Pub Date : 2024-04-08DOI: 10.1088/1361-6595/ad3be9
Yuanmeng Lu, Ryo Ono, A. Komuro
Dielectric barrier discharges (DBDs) are widely used for ozone generation and surface treatment owing to their ability to generate reactive species. Surface charges generated during discharges distort the electric field between the dielectrics and affect the generation of reactive species. Therefore, the net electric field variations are of significant interest. Herein, a DBD measurement system based on the Pockels effect is established for the first time. The proposed system can simultaneously measure the surface potentials on both sides of the dielectric, thereby obtaining the net electric field at the discharge gap. The net electric field distribution varies insignificantly with the magnitude of the applied voltage but significantly with gap length. Moreover, the breakdown electric field increases with a decreasing gap length. This study provides a physical explanation for microgap reactors, demonstrating that the electric field in a DBD can be manipulated.
{"title":"Simultaneous measurement of electrical potential on both sides of the dielectric surface in a parallel-plate dielectric barrier discharges and analysis of net electric field","authors":"Yuanmeng Lu, Ryo Ono, A. Komuro","doi":"10.1088/1361-6595/ad3be9","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3be9","url":null,"abstract":"\u0000 Dielectric barrier discharges (DBDs) are widely used for ozone generation and surface treatment owing to their ability to generate reactive species. Surface charges generated during discharges distort the electric field between the dielectrics and affect the generation of reactive species. Therefore, the net electric field variations are of significant interest. Herein, a DBD measurement system based on the Pockels effect is established for the first time. The proposed system can simultaneously measure the surface potentials on both sides of the dielectric, thereby obtaining the net electric field at the discharge gap. The net electric field distribution varies insignificantly with the magnitude of the applied voltage but significantly with gap length. Moreover, the breakdown electric field increases with a decreasing gap length. This study provides a physical explanation for microgap reactors, demonstrating that the electric field in a DBD can be manipulated.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"114 S144","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140731908","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}
Mechanisms of cavity resonance and antenna resonance and their coupling effect on mode transition in argon helicon plasma excited by a half-helical antenna (14 cm in length) were investigated in this paper. Cavity length was changed to distinguish the effects of cavity and antenna resonances. Plasma parameters in various conditions such as input power (0-2500 W), magnetic field (0-1000 G) and cavity length (10-42 cm) were measured. Characteristics of helicon discharges and mode transitions in cases of fixed and continuously changed cavity lengths were compared. The results show that multiple axial eigenmodes (at least five in the present work) were observed in both cases. In fixed-length cavity, helicon discharge changes abruptly during mode transitions, while in changeable-length cavity, discharge features can change continuously (e.g. in large range of density from 1.7×1012 to 1.3×1013 cm-3) without mode transition. Mode transitions also occur as the cavity length increasing at fixed input power and magnetic field with periodical variations of plasma parameters. Cavity resonance plays a dominant role in formation of standing helicon wave of eigenmodes and mode transition, while antenna resonance affects significantly the transition from inductively coupled mode to helicon wave mode. Enhanced inter-coupling of cavity resonance and antenna resonance appears at specific axial wavelengths of eigenmodes. Threshold conditions for mode transitions were deduced and the overall transition path and the corresponding density were predicted quantitatively, which shows that cavity resonance determines the transition path, while antenna resonance gives the lower limit of the path. Axial wavenumber is closely related to the helicon discharge characteristics. Cavity and antenna resonances influence the helicon discharge and mode transition by determining the axial wavenumber of eigenmodes.
{"title":"Effects of cavity resonance and antenna resonance on mode transitions in helicon plasma","authors":"Tianliang Zhang, Ying Cui, Zhangyu Xia, Bocong Zheng, Feng He, J. Ouyang","doi":"10.1088/1361-6595/ad3bea","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3bea","url":null,"abstract":"\u0000 Mechanisms of cavity resonance and antenna resonance and their coupling effect on mode transition in argon helicon plasma excited by a half-helical antenna (14 cm in length) were investigated in this paper. Cavity length was changed to distinguish the effects of cavity and antenna resonances. Plasma parameters in various conditions such as input power (0-2500 W), magnetic field (0-1000 G) and cavity length (10-42 cm) were measured. Characteristics of helicon discharges and mode transitions in cases of fixed and continuously changed cavity lengths were compared. The results show that multiple axial eigenmodes (at least five in the present work) were observed in both cases. In fixed-length cavity, helicon discharge changes abruptly during mode transitions, while in changeable-length cavity, discharge features can change continuously (e.g. in large range of density from 1.7×1012 to 1.3×1013 cm-3) without mode transition. Mode transitions also occur as the cavity length increasing at fixed input power and magnetic field with periodical variations of plasma parameters. Cavity resonance plays a dominant role in formation of standing helicon wave of eigenmodes and mode transition, while antenna resonance affects significantly the transition from inductively coupled mode to helicon wave mode. Enhanced inter-coupling of cavity resonance and antenna resonance appears at specific axial wavelengths of eigenmodes. Threshold conditions for mode transitions were deduced and the overall transition path and the corresponding density were predicted quantitatively, which shows that cavity resonance determines the transition path, while antenna resonance gives the lower limit of the path. Axial wavenumber is closely related to the helicon discharge characteristics. Cavity and antenna resonances influence the helicon discharge and mode transition by determining the axial wavenumber of eigenmodes.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140728090","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 : 2024-04-04DOI: 10.1088/1361-6595/ad3a9e
Bangfa Peng, Nan Jiang, Yifei Zhu, Jie Li, Yan Wu
The streamer dynamic evolution and discharge mode transition of three-electrode surface dielectric barrier discharge (SDBD) driven by repetitive pulses are studied experimentally and numerically for better plasma-mode controlling and optimized application. Spatial-temporal plasma morphologic features together with electro-optical behaviors are utilized to analyze the streamer dynamic evolution and streamer-to-spark transition. To have a deep insight into the physical mechanism of the discharge mode transition in repetitive pulses, a 2D fluid model combined with 0D kinetic model is built and studied. A good agreement between experimental measurements and numerical simulation in the propagation dynamics and voltage-current characteristics is achieved. Results show that the surface-streamer discharge in the form of primary and transitional streamers can transform into a surface-spark discharge characterized with the primary streamer, transitional streamer and spark phase in repetitive pulses under the high applied electric field. A high gas temperature will result in a large reduced electric field after the transitional streamer, which exceeds the ionization threshold and thus promotes the discharge mode transition. The most electrons can be released from the negative charges by oxygen atoms during the inter-pulse period, which is favor to the re-ignition and ionization process of the subsequent pulse discharge.
{"title":"Three-electrode surface dielectric barrier discharge driven by repetitive pulses: streamer dynamic evolution and discharge mode transition","authors":"Bangfa Peng, Nan Jiang, Yifei Zhu, Jie Li, Yan Wu","doi":"10.1088/1361-6595/ad3a9e","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3a9e","url":null,"abstract":"\u0000 The streamer dynamic evolution and discharge mode transition of three-electrode surface dielectric barrier discharge (SDBD) driven by repetitive pulses are studied experimentally and numerically for better plasma-mode controlling and optimized application. Spatial-temporal plasma morphologic features together with electro-optical behaviors are utilized to analyze the streamer dynamic evolution and streamer-to-spark transition. To have a deep insight into the physical mechanism of the discharge mode transition in repetitive pulses, a 2D fluid model combined with 0D kinetic model is built and studied. A good agreement between experimental measurements and numerical simulation in the propagation dynamics and voltage-current characteristics is achieved. Results show that the surface-streamer discharge in the form of primary and transitional streamers can transform into a surface-spark discharge characterized with the primary streamer, transitional streamer and spark phase in repetitive pulses under the high applied electric field. A high gas temperature will result in a large reduced electric field after the transitional streamer, which exceeds the ionization threshold and thus promotes the discharge mode transition. The most electrons can be released from the negative charges by oxygen atoms during the inter-pulse period, which is favor to the re-ignition and ionization process of the subsequent pulse discharge.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"2 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140745954","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 : 2024-03-20DOI: 10.1088/1361-6595/ad35e5
Scherezade Barquero, J. Navarro-Cavallé, M. Merino
The transient exhaust of an ablative pulsed plasma thruster is characterized experimentally for three capacitances and three discharge voltages, for discharge energies below 11 J. A novel analysis technique is introduced, which reconstructs the exhaust as a superposition of different Maxwellian-like ion groups. Each ion group is characterized by its own mean velocity, thermal spread, initial density, generation time and divergence rate. The time series of three probes working in the ion saturation regime are used to determine the value of the model parameters by least-squares fitting. This approach allows a higher level of accuracy and insight than time-of-flight analysis based on direct feature correlation alone. A good fit of the main part of the discharge time series is achieved with just three ion groups, with mean velocities ranging in 50–70, 30–45 and 10–25 km/s respectively. Each ion group differs in the lateral divergence rate and axial thermal spread, and potentially corresponds with a different charge/mass ratio and/or creation time. Some trends with bank capacitance and discharge voltage are identified and discussed.
