Atmospheric pressure plasma jets can generate a remote plasma plume,which usually presents a conical or cylindrical morphology.Despite a few morphologies being observed,efforts should be made to obtain more plume stru...Atmospheric pressure plasma jets can generate a remote plasma plume,which usually presents a conical or cylindrical morphology.Despite a few morphologies being observed,efforts should be made to obtain more plume structures because streamer dynamics may be revealed from them.For this purpose,an argon plasma plume excited by a trapezoidal voltage is investigated,which presents two kinds of swells(a hollow swell and a diffuse swell)with increasing voltage amplitude(V).The results indicate that there are two positive discharges(Dand D)and one negative discharge(D)per voltage cycle for both of the swells.With increasing V,the inception voltage and discharge intensity increase for every positive discharge,while they decrease for the negative discharge.Fast photography reveals that the positive streamer(D)leaves different tracks in the two swells,which are curved in the hollow swell and randomly branched in the diffuse swell.The different tracks of Dare explained with the consideration of applied field strength and residual positive ions of D.The existence of residual positive ions is finally verified from optical emission spectra.展开更多
State-selective single-and double-electron capture processes in collisions of S^(5+)ions with helium at energies ranging from 50.8 keV to 100 keV were investigated using cold target recoil ion momentum spectroscopy(CO...State-selective single-and double-electron capture processes in collisions of S^(5+)ions with helium at energies ranging from 50.8 keV to 100 keV were investigated using cold target recoil ion momentum spectroscopy(COLTRIMS).Q-value spectra and projectile scattering angle distributions were obtained.For single-electron capture,single electron capture into n=3 states of the projectile ion is dominant.As the projectile energy increases,the contribution of single electron capture into n=4 states is observed.Experimental relative cross-sections for single-electron capture into different projectile final states were compared with theoretical predictions based on the molecular orbital close-coupling(MOCC)method.In double-electron capture,two-electron populating into the 3s^(2)3p and 3s3p^(2)states of projectile dominates.The reaction window calculated from the classical molecular Coulombic barrier model can qualitatively explain the experimental results.The scattering angle distribution of the multi-peak structure of the double-electron capture process is observed.The database is openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.j00113.00233.展开更多
This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered ...This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.展开更多
Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence o...Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear.Aim to this status,an argon plasma jet in a singleelectrode geometry is employed to investigate the influence of oxygen concentration(CO)on discharge aspects.Results indicate that with increasing CO(≤0.6%),the plume transits from a diffuse morphology to a hollow structure.Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying CO.Moreover,discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying CO.Besides,optical emission spectra are collected to investigate atomic CO,electron density,and electron temperature.The results mentioned above are explained qualitatively,which are believed to be of great significance for the applications of atmospheric pressure plasma jet.展开更多
A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(...A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(b))applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage.The results indicate that the plume is filamentary when U_(b)is low,which transits to the diffuse plume with increasing U_(b).The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume,while that at the falling edge contributes to the filament in the plume.For the diffuse plume,the discharge intensity decreases with the increasing oxygen content(C_o).Fast photography reveals that the diffuse plume results from a negative streamer,which has a dark region near the nozzle with C_o=0%.However,the dark region is absent with C_o=0.5%.From the optical emission spectrum,the electron density,electron excitation temperature,gas temperature,and oxygen atom concentration are investigated.展开更多
In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with ...In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with an intensified charge-coupled device and photomultiplier tubes.The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sublattices.These are bright concentric-ring structures,dark concentric-ring structures and wider concentric-ring structures,respectively.The bright concentric-ring structures and dark concentricring structures are alternately distributed.The bright concentric-ring structures are located at the centre of the wider concentric-ring structures.The wider concentric-ring structures first form from the outer edge and gradually develop to the centre.The essence of all three concentric-ring structures is the individual discharge filaments.The optical emission spectra of different sublattices are acquired and analysed.It is found that the plasma parameters of the three concentricring sublattices are different.Finally,the formation mechanism of the bright and dark concentricring pattern is discussed.展开更多
Fast photography and optical emission spectroscopy are implemented in a 5 mm neon gap dielectric barrier discharge(DBD) at atmospheric pressure with quartz glass used as the dielectric layer. Results show that it star...Fast photography and optical emission spectroscopy are implemented in a 5 mm neon gap dielectric barrier discharge(DBD) at atmospheric pressure with quartz glass used as the dielectric layer. Results show that it starts with a Townsend discharge and ends at a sub-normal glow discharge in neon DBD. Based on the Townsend discharge, the first ionization coefficient of neon is measured. The measurements are consistent with those at low pressure. Optical emission spectroscopy indicates that the spectra are mainly composed of atomic lines of neon, molecular bands and molecular ion bands originating from inevitable gas impurities(mainly nitrogen).Moreover, spectral lines emitted from atomic neon corresponding to the transitions(2p^5 3p→2p^5 3s) are predominant. Although the second positive system of N_2(C^3Π_u→B^3Π_g) is observed, their intensities are too weak compared with neon's spectrum. The molecular nitrogen ion line of 391.4 nm is observed. It reveals that Penning ionization between high energy neon excited states and the inevitable gas impurities plays an important role in the value of the αcoefficient.展开更多
