Pub Date : 2023-12-14DOI: 10.1088/1361-6595/ad15af
Weisheng Cui, Li Chai, Ruobing Zhang
This paper reports a unique trumpet-shaped diffuse plasma jet (TDPJ) with a caliber exceeding 30 mm in a semi-confined environment, which is larger than the diameter of existing atmospheric pressure plasma jets (APPJs) in an open environment. The morphology of the TDPJ is attributed to the influence of the electric field on the development characteristics of ionization waves in the ambient environment. High-speed ICCD camera images show that the plasma bullets in the TDPJ have a completely different propagation trajectory compared to the APPJ. Different shapes of diffuse plasma jets can also be formed by adjusting the doping gas, which is due to the Penning ionization and consistent with the impact of the electric field. This research reveals the long-neglected effect of the electric field on ionization waves and provides a way to manipulate the morphology of plasma jets efficiently. The generation mechanism of the TDPJ can provide preliminary guidance for the effective medical treatment of plasma jets in semi-confined environments, such as human internal organs.
{"title":"Trumpet-shaped diffuse plasma jet in a semi-confined environment","authors":"Weisheng Cui, Li Chai, Ruobing Zhang","doi":"10.1088/1361-6595/ad15af","DOIUrl":"https://doi.org/10.1088/1361-6595/ad15af","url":null,"abstract":"\u0000 This paper reports a unique trumpet-shaped diffuse plasma jet (TDPJ) with a caliber exceeding 30 mm in a semi-confined environment, which is larger than the diameter of existing atmospheric pressure plasma jets (APPJs) in an open environment. The morphology of the TDPJ is attributed to the influence of the electric field on the development characteristics of ionization waves in the ambient environment. High-speed ICCD camera images show that the plasma bullets in the TDPJ have a completely different propagation trajectory compared to the APPJ. Different shapes of diffuse plasma jets can also be formed by adjusting the doping gas, which is due to the Penning ionization and consistent with the impact of the electric field. This research reveals the long-neglected effect of the electric field on ionization waves and provides a way to manipulate the morphology of plasma jets efficiently. The generation mechanism of the TDPJ can provide preliminary guidance for the effective medical treatment of plasma jets in semi-confined environments, such as human internal organs.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"385 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138974203","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 : 2023-12-13DOI: 10.1088/1361-6595/ad1513
Niklas Nawrath, Ihor Korolov, N. Bibinov, P. Awakowicz, A. Gibson
A uniform atmospheric pressure dielectric barrier discharge is operated in helium with an admixture (0.45%) of nitrogen. The discharge is ignited in the gas gap between a driven and a grounded electrode and propagates along the dielectric surface outside the gap. Plasma conditions are characterized with current and voltage measurements and by application of absolutely calibrated optical emission spectroscopy, with a focus on nitrogen molecular emission. Plasma parameters, namely electron density and reduced electric field are determined with spatial and temporal resolution in the frame of collisional-radiative model by application of calibrated intensified CCD camera and Abel inversion of measured images. The density of helium metastable states is calculated using the measured plasma parameters and successfully compared with values measured using tunable diode laser absorption spectroscopy.
{"title":"Spatio-temporal dynamics of electrons and helium metastables in uniform dielectric barrier discharges formed in He/N₂","authors":"Niklas Nawrath, Ihor Korolov, N. Bibinov, P. Awakowicz, A. Gibson","doi":"10.1088/1361-6595/ad1513","DOIUrl":"https://doi.org/10.1088/1361-6595/ad1513","url":null,"abstract":"\u0000 A uniform atmospheric pressure dielectric barrier discharge is operated in helium with an admixture (0.45%) of nitrogen. The discharge is ignited in the gas gap between a driven and a grounded electrode and propagates along the dielectric surface outside the gap. Plasma conditions are characterized with current and voltage measurements and by application of absolutely calibrated optical emission spectroscopy, with a focus on nitrogen molecular emission. Plasma parameters, namely electron density and reduced electric field are determined with spatial and temporal resolution in the frame of collisional-radiative model by application of calibrated intensified CCD camera and Abel inversion of measured images. The density of helium metastable states is calculated using the measured plasma parameters and successfully compared with values measured using tunable diode laser absorption spectroscopy.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"70 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139004621","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 : 2023-12-12DOI: 10.1088/1361-6595/ad10f0
Brian N Bayer, Sai Raskar, Igor V Adamovich, Peter J Bruggeman, Aditya Bhan
Production of vibrationally excited N2 (N2(v)) in atmospheric pressure nonthermal plasma and loss of N2(v) by gas-phase reactions and reactions on catalytic surfaces are analyzed to examine the role of N2(v) in NH3 formation by plasma catalysis. Vibrational state-to-state kinetic models complemented with molecular beam mass spectrometry (MBMS) measurements demonstrate that N2(v> 0) is produced with densities 100× greater than the density of N radicals by a radiofrequency atmospheric pressure plasma jet. The experimentally measured loss of N2(v) corresponds with a state-to-state kinetic model that describes loss of N2(v) by surface-mediated vibrational relaxation without consideration of reactions that convert N2(v) to NH3 over the catalyst surface. Rate constants for vibrational relaxation of N2(v) on catalyst surfaces exceed upper bounds on proposed rate constants for NH3 formation reactions from N2(v) over Fe when v < 9, Ni when v < 18, and Ag when v < 39, which indicates that only higher vibrational levels can possibly contribute to catalytic NH3 formation faster than they undergo vibrational relaxation on the surface. Densities of N2(v> 8), vibrational levels that can possibly react over Fe to form NH3 faster than they undergo vibrational relaxation, are less than or similar to N densities at the inlet of the catalyst bed and measured NH3 formation for the investigated conditions in this work, while densities of N2(v> 17) and N2(v> 38) are orders of magnitude below the N density at the inlet of the catalyst bed and the measured NH3 formation. The loss of N2(v) by vibrational relaxation on the surface limits the ability of N2(v) to contribute to catalytic NH3 formation and explains why N2(v) does not produce NH3 in quantities that are comparable to NH3 formation from N even though N2(v > 0) is more abundantly produced by the plasma.
{"title":"Availability and reactivity of N2(v) for NH3 synthesis by plasma catalysis","authors":"Brian N Bayer, Sai Raskar, Igor V Adamovich, Peter J Bruggeman, Aditya Bhan","doi":"10.1088/1361-6595/ad10f0","DOIUrl":"https://doi.org/10.1088/1361-6595/ad10f0","url":null,"abstract":"Production of vibrationally excited N<sub>2</sub> (N<sub>2</sub>(<italic toggle=\"yes\">v</italic>)) in atmospheric pressure nonthermal plasma and loss of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) by gas-phase reactions and reactions on catalytic surfaces are analyzed to examine the role of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) in NH<sub>3</sub> formation by plasma catalysis. Vibrational state-to-state kinetic models complemented with molecular beam mass spectrometry (MBMS) measurements demonstrate that N<sub>2</sub>(<italic toggle=\"yes\">v</italic>> 0) is produced with densities 100× greater than the density of N radicals by a radiofrequency atmospheric pressure plasma jet. The experimentally measured loss of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) corresponds with a state-to-state kinetic model that describes loss of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) by surface-mediated vibrational relaxation without consideration of reactions that convert N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) to NH<sub>3</sub> over the catalyst surface. Rate constants for vibrational relaxation of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) on catalyst surfaces exceed upper bounds on proposed rate constants for NH<sub>3</sub> formation reactions from N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) over Fe when <italic toggle=\"yes\">v</italic> < 9, Ni when <italic toggle=\"yes\">v</italic> < 18, and Ag when <italic toggle=\"yes\">v</italic> < 39, which indicates that only higher vibrational levels can possibly contribute to catalytic