Plasma Sources Science and Technology最新文献

{"title":"A 3D kinetic Monte Carlo study of streamer discharges in CO2","authors":"R Marskar","doi":"10.1088/1361-6595/ad28cf","DOIUrl":"https://doi.org/10.1088/1361-6595/ad28cf","url":null,"abstract":"We theoretically study the inception and propagation of positive and negative streamers in <inline-formula>\u0000<tex-math><?CDATA $mathrm{CO_{2}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi><mml:msub><mml:mi mathvariant=\"normal\">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad28cfieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>. Our study is done in 3D, using a newly formulated kinetic Monte Carlo discharge model where the electrons are described as drifting and diffusing particles that adhere to the local field approximation. Our emphasis lies on electron attachment and photoionization. For negative streamers we find that dissociative attachment in the streamer channels leads to appearance of localized segments of increased electric fields, while an analogous feature is not observed for positive-polarity discharges. Positive streamers, unlike negative streamers, require free electrons ahead of them in order to propagate. In <inline-formula>\u0000<tex-math><?CDATA $mathrm{CO_{2}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi><mml:msub><mml:mi mathvariant=\"normal\">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad28cfieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, just as in air, these electrons are supplied through photoionization. However, ionizing radiation in <inline-formula>\u0000<tex-math><?CDATA $mathrm{CO_{2}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi><mml:msub><mml:mi mathvariant=\"normal\">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad28cfieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> is absorbed quite rapidly and is also weaker than in air, which has important ramifications for the emerging positive streamer morphology (radius, velocity, and fields). We perform a computational analysis which shows that positive streamers can propagate due to photoionization in <inline-formula>\u0000<tex-math><?CDATA $mathrm{CO_{2}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi><mml:msub><mml:mi mathvariant=\"normal\">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad28cfieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>. Conversely, photoionization has no effect on negative streamer fronts, but plays a major role in the coupling between negative streamers and the cathode. Photoionization in <inline-formula>\u0000<tex-math><?CDATA $mathrm{CO_{2}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi><mml:msub><mml:mi mathvariant=\"normal\">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<i","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140002140","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}

{"title":"A tutorial overview of the angular scattering models of electron–neutral, ion–neutral, neutral–neutral, and Coulomb collisions in Monte Carlo collision modeling on low-temperature plasma","authors":"Wei Yang","doi":"10.1088/1361-6595/ad2491","DOIUrl":"https://doi.org/10.1088/1361-6595/ad2491","url":null,"abstract":"Over the past decade, extensive modeling practices on low-temperature plasmas have revealed that input data such as microscopic scattering cross-sections are crucial to output macroscopic phenomena. In Monte Carlo collision (MCC) modeling of natural and laboratory plasma, the angular scattering model is a non-trivial topic. Conforming to the pedagogical purpose of this overview, the classical and quantum theories of binary scattering, such as the commonly used Born–Bethe approximation, are first introduced. Adequate angular scattering models, which MCC simulation can handle as input, are derived based on the above theories for electron–neutral, ion–neutral, neutral–neutral, and Coulomb collisions. This tutorial does not aim to provide accurate cross-sectional data by modern approaches in quantum theory, but rather to introduce analytical angular scattering models from classical, semi-empirical, and first-order perturbation theory. The reviewed models are expected to be readily incorporated into the MCC codes, in which the scattering angle is randomly sampled through analytical inversion instead of the numerical accept–reject method. These simplified approaches are very attractive, and demonstrate in many cases the ability to achieve a striking agreement with experiments. Energy partition models on electron–neutral ionization are also discussed with insight from the binary-encounter Bethe theory. This overview is written in a tutorial style in order to serve as a guide for novices in this field, and at the same time as a comprehensive reference for practitioners of MCC modeling on plasma.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140008568","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}

{"title":"Zeeman effect of isotopes of Kr and Xe investigated at the linear plasma device PSI-2","authors":"M Sackers, O Marchuk, D Dipti, Yu Ralchenko, S Ertmer, S Brezinsek, A Kreter","doi":"10.1088/1361-6595/ad23fa","DOIUrl":"https://doi.org/10.1088/1361-6595/ad23fa","url":null,"abstract":"Laser absorption spectroscopy provides high-resolution spectra of atomic transitions that reveal many often inaccessible features. The line shapes of krypton and xenon measured in magnetized plasmas are strongly affected by the contribution of the odd-numbered isotopes ⁸³Kr, ¹²⁹Xe and ¹³¹Xe due to their hyperfine structure, creating more challenging spectra in comparison to even-numbered ones. The lines originating from metastable levels of krypton and xenon with <italic toggle=\"yes\">J</italic> = 2 (Kr I 760.4 nm) and <italic toggle=\"yes\">J</italic> = 0 (Kr I 785.7 nm, Xe I 764.4 nm) were measured and analyzed in the linear plasma device PSI-2 in the field range of 22.5 mT–90 mT. Evaluating the Hamiltonian, including hyperfine and Zeeman interaction terms for these magnetic field strengths, unveils a deviation from the linear energy shift of the sublevels as a function of the magnetic field and from constant relative intensities that the weak field formulas provide. We prove that modeling the transitions in Xe using the weak field approximation, frequently used in magnetized plasma, becomes inadequate at ≈50 mT. In particular, the spectra of the ¹³¹Xe isotope show pronounced deviations from the weak field results. For krypton, however, the situation is less critical compared to xenon due to the low natural abundance of the odd-numbered isotope.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140002092","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}