Atmospheric pressure planar plumes are desirable for the applications of low temperature plasmas,such as rapid modification of large‐scale surfaces.Up to now,only single‐mode planar plumes with either a streamer mod...Atmospheric pressure planar plumes are desirable for the applications of low temperature plasmas,such as rapid modification of large‐scale surfaces.Up to now,only single‐mode planar plumes with either a streamer mode or a filamentary mode have been reported in the literature.Distinctive from the single‐mode planar plumes,a double‐mode argon planar plume has been generated in this article,which operates in the streamer mode with a larger distance away from a plasma jet and transits to the filamentary mode with decreasing the distance.Discharge characteristics and plasma parameters are compared for the two modes.Results indicate that the streamer mode and the filamentary mode correspond to pulsed and humped discharges respectively.Fast photography reveals that the streamer‐mode plume is composed of stochastically branching streamers,while the filamentary‐mode plume results from a series of moving filaments similar to those in barrier discharge.In contrast to the streamer mode,the filamentary mode has lower excited electron temperature and vibrational temperature,whereas higher electron density and gas temperature.In addition,better hydrophilicity of polyethylene terephthalate surface is achieved in the filamentary mode.展开更多
基金supported by National Natural Science Foundation of China(Nos.51977057,11875121)the Natural Science Foundation of Hebei Province,China(Nos.A2020201025,A2019201100)+2 种基金the Natural Science Interdisciplinary Research Program of Hebei University(Nos.DXK201908,DXK202011)Post-graduate’s Innovation Fund Project of Hebei Province(Nos.CXZZBS2019023,CXZZBS2019029)Post-graduate’s Innovation Fund Project of Hebei University(Nos.HBU2021ss063,HBU2021bs011)。
文摘Atmospheric pressure plasma jets can generate a remote plasma plume,which usually presents a conical or cylindrical morphology.Despite a few morphologies being observed,efforts should be made to obtain more plume structures because streamer dynamics may be revealed from them.For this purpose,an argon plasma plume excited by a trapezoidal voltage is investigated,which presents two kinds of swells(a hollow swell and a diffuse swell)with increasing voltage amplitude(V).The results indicate that there are two positive discharges(Dand D)and one negative discharge(D)per voltage cycle for both of the swells.With increasing V,the inception voltage and discharge intensity increase for every positive discharge,while they decrease for the negative discharge.Fast photography reveals that the positive streamer(D)leaves different tracks in the two swells,which are curved in the hollow swell and randomly branched in the diffuse swell.The different tracks of Dare explained with the consideration of applied field strength and residual positive ions of D.The existence of residual positive ions is finally verified from optical emission spectra.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1602500)the National Natural Science Foundation of China(Grant No.11974358)。
文摘State-selective single-and double-electron capture processes in collisions of S^(5+)ions with helium at energies ranging from 50.8 keV to 100 keV were investigated using cold target recoil ion momentum spectroscopy(COLTRIMS).Q-value spectra and projectile scattering angle distributions were obtained.For single-electron capture,single electron capture into n=3 states of the projectile ion is dominant.As the projectile energy increases,the contribution of single electron capture into n=4 states is observed.Experimental relative cross-sections for single-electron capture into different projectile final states were compared with theoretical predictions based on the molecular orbital close-coupling(MOCC)method.In double-electron capture,two-electron populating into the 3s^(2)3p and 3s3p^(2)states of projectile dominates.The reaction window calculated from the classical molecular Coulombic barrier model can qualitatively explain the experimental results.The scattering angle distribution of the multi-peak structure of the double-electron capture process is observed.The database is openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.j00113.00233.
基金supported by National Natural Science Foundation of China(Nos.11875121,51977057,11575050,11875014)the Hebei Province Natural Science Foundation(No.A2022201036)。
文摘This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.
基金supported by the National Natural Science Foundation of China(Grant Nos.51977057 and 11875121)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2020201025 and A2019201100)+2 种基金the Natural Science Interdisciplinary Research Program of Hebei University(Grant Nos.DXK202011 and DXK201908)Post-graduate’s Innovation Fund Project of Hebei Province,China(Grant Nos.CXZZBS2019023 and CXZZBS2019029)Postgraduate’s Innovation Fund Project of Hebei University(Grant Nos.HBU2021ss063 and HBU2021bs011)。
文摘Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear.Aim to this status,an argon plasma jet in a singleelectrode geometry is employed to investigate the influence of oxygen concentration(CO)on discharge aspects.Results indicate that with increasing CO(≤0.6%),the plume transits from a diffuse morphology to a hollow structure.Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying CO.Moreover,discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying CO.Besides,optical emission spectra are collected to investigate atomic CO,electron density,and electron temperature.The results mentioned above are explained qualitatively,which are believed to be of great significance for the applications of atmospheric pressure plasma jet.
基金supported by National Natural Science Foundation of China(Nos.12375250,11875121,51977057 and 11805013)the Natural Science Foundation of Hebei Province(Nos.A2020201025 and A2022201036)+3 种基金Hebei Province Optoelectronic Information Materials Laboratory Performance Subsidy Fund Project(No.22567634H)Funds for Distinguished Young Scientists of Hebei Province(No.A2012201045)the Natural Science Interdisciplinary Research Program of Hebei University(Nos.DXK201908 and DXK202011)the Post-graduate’s Innovation Fund Project of Hebei University(No.HBU2022bs004)。
文摘A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(b))applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage.The results indicate that the plume is filamentary when U_(b)is low,which transits to the diffuse plume with increasing U_(b).The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume,while that at the falling edge contributes to the filament in the plume.For the diffuse plume,the discharge intensity decreases with the increasing oxygen content(C_o).Fast photography reveals that the diffuse plume results from a negative streamer,which has a dark region near the nozzle with C_o=0%.However,the dark region is absent with C_o=0.5%.From the optical emission spectrum,the electron density,electron excitation temperature,gas temperature,and oxygen atom concentration are investigated.
基金supported by National Natural Science Foundation of China(No.12075075)the Natural Science Foundation of Hebei Province,China(Nos.2020201016,A2018201154,A2023201012)Scientific Research and Innovation Team of Hebei University(No.IT2023B03)。
文摘In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with an intensified charge-coupled device and photomultiplier tubes.The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sublattices.These are bright concentric-ring structures,dark concentric-ring structures and wider concentric-ring structures,respectively.The bright concentric-ring structures and dark concentricring structures are alternately distributed.The bright concentric-ring structures are located at the centre of the wider concentric-ring structures.The wider concentric-ring structures first form from the outer edge and gradually develop to the centre.The essence of all three concentric-ring structures is the individual discharge filaments.The optical emission spectra of different sublattices are acquired and analysed.It is found that the plasma parameters of the three concentricring sublattices are different.Finally,the formation mechanism of the bright and dark concentricring pattern is discussed.
基金supported by Postdoctoral Project of Hebei University, National Natural Science Foundation of China (Nos. 11575050, 11875121, 51977057)Hebei Natural Science Fund (Nos. A2017201099, A2020201008)。
文摘Fast photography and optical emission spectroscopy are implemented in a 5 mm neon gap dielectric barrier discharge(DBD) at atmospheric pressure with quartz glass used as the dielectric layer. Results show that it starts with a Townsend discharge and ends at a sub-normal glow discharge in neon DBD. Based on the Townsend discharge, the first ionization coefficient of neon is measured. The measurements are consistent with those at low pressure. Optical emission spectroscopy indicates that the spectra are mainly composed of atomic lines of neon, molecular bands and molecular ion bands originating from inevitable gas impurities(mainly nitrogen).Moreover, spectral lines emitted from atomic neon corresponding to the transitions(2p^5 3p→2p^5 3s) are predominant. Although the second positive system of N_2(C^3Π_u→B^3Π_g) is observed, their intensities are too weak compared with neon's spectrum. The molecular nitrogen ion line of 391.4 nm is observed. It reveals that Penning ionization between high energy neon excited states and the inevitable gas impurities plays an important role in the value of the αcoefficient.
基金sponsored by the National Natural Science Foundation of China(Grant No.11875121)the Natural Science Foundation of Hebei Province,China(Grant No.A2022201036).
文摘Atmospheric pressure planar plumes are desirable for the applications of low temperature plasmas,such as rapid modification of large‐scale surfaces.Up to now,only single‐mode planar plumes with either a streamer mode or a filamentary mode have been reported in the literature.Distinctive from the single‐mode planar plumes,a double‐mode argon planar plume has been generated in this article,which operates in the streamer mode with a larger distance away from a plasma jet and transits to the filamentary mode with decreasing the distance.Discharge characteristics and plasma parameters are compared for the two modes.Results indicate that the streamer mode and the filamentary mode correspond to pulsed and humped discharges respectively.Fast photography reveals that the streamer‐mode plume is composed of stochastically branching streamers,while the filamentary‐mode plume results from a series of moving filaments similar to those in barrier discharge.In contrast to the streamer mode,the filamentary mode has lower excited electron temperature and vibrational temperature,whereas higher electron density and gas temperature.In addition,better hydrophilicity of polyethylene terephthalate surface is achieved in the filamentary mode.
