查看更多>>摘要：Atmospheric pressure cold plasma jets(APCPJs)typically exhibit a slender,conical structure,which imposes limitations on their application for surface modification due to the restricted treatment area.In this paper,we introduce a novel plasma jet morphology known as the large-scale cold plasma jet(LSCPJ),characterized by the presence of both a central conical plasma jet and a peripheral trumpet-like diffuse plasma jet.The experimental investigations have identified the factors influencing the conical and the trumpet-like diffuse plasma jet,and theoretical simulations have shed light on the role of the flow field and the electric field in shaping the formation of the LSCPJ.It is proved that,under conditions of elevated helium concentration,the distributions of impurity gas particles and the electric field jointly determine the plasma jet's morphology.High-speed ICCD camera images confirm the dynamic behavior of plasma bullets in LSCPJ,which is consistent with the theoretical analysis.Finally,it is demonstrated that when applied to the surface treatment of silicone rubber,LSCPJ can achieve a treatment area over 28 times larger than that of APCPJ under equivalent conditions.This paper uncovers the crucial role of impurity gases and electric fields in shaping plasma jet morphology and opens up the possibility of efficiently diversifying plasma jet generation effects through external electromagnetic fields.These insights hold the promise of reducing the generation cost of plasma jets and expanding their applications across various industrial sectors.
查看更多>>摘要：Plasma-enhanced transdermal drug delivery(TDD)presents advantages over traditional methods,including painless application,minimal skin damage,and rapid recovery of permeability.To harness its clinical potential,factors related to plasma's unique properties,such as reactive species and electric fields,must be carefully considered.This review provides a concise summary of conventional TDD methods and subsequently offers a comprehensive examination of the current state-of-the-art in plasma-enhanced TDD.This includes an analysis of the impact of plasma on HaCaT human keratinocyte cells,ex vivo/in vivo studies,and clinical research on plasma-assisted TDD.Moreover,the review explores the effects of plasma on skin physical characteristics such as microhole formation,transepidermal water loss(TEWL),molecular structure of the stratum corneum(SC),and skin resistance.Additionally,it discusses the involvement of various reactive agents in plasma-enhanced TDD,encompassing electric fields,charged particles,UV/VUV radiation,heat,and reactive species.Lastly,the review briefly addresses the temporal behavior of the skin after plasma treatment,safety considerations,and potential risks associated with plasma-enhanced TDD.
查看更多>>摘要：The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse.Plasma has been employed in recent years for the remediation of antibiotic pollution in the environment.In this work,a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline(TC)in water.The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance.The discharge characteristics,chemical species'concentration,and degradation rates at different parameters were systematically studied.Under the optimized conditions(working gas was pure oxygen,liquid flow rate was 100 mL/min,gas flow rate was 1 L/min,voltage was 20 kV,single treatment),TC was removed beyond 70％in a single flow treatment with an energy efficiency of 145 mg/(kW·h).The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after a single flow under pure oxygen conditions,affording fast TC degradation.Furthermore,long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC.Compared with other plasma treatment systems,this work offers a fast and efficient degradation method,showing significant potential in practical industrial applications.
查看更多>>摘要：Ionic liquid electrospray(ILE)in an atmospheric environment is often accompanied by the gas discharge phenomenon.It interferes with the normal operation of the electrospray and the measurement of experimental parameters.In this study,electrospray experiments were conducted on the ionic liquid EMI-BF4.The observations revealed that the operating modes of the ionic liquid depend on the voltage polarity at high voltages.Additionally,a correspondence between the operating mode of ILE and the current signal in the circuit was established.The shape of the liquid cone formed at the needle tip bore a striking resemblance to the plume of corona discharge,suggesting that the motion trajectory of electrons influenced the curvature of the liquid cone.Steamer theory provided a clear explanation for the change in curvature as the voltage increased.
查看更多>>摘要：The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency(RF)discharges is investigated by a two-dimensional(2D)particle-in-cell/Monte-Carlo collision(PIC/MCC)model.Results show that plasma exists inside the cavity when the sheath inside the hollow electrode hole is fully collapsed,which is an essential condition for the plasma density enhancement outside hollow electrodes.In addition,the existence of the electron density peak at the orifice is generated via the hollow cathode effect(HCE),which plays an important role in the density enhancement.It is also found that the radial width of bulk plasma at the orifice affects the magnitude of the density enhancement,and narrow radial plasma bulk width at the orifice is not beneficial to obtain high-density plasma outside hollow electrodes.Higher electron density at the orifice,combined with larger radial plasma bulk width at the orifice,causes higher electron density outside hollow electrodes.The results also imply that the HCE strength inside the cavity cannot be determined by the magnitude of the electron density outside hollow electrodes.
