Pub Date : 2024-01-03DOI: 10.1088/1361-6595/ad1a79
S. Rogers, A. Bond, R. Peverall, G. Hancock, Grant Ritchie
Cavity ringdown spectroscopy (CRDS) has been used to investigate the translational and rotational temperatures of the v = 0 and 1 vibrational levels of O2(X) in an inductively coupled plasma at 100 mTorr (13.332 Pa) pressure. All rotational states probed display a clear increase in temperature as plasma power increases: at fixed power, the translational temperature appears largest for rotational states in v = 1 (J = 7, 16, 17, 22) and lowest in the low energy states (J = 1, 18, 19) in v = 0; highly excited rotational states (J = 28, 30, 31) of v = 0 show intermediate behaviour. The rotational temperature values behave similarly. These observations are consistent with the effects of plasma inhomogeneity and can be interpreted with a simple one-dimensional model whereby the pressure, temperature and mole fractions of the various species across the chamber (and arms) are approximated with rational profiles and the corresponding line-of-sight averaged densities and temperatures calculated. This basic model is reasonably successful at reproducing the observations for O2(X, v = 0) and O(3P) densities. The fact that resolving several rotational transitions allows spatial variations within the plasma to be inferred from line-of-sight averaged measurements is an extremely powerful result that could be of great utility in future work.
{"title":"Insights into spatial inhomogeneity in an oxygen plasma from cavity ringdown spectroscopy","authors":"S. Rogers, A. Bond, R. Peverall, G. Hancock, Grant Ritchie","doi":"10.1088/1361-6595/ad1a79","DOIUrl":"https://doi.org/10.1088/1361-6595/ad1a79","url":null,"abstract":"\u0000 Cavity ringdown spectroscopy (CRDS) has been used to investigate the translational and rotational temperatures of the v = 0 and 1 vibrational levels of O2(X) in an inductively coupled plasma at 100 mTorr (13.332 Pa) pressure. All rotational states probed display a clear increase in temperature as plasma power increases: at fixed power, the translational temperature appears largest for rotational states in v = 1 (J = 7, 16, 17, 22) and lowest in the low energy states (J = 1, 18, 19) in v = 0; highly excited rotational states (J = 28, 30, 31) of v = 0 show intermediate behaviour. The rotational temperature values behave similarly. These observations are consistent with the effects of plasma inhomogeneity and can be interpreted with a simple one-dimensional model whereby the pressure, temperature and mole fractions of the various species across the chamber (and arms) are approximated with rational profiles and the corresponding line-of-sight averaged densities and temperatures calculated. This basic model is reasonably successful at reproducing the observations for O2(X, v = 0) and O(3P) densities. The fact that resolving several rotational transitions allows spatial variations within the plasma to be inferred from line-of-sight averaged measurements is an extremely powerful result that could be of great utility in future work.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"14 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389264","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}
The presence of water molecules in air introduces complexities to residual charge transports and energy relaxations that may provoke streamer discharge instabilities under repetitive pulses. Evolutions of pulse-periodic positive streamer dynamics were investigated in humid air. Pulse-sequence and temporally resolved diagnostics were implemented to capture discharge evolutions. The streamer development and evolutions of charged species in humid air are qualitatively analyzed based on a 2D–0D combined simulation. Evolution features of streamer behaviors in humid air include the faster filamentation of the primary streamer, pronounced propagation selectivity to previous secondary streamers, more branches of both primary and secondary streamers, and accelerated secondary streamer into stagnation. The repetitively pulsed breakdown is proceeded by the progressive axial prolongation of secondary streamers with bright heads and faint tails. Nonintuitively, the withstanding capability does not illustrate dramatic differences in dry air and humid air especially at high pulse repetition frequency. High-density residing hydrated ions with high electron bound energies (impeding streamer propagation) and the enhanced thermal release to cause higher reduced electric field (facilitating streamer propagation) may contrarily affect evolutions and discharge instability developments of positive streamer in humid air.