NH<sub>3</sub> formation faster than they undergo vibrational relaxation on the surface. Densities of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>> 8), vibrational levels that can possibly react over Fe to form NH<sub>3</sub> faster than they undergo vibrational relaxation, are less than or similar to N densities at the inlet of the catalyst bed and measured NH<sub>3</sub> formation for the investigated conditions in this work, while densities of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>> 17) and N<sub>2</sub>(<italic toggle=\"yes\">v</italic>> 38) are orders of magnitude below the N density at the inlet of the catalyst bed and the measured NH<sub>3</sub> formation. The loss of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) by vibrational relaxation on the surface limits the ability of N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) to contribute to catalytic NH<sub>3</sub> formation and explains why N<sub>2</sub>(<italic toggle=\"yes\">v</italic>) does not produce NH<sub>3</sub> in quantities that are comparable to NH<sub>3</sub> formation from N even though N<sub>2</sub>(<italic toggle=\"yes\">v</italic> > 0) is more abundantly produced by the plasma.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"71 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138682967","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 : 2023-12-11DOI: 10.1088/1361-6595/ad1421
Julien Bissonnette-Dulude, Pepijn Heirman, Sylvain Coulombe, Annemie Bogaerts, Thomas Gervais, Stephan Reuter
The use of microfluidic devices in the field of plasma-liquid interaction can unlock unique possibilities to investigate the effects of plasma-generated reactive species for environmental and biomedical applications. So far, very little simulation work has been performed on microfluidic devices in contact with a plasma source. We report on the modelling and computational simulation of physical and chemical processes taking place in a novel plasma-microfluidic platform. The main production and transport pathways of reactive species both in plasma and liquid are modelled by a novel modelling approach that combines 0D chemical kinetics and 2D transport mechanisms. This combined approach, applicable to systems where the transport of chemical species occurs in unidirectional flows at high Péclet numbers, decreases calculation times considerably compared to regular 2D simulations. It takes advantage of the low computational time of the 0D reaction models while providing spatial information through multiple plug-flow simulations to yield a quasi-2D model. The gas and liquid flow profiles are simulated entirely in 2D, together with the chemical reactions and transport of key chemical species. The model correctly predicts increased transport of hydrogen peroxide into the liquid when the microfluidic opening is placed inside the plasma effluent region, as opposed to inside the plasma region itself. Furthermore, the modelled hydrogen peroxide production and transport in the microfluidic liquid differs by less than 50% compared with experimental results. To explain this discrepancy, the limits of the 0D-2D combined approach are discussed.
{"title":"Coupling the COST reference plasma jet to a microfluidic device: a computational study","authors":"Julien Bissonnette-Dulude, Pepijn Heirman, Sylvain Coulombe, Annemie Bogaerts, Thomas Gervais, Stephan Reuter","doi":"10.1088/1361-6595/ad1421","DOIUrl":"https://doi.org/10.1088/1361-6595/ad1421","url":null,"abstract":"\u0000 The use of microfluidic devices in the field of plasma-liquid interaction can unlock unique possibilities to investigate the effects of plasma-generated reactive species for environmental and biomedical applications. So far, very little simulation work has been performed on microfluidic devices in contact with a plasma source. We report on the modelling and computational simulation of physical and chemical processes taking place in a novel plasma-microfluidic platform. The main production and transport pathways of reactive species both in plasma and liquid are modelled by a novel modelling approach that combines 0D chemical kinetics and 2D transport mechanisms. This combined approach, applicable to systems where the transport of chemical species occurs in unidirectional flows at high Péclet numbers, decreases calculation times considerably compared to regular 2D simulations. It takes advantage of the low computational time of the 0D reaction models while providing spatial information through multiple plug-flow simulations to yield a quasi-2D model. The gas and liquid flow profiles are simulated entirely in 2D, together with the chemical reactions and transport of key chemical species. The model correctly predicts increased transport of hydrogen peroxide into the liquid when the microfluidic opening is placed inside the plasma effluent region, as opposed to inside the plasma region itself. Furthermore, the modelled hydrogen peroxide production and transport in the microfluidic liquid differs by less than 50% compared with experimental results. To explain this discrepancy, the limits of the 0D-2D combined approach are discussed.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"79 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138979436","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 : 2023-12-08DOI: 10.1088/1361-6595/ad0fb0