查看更多>>摘要：Anomalous ion heat transport is analyzed in the T-10 tokamak plasma heated with electron cyclotron resonance heating(ECRH)in second-harmonic extra-ordinary mode.Predictive modeling with empirical scaling for Ohmical heat conductivity shows that in ECRH plasmas the calculated ion temperature could be overestimated,so an increase of anomalous ion heat transport is required.To study this effect two scans are presented:over the EC resonance position and over the ECRH power.The EC resonance position varies from the high-field side to the low-field side by variation of the toroidal magnetic field.The scan over the heating power is presented with on-axis and mixed ECRH regimes.Discharges with high anomalous ion heat transport are obtained in all considered regimes.In these discharges the power balance ion heat conductivity exceeds the neoclassical level by up to 10 times.The high ion heat transport regimes are distinguished by three parameters:the Te/Ti ratio,the normalized electron density gradient R/Lne,and the ion-ion collisionality vii*.The combination of high Te/Ti,high vii*,and R/Lne=6-10 results in values of normalized anomalous ion heat fluxes up to 10 times higher than in the low transport scenario.
查看更多>>摘要：Reconstruction of plasma equilibrium plays an important role in the analysis and simulation of plasma experiments.The kinetic equilibrium reconstruction with pressure and edge current constraints has been employed on EAST tokamak.However,the internal safety factor(q)profile is not accurate.This paper proposes a new way of incorporating q profile constraints into kinetic equilibrium reconstruction.The q profile is yielded from the Polarimeter Interferometer(POINT)reconstruction.Virtual probes containing information on q profile constraints are added to inputs of the kinetic equilibrium reconstruction program to obtain the final equilibrium.The new equilibrium produces a more accurate internal q profile.This improved method would help analyze EAST experiments.
查看更多>>摘要：At the EAST tokamak,the ion temperature(Ti)is observed to be clamped around 1.25 keV in electron cyclotron resonance(ECR)-heated plasmas,even at core electron temperatures up to 10 keV(depending on the ECR heating power and the plasma density).This clamping results from the lack of direct ion heating and high levels of turbulence-driven transport.Turbulent transport analysis shows that trapped electron mode and electron temperature gradient-driven modes are the most unstable modes in the core of ECR-heated H-mode plasmas.Nevertheless,recently it was found that the Ti/Te ratio can increase further with the fraction of the neutral beam injection(NBI)power,which leads to a higher core ion temperature(Ti0).In NBI heating-dominant H-mode plasmas,the ion temperature gradient-driven modes become the most unstable modes.Furthermore,a strong and broad internal transport barrier(ITB)can form at the plasma core in high-power NBI-heated H-mode plasmas when the Ti/Te ratio approaches～1,which results in steep core Te and Ti profiles,as well as a peaked ne profile.Power balance analysis shows a weaker Te profile stiffness after the formation of ITBs in the core plasma region,where Ti clamping is broken,and the core Ti can increase further above 2 keV,which is 80％higher than the value of Ti clamping in ECR-heated plasmas.This finding proposes a possible solution to the problem of Ti clamping on EAST and demonstrates an advanced operational regime with the formation of a strong and broad ITB for future fusion plasmas dominated by electron heating.
查看更多>>摘要：We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection.The results demonstrate that the boundary conditions are crucial to this evolution.Specifically,in the cases of traditional periodic boundary(PB)and fully-opened boundary(OB)conditions,the evolutions are quite similar before the system achieves the fastest reconnection rate.However,differences emerge between the two cases afterward.In the PB case,the reconnection electric field experiences a rapid decline and even becomes negative,indicating a reversal of the reconnection process.In contrast,the system maintains a fast reconnection stage in the OB case.Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases.In the electron density depletion layer and the dipolarization front region,a larger proportion of suprathermal electrons are produced in the OB case.Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases.However,in the OB case,they can also be generated in the electron holes along the separatrix.Before the reverse reconnection stage,no high-energy electrons are present in the PB case.In contrast,about 20％of the electrons in the thin and elongated electron current layer are high-energy in the OB case.
查看更多>>摘要：The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window.In this paper,the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision(PIC-MCC)model.The process of desorption of gas and its influence on the breakdown characteristics are studied.The simulation results show that,due to the accumulation of desorbed gas,the pressure near the dielectric surface increases in time,and the breakdown mechanism transitions from secondary electron multipactor to collision ionization.More and more electrons generated by collision ionization drift to the dielectric surface,so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface.Nevertheless,the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons.In the early and middle stages of breakdown,the attenuation of the microwave electric field near the dielectric surface is very small.However,the collision ionization causes a sharp increase in the number density of electrons,and the microwave electric field decays rapidly in the later stage of breakdown.Compared with the electromagnetic PIC-MCC simulation results,the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field.The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value,when the number of gas atoms desorbed by an incident electron is taken as 0.4.
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