{"title":"Pulsed plasma thruster exhaust reconstruction.","authors":"Scherezade Barquero, J. Navarro-Cavallé, M. Merino","doi":"10.1088/1361-6595/ad35e5","DOIUrl":"https://doi.org/10.1088/1361-6595/ad35e5","url":null,"abstract":"\u0000 The transient exhaust of an ablative pulsed plasma thruster is characterized experimentally for three capacitances and three discharge voltages, for discharge energies below 11 J. A novel analysis technique is introduced, which reconstructs the exhaust as a superposition of different Maxwellian-like ion groups. Each ion group is characterized by its own mean velocity, thermal spread, initial density, generation time and divergence rate. The time series of three probes working in the ion saturation regime are used to determine the value of the model parameters by least-squares fitting. This approach allows a higher level of accuracy and insight than time-of-flight analysis based on direct feature correlation alone. A good fit of the main part of the discharge time series is achieved with just three ion groups, with mean velocities ranging in 50–70, 30–45 and 10–25 km/s respectively. Each ion group differs in the lateral divergence rate and axial thermal spread, and potentially corresponds with a different charge/mass ratio and/or creation time. Some trends with bank capacitance and discharge voltage are identified and discussed.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"81 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140225113","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 : 2024-03-18DOI: 10.1088/1361-6595/ad34f7
M. Rudolph, Wahyu Diyatmika, Oliver Rattunde, Edmund Schüngel, D. Kalanov, Jörg Patscheider, André Anders
Spokes are regions of enhanced ionization in magnetron sputtering discharges that are interesting because of their role for magnetron operation and their potential effect on deposition processes. Here, we show that spokes can intentionally be generated by introducing a strong-to-weak magnetic field strength transition along the racetrack. Spokes are triggered at the transition point from an accelerating electron drift when weakening the magnetic field strength. The spokes are then propagating against the electron drift into the strong magnetic field strength section of the racetrack. At the weak-to-strong magnetic field transition, we observe the inverse effect. The electron drift is decelerated at this point, creating a region of enhanced optical emission. From rectangular racetracks this is known as the cross-corner effect. Here, we show that a corner is not necessary for observing that effect. Pronounced spokes at low working gas pressure of 0.2 Pa exhibit a substructure that could be caused by the diocotron instability previously predicted by computer simulations.
辐条是磁控溅射放电中电离增强的区域，由于其对磁控管运行的作用及其对沉积过程的潜在影响，因此非常有趣。在这里，我们展示了可以通过沿赛道引入强弱磁场强度转换来有意生成辐条。磁场强度减弱时，加速电子漂移会在过渡点触发辐条。然后，辐条逆着电子漂移传播到赛道的强磁场强度部分。在弱磁场向强磁场过渡时，我们观察到了反向效应。此时电子漂移减速，形成一个增强的光发射区域。在矩形赛道中，这种现象被称为交叉角效应。在这里，我们展示了观察这种效应并不需要拐角。在 0.2 Pa 的低工作气体压力下，发音辐条显示出一种亚结构，这种亚结构可能是由之前计算机模拟预测的二重子不稳定性引起的。
{"title":"Generating spokes in direct current magnetron sputtering discharges by an azimuthal strong-to-weak magnetic field strength transition","authors":"M. Rudolph, Wahyu Diyatmika, Oliver Rattunde, Edmund Schüngel, D. Kalanov, Jörg Patscheider, André Anders","doi":"10.1088/1361-6595/ad34f7","DOIUrl":"https://doi.org/10.1088/1361-6595/ad34f7","url":null,"abstract":"\u0000 Spokes are regions of enhanced ionization in magnetron sputtering discharges that are interesting because of their role for magnetron operation and their potential effect on deposition processes. Here, we show that spokes can intentionally be generated by introducing a strong-to-weak magnetic field strength transition along the racetrack. Spokes are triggered at the transition point from an accelerating electron drift when weakening the magnetic field strength. The spokes are then propagating against the electron drift into the strong magnetic field strength section of the racetrack. At the weak-to-strong magnetic field transition, we observe the inverse effect. The electron drift is decelerated at this point, creating a region of enhanced optical emission. From rectangular racetracks this is known as the cross-corner effect. Here, we show that a corner is not necessary for observing that effect. Pronounced spokes at low working gas pressure of 0.2 Pa exhibit a substructure that could be caused by the diocotron instability previously predicted by computer simulations.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"84 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140232270","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 : 2024-03-18DOI: 10.1088/1361-6595/ad34f8
J. Yao, Vasily Yurievich Kozhevnikov, Vladislav Igumnov, Zijia Chu, C. Yuan, Zhongxian Zhou
This paper presents a theoretical explanation for the occurrence of anomalous ion acceleration in vacuum diodes, leading to the expansion of cathode plasma towards the anode, a characteristic phenomenon of vacuum breakdown. The explanation is derived from first principles based on equations of collisionless physical kinetics, using the example of an axisymmetric vacuum diode. The proposed theoretical interpretation convincingly demonstrates that the primary mechanism behind the anomalous ion acceleration of cathode plasma is the collisionless motion of ions in a self-consistent electric field.
