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
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
Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based o...Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based on the interplanetary magnetic field(IMF)and solar wind conditions~3 h before this event,it is inferred that these mantle ions originate from the cusp.By analyzing the magnetohydrodynamic(MHD)Bernoulli integral(MBI)of this event,it was found that the plasma mantle is composed of many independent streamline-tubes,a few streamline-tube bundles,and transition layers between them.The MBI of streamline-tube is slightly higher than that in the typical magnetosheath,and one order higher than that in the solar wind.Most of the time,the kinetic energy density and enthalpy of mantle ions are the main components of MBI.Based on the homogeneous MBI method,more than 700 polytropic processes occurring in the plasma mantle streamline-tubes were identified,and their accurate ion polytropic indices were calculated.It shows that the range of these polytropic indices is broad,mainly from-1.6 to 3.5,with median and mean values of 1.12 and 1.08.The distribution of these indices is similar to that of the magnetosheath and wider than that of the central plasma sheet(CPS),and they are all within the coverage range of the solar wind.This indicates that there is a certain spatial evolution in the polytropic processes of solar wind,magnetosheath,plasma mantle,and plasma sheet ions,which also reflects the continuous conversion of kinetic energy into internal and static-pressure energy for plasma in these regions.These results indicate that plasma mantle ions can frequently experience various types of short-lived polytropic processes.These polytropic processes are direct manifestations of internal energy changes,and clarifying these polytropic processes and their evolutionary laws is crucial for understanding the mechanism of energy transport in the solar-terrestrial space.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 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(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supported by the National Natural Science Foundation of China(Grant No.12375250)。
文摘Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based on the interplanetary magnetic field(IMF)and solar wind conditions~3 h before this event,it is inferred that these mantle ions originate from the cusp.By analyzing the magnetohydrodynamic(MHD)Bernoulli integral(MBI)of this event,it was found that the plasma mantle is composed of many independent streamline-tubes,a few streamline-tube bundles,and transition layers between them.The MBI of streamline-tube is slightly higher than that in the typical magnetosheath,and one order higher than that in the solar wind.Most of the time,the kinetic energy density and enthalpy of mantle ions are the main components of MBI.Based on the homogeneous MBI method,more than 700 polytropic processes occurring in the plasma mantle streamline-tubes were identified,and their accurate ion polytropic indices were calculated.It shows that the range of these polytropic indices is broad,mainly from-1.6 to 3.5,with median and mean values of 1.12 and 1.08.The distribution of these indices is similar to that of the magnetosheath and wider than that of the central plasma sheet(CPS),and they are all within the coverage range of the solar wind.This indicates that there is a certain spatial evolution in the polytropic processes of solar wind,magnetosheath,plasma mantle,and plasma sheet ions,which also reflects the continuous conversion of kinetic energy into internal and static-pressure energy for plasma in these regions.These results indicate that plasma mantle ions can frequently experience various types of short-lived polytropic processes.These polytropic processes are direct manifestations of internal energy changes,and clarifying these polytropic processes and their evolutionary laws is crucial for understanding the mechanism of energy transport in the solar-terrestrial space.
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.