Kazunori Takahashi, Yume Teranishi
A linear radiofrequency plasma device is constructed, where a source operating at a frequency of 13.56 MHz and a maximum power of several kW is attached to a cylindrical vacuum chamber about 1 m in length. Seven solenoids are located around the source and the chamber, providing various magnetic field configurations by changing the solenoid currents. The plasma density of the radiofrequency linear plasma device is initially characterized in uniform and convergent magnetic field configurations. A blue mode argon plasma, being inherent to the helicon or high-density discharge, is observed in the chamber downstream of the source for both configurations, while the density near the antenna is lower than that in the chamber. Furthermore, the density for the convergent magnetic field configuration is found to be larger than that for the uniform case, providing a maximum density of about 2×1019m−3. Spatiotemporal measurements of the ion saturation current reveal that the density peak is formed near the rf antenna at the initial time of the discharge and the peripheral high-density region subsequently appears downstream of the antenna, implying that the rf power is efficiently coupled with the electrons downstream of the antenna once the initial plasma is created. A few ms after turning on the rf power, the density over the whole region reduces, which seems to be due to a neutral depletion.
{"title":"Characterization of a radiofrequency linear plasma device in uniform and convergent magnetic fields","authors":"Kazunori Takahashi, Yume Teranishi","doi":"10.1088/1361-6595/ad0fb0","DOIUrl":"https://doi.org/10.1088/1361-6595/ad0fb0","url":null,"abstract":"A linear radiofrequency plasma device is constructed, where a source operating at a frequency of 13.56 MHz and a maximum power of several kW is attached to a cylindrical vacuum chamber about 1 m in length. Seven solenoids are located around the source and the chamber, providing various magnetic field configurations by changing the solenoid currents. The plasma density of the radiofrequency linear plasma device is initially characterized in uniform and convergent magnetic field configurations. A blue mode argon plasma, being inherent to the helicon or high-density discharge, is observed in the chamber downstream of the source for both configurations, while the density near the antenna is lower than that in the chamber. Furthermore, the density for the convergent magnetic field configuration is found to be larger than that for the uniform case, providing a maximum density of about <inline-formula>\u0000<tex-math><?CDATA $2times10^{19}~textrm{m}^{-3}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mn>2</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mn>19</mml:mn></mml:mrow></mml:msup><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mtext>m</mml:mtext></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:math>\u0000<inline-graphic xlink:href=\"psstad0fb0ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>. Spatiotemporal measurements of the ion saturation current reveal that the density peak is formed near the rf antenna at the initial time of the discharge and the peripheral high-density region subsequently appears downstream of the antenna, implying that the rf power is efficiently coupled with the electrons downstream of the antenna once the initial plasma is created. A few ms after turning on the rf power, the density over the whole region reduces, which seems to be due to a neutral depletion.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138683155","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 : 2023-12-08DOI: 10.1088/1361-6595/ad13a3
A. Saifutdinov, Elena Kustova
The present study deals with numerical simulations of microwave discharges in nitrogen based on extended fluid-dynamic model. The set of governing equations for non-equilibrium gas-discharge plasma includes conservation equations for species number densities, electron energy density, Poisson equation for the electric field coupled to the multi-temperature Navier--Stokes fluid-dynamic equations taking into account thermal nonequilibrium; the power transmitted from microwave radiation to electrons is determined from the Helmholtz equation. The kinetic scheme includes 62 reactions involving neutral molecules and atoms in the ground and electronically excited states, ions and electrons. The set of equations is solved for a two-dimensional problem under conditions of experiments at a pressure of 40 and 50~Torr and different electromagnetic wave frequencies and pulse duration. The dynamics of discharge formation and transition from the diffuse to the filament form is studied. The results are compared with experimental data, and a good agreement is shown for the time larger than 10~$mu$s. The possible reasons for discrepancies at a shorter time are discussed and the effect of small oxygen impurities on the quantitative characteristics of the discharge are evaluated. The presence of a small oxygen impurity and seed electrons in the region of discharge formation yields a better agreement between numerical and experimental data.