{"title":"The kinetic theory of cathode plasma expansion in a spatially non-uniform geometric configuration of a vacuum diode","authors":"J. Yao, Vasily Yurievich Kozhevnikov, Vladislav Igumnov, Zijia Chu, C. Yuan, Zhongxian Zhou","doi":"10.1088/1361-6595/ad34f8","DOIUrl":"https://doi.org/10.1088/1361-6595/ad34f8","url":null,"abstract":"\u0000 This paper presents a theoretical explanation for the occurrence of anomalous ion acceleration in vacuum diodes, leading to the expansion of cathode plasma towards the anode, a characteristic phenomenon of vacuum breakdown. The explanation is derived from first principles based on equations of collisionless physical kinetics, using the example of an axisymmetric vacuum diode. The proposed theoretical interpretation convincingly demonstrates that the primary mechanism behind the anomalous ion acceleration of cathode plasma is the collisionless motion of ions in a self-consistent electric field.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"226 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140233457","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 : 2024-03-08DOI: 10.1088/1361-6595/ad31b2
Hamzeh Telfah, S. Raskar, I. V. Adamovich
The absolute, spatially-resolved, and time-resolved number density of the hydroperoxyl radical is measured in a quasi-two-dimensional, atmospheric pressure “curtain” plasma jet powered by a train of ns discharge pulses. The spatial distribution of HO2 is measured across the shorter dimension of the jet. The measurements are made in two different configurations, (a) H2O-O2-He jet impinging on a copper foil target, and (b) O2-He jet incident on the liquid water surface. In the first configuration, the water vapor is added to the O2-He flow in a bubbler filled with distilled, deionized water. The measurements are made using the previously developed pulsed Cavity Ring Down Spectroscopy (CRDS) diagnostic near 1.5 μm. The ring-down cavity is formed between two high-reflectivity mirrors placed at the ends of the stainless steel “arms” purged with dry air, with the plasma jet placed in the gap between the arms. The objectives of this work are to use the HO2 number density to assess the accuracy of the modeling predictions using a previously developed “global” reaction mechanism, and to estimate the efficiency of hydrogen peroxide generation in the ns pulse discharge plasma. HO2 was detected only in the first configuration, most likely due to the rapid decay of the metastable He atoms and O atoms generated in the plasma, which prevents the generation of H atoms (dominant HO2 precursors) in the evaporation/mixing layer. Both the water vapor in the jet and HO2 generated in the plasma have been measured. The results exhibit a rapid accumulation of HO2 during the ns pulse discharge burst, followed by the decay in the afterglow on a ms time scale. The kinetic model overpredicts the quasi-steady-state HO2 number density, as well as the HO2 decay rate after the discharge is turned off. The relatively slow HO2 decay in the afterglow suggests that it may be affected by diffusion, along with the surface adsorption and desorption of radicals. The present approach demonstrates the utility of a 2-D curtain plasma jet for the line-of-sight absorption spectroscopy measurements of radicals and excited species present in small concentrations in ambient plasma environments.