{"title":"Evolutions of streamer dynamics and discharge instabilities under repetitive pulses in humid air","authors":"Zheng Zhao, Qiuyu Gao, Xinlei Zheng, Haowei Zhang, Haotian Zheng, Anbang Sun, Jiangtao Li","doi":"10.1088/1361-6595/ad0d08","DOIUrl":"https://doi.org/10.1088/1361-6595/ad0d08","url":null,"abstract":"The presence of water molecules in air introduces complexities to residual charge transports and energy relaxations that may provoke streamer discharge instabilities under repetitive pulses. Evolutions of pulse-periodic positive streamer dynamics were investigated in humid air. Pulse-sequence and temporally resolved diagnostics were implemented to capture discharge evolutions. The streamer development and evolutions of charged species in humid air are qualitatively analyzed based on a 2D–0D combined simulation. Evolution features of streamer behaviors in humid air include the faster filamentation of the primary streamer, pronounced propagation selectivity to previous secondary streamers, more branches of both primary and secondary streamers, and accelerated secondary streamer into stagnation. The repetitively pulsed breakdown is proceeded by the progressive axial prolongation of secondary streamers with bright heads and faint tails. Nonintuitively, the withstanding capability does not illustrate dramatic differences in dry air and humid air especially at high pulse repetition frequency. High-density residing hydrated ions with high electron bound energies (impeding streamer propagation) and the enhanced thermal release to cause higher reduced electric field (facilitating streamer propagation) may contrarily affect evolutions and discharge instability developments of positive streamer in humid air.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139051136","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 : 2023-12-19DOI: 10.1088/1361-6595/ad171d
Ho Jun Kim, Kyungjun Lee, Hwanyeol Park
This paper presents the results of our numerical analysis to optimize the dielectric properties to achieve process uniformity in the thin film deposition process using capacitively coupled plasma. The difference in the plasma density distribution was analyzed by changing the wafer material from silicon to quartz (or Teflon). Similarly, aluminum was compared with aluminum nitride as the electrode material, and the sidewall material was varied from quartz to a perfect dielectric to study the effect on the plasma characteristics. A two-dimensional self-consistent fluid model was used to analyze the spatial distribution of the plasma parameters. In terms of the process conditions, the gas pressure was set to 400 Pa, the input power was fixed to 100 W, and a radio frequency of 13.56 MHz was used. SiH4/Ar was used as the gas mixture, and these conditions were used as input for numerical simulations of the deposition state of the hydrogenated amorphous silicon layer. The radial spatial distribution of plasma parameters was confirmed to be modified by dielectric elements with low dielectric constants regardless of the type of element. Despite the thin wafer thickness, the use of a wafer with low permittivity weakens the electric field near the electrode edge due to the stronger surface charge effect. Additionally, by changing the material of the sidewall to a perfect dielectric, a more uniform distribution of plasma could be obtained. This is achieved as the peak values of the plasma parameters are located away from the wafer edge. Interestingly, the case in which half of the sidewall was specified as comprising a perfect dielectric and the other half quartz had a more uniform distribution than the case in which the sidewalls consisted entirely of a perfect dielectric.