{"title":"Simulation of filamentation dynamics of microwave discharge in nitrogen","authors":"A. Saifutdinov, Elena Kustova","doi":"10.1088/1361-6595/ad13a3","DOIUrl":"https://doi.org/10.1088/1361-6595/ad13a3","url":null,"abstract":"\u0000 The present study deals with numerical simulations of microwave discharges in nitrogen based on extended fluid-dynamic model. The set of governing equations for non-equilibrium gas-discharge plasma includes conservation equations for species number densities, electron energy density, Poisson equation for the electric field coupled to the multi-temperature Navier--Stokes fluid-dynamic equations taking into account thermal nonequilibrium; the power transmitted from microwave radiation to electrons is determined from the Helmholtz equation. The kinetic scheme includes 62 reactions involving neutral molecules and atoms in the ground and electronically excited states, ions and electrons. The set of equations is solved for a two-dimensional problem under conditions of experiments at a pressure of 40 and 50~Torr and different electromagnetic wave frequencies and pulse duration. The dynamics of discharge formation and transition from the diffuse to the filament form is studied. The results are compared with experimental data, and a good agreement is shown for the time larger than 10~$mu$s. The possible reasons for discrepancies at a shorter time are discussed and the effect of small oxygen impurities on the quantitative characteristics of the discharge are evaluated. The presence of a small oxygen impurity and seed electrons in the region of discharge formation yields a better agreement between numerical and experimental data.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"41 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138588731","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 : 2023-12-07DOI: 10.1088/1361-6595/ad0fb1
M Osca Engelbrecht, C P Ridgers, J Dedrick, R Boswell
High frequency (HF) capacitively coupled plasmas (CCPs) are ubiquitous, having several industrial applications, especially in the semiconductor industry. Inductive heating effects within these plasmas play an important role and therefore understanding them is key to improve industrial applications. For this purpose kinetic research, using particle-in-cell (PIC) codes, offers significant opportunity to study, and improve, industrial plasma processes that operate at the atomic level. However, PIC codes commonly used for CCPs are electrostatic and thus cannot be used to simulate electromagnetically induced currents. Therefore we have developed EPOCH-LTP, a 1D PIC code with a current heating model, that enables the simulation of inductive heating effects in HF CCPs. First simulation results, from an HF CCP (60 MHz) operated at 1 mTorr of argon, show that inductive currents couple most of their power to the electrons at the interface between the bulk plasma and the sheath. Furthermore, the simulation of a dual-frequency CCP, where a HF inductive current and a low-frequency (LF) voltage waveform at 400 kHz are applied, have shown a synergy between the HF and LF waveforms that increase the inductive heating rate.