{"title":"Spatially- and time-resolved measurements of HO2 radicals in a Ns pulse atmospheric pressure plasma jet","authors":"Hamzeh Telfah, S. Raskar, I. V. Adamovich","doi":"10.1088/1361-6595/ad31b2","DOIUrl":"https://doi.org/10.1088/1361-6595/ad31b2","url":null,"abstract":"\u0000 The absolute, spatially-resolved, and time-resolved number density of the hydroperoxyl radical is measured in a quasi-two-dimensional, atmospheric pressure “curtain” plasma jet powered by a train of ns discharge pulses. The spatial distribution of HO2 is measured across the shorter dimension of the jet. The measurements are made in two different configurations, (a) H2O-O2-He jet impinging on a copper foil target, and (b) O2-He jet incident on the liquid water surface. In the first configuration, the water vapor is added to the O2-He flow in a bubbler filled with distilled, deionized water. The measurements are made using the previously developed pulsed Cavity Ring Down Spectroscopy (CRDS) diagnostic near 1.5 μm. The ring-down cavity is formed between two high-reflectivity mirrors placed at the ends of the stainless steel “arms” purged with dry air, with the plasma jet placed in the gap between the arms. The objectives of this work are to use the HO2 number density to assess the accuracy of the modeling predictions using a previously developed “global” reaction mechanism, and to estimate the efficiency of hydrogen peroxide generation in the ns pulse discharge plasma. HO2 was detected only in the first configuration, most likely due to the rapid decay of the metastable He atoms and O atoms generated in the plasma, which prevents the generation of H atoms (dominant HO2 precursors) in the evaporation/mixing layer. Both the water vapor in the jet and HO2 generated in the plasma have been measured. The results exhibit a rapid accumulation of HO2 during the ns pulse discharge burst, followed by the decay in the afterglow on a ms time scale. The kinetic model overpredicts the quasi-steady-state HO2 number density, as well as the HO2 decay rate after the discharge is turned off. The relatively slow HO2 decay in the afterglow suggests that it may be affected by diffusion, along with the surface adsorption and desorption of radicals. The present approach demonstrates the utility of a 2-D curtain plasma jet for the line-of-sight absorption spectroscopy measurements of radicals and excited species present in small concentrations in ambient plasma environments.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"104 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140257055","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 : 2024-03-01DOI: 10.1088/1361-6595/ad35e6
M. Acciarri, C. Moore, L. Beving, S. Baalrud
Molecular dynamics simulations are used to test when the particle-in-cell (PIC) method applies to atmospheric pressure plasmas. It is found that PIC applies only when the plasma density and macroparticle weight are sufficiently small because of two effects associated with correlation heating. The first is the physical effect of disorder-induced heating (DIH). This occurs if the plasma density is large enough that a species (typically ions) is strongly correlated in the sense that the Coulomb coupling parameter exceeds one. In this situation, DIH causes ions to rapidly heat following ionization. PIC is not well suited to capture DIH because doing so requires using a macroparticle weight of one and a grid that well resolves the physical interparticle spacing. These criteria render PIC intractable for macroscale domains. The second effect is a numerical error due to Artificial Correlation Heating (ACH). ACH is like DIH in that it is caused by the Coulomb repulsion between particles, but differs in that it is a numerical effect caused by a macroparticle weight larger than one. Like DIH, it is associated with strong correlations. However, here the macroparticle coupling strength is found to scale as Γ w2/3, where Γ is the physical coupling strength and w is the macroparticle weight. So even if the physical coupling strength of a species is small, as is expected for electrons in atmospheric pressure plasmas, a sufficiently large macroparticle weight can cause the macroparticles to be strongly coupled and therefore heat due to ACH. Furthermore, it is shown that simulations in reduced dimensions exacerbate these issues.
{"title":"When should PIC simulations be applied to atmospheric pressure plasmas? Impact of correlation heating","authors":"M. Acciarri, C. Moore, L. Beving, S. Baalrud","doi":"10.1088/1361-6595/ad35e6","DOIUrl":"https://doi.org/10.1088/1361-6595/ad35e6","url":null,"abstract":"\u0000 Molecular dynamics simulations are used to test when the particle-in-cell (PIC) method applies to atmospheric pressure plasmas. It is found that PIC applies only when the plasma density and macroparticle weight are sufficiently small because of two effects associated with correlation heating. The first is the physical effect of disorder-induced heating (DIH). This occurs if the plasma density is large enough that a species (typically ions) is strongly correlated in the sense that the Coulomb coupling parameter exceeds one. In this situation, DIH causes ions to rapidly heat following ionization. PIC is not well suited to capture DIH because doing so requires using a macroparticle weight of one and a grid that well resolves the physical interparticle spacing. These criteria render PIC intractable for macroscale domains. The second effect is a numerical error due to Artificial Correlation Heating (ACH). ACH is like DIH in that it is caused by the Coulomb repulsion between particles, but differs in that it is a numerical effect caused by a macroparticle weight larger than one. Like DIH, it is associated with strong correlations. However, here the macroparticle coupling strength is found to scale as Γ w2/3, where Γ is the physical coupling strength and w is the macroparticle weight. So even if the physical coupling strength of a species is small, as is expected for electrons in atmospheric pressure plasmas, a sufficiently large macroparticle weight can cause the macroparticles to be strongly coupled and therefore heat due to ACH. Furthermore, it is shown that simulations in reduced dimensions exacerbate these issues.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"49 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140282698","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 : 2024-02-15DOI: 10.1088/1361-6595/ad29bf
Yiqian Li, F. Zhao, DaWei Liu, L. Nie, Xinpei Lu
Since the publication of the initial paper on atmospheric pressure plasma sterilization by Dr. Laroussi in 1996, researchers have contributed to the field with an extensive number of papers on plasma medicine. However, these studies have primarily concentrated on the biological impacts of the chemical reactive components generated by plasma, specifically focusing on the effects of reactive oxygen and nitrogen species (RONS). Conversely, when plasma directly interacts with biological organisms, there are additional physical energies involved, such as electric fields, UV/VUV radiation, heat, etc., which may also play crucial roles in their interaction. This paper delves into this aspect by using the simplest bactericidal effect as a model for biological effects. Three dielectrics—Al2O3, quartz, and MgF2 glass—are employed to isolate the chemical active components, enabling the examination of the bactericidal effects of the electric field, UV, and VUV, respectively. The findings indicate that the plasma-induced electric field can induce irreversible electroporation, effectively eliminating bacteria at 27 kV/cm. Notably, at a plasma-induced electric field of 40 kV/cm, sterilization efficiency experiences a significant enhancement. The bactericidal effects of UV and VUV are closely linked to the choice of the plasma's working gas. Specifically, when Ar is the working gas, the bactericidal effect of UV surpasses that of using only the plasma-induced electric field by two orders of magnitude, while using He results in only a one-order increase. Despite VUV radiation being considerably weaker than UV, its bactericidal effect remains substantial. In instances where He plasma is utilized, the addition of VUV doubles the bactericidal effect. In short, this paper pioneers the exploration of the biological effects of plasma's physical energy, providing essential insights for the advancement of plasma medicine.
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Pub Date : 2024-02-15DOI: 10.1088/1361-6595/ad29bf
Yiqian Li, F. Zhao, DaWei Liu, L. Nie, Xinpei Lu
Since the publication of the initial paper on atmospheric pressure plasma sterilization by Dr. Laroussi in 1996, researchers have contributed to the field with an extensive number of papers on plasma medicine. However, these studies have primarily concentrated on the biological impacts of the chemical reactive components generated by plasma, specifically focusing on the effects of reactive oxygen and nitrogen species (RONS). Conversely, when plasma directly interacts with biological organisms, there are additional physical energies involved, such as electric fields, UV/VUV radiation, heat, etc., which may also play crucial roles in their interaction. This paper delves into this aspect by using the simplest bactericidal effect as a model for biological effects. Three dielectrics—Al2O3, quartz, and MgF2 glass—are employed to isolate the chemical active components, enabling the examination of the bactericidal effects of the electric field, UV, and VUV, respectively. The findings indicate that the plasma-induced electric field can induce irreversible electroporation, effectively eliminating bacteria at 27 kV/cm. Notably, at a plasma-induced electric field of 40 kV/cm, sterilization efficiency experiences a significant enhancement. The bactericidal effects of UV and VUV are closely linked to the choice of the plasma's working gas. Specifically, when Ar is the working gas, the bactericidal effect of UV surpasses that of using only the plasma-induced electric field by two orders of magnitude, while using He results in only a one-order increase. Despite VUV radiation being considerably weaker than UV, its bactericidal effect remains substantial. In instances where He plasma is utilized, the addition of VUV doubles the bactericidal effect. In short, this paper pioneers the exploration of the biological effects of plasma's physical energy, providing essential insights for the advancement of plasma medicine.
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