{"title":"Numerical optimization of dielectric properties to achieve process uniformity in capacitively coupled plasma reactors","authors":"Ho Jun Kim, Kyungjun Lee, Hwanyeol Park","doi":"10.1088/1361-6595/ad171d","DOIUrl":"https://doi.org/10.1088/1361-6595/ad171d","url":null,"abstract":"\u0000 This paper presents the results of our numerical analysis to optimize the dielectric properties to achieve process uniformity in the thin film deposition process using capacitively coupled plasma. The difference in the plasma density distribution was analyzed by changing the wafer material from silicon to quartz (or Teflon). Similarly, aluminum was compared with aluminum nitride as the electrode material, and the sidewall material was varied from quartz to a perfect dielectric to study the effect on the plasma characteristics. A two-dimensional self-consistent fluid model was used to analyze the spatial distribution of the plasma parameters. In terms of the process conditions, the gas pressure was set to 400 Pa, the input power was fixed to 100 W, and a radio frequency of 13.56 MHz was used. SiH4/Ar was used as the gas mixture, and these conditions were used as input for numerical simulations of the deposition state of the hydrogenated amorphous silicon layer. The radial spatial distribution of plasma parameters was confirmed to be modified by dielectric elements with low dielectric constants regardless of the type of element. Despite the thin wafer thickness, the use of a wafer with low permittivity weakens the electric field near the electrode edge due to the stronger surface charge effect. Additionally, by changing the material of the sidewall to a perfect dielectric, a more uniform distribution of plasma could be obtained. This is achieved as the peak values of the plasma parameters are located away from the wafer edge. Interestingly, the case in which half of the sidewall was specified as comprising a perfect dielectric and the other half quartz had a more uniform distribution than the case in which the sidewalls consisted entirely of a perfect dielectric.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":" 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138960794","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 : 2023-12-19DOI: 10.1088/1361-6595/ad171c
K. Konina, S. Raskar, Igor V Adamovich, M. Kushner
Atmospheric pressure plasma jets (APPJs) are increasingly being used to functionalize polymers and dielectric materials for biomedical and biotechnology applications. Once such application is microfluidic labs-on-a-chip consisting of dielectric slabs with microchannel grooves hundreds of microns in width and depth. The periodic channels, an example of a complex surface, present challenges in terms of directly and uniformly exposing the surface to the plasma. In this paper, we discuss results from computational and experimental investigations of negative APPJs sustained in Ar/N2 mixtures flowing into ambient air and incident onto a series of microchannels. Results from 2-dimensional plasma hydrodynamics modeling are compared to experimental measurements of electric field and fast-camera imaging. The propagation of the plasma across dry microchannels largely consists of a sequence of surface ionization waves (SIWs) on the top ridges of the channels and bulk ionization waves (IWs) crossing over the channels. The IWs are directed into electric field enhanced vertices of the next ridge. The charging of these ridges produce reverse IWs responsible for the majority of the ionization. The propagation of the plasma across water filled microchannels evolve into hopping SIWs between the leading edges of the water channels, regions of electric enhancement due to polarization of the water. Positive, reverse IWs follow the pre-ionized path of the initial negative waves.
{"title":"Atmospheric Pressure Plasmas Interacting with Wet and Dry Microchannels: Reverse Surface Ionization Waves","authors":"K. Konina, S. Raskar, Igor V Adamovich, M. Kushner","doi":"10.1088/1361-6595/ad171c","DOIUrl":"https://doi.org/10.1088/1361-6595/ad171c","url":null,"abstract":"\u0000 Atmospheric pressure plasma jets (APPJs) are increasingly being used to functionalize polymers and dielectric materials for biomedical and biotechnology applications. Once such application is microfluidic labs-on-a-chip consisting of dielectric slabs with microchannel grooves hundreds of microns in width and depth. The periodic channels, an example of a complex surface, present challenges in terms of directly and uniformly exposing the surface to the plasma. In this paper, we discuss results from computational and experimental investigations of negative APPJs sustained in Ar/N2 mixtures flowing into ambient air and incident onto a series of microchannels. Results from 2-dimensional plasma hydrodynamics modeling are compared to experimental measurements of electric field and fast-camera imaging. The propagation of the plasma across dry microchannels largely consists of a sequence of surface ionization waves (SIWs) on the top ridges of the channels and bulk ionization waves (IWs) crossing over the channels. The IWs are directed into electric field enhanced vertices of the next ridge. The charging of these ridges produce reverse IWs responsible for the majority of the ionization. The propagation of the plasma across water filled microchannels evolve into hopping SIWs between the leading edges of the water channels, regions of electric enhancement due to polarization of the water. Positive, reverse IWs follow the pre-ionized path of the initial negative waves.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":" 48","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138962132","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 : 2023-12-18DOI: 10.1088/1361-6595/ad0ede
Fatima Jenina Arellano, Márton Gyulai, Zoltán Donkó, Peter Hartmann, Tsanko V Tsankov, Uwe Czarnetzki, Satoshi Hamaguchi
Various spectral line emissions are often used for the experimental characterization of low-temperature plasmas. For a better understanding of the relation between the plasma characteristics and optical emission spectra, first-principle numerical simulations for low-pressure radio-frequency driven capacitively-coupled plasmas (CCPs) of argon have been performed by coupling one-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) simulations with a global collisional-radiative model (CRM). The only ionization and excitation mechanisms included in the PIC/MCC simulations of this study are the electron-impact ionization and excitations of the ground-state Ar atoms, as done commonly, whereas the electron-impact ionization of metastable states and other ionization mechanisms are also included in the CRM to account for the optical emission spectra. The PIC/MCC coupled CRM provides the emission spectra, which are then compared with experimental data obtained from the corresponding Ar CCPs with a gas pressure ranging from 2 Pa to 100 Pa. The comparison has shown good agreement for pressures up to about 20 Pa but increasingly notable deviations at higher pressures. The deviation is ascribed to the missing consistency between the PIC/MCC simulations and CRM at higher pressures, where the ionization from the metastable states is more dominant than that from the ground states, indicating a significant change in the electron energy distribution function due to the electron collisions with excited Ar atoms at higher pressures.