{"title":"Particle-in-cell simulations of high frequency capacitively coupled plasmas including spatially localised inductive-like heating","authors":"M Osca Engelbrecht, C P Ridgers, J Dedrick, R Boswell","doi":"10.1088/1361-6595/ad0fb1","DOIUrl":"https://doi.org/10.1088/1361-6595/ad0fb1","url":null,"abstract":"High frequency (HF) capacitively coupled plasmas (CCPs) are ubiquitous, having several industrial applications, especially in the semiconductor industry. Inductive heating effects within these plasmas play an important role and therefore understanding them is key to improve industrial applications. For this purpose kinetic research, using particle-in-cell (PIC) codes, offers significant opportunity to study, and improve, industrial plasma processes that operate at the atomic level. However, PIC codes commonly used for CCPs are electrostatic and thus cannot be used to simulate electromagnetically induced currents. Therefore we have developed EPOCH-LTP, a 1D PIC code with a current heating model, that enables the simulation of inductive heating effects in HF CCPs. First simulation results, from an HF CCP (60 MHz) operated at 1 mTorr of argon, show that inductive currents couple most of their power to the electrons at the interface between the bulk plasma and the sheath. Furthermore, the simulation of a dual-frequency CCP, where a HF inductive current and a low-frequency (LF) voltage waveform at 400 kHz are applied, have shown a synergy between the HF and LF waveforms that increase the inductive heating rate.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"197 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138683030","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 : 2023-12-06DOI: 10.1088/1361-6595/ad12dd
D. Levko, V. Subramaniam, L. Raja
The mechanism of gas heating in low-pressure inductively coupled chlorine plasma is analyzed using a self-consistent two-dimensional axisymmetric fluid plasma model that is coupled with the compressible Navier-Stokes equations. For gas pressures of 10 and 20 mTorr and the discharge powers in the range 0.1 – 1.3 kW, the main reactions contributing to gas heating were the ion-ion recombination reactions and the quenching of electronically excited chlorine atoms. At the same time, the energy released by the electron impact dissociation reaction of molecular chlorine is negligible due to its high degree of dissociation within the plasma bulk. The comparison between the results of our simulations and the fitting equation proposed in the literature show qualitative agreement, although there is significant quantitative discrepancy.
{"title":"Gas heating by inductively coupled low-pressure chlorine process plasmas","authors":"D. Levko, V. Subramaniam, L. Raja","doi":"10.1088/1361-6595/ad12dd","DOIUrl":"https://doi.org/10.1088/1361-6595/ad12dd","url":null,"abstract":"\u0000 The mechanism of gas heating in low-pressure inductively coupled chlorine plasma is analyzed using a self-consistent two-dimensional axisymmetric fluid plasma model that is coupled with the compressible Navier-Stokes equations. For gas pressures of 10 and 20 mTorr and the discharge powers in the range 0.1 – 1.3 kW, the main reactions contributing to gas heating were the ion-ion recombination reactions and the quenching of electronically excited chlorine atoms. At the same time, the energy released by the electron impact dissociation reaction of molecular chlorine is negligible due to its high degree of dissociation within the plasma bulk. The comparison between the results of our simulations and the fitting equation proposed in the literature show qualitative agreement, although there is significant quantitative discrepancy.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138597712","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 : 2023-12-06DOI: 10.1088/1361-6595/ad0f47
Michael Hinshelwood, Gottlieb S Oehrlein
Atmospheric pressure non-equilibrium plasmas can form nitrogen oxide (NOx) compounds directly from nitrogen and oxygen without a catalyst, and at lower catalyst temperatures than would be possible without plasma. In this work, the oxidation of plasma-produced NO from an Ar/N2/O2 non-equilibrium atmospheric-pressure plasma-jet (APPJ) over a platinum-on-alumina powder catalyst was investigated with in-situ infrared spectroscopy. Products downstream of the catalyst bed were analyzed along with catalyst surface species. The catalyst was exposed to plasma at both constant temperature and a cyclic temperature ramp in order to study long-lasting and transient surface changes. Primary incident reactive species to the catalyst were assessed to be NO and O3. Pt-Al2O3 at 350 °C increased oxidation of NO relative to Al2O3 or an empty chamber. The surface state of Pt-Al2O3 evolves during plasma-effluent exposure and requires upwards of 20 min exposure for stabilization compared to Al2O3. Once stable surface conditions are achieved, thermal cycling reveals a repeatable hysteresis pattern in downstream products. At low temperature, oxygen and NOx accumulate on the catalyst surface and react at elevated temperatures to form NO2. Increasing plasma power and O2:N2 ratio increases the hysteresis of the heating relative to the cooling curves in the pattern of NO2 formation. The limitation on NO oxidation at high temperatures was assessed to be Pt-O which is depleted as the catalyst is heated. Once stored species have been depleted, NO oxidation rates are determined by incoming reactants. Two overlapping NO oxidation patterns are identified, one determined by surface reactants formed at low temperature, and the other by reactants arriving at the surface at high temperature. The plasma is responsible for providing the reactants to the catalyst surface, while the catalyst enables reaction at high temperature or storage at low temperature for subsequent reaction.
常压非平衡等离子体可以在没有催化剂的情况下直接从氮气和氧气中生成氧化氮（NOx）化合物，而且催化剂温度比没有等离子体时更低。在这项研究中，使用原位红外光谱法研究了 Ar/N2/O2 非平衡常压等离子体喷射（APPJ）在铂-氧化铝粉末催化剂上等离子体生成的氮氧化物的氧化过程。在分析催化剂床层下游产物的同时，还分析了催化剂表面的物种。催化剂暴露在恒温和循环温度斜坡的等离子体中，以研究长期和瞬时的表面变化。经评估，催化剂的主要入射反应物为 NO 和 O3。与 Al2O3 或空腔相比，350 ℃ 下的 Pt-Al2O3 增加了 NO 的氧化。与 Al2O3 相比，Pt-Al2O3 的表面状态在等离子体流出物暴露过程中不断变化，需要 20 分钟以上的暴露时间才能稳定下来。一旦达到稳定的表面状态，热循环就会在下游产品中显示出可重复的滞后模式。在低温条件下，氧气和氮氧化物会在催化剂表面聚集，并在高温下反应生成二氧化氮。增加等离子体功率和 O2:N2 比率会增加二氧化氮形成模式中加热曲线相对于冷却曲线的滞后性。据评估，NO 在高温下氧化的限制因素是 Pt-O，它会随着催化剂的加热而耗尽。一旦储存的物种耗尽，NO 氧化速率将由进入的反应物决定。确定了两种重叠的 NO 氧化模式，一种由低温下形成的表面反应物决定，另一种由高温下到达表面的反应物决定。等离子体负责向催化剂表面提供反应物，而催化剂则可在高温下进行反应或在低温下储存以进行后续反应。
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Pub Date : 2023-12-06DOI: 10.1088/1361-6595/ad0edf
Wensheng Zhao, Qizhen Hong, Chao Yang, Quanhua Sun, Yuan Hu
The current work presents the collision integral data for N(4S)–N(4S, 2D, 2P) and O(3P, 1D, 1S)–O(3P, 1D, 1S) interactions in the temperature range of 500–50 000 K. The collision integrals are calculated based on high-quality potential energy curves (PECs) obtained from fitting the high-level abinitio calculation data in a wide energy range to the neural network (NN) functions. In the construction of PECs, the diabatic PECs are adopted when avoided crossings exist because the diabatic paths are much more likely to be followed for such situations. Moreover, the nonadiabatic transition effects are estimated to be negligible for PECs crossings. The accuracy of traditional analytical formulas to fit PECs are also examined. It is found that the collision integral calculations are sensitive to the accuracy of PECs and the NN based PECs overwhelm the others. The contribution of inelastic excitation exchange processes to the diffusion collision integrals are also computed by using an accurate evaluation of the differences of PECs for gerade and ungerade pairs of excited atoms. Finally, based on the new collision integral data, we calibrate the collision model parameters suitable for the widely used particle simulation methods. The collision integrals and collision models developed in this work can be used to support high-confidence simulations of weakly ionized air plasma problems.
