Spectroscopy,especially for plasma spectroscopy,provides a powerful platform for biological and material analysis with its elemental and molecular fingerprinting capability.Artificial intelligence(AI)has the tremendou...Spectroscopy,especially for plasma spectroscopy,provides a powerful platform for biological and material analysis with its elemental and molecular fingerprinting capability.Artificial intelligence(AI)has the tremendous potential to build a universal quantitative framework covering all branches of plasma spectroscopy based on its unmatched representation and generalization ability.Herein,we introduce an AI-based unified method called self-supervised image-spectrum twin information fusion detection(SISTIFD)to collect twin co-occurrence signals of the plasma and to intelligently predict the physical parameters for improving the performances of all plasma spectroscopic techniques.It can fuse the spectra and plasma images in synchronization,derive the plasma parameters(total number density,plasma temperature,electron density,and other implicit factors),and provide accurate results.The experimental data demonstrate their excellent utility and capacity,with a reduction of 98%in evaluation indices(root mean square error,relative standard deviation,etc.)and an analysis frequency of 143 Hz(much faster than the mainstream detection frame rate of 1 Hz).In addition,as a completely end-to-end and self-supervised framework,the SISTIFD enables automatic detection without manual preprocessing or intervention.With these advantages,it has remarkably enhanced various plasma spectroscopic techniques with state-of-the-art performance and unsealed their possibility in industry,especially in the regions that require both capability and efficiency.This scheme brings new inspiration to the whole field of plasma spectroscopy and enables in situ analysis with a real-world scenario of high throughput,cross-interference,various analyte complexity,and diverse applications.展开更多
A theoretical model is presented to describe the electromagnetic, heat transfer and fluid flow phenomena within a magnetron plasma torch and in the resultant plume, by using a commercial computational fluid dynamics ...A theoretical model is presented to describe the electromagnetic, heat transfer and fluid flow phenomena within a magnetron plasma torch and in the resultant plume, by using a commercial computational fluid dynamics （CFD） code FLUENT. Specific calculations are pre- sented for a pