Pub Date : 2024-05-12DOI: 10.1088/1361-6595/ad4587
Yu Wang, Youyou Zhou, Jian Chen, Yong Cao, Zhijiang Wang, Xiaojiang Huang and Ya Zhang
Capacitively coupled plasma (CCP) is widely used in plasma etching and deposition processes because of its low cost, simple structure, and easy generation of a uniform plasma in large areas. Conventional CCPs are operated under a fixed frequency power source; however, CCPs driven by a variable frequency power source are poorly understood. In this paper, numerical simulations of CCPs driven by frequency modulated (FM) radio frequency (RF) sources within the frequency range of 2 MHz–18 MHz are carried out with a particle-in-cell/Monte Carlo collision model. Our research indicates that the CCP driven by an FM RF source can maintain a stable glow discharge and form a time-dependent plasma. Plasma density, electron and ion current, energy and heating rate, ion flux, and energy on the electrodes fluctuate consistently with the FM period. The electron and ion energy distribution function can also be modulated by the frequency variation of the FM source. A multi-peak structure that varies and shifts with frequency variation is observed in the ion energy distribution function. In addition, by fixing the chirp period while varying the start or end frequency of the chirp signal (start frequency from 0.4 to 6 MHz, or end frequency from 18 to 48 MHz), effective modulations can be produced on the electron density, electron energy, and the shape of the EEPF and IEDF.
{"title":"Numerical characterization of capacitively coupled plasma driven by tailored frequency modulated radio frequency source","authors":"Yu Wang, Youyou Zhou, Jian Chen, Yong Cao, Zhijiang Wang, Xiaojiang Huang and Ya Zhang","doi":"10.1088/1361-6595/ad4587","DOIUrl":"https://doi.org/10.1088/1361-6595/ad4587","url":null,"abstract":"Capacitively coupled plasma (CCP) is widely used in plasma etching and deposition processes because of its low cost, simple structure, and easy generation of a uniform plasma in large areas. Conventional CCPs are operated under a fixed frequency power source; however, CCPs driven by a variable frequency power source are poorly understood. In this paper, numerical simulations of CCPs driven by frequency modulated (FM) radio frequency (RF) sources within the frequency range of 2 MHz–18 MHz are carried out with a particle-in-cell/Monte Carlo collision model. Our research indicates that the CCP driven by an FM RF source can maintain a stable glow discharge and form a time-dependent plasma. Plasma density, electron and ion current, energy and heating rate, ion flux, and energy on the electrodes fluctuate consistently with the FM period. The electron and ion energy distribution function can also be modulated by the frequency variation of the FM source. A multi-peak structure that varies and shifts with frequency variation is observed in the ion energy distribution function. In addition, by fixing the chirp period while varying the start or end frequency of the chirp signal (start frequency from 0.4 to 6 MHz, or end frequency from 18 to 48 MHz), effective modulations can be produced on the electron density, electron energy, and the shape of the EEPF and IEDF.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"155 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140928565","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 : 2024-05-12DOI: 10.1088/1361-6595/ad466f
Shun-xin Zhang, Shuo Wang, Ting-yu Yao, Miao Tian, Wei-li Fan, Fu-cheng Liu and Ya-feng He
Dust particles are often electrostatically trapped and levitated within the non-electroneutral region of a sheath. The fascinating transport phenomena of dust particles strongly depend on the plasma parameters surrounding them within the sheath, whereas, that are quite difficult to obtain, leading to an unclear understanding of particle transport mechanisms. Here, we demonstrate a tunable horizontal transport of micron-sized dust particles by precisely manipulating their vertically suspended heights in an asymmetric ratchet sheath by designing dusty plasma ratchet. A collection of dust particles serves as micro-probes to detect the height-dependent transport properties and the feature of the sheath. Two methods are employed to lift or reduce the suspended heights of dust particles while maintaining the sheath unchanged. As the suspended heights of dust particles vary, their directional transport changes accordingly, including a flow reversal. A two-dimensional model of the ratchet sheath depicts the nonlinear distributions of plasma parameters and reveals that these unexpected transport phenomena can be attributed to the dependence of the electric ratchet potential and the resulting non-equilibrium net ion drag force on the suspended heights of dust particles. Our combined experimental and theoretical study provides insights into the fundamental transport properties of dust particles in an asymmetrical sheath.
{"title":"Height-modulating horizontal transport of dust particles in a dusty plasma ratchet","authors":"Shun-xin Zhang, Shuo Wang, Ting-yu Yao, Miao Tian, Wei-li Fan, Fu-cheng Liu and Ya-feng He","doi":"10.1088/1361-6595/ad466f","DOIUrl":"https://doi.org/10.1088/1361-6595/ad466f","url":null,"abstract":"Dust particles are often electrostatically trapped and levitated within the non-electroneutral region of a sheath. The fascinating transport phenomena of dust particles strongly depend on the plasma parameters surrounding them within the sheath, whereas, that are quite difficult to obtain, leading to an unclear understanding of particle transport mechanisms. Here, we demonstrate a tunable horizontal transport of micron-sized dust particles by precisely manipulating their vertically suspended heights in an asymmetric ratchet sheath by designing dusty plasma ratchet. A collection of dust particles serves as micro-probes to detect the height-dependent transport properties and the feature of the sheath. Two methods are employed to lift or reduce the suspended heights of dust particles while maintaining the sheath unchanged. As the suspended heights of dust particles vary, their directional transport changes accordingly, including a flow reversal. A two-dimensional model of the ratchet sheath depicts the nonlinear distributions of plasma parameters and reveals that these unexpected transport phenomena can be attributed to the dependence of the electric ratchet potential and the resulting non-equilibrium net ion drag force on the suspended heights of dust particles. Our combined experimental and theoretical study provides insights into the fundamental transport properties of dust particles in an asymmetrical sheath.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140941910","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 : 2024-04-21DOI: 10.1088/1361-6595/ad3d84
J LeVan, M D Acciarri and S D Baalrud
Recent work has shown that ions are strongly coupled in atmospheric pressure plasmas when the ionization fraction is sufficiently large, leading to a temperature increase from disorder-induced heating (DIH) that is not accounted for in standard modelling techniques. Here, we extend this study to molecular plasmas. A main finding is that the energy gained by ions in DIH gets spread over both translational and rotational degrees of freedom on a nanosecond timescale, causing the final ion and neutral gas temperatures to be lower in the molecular case than in the atomic case. A model is developed for the equilibrium temperature that agrees well with molecular dynamics simulations. The model and simulations are also applied to pressures up to ten atmospheres. We conclude that DIH is a significant and predictable phenomena in molecular atmospheric pressure plasmas.
{"title":"Disorder-induced heating in molecular atmospheric pressure plasmas","authors":"J LeVan, M D Acciarri and S D Baalrud","doi":"10.1088/1361-6595/ad3d84","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3d84","url":null,"abstract":"Recent work has shown that ions are strongly coupled in atmospheric pressure plasmas when the ionization fraction is sufficiently large, leading to a temperature increase from disorder-induced heating (DIH) that is not accounted for in standard modelling techniques. Here, we extend this study to molecular plasmas. A main finding is that the energy gained by ions in DIH gets spread over both translational and rotational degrees of freedom on a nanosecond timescale, causing the final ion and neutral gas temperatures to be lower in the molecular case than in the atomic case. A model is developed for the equilibrium temperature that agrees well with molecular dynamics simulations. The model and simulations are also applied to pressures up to ten atmospheres. We conclude that DIH is a significant and predictable phenomena in molecular atmospheric pressure plasmas.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"226 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798480","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 : 2024-04-16DOI: 10.1088/1361-6595/ad3a9d
R Jean-Marie-Desiree, A Najah, C Noël, L De Poucques, S Cuynet
Time-resolved electric field strength measurements have been performed, using an electric-field induced second harmonic (E-FISH) diagnostic, in a nanosecond glow discharge of an impulse dielectric barrier discharge, in an ammonia gas environment. A temporal resolution of 2 ns and a spatial resolution estimated at 70 µm (given by laser waist) have been achieved. The comparative study of E-FISH measurements with and without a plasma discharge, operated at 4 kHz, reveal the presence of a persistent counter electric field, which is assumed to be caused by charge accumulation in between the AlN dielectrics used. Furthermore, by studying the influence of the applied voltage, the pressure, and the inter-dielectric distance, measurements seem to indicate the presence of charges remaining also in the post-discharge volume from the previous discharge to the next one.
{"title":"Time-resolved investigations of a glow mode impulse dielectric barrier discharge in pure ammonia gas by means of E-FISH diagnostic","authors":"R Jean-Marie-Desiree, A Najah, C Noël, L De Poucques, S Cuynet","doi":"10.1088/1361-6595/ad3a9d","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3a9d","url":null,"abstract":"Time-resolved electric field strength measurements have been performed, using an electric-field induced second harmonic (E-FISH) diagnostic, in a nanosecond glow discharge of an impulse dielectric barrier discharge, in an ammonia gas environment. A temporal resolution of 2 ns and a spatial resolution estimated at 70 <italic toggle=\"yes\">µ</italic>m (given by laser waist) have been achieved. The comparative study of E-FISH measurements with and without a plasma discharge, operated at 4 kHz, reveal the presence of a persistent counter electric field, which is assumed to be caused by charge accumulation in between the AlN dielectrics used. Furthermore, by studying the influence of the applied voltage, the pressure, and the inter-dielectric distance, measurements seem to indicate the presence of charges remaining also in the post-discharge volume from the previous discharge to the next one.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140613471","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 : 2024-04-12DOI: 10.1088/1361-6595/ad3a9c
K J Stevenson, T J Gilbert, T N Good, M Paul, P Shi, R Nirwan, P Srivastav, T E Steinberger, E E Scime
Experiments have demonstrated that ion phenomena, such as the lower hybrid resonance, play an important role in helicon source operation. Damping of the slow branch of the bounded whistler wave at the edge of a helicon source (i.e. the Trivelpiece-Gould mode) has been correlated with the creation of energetic electrons, heating of ions at the plasma edge, and anisotropic ion heating. Here we present ion velocity distribution function measurements, electron density and temperature measurements, and magnetic fluctuation measurements on both sides of an m=|1| helical antenna in a helicon source as a function of the driving frequency, magnetic field strength, and magnetic field orientation relative to the antenna helicity. Significant electron and ion heating (up to two times larger) occurs on the side of the antenna consistent with the launch of the m=+1 mode. The electron and ion heating occurs within one electron skin depth of the plasma edge, where slow wave damping is expected. The source parameters for enhanced particle heating are also consistent with lower hybrid resonance effects, which can only occur for Trivelpiece-Gould wave excitation.
{"title":"RF antenna helicity dependent particle heating in a helicon source","authors":"K J Stevenson, T J Gilbert, T N Good, M Paul, P Shi, R Nirwan, P Srivastav, T E Steinberger, E E Scime","doi":"10.1088/1361-6595/ad3a9c","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3a9c","url":null,"abstract":"Experiments have demonstrated that ion phenomena, such as the lower hybrid resonance, play an important role in helicon source operation. Damping of the slow branch of the bounded whistler wave at the edge of a helicon source (i.e. the Trivelpiece-Gould mode) has been correlated with the creation of energetic electrons, heating of ions at the plasma edge, and anisotropic ion heating. Here we present ion velocity distribution function measurements, electron density and temperature measurements, and magnetic fluctuation measurements on both sides of an <inline-formula>\u0000<tex-math><?CDATA $m = |1|$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi>m</mml:mi><mml:mo>=</mml:mo><mml:mrow><mml:mo stretchy=\"false\">|</mml:mo></mml:mrow><mml:mn>1</mml:mn><mml:mo stretchy=\"false\">|</mml:mo></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad3a9cieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> helical antenna in a helicon source as a function of the driving frequency, magnetic field strength, and magnetic field orientation relative to the antenna helicity. Significant electron and ion heating (up to two times larger) occurs on the side of the antenna consistent with the launch of the <inline-formula>\u0000<tex-math><?CDATA $m = +1$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi>m</mml:mi><mml:mo>=</mml:mo><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad3a9cieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> mode. The electron and ion heating occurs within one electron skin depth of the plasma edge, where slow wave damping is expected. The source parameters for enhanced particle heating are also consistent with lower hybrid resonance effects, which can only occur for Trivelpiece-Gould wave excitation.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140613814","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}
We report an ultrafast oscillation (up to ∼104 GHz) in the early stage of field emission-driven microdischarges. Spatiotemporal behaviors of electron density, space charge density, and electric field, exhibiting high-frequency oscillations, are demonstrated based on first-principle particle-in-cell/Monte Carlo collision simulations. Intermittent electron emission fluxes are identified from the electron phase space distributions whereas the ions are rather non-oscillatory in the transient timescale. The mechanisms of oscillation with growing amplitude are found to be related to the rapid modification of the field emission current affected by the space charge electric field, which is also accompanied by the fast response of the electron transport and ionization in a dynamic double-layer sheath. Further, a transport equation for emission current is solved to estimate the oscillation frequency, which agrees well with the simulation results. This study provides a more precise understanding of the formation of the field emission-driven microdischarge, which informs the design and optimization of miniaturized gaseous electronic devices.
{"title":"Ultrafast oscillation in a field emission-driven miniaturized gaseous diode","authors":"Jiandong Chen, Chubin Lin, Huihui Wang, Lay Kee Ang, Yangyang Fu","doi":"10.1088/1361-6595/ad36df","DOIUrl":"https://doi.org/10.1088/1361-6595/ad36df","url":null,"abstract":"We report an ultrafast oscillation (up to <inline-formula>\u0000<tex-math><?CDATA ${sim} 10^4$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:msup><mml:mn>10</mml:mn><mml:mn>4</mml:mn></mml:msup></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad36dfieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> GHz) in the early stage of field emission-driven microdischarges. Spatiotemporal behaviors of electron density, space charge density, and electric field, exhibiting high-frequency oscillations, are demonstrated based on first-principle particle-in-cell/Monte Carlo collision simulations. Intermittent electron emission fluxes are identified from the electron phase space distributions whereas the ions are rather non-oscillatory in the transient timescale. The mechanisms of oscillation with growing amplitude are found to be related to the rapid modification of the field emission current affected by the space charge electric field, which is also accompanied by the fast response of the electron transport and ionization in a dynamic double-layer sheath. Further, a transport equation for emission current is solved to estimate the oscillation frequency, which agrees well with the simulation results. This study provides a more precise understanding of the formation of the field emission-driven microdischarge, which informs the design and optimization of miniaturized gaseous electronic devices.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140574986","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 : 2024-03-28DOI: 10.1088/1361-6595/ad331c
Kolter Bradshaw, Bhuvana Srinivasan
The plasma-material interactions present in multiple fusion and propulsion concepts between the flow of plasma through a channel and a material wall drive the emission of secondary electrons. This emission is capable of altering the fundamental structure of the sheath region, significantly changing the expected particle fluxes to the wall. The emission spectrum is separated into two major energy regimes, a peak of elastically backscattered primary electrons at the incoming energy, and cold secondary electrons inelastically emitted directly from the material. The ability of continuum kinetic simulations to accurately represent the secondary electron emission is limited by relevant models being formulated in terms of monoenergetic particle interactions which cannot be applied directly to the discrete distribution function. As a result, rigorous implementation of energy-dependent physics is often neglected in favor of simplified, constant models. We present here a novel implementation of semi-empirical models in the boundary of continuum kinetic simulations which allows the full range of this emission to be accurately captured in physically-relevant regimes.
{"title":"Energy-dependent implementation of secondary electron emission models in continuum kinetic sheath simulations","authors":"Kolter Bradshaw, Bhuvana Srinivasan","doi":"10.1088/1361-6595/ad331c","DOIUrl":"https://doi.org/10.1088/1361-6595/ad331c","url":null,"abstract":"The plasma-material interactions present in multiple fusion and propulsion concepts between the flow of plasma through a channel and a material wall drive the emission of secondary electrons. This emission is capable of altering the fundamental structure of the sheath region, significantly changing the expected particle fluxes to the wall. The emission spectrum is separated into two major energy regimes, a peak of elastically backscattered primary electrons at the incoming energy, and cold secondary electrons inelastically emitted directly from the material. The ability of continuum kinetic simulations to accurately represent the secondary electron emission is limited by relevant models being formulated in terms of monoenergetic particle interactions which cannot be applied directly to the discrete distribution function. As a result, rigorous implementation of energy-dependent physics is often neglected in favor of simplified, constant models. We present here a novel implementation of semi-empirical models in the boundary of continuum kinetic simulations which allows the full range of this emission to be accurately captured in physically-relevant regimes.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140574904","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 : 2024-03-28DOI: 10.1088/1361-6595/ad38d6
S. C. L. Vervloedt, A. von Keudell
The in-plasma-catalytic synthesis of ammonia from nitrogen and hydrogen admixed to a helium RF plasma is studied with infrared absorption spectroscopy, optical emission spectroscopy, and through chemical kinetics modeling. Sandblasted glass is used as support for iron, platinum, and copper catalysts up to a surface temperature of 150 ○C. It is shown that the optimum ammonia production occurs at very small N2/(N2+H2) ratios with an increase of concentration with plasma power. The global kinetic modelling agrees well with the data for a variation of the N2+H2 admixture and the absorbed plasma power. The introduction of the catalyst enhances ammonia production by up to a factor of 2. Based on the comparison with the modelling, this is linked to a change in the electron kinetics due to the presence of the catalyst. It is postulated that introducing the catalyst increases the reduced electric field, because it reduces the secondary electron emission coefficient. As a result, the dissociation of N2 is stimulated, thereby enhancing the NH3 formation. These experiments show that the impact of the catalyst on the plasma performance in noble gas-diluted RF plasmas can be more important than the impact of the plasma on any catalytic surface process.
{"title":"Ammonia synthesis by plasma catalysis in an atmospheric RF helium plasma","authors":"S. C. L. Vervloedt, A. von Keudell","doi":"10.1088/1361-6595/ad38d6","DOIUrl":"https://doi.org/10.1088/1361-6595/ad38d6","url":null,"abstract":"\u0000 The in-plasma-catalytic synthesis of ammonia from nitrogen and hydrogen admixed to a helium RF plasma is studied with infrared absorption spectroscopy, optical emission spectroscopy, and through chemical kinetics modeling. Sandblasted glass is used as support for iron, platinum, and copper catalysts up to a surface temperature of 150 ○C. It is shown that the optimum ammonia production occurs at very small N2/(N2+H2) ratios with an increase of concentration with plasma power. The global kinetic modelling agrees well with the data for a variation of the N2+H2 admixture and the absorbed plasma power. The introduction of the catalyst enhances ammonia production by up to a factor of 2. Based on the comparison with the modelling, this is linked to a change in the electron kinetics due to the presence of the catalyst. It is postulated that introducing the catalyst increases the reduced electric field, because it reduces the secondary electron emission coefficient. As a result, the dissociation of N2 is stimulated, thereby enhancing the NH3 formation. These experiments show that the impact of the catalyst on the plasma performance in noble gas-diluted RF plasmas can be more important than the impact of the plasma on any catalytic surface process.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"87 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140371176","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 : 2024-03-27DOI: 10.1088/1361-6595/ad3847
H. Sekine, A. Diallo, S. Abe, Y. Raitses, Hiroyuki Koizumi
We propose the application of helium line intensity ratio spectroscopy in a low-pressure (0.3 mTorr) xenon E×B discharge at an electron temperature of $sim$2 eV and a density of 1010-1011 cm-3. We successfully identified the helium atom line emissions at 388.9, 447.1, 501.6, 504.8, and 706.5 nm with helium pressures of up to ~20 mTorr. The measured electron temperature, density, and I-V characteristics of discharge remained almost constant in all helium pressures in the present experiment, indicating the suitability of the helium gas as a diagnostic gas. The results of helium line intensity ratio spectroscopy using the line emissions at 388.9, 447.1, and 504.8 nm showed fair agreement with the Langmuir probe measurement. Considering the trade-off relationship between the disturbance introduced by the helium gas and the signal-to-noise ratio, we conclude that a helium pressure of approximately 4 mTorr (approximately 13 times the partial pressure of xenon) represents the optimal pressure range for the application of the helium LIR method to this xenon plasma. It is found that the use of the line emissions at 501.6 and 706.5 nm result in a significant disturbance in the helium line intensity ratio method due to the radiation trapping effect.
{"title":"Application of helium line intensity ratio spectroscopy to xenon plasma in E×B penning discharge","authors":"H. Sekine, A. Diallo, S. Abe, Y. Raitses, Hiroyuki Koizumi","doi":"10.1088/1361-6595/ad3847","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3847","url":null,"abstract":"\u0000 We propose the application of helium line intensity ratio spectroscopy in a low-pressure (0.3 mTorr) xenon E×B discharge at an electron temperature of $sim$2 eV and a density of 1010-1011 cm-3. We successfully identified the helium atom line emissions at 388.9, 447.1, 501.6, 504.8, and 706.5 nm with helium pressures of up to ~20 mTorr. The measured electron temperature, density, and I-V characteristics of discharge remained almost constant in all helium pressures in the present experiment, indicating the suitability of the helium gas as a diagnostic gas. The results of helium line intensity ratio spectroscopy using the line emissions at 388.9, 447.1, and 504.8 nm showed fair agreement with the Langmuir probe measurement. Considering the trade-off relationship between the disturbance introduced by the helium gas and the signal-to-noise ratio, we conclude that a helium pressure of approximately 4 mTorr (approximately 13 times the partial pressure of xenon) represents the optimal pressure range for the application of the helium LIR method to this xenon plasma. It is found that the use of the line emissions at 501.6 and 706.5 nm result in a significant disturbance in the helium line intensity ratio method due to the radiation trapping effect.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"55 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140376544","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 : 2024-03-27DOI: 10.1088/1361-6595/ad3848
Margherita Altin, P. Viegas, L. Vialetto, G. V. van Rooij, P. Diomede
Vibrational excitation of N2 beyond thermodynamic equilibrium enhances the reactivity of this molecule and the production of radicals. Experimentally measured temporal and spatial profiles of gas and vibrational temperature show that strong vibrational non-equilibrium is found in a pulsed microwave (MW) discharges at moderate pressure (25 mbar) in pure N2 outside the plasma core and as an effect of power pulsing. A 1D radial time-resolved self-consistent fluid model has been developed to study the mechanism of formation of vibrationally excited N2. In addition to the temperature maps, time-resolved measurements of spontaneous optical emission, electron density and electron temperature are used to validate the model and the choice of input power density. The model reveals two regions in the plasma: a core where chemistry is dominated by power deposition and where vibrational excitation starts within the first ~10 μs and an outer region reliant on radial transport, where vibrational excitation is activated slowly during the whole length of the pulse (200 μs). The two regions are separated by a sharp gradient in the estimated deposited power density, which is revealed to be wider than the emission intensity profile used to estimate the plasma size. The low concentration of excited species outside the core prevents the gas from heating and the reduced quenching rates prevent the destruction of vibrationally excited N2, thereby maintaining the observed high non-equilibrium.
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