied to the magnetron. Due to the magnetic field, electrons accumulated behind the magnetic trap are prevented from reaching the positive target. Consequently, a space charge double layer (DL) is formed between the positive target and the plasma behind the magnetic trap, leading to electron acceleration across the DL and RD ignition. This study reveals the significant impact of the magnetic field configuration on RD ignition. Experiments are performed using a Ti target involving magnetic field variation, wire probe measurements of floating potential, and optical emission spectroscopy imaging. It is found that adjusting the magnetic field to a more balanced configuration leads to earlier RD ignition, while a more unbalanced one delays or even prevents it. Specifically, the time of RD ignition decreases with an increase in the magnetic null point distance from the target. Moreover, the size and shape of optical emission in the RD varies with nearby probe placement, suggesting sensitivity to external electrodes.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-16DOI: 10.1088/1361-6595/ad52be
Leanne L Su, Thomas A Marks and Benjamin A Jorns
The trends in mass utilization with increasing discharge voltage and current are investigated for a magnetically shielded Hall thruster operating on xenon and krypton. A 9 kW class shielded thruster is operated with discharge voltages from 300 to 600 V and discharge currents from 15 to 30 A on xenon and krypton. Experimental measurements of discharge current, thrust, anode efficiency, and ion velocity as a function of axial position are used to calibrate a multi-fluid 2D Hall thruster code at all operating conditions. The results of these calibrated simulations are employed to interrogate the plasma properties inside the thruster channel. A simplified 0D model for mass utilization evaluated on spatial averages of the simulated plasma parameters is employed to interpret the response of this efficiency mode with power for each propellant. It is found that with both higher voltage and current, mass utilization increases for both gases and their relative gap in this efficiency decreases. This can be attributed to the higher plasma densities and ionization rate coefficients at high voltage, and solely to higher plasma densities at high current. The driving factors for the increase in mass utilization are examined in the context of its nonlinear response to internal plasma properties. The behavior of mass utilization is also discussed in context of the gap in overall efficiency between the propellants. Finally, the implications of these results for improving the performance of high power Hall thrusters operating on krypton are examined.
{"title":"Trends in mass utilization of a magnetically shielded Hall thruster operating on xenon and krypton","authors":"Leanne L Su, Thomas A Marks and Benjamin A Jorns","doi":"10.1088/1361-6595/ad52be","DOIUrl":"https://doi.org/10.1088/1361-6595/ad52be","url":null,"abstract":"The trends in mass utilization with increasing discharge voltage and current are investigated for a magnetically shielded Hall thruster operating on xenon and krypton. A 9 kW class shielded thruster is operated with discharge voltages from 300 to 600 V and discharge currents from 15 to 30 A on xenon and krypton. Experimental measurements of discharge current, thrust, anode efficiency, and ion velocity as a function of axial position are used to calibrate a multi-fluid 2D Hall thruster code at all operating conditions. The results of these calibrated simulations are employed to interrogate the plasma properties inside the thruster channel. A simplified 0D model for mass utilization evaluated on spatial averages of the simulated plasma parameters is employed to interpret the response of this efficiency mode with power for each propellant. It is found that with both higher voltage and current, mass utilization increases for both gases and their relative gap in this efficiency decreases. This can be attributed to the higher plasma densities and ionization rate coefficients at high voltage, and solely to higher plasma densities at high current. The driving factors for the increase in mass utilization are examined in the context of its nonlinear response to internal plasma properties. The behavior of mass utilization is also discussed in context of the gap in overall efficiency between the propellants. Finally, the implications of these results for improving the performance of high power Hall thrusters operating on krypton are examined.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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