{"title":"3D simulations of positive streamers in air in a strong external magnetic field","authors":"Zhen Wang, Anbang Sun, Saša Dujko, Ute Ebert, Jannis Teunissen","doi":"10.1088/1361-6595/ad227f","DOIUrl":"https://doi.org/10.1088/1361-6595/ad227f","url":null,"abstract":"We study how external magnetic fields from 0 to 40 T influence positive streamers in atmospheric pressure air, using 3D PIC-MCC (particle-in-cell, Monte Carlo collision) simulations. When a magnetic field <bold>\u0000<italic toggle=\"yes\">B</italic>\u0000</bold> is applied perpendicular to the background electric field <bold>\u0000<italic toggle=\"yes\">E</italic>\u0000</bold>, the streamers deflect towards the <inline-formula>\u0000<tex-math><?CDATA $+boldsymbol{B}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mo>+</mml:mo><mml:mi mathvariant=\"bold-italic\">B</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"psstad227fieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> and <inline-formula>\u0000<tex-math><?CDATA $-boldsymbol{B}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mo>−</mml:mo><mml:mi mathvariant=\"bold-italic\">B</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"psstad227fieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> directions which results in a branching into two main channels. With a stronger magnetic field the angle between the branches increases, and for the 40 T case the branches grow almost parallel to the magnetic field. Due to the <inline-formula>\u0000<tex-math><?CDATA $boldsymbol{E}timesboldsymbol{B}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi mathvariant=\"bold-italic\">E</mml:mi><mml:mo>×</mml:mo><mml:mi mathvariant=\"bold-italic\">B</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"psstad227fieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> drift of electrons we also observe a streamer deviation in the opposite <inline-formula>\u0000<tex-math><?CDATA $-boldsymbol{E}timesboldsymbol{B}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mo>−</mml:mo><mml:mi mathvariant=\"bold-italic\">E</mml:mi><mml:mo>×</mml:mo><mml:mi mathvariant=\"bold-italic\">B</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"psstad227fieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> direction, where the minus sign appears because positive streamers propagate opposite to the electron drift velocity. The deviation due to this <inline-formula>\u0000<tex-math><?CDATA $boldsymbol{E}timesboldsymbol{B}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi mathvariant=\"bold-italic\">E</mml:mi><mml:mo>×</mml:mo><mml:mi mathvariant=\"bold-italic\">B</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"psstad227fieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> effect is smaller than the deviation parallel to <bold>\u0000<italic toggle=\"yes\">B</italic>\u0000</bold>. In both cases of <bold>\u0000<italic toggle=\"yes\">B</italic>\u0000</bold> perpendicular and parallel to <bold>\u0000<italic toggle=\"yes\">E</italic>\u0000</bold>, the streamer radius decreases with the magnetic field strength. We relate our observations to the effects of electric and magnetic fields on electron transport and reaction coefficients.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139762031","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}