低温等离子体的实验表征通常使用各种光谱线发射。为了更好地理解等离子体特性与光学发射光谱之间的关系，通过将一维粒子入胞/蒙特卡洛碰撞（PIC/MCC）模拟与全局碰撞辐射模型（CRM）相结合，对氩的低压射频驱动电容耦合等离子体（CCPs）进行了第一原理数值模拟。本研究的 PIC/MCC 模拟只包括基态氩原子的电子撞击电离和激发机制，这也是常用的方法，而在 CRM 中还包括了逸散态的电子撞击电离和其他电离机制，以解释光学发射光谱。PIC/MCC 耦合 CRM 提供了发射光谱，然后将其与从相应的氩气 CCP（气体压力范围为 2 Pa 至 100 Pa）中获得的实验数据进行比较。比较结果表明，在最高约 20 Pa 的压力下，两者的一致性很好，但在更高压力下，偏差越来越明显。出现偏差的原因是 PIC/MCC 模拟与 CRM 在较高压力下的一致性缺失，在较高压力下，来自逸散态的电离比来自基态的电离更主要，这表明在较高压力下电子与激发的 Ar 原子碰撞导致电子能量分布函数发生了显著变化。
{"title":"First-principles simulation of optical emission spectra for low-pressure argon plasmas and its experimental validation","authors":"Fatima Jenina Arellano, Márton Gyulai, Zoltán Donkó, Peter Hartmann, Tsanko V Tsankov, Uwe Czarnetzki, Satoshi Hamaguchi","doi":"10.1088/1361-6595/ad0ede","DOIUrl":"https://doi.org/10.1088/1361-6595/ad0ede","url":null,"abstract":"Various spectral line emissions are often used for the experimental characterization of low-temperature plasmas. For a better understanding of the relation between the plasma characteristics and optical emission spectra, first-principle numerical simulations for low-pressure radio-frequency driven capacitively-coupled plasmas (CCPs) of argon have been performed by coupling one-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) simulations with a global collisional-radiative model (CRM). The only ionization and excitation mechanisms included in the PIC/MCC simulations of this study are the electron-impact ionization and excitations of the ground-state Ar atoms, as done commonly, whereas the electron-impact ionization of metastable states and other ionization mechanisms are also included in the CRM to account for the optical emission spectra. The PIC/MCC coupled CRM provides the emission spectra, which are then compared with experimental data obtained from the corresponding Ar CCPs with a gas pressure ranging from 2 Pa to 100 Pa. The comparison has shown good agreement for pressures up to about 20 Pa but increasingly notable deviations at higher pressures. The deviation is ascribed to the missing consistency between the PIC/MCC simulations and CRM at higher pressures, where the ionization from the metastable states is more dominant than that from the ground states, indicating a significant change in the electron energy distribution function due to the electron collisions with excited Ar atoms at higher pressures.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139055546","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 : 2023-12-18DOI: 10.1088/1361-6595/ad1014
Jing-Yu Sun, Xing Chen, Kai Zhao, Cheng Yuan, Xiao-Yong Lu, Fei Gao, You-Nian Wang
In this study, two-dimensional kinetic particle simulations were employed to examine the potential of radio-frequency (rf) plasma heating in enhancing ion extraction efficiency in a decaying plasma with the configuration of parallel plates. The numerical results suggest that the application of rf power based on the direct current electrostatic method leads to a remarkable increase in the ion extraction flux, thereby reducing the time required for ion extraction. The increase in the ion extraction flux is attributed to the enhancement of the penetration ability of the rf electric field into the plasma, especially in cases of high rf frequencies, which can elevate the bulk electron temperature to approach 10 eV. The propagation speed of ion rarefaction waves is enhanced by the increased electron temperature, speeding up the process of ion extraction. The study also found that an increase in rf voltage causes more intense plasma oscillations to screen out the rf disturbance, further increasing the electron temperature. Furthermore, as ion extraction continues, the heating effect of rf frequencies was found to be enhanced due to the decay of plasma density.
{"title":"Particle simulations of ion-extraction process from a decaying plasma assisted by radio-frequency plasma heating","authors":"Jing-Yu Sun, Xing Chen, Kai Zhao, Cheng Yuan, Xiao-Yong Lu, Fei Gao, You-Nian Wang","doi":"10.1088/1361-6595/ad1014","DOIUrl":"https://doi.org/10.1088/1361-6595/ad1014","url":null,"abstract":"In this study, two-dimensional kinetic particle simulations were employed to examine the potential of radio-frequency (rf) plasma heating in enhancing ion extraction efficiency in a decaying plasma with the configuration of parallel plates. The numerical results suggest that the application of rf power based on the direct current electrostatic method leads to a remarkable increase in the ion extraction flux, thereby reducing the time required for ion extraction. The increase in the ion extraction flux is attributed to the enhancement of the penetration ability of the rf electric field into the plasma, especially in cases of high rf frequencies, which can elevate the bulk electron temperature to approach 10 eV. The propagation speed of ion rarefaction waves is enhanced by the increased electron temperature, speeding up the process of ion extraction. The study also found that an increase in rf voltage causes more intense plasma oscillations to screen out the rf disturbance, further increasing the electron temperature. Furthermore, as ion extraction continues, the heating effect of rf frequencies was found to be enhanced due to the decay of plasma density.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139055501","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 : 2023-12-18DOI: 10.1088/1361-6595/ad10ef
J Fischer, M Renner, J T Gudmundsson, M Rudolph, H Hajihoseini, N Brenning, D Lundin
The influence of pulse length, working gas pressure, and peak discharge current density on the deposition rate and ionised flux fraction in high power impulse magnetron sputtering discharges of copper is investigated experimentally using a charge-selective (electrically biasable) magnetically shielded quartz crystal microbalance (or ionmeter). The large explored parameter space covers both common process conditions and extreme cases. The measured ionised flux fraction for copper is found to be in the range from ≈10% to 80%, and to increase with increasing peak discharge current density up to a maximum at ≈1.25Acm−2, before abruptly falling off at even higher current density values. Low working gas pressure is shown to be beneficial in terms of both ionised flux fraction and deposition rate fraction. For example, decreasing the working gas pressure from 1.0 Pa to 0.5 Pa leads on average to an increase of the ionised flux fraction by ≈14 percentage points (pp) and of the deposition rate fraction by ≈4pp taking into account all the investigated pulse lengths.
{"title":"Insights into the copper HiPIMS discharge: deposition rate and ionised flux fraction","authors":"J Fischer, M Renner, J T Gudmundsson, M Rudolph, H Hajihoseini, N Brenning, D Lundin","doi":"10.1088/1361-6595/ad10ef","DOIUrl":"https://doi.org/10.1088/1361-6595/ad10ef","url":null,"abstract":"The influence of pulse length, working gas pressure, and peak discharge current density on the deposition rate and ionised flux fraction in high power impulse magnetron sputtering discharges of copper is investigated experimentally using a charge-selective (electrically biasable) magnetically shielded quartz crystal microbalance (or ionmeter). The large explored parameter space covers both common process conditions and extreme cases. The measured ionised flux fraction for copper is found to be in the range from ≈10% to 80%, and to increase with increasing peak discharge current density up to a maximum at <inline-formula>\u0000<tex-math><?CDATA ${approx}{1.25},textrm{A},textrm{cm}^{-2}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo>≈</mml:mo></mml:mrow><mml:mrow><mml:mn>1.25</mml:mn></mml:mrow><mml:mrow><mml:mtext>A</mml:mtext></mml:mrow><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math>\u0000<inline-graphic xlink:href=\"psstad10efieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, before abruptly falling off at even higher current density values. Low working gas pressure is shown to be beneficial in terms of both ionised flux fraction and deposition rate fraction. For example, decreasing the working gas pressure from 1.0 Pa to 0.5 Pa leads on average to an increase of the ionised flux fraction by <inline-formula>\u0000<tex-math><?CDATA ${approx}{14}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo>≈</mml:mo></mml:mrow><mml:mrow><mml:mn>14</mml:mn></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad10efieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> percentage points (pp) and of the deposition rate fraction by <inline-formula>\u0000<tex-math><?CDATA ${approx}{4},textrm{pp}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo>≈</mml:mo></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mtext>pp</mml:mtext></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad10efieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> taking into account all the investigated pulse lengths.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139055507","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 : 2023-12-18DOI: 10.1088/1361-6595/ad169d
B. Esteves, Christophe Blondel, Pascal Chabert, Tanguy Michel, Cyril Drag
Iodine is a promising propellant for future plasma thrusters used in space propulsion. It is therefore important to understand the basic physics and chemistry of low pressure iodine plasma plasmas. In the present work, optical absorption methods are used to measure the densities of iodine molecules, I2, and iodine atoms, I, the translational temperature of the atoms and the dissociation fraction. The plasma is generated in a long quartz tube by a capacitively coupled RF discharge, and the pressure is varied between a few Pa and a few tens of Pa. The translational temperature of the atom vapour increases both with RF power and with pressure and reaches 1000 Kat 50 watts and 25 Pa. The molecules appear to be efficiently dissociated, with a dissociation fraction found above 65 %, on average along the line-of-sight, at 120 watts and 5 Pa. The population of the upper, 2Po 1/2, fine-structure level of the atomic ground term is found to be negligible, which confirms the existence of a high quenching rate, due to collisions with molecules and/or atoms. These measurements can be helpful for chemistry models of iodine plasmas.
碘是一种很有前途的推进剂，可用于未来太空推进中使用的等离子推进器。因此，了解低压碘等离子体的基本物理和化学性质非常重要。本研究采用光吸收方法测量碘分子 I2 和碘原子 I 的密度、原子的平移温度和解离分数。等离子体是通过电容耦合射频放电在长石英管中产生的，压力在几帕到几十帕之间变化。原子蒸汽的平移温度随射频功率和压力的增加而增加，达到 1000 Kat 50 瓦和 25 帕。在 120 瓦和 5 帕的条件下，分子似乎可以有效地解离，沿视线方向的平均解离率超过 65%。这些测量结果有助于建立碘等离子体的化学模型。
{"title":"Measurement of the main neutral species densities and temperatures in iodine plasmas using optical absorption techniques","authors":"B. Esteves, Christophe Blondel, Pascal Chabert, Tanguy Michel, Cyril Drag","doi":"10.1088/1361-6595/ad169d","DOIUrl":"https://doi.org/10.1088/1361-6595/ad169d","url":null,"abstract":"Iodine is a promising propellant for future plasma thrusters used in space propulsion. It is therefore important to understand the basic physics and chemistry of low pressure iodine plasma plasmas. In the present work, optical absorption methods are used to measure the densities of iodine molecules, I2, and iodine atoms, I, the translational temperature of the atoms and the dissociation fraction. The plasma is generated in a long quartz tube by a capacitively coupled RF discharge, and the pressure is varied between a few Pa and a few tens of Pa. The translational temperature of the atom vapour increases both with RF power and with pressure and reaches 1000 Kat 50 watts and 25 Pa. The molecules appear to be efficiently dissociated, with a dissociation fraction found above 65 %, on average along the line-of-sight, at 120 watts and 5 Pa. The population of the upper, 2Po 1/2, fine-structure level of the atomic ground term is found to be negligible, which confirms the existence of a high quenching rate, due to collisions with molecules and/or atoms. These measurements can be helpful for chemistry models of iodine plasmas.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"93 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139175068","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 : 2023-12-15DOI: 10.1088/1361-6595/ad1623
M. Sobolewski
Plasma simulations require accurate input data that describe the interactions of electrons with plasma-exposed surfaces. One important, rarely studied interaction is elastic reflection. This article presents measurements of the elastic reflection coefficient made in situ, i.e., during plasma exposure, in an inductively coupled plasma (icp) reactor that has an azimuthally asymmetric, rf-biased substrate electrode. The rf current and voltage across the sheath adjacent to this electrode were measured, along with the ion current density and electron temperature, for argon plasmas at 0.67 and 1.33 Pa. Using the measurements and a numerical sheath model, the currents contributed by electrons that are emitted from the rf-biased electrode are determined. Some emitted electrons are elastically reflected from the opposing surface, the fused quartz window below the icp source. Deflection of these electrons by 13.56 MHz electric and magnetic fields in the plasma can prevent them from returning to the rf-biased electrode, producing a second-harmonic current at 27.12 MHz. The transport of the emitted electrons is simulated by a plasma model that includes electric and magnetic effects, transit-time effects, elastic reflection at the electrode as well as the window, and multiple passes through the plasma. From the plasma model and the measured 27.12 MHz current, the elastic reflection coefficient at the quartz window was determined, for electron energies from 25 eV to 1.2 keV. The measured reflection coefficient was higher than literature values for clean Si, but it had a similar energy-dependence. An approximate analytical form for its energy-dependence is presented, as well as an uncertainty analysis.
{"title":"In situ measurement of the electron elastic reflection coefficient at a plasma-exposed silicon dioxide surface","authors":"M. Sobolewski","doi":"10.1088/1361-6595/ad1623","DOIUrl":"https://doi.org/10.1088/1361-6595/ad1623","url":null,"abstract":"\u0000 Plasma simulations require accurate input data that describe the interactions of electrons with plasma-exposed surfaces. One important, rarely studied interaction is elastic reflection. This article presents measurements of the elastic reflection coefficient made in situ, i.e., during plasma exposure, in an inductively coupled plasma (icp) reactor that has an azimuthally asymmetric, rf-biased substrate electrode. The rf current and voltage across the sheath adjacent to this electrode were measured, along with the ion current density and electron temperature, for argon plasmas at 0.67 and 1.33 Pa. Using the measurements and a numerical sheath model, the currents contributed by electrons that are emitted from the rf-biased electrode are determined. Some emitted electrons are elastically reflected from the opposing surface, the fused quartz window below the icp source. Deflection of these electrons by 13.56 MHz electric and magnetic fields in the plasma can prevent them from returning to the rf-biased electrode, producing a second-harmonic current at 27.12 MHz. The transport of the emitted electrons is simulated by a plasma model that includes electric and magnetic effects, transit-time effects, elastic reflection at the electrode as well as the window, and multiple passes through the plasma. From the plasma model and the measured 27.12 MHz current, the elastic reflection coefficient at the quartz window was determined, for electron energies from 25 eV to 1.2 keV. The measured reflection coefficient was higher than literature values for clean Si, but it had a similar energy-dependence. An approximate analytical form for its energy-dependence is presented, as well as an uncertainty analysis.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"6 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139000962","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 : 2023-12-14DOI: 10.1088/1361-6595/ad15b0
Geonwoong Moon, Wonho Choe, Eunji Jun
The plasma plume flow of an atomic oxygen-fed (AO-fed) ion thruster is numerically investigated as a simplification of the atmosphere-breathing electric propulsion (ABEP). A predictive analysis is conducted focusing on the ion backflow phenomenon and plume-background interaction in very-low-earth-orbit (VLEO). The computational framework employs two sequentially integrated numerical methods: a zero-dimensional (0-D) analytical model for the radio-frequency ion thruster and a hybrid method of the particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) techniques. The 0-D analytic model is employed for the prediction of exhaust conditions, while the hybrid PIC-DSMC method adopts these predictions to conduct the plasma plume simulations. A generalized collision cross-section model is introduced to enable consistent kinetic simulations for both AO and xenon propellants in VLEO atmosphere. The plasma plume simulations are conducted in an axisymmetric domain, including a cylindrical satellite body to consider wake flow. The exhaust ions exhibit diffusive transport transverse to the ion beam direction, implying the ion backflow. The backflowing ion current density can be increased in AO-fed thrusters, which require a high propellant flow rate to achieve a practical thrust. The AO-fed ion thruster shows a more active interaction between its plasma plume and the VLEO atmosphere compared to conventional xenon-based thrusters. The intensified plume-background interaction modifies the backflowing ion current density and the kinetic energy of individual ions, factors related to the spacecraft's surface contamination.
作为大气层呼吸电推进器（ABEP）的简化，对原子供氧（AO-feed）离子推进器的等离子体羽流进行了数值研究。预测分析的重点是极低地球轨道（VLEO）中的离子回流现象和羽流-背景相互作用。计算框架采用了两种相继集成的数值方法：射频离子推进器的零维（0-D）分析模型以及粒子入胞（PIC）和直接模拟蒙特卡罗（DSMC）技术的混合方法。0-D 分析模型用于预测排气条件，而 PIC-DSMC 混合方法则采用这些预测结果来进行等离子体羽流模拟。引入了通用碰撞截面模型，以便对 VLEO 大气中的 AO 和氙推进剂进行一致的动力学模拟。等离子体羽流模拟在轴对称域中进行，包括一个圆柱形卫星体，以考虑尾流。排出的离子表现出横向于离子束方向的扩散输运，这意味着离子逆流。在 AO 供能推进器中，逆流离子电流密度可以增加，而这种推进器需要较高的推进剂流速才能获得实际推力。与传统的氙推进器相比，AO-馈源离子推进器的等离子体羽流与 VLEO 大气层之间的相互作用更为活跃。增强的羽流-背景相互作用改变了回流离子电流密度和单个离子的动能，这些因素与航天器的表面污染有关。
{"title":"Plasma plume simulation of an atomic oxygen-fed ion thruster in very-low-earth-orbit","authors":"Geonwoong Moon, Wonho Choe, Eunji Jun","doi":"10.1088/1361-6595/ad15b0","DOIUrl":"https://doi.org/10.1088/1361-6595/ad15b0","url":null,"abstract":"\u0000 The plasma plume flow of an atomic oxygen-fed (AO-fed) ion thruster is numerically investigated as a simplification of the atmosphere-breathing electric propulsion (ABEP). A predictive analysis is conducted focusing on the ion backflow phenomenon and plume-background interaction in very-low-earth-orbit (VLEO). The computational framework employs two sequentially integrated numerical methods: a zero-dimensional (0-D) analytical model for the radio-frequency ion thruster and a hybrid method of the particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) techniques. The 0-D analytic model is employed for the prediction of exhaust conditions, while the hybrid PIC-DSMC method adopts these predictions to conduct the plasma plume simulations. A generalized collision cross-section model is introduced to enable consistent kinetic simulations for both AO and xenon propellants in VLEO atmosphere. The plasma plume simulations are conducted in an axisymmetric domain, including a cylindrical satellite body to consider wake flow. The exhaust ions exhibit diffusive transport transverse to the ion beam direction, implying the ion backflow. The backflowing ion current density can be increased in AO-fed thrusters, which require a high propellant flow rate to achieve a practical thrust. The AO-fed ion thruster shows a more active interaction between its plasma plume and the VLEO atmosphere compared to conventional xenon-based thrusters. The intensified plume-background interaction modifies the backflowing ion current density and the kinetic energy of individual ions, factors related to the spacecraft's surface contamination.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"39 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138974742","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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