本研究介绍了在 500-50 000 K 温度范围内 N(4S)-N(4S，2D，2P) 和 O(3P，1D，1S)-O(3P，1D，1S) 相互作用的碰撞积分数据。碰撞积分是根据神经网络（NN）函数在宽能量范围内拟合高水平 ab initio 计算数据而得到的高质量势能曲线（PEC）计算的。在构建势能曲线时，如果存在避免交叉的情况，则采用二消旋势能曲线，因为在这种情况下，二消旋路径更有可能被遵循。此外，据估计，非绝热过渡效应在 PECs 交叉时可以忽略不计。此外，还考察了拟合 PEC 的传统分析公式的准确性。结果发现，碰撞积分计算对 PECs 的准确性非常敏感，而基于 NN 的 PECs 则压倒了其他公式。通过精确评估激发原子对的gerade 和 ungerade 的 PECs 差异，还计算了非弹性激发交换过程对扩散碰撞积分的贡献。最后，根据新的碰撞积分数据，我们校准了适用于广泛使用的粒子模拟方法的碰撞模型参数。本研究开发的碰撞积分和碰撞模型可用于支持弱电离空气等离子体问题的高可信度模拟。
{"title":"Collision integrals of electronically excited atoms in air plasmas. I. N–N and O–O interactions","authors":"Wensheng Zhao, Qizhen Hong, Chao Yang, Quanhua Sun, Yuan Hu","doi":"10.1088/1361-6595/ad0edf","DOIUrl":"https://doi.org/10.1088/1361-6595/ad0edf","url":null,"abstract":"The current work presents the collision integral data for N(<sup>4</sup>\u0000<italic toggle=\"yes\">S</italic>)–N(<sup>4</sup>\u0000<italic toggle=\"yes\">S</italic>, <sup>2</sup>\u0000<italic toggle=\"yes\">D</italic>, <sup>2</sup>\u0000<italic toggle=\"yes\">P</italic>) and O(<sup>3</sup>\u0000<italic toggle=\"yes\">P</italic>, <sup>1</sup>\u0000<italic toggle=\"yes\">D</italic>, <sup>1</sup>\u0000<italic toggle=\"yes\">S</italic>)–O(<sup>3</sup>\u0000<italic toggle=\"yes\">P</italic>, <sup>1</sup>\u0000<italic toggle=\"yes\">D</italic>, <sup>1</sup>\u0000<italic toggle=\"yes\">S</italic>) interactions in the temperature range of 500–50 000 K. The collision integrals are calculated based on high-quality potential energy curves (PECs) obtained from fitting the high-level <inline-formula>\u0000<tex-math><?CDATA $ab~initio$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>a</mml:mi><mml:mi>b</mml:mi><mml:mtext> </mml:mtext><mml:mi>i</mml:mi><mml:mi>n</mml:mi><mml:mi>i</mml:mi><mml:mi>t</mml:mi><mml:mi>i</mml:mi><mml:mi>o</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"psstad0edfieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> calculation data in a wide energy range to the neural network (NN) functions. In the construction of PECs, the diabatic PECs are adopted when avoided crossings exist because the diabatic paths are much more likely to be followed for such situations. Moreover, the nonadiabatic transition effects are estimated to be negligible for PECs crossings. The accuracy of traditional analytical formulas to fit PECs are also examined. It is found that the collision integral calculations are sensitive to the accuracy of PECs and the NN based PECs overwhelm the others. The contribution of inelastic excitation exchange processes to the diffusion collision integrals are also computed by using an accurate evaluation of the differences of PECs for <italic toggle=\"yes\">gerade</italic> and <italic toggle=\"yes\">ungerade</italic> pairs of excited atoms. Finally, based on the new collision integral data, we calibrate the collision model parameters suitable for the widely used particle simulation methods. The collision integrals and collision models developed in this work can be used to support high-confidence simulations of weakly ionized air plasma problems.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138683092","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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