{"title":"Frequency-dependent electron power absorption mode transitions in capacitively coupled argon-oxygen plasmas","authors":"A Derzsi, M Vass, R Masheyeva, B Horváth, Z Donkó, P Hartmann","doi":"10.1088/1361-6595/ad1fd5","DOIUrl":"https://doi.org/10.1088/1361-6595/ad1fd5","url":null,"abstract":"Phase Resolved Optical Emission Spectroscopy (PROES) measurements combined with 1d3v Particle-in-Cell/Monte Carlo Collisions simulations are performed to investigate the excitation dynamics in low-pressure capacitively coupled plasmas (CCPs) in argon-oxygen mixtures. The system used for this study is a geometrically symmetric CCP reactor operated in a 70% Ar-30% O₂ mixture at 120 Pa, applying a peak-to-peak voltage of 350 V, with a wide range of driving RF frequencies (2 MHz <inline-formula>\u0000<tex-math><?CDATA $unicode{x2A7D} f unicode{x2A7D}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mtext>⩽</mml:mtext><mml:mi>f</mml:mi><mml:mtext>⩽</mml:mtext></mml:math>\u0000<inline-graphic xlink:href=\"psstad1fd5ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> 15 MHz). The measured and calculated spatio-temporal distributions of the electron impact excitation rates from the Ar ground state to the Ar <inline-formula>\u0000<tex-math><?CDATA $mathrm{2p_1}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mn>2</mml:mn><mml:msub><mml:mi mathvariant=\"normal\">p</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"psstad1fd5ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> level show good qualitative agreement. The distributions show significant frequency dependence, which is generally considered to be predictive of transitions in the dominant discharge operating mode. Three frequency ranges can be distinguished, showing distinctly different excitation characteristics: (i) in the low frequency range (<inline-formula>\u0000<tex-math><?CDATA $f unicode{x2A7D}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>f</mml:mi><mml:mtext>⩽</mml:mtext></mml:math>\u0000<inline-graphic xlink:href=\"psstad1fd5ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> 3 MHz), excitation is strong at the sheaths and weak in the bulk region; (ii) at intermediate frequencies (3.5 MHz <inline-formula>\u0000<tex-math><?CDATA $unicode{x2A7D} f unicode{x2A7D}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mtext>⩽</mml:mtext><mml:mi>f</mml:mi><mml:mtext>⩽</mml:mtext></mml:math>\u0000<inline-graphic xlink:href=\"psstad1fd5ieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> 5 MHz), the excitation rate in the bulk region is enhanced and shows striation formation; (iii) above 6 MHz, excitation in the bulk gradually decreases with increasing frequency. Boltzmann term analysis was performed to quantify the frequency-dependent contributions of the Ohmic and ambipolar terms to the electron power absorption.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139762038","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}

{"title":"Absolute atomic nitrogen density spatial mapping in three MHCD configurations","authors":"A. Remigy, Belkacem Menacer, Konstantinos Kourtzanidis, Odyssea Gazeli, K. Gazeli, G. Lombardi, C. Lazzaroni","doi":"10.1088/1361-6595/ad227b","DOIUrl":"https://doi.org/10.1088/1361-6595/ad227b","url":null,"abstract":"\u0000 In this work, nanosecond Two-photon Absorption Laser Induced Fluorescence is used to perform spatial mappings of the absolute density of nitrogen atoms generated in a micro-hollow cathode discharge (MHCD). The MHCD is operated in the normal regime, with a DC discharge current of 1.6 mA and a plasma is ignited in a 20% Ar/ 80% N2 gas mixture. A 1-inch diameter aluminum substrate acting as a third electrode (second anode) is placed further away from the MHCD to emulate a deposition substrate. The spatial profile of the N atoms is measured in three MHCD configurations. First, we study a MHCD having the same pressure (50 mbar) on both sides of the anode/cathode electrodes and the N atoms diffuse in three dimensions from the MHCD. The recorded N atoms density profile in this case satisfies our expectations, i.e., the maximal density is found at the axis of the hole, close to the MHCD. However, when we introduce a pressure differential, thus creating a plasma jet, an unexpected N atoms distribution is measured with maximum densities away from the jet axis. This behavior cannot be simply explained by the TALIF measurements. Then, as a first simplified approach in this work, we turn our attention to the role of the gas flow pattern. Compressible gas flow simulations show a correlation between the jet width and the radial distribution of the N atoms at different axial distances from the gap. Finally, a DC positive voltage is applied to the third electrode (second anode), which ignites a Micro Cathode Sustained Discharge (MCSD). The presence of the pressure differential unveils two stable working regimes depending on the current repartition between the two anodes. The MCSD enables an homogenization of the density profile along the surface of the substrate, which is suitable for nitride deposition applications.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"121 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139596480","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}

{"title":"Non-Maxwellian electron effects on the macroscopic response of a Hall thruster discharge from an axial-radial kinetic model","authors":"A. Marín-Cebrián, E. Bello-Benítez, A. Domínguez-Vázquez, E. Ahedo","doi":"10.1088/1361-6595/ad227c","DOIUrl":"https://doi.org/10.1088/1361-6595/ad227c","url":null,"abstract":"\u0000 A 2D axial-radial particle-in-cell (PIC) model of a Hall thruster discharge has been developed to analyze (mainly) the fluid equations satisfied by the azimuthally-averaged slow dynamics of electrons. Their weak collisionality together with a strong interaction with the thruster walls lead to a non-Maxwellian velocity distribution function (VDF). Consequently, the resulting macroscopic response differs from a conventional collisional fluid. First, the gyrotropic (diagonal) part of the pressure tensor is anisotropic. Second, its gyroviscous part, although small, is relevant in the azimuthal momentum balance, where the dominant contributions are orders of magnitude lower than in the axial momentum balance. Third, the heat flux vector does not satisfy simple laws, although convective and conductive behaviors can be identified for the parallel and perpendicular components, respectively. And fourth, the electron wall interaction parameters can differ largely from the classical sheath theory, based on near Maxwellian VDF. Furthermore, these effects behave differently in the near-anode and near-exit regions of the channel. Still, the profiles of basic plasma magnitudes agree well with those of 1D axial fluid models. To facilitate the interpretation of the plasma response, a quasiplanar geometry, a purely-radial magnetic field, and a simple empirical model of cross-field transport were used; but realistic configurations and a more elaborated anomalous diffusion formulation can be incorporated. Computational time was controlled by using an augmented vacuum permittivity and a stationary depletion law for neutrals.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"58 36","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139598484","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}

{"title":"Dynamic Response of Nanosecond Repetitively Pulsed Discharges to Combustion Dynamics: Regime Transitions Driven by Flame Oscillations","authors":"C. Pavan, Santosh J. Shanbhogue, D. Weibel, Felipe Gomez del Campo, Ahmed Ghoniem, C. Guerra-Garcia","doi":"10.1088/1361-6595/ad227d","DOIUrl":"https://doi.org/10.1088/1361-6595/ad227d","url":null,"abstract":"\u0000 When using nanosecond repetitively pulsed discharges to actuate on dynamic combustion instabilities, the environment the discharge is created in is unsteady and changing on the timescale of the combustion processes. As a result, individual discharge pulses are triggered in a background gas that evolves at the timescale of combustion dynamics, and pulse-to-pulse variations may be observed during the instability cycle. Prior work has studied nanosecond pulsed discharges in pin-to-ring configurations used to control instabilities in lean-operating swirl-stabilized combustors, and observed variable discharge behaviour. The focus of this work is on characterizing how the pulse-to-pulse discharge morphology, energy deposition, and actuation authority, evolve during the combustion instability cycle. This has important implications for designing effective plasma-assisted combustion control schemes. The discharge is observed in two distinct modes, a streamer corona and a nanosecond spark, with the occurrence of each regime directly linked to the phase of the combustor instability. Variation of pulse repetition frequency affects the total fraction of pulses in each mode, while variation of voltage affects the onset of the nanosecond spark mode. The transitions are described in terms of ratios of the relevant combustion and plasma timescales and the implications of this coupled interaction on the design of an effective control scheme is discussed.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"8 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139595851","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}

{"title":"Detection of negative ions in streamer discharge in air by transient cavity ringdown spectroscopy","authors":"Kimika Fushimi, Naoki Shirai, Koichi Sasaki","doi":"10.1088/1361-6595/ad227e","DOIUrl":"https://doi.org/10.1088/1361-6595/ad227e","url":null,"abstract":"\u0000 Atmospheric-pressure discharges generated in air are expected to be electronegative, but experiments that examine negative ion densities are limited to date. In this work, we measured the temporal variation of the negative ion density in a streamer discharge generated in air. We adopted cavity ringdown spectroscopy, where negative ions were detected via weak optical absorption caused by laser photodetachment. The temporal variation of the absolute negative ion density was deduced by the transient analysis of the ringdown curve. Negative ions were detected after the disappearance of the discharge voltage and current. The negative ion density started the increase at 0.4 μs after the initiation of the discharge. The increase means the enhancement of the electron attachment frequency in the late phase of the secondary streamer with electron cooling. The survival of electrons until 0.4 μs is understood by the steep decrease in the cross section of dissociative recombination with the electron energy. The maximum negative ion density was observed at 1 μs, and it was around the noise level at 1.5 μs. The rapid decay is consistent with the destruction of negative ions by mutual neutralization with positive ions.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"99 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139596772","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}

{"title":"A pointwise separation algorithm to separate plasma density and thickness in two-beam interferometry","authors":"Malong Fu, Haitao Wang, Z. Hou","doi":"10.1088/1361-6595/ad2116","DOIUrl":"https://doi.org/10.1088/1361-6595/ad2116","url":null,"abstract":"\u0000 The conventional two-beam interferometry adopts only one expression about plasma density and thickness because only fringe shift is recognized from the recorded fringes. Therefore, the prior hypotheses that the plasma is thickness-uniform or circular symmetry have to be introduced to separate them, which limits the applied range and accuracy of the conventional method. This paper found that the laser beam will be deflected if the thickness changes, leading the recorded fringes to be defocused. As a result, a new expression relying on recognizing the defocus parameter of the recorded fringes is derived, and a pointwise separation algorithm to separate density and thickness is proposed based on the two expressions. Compared to the conventional algorithms, the new algorithm requires no hypotheses and thus has a wider applied range.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"31 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139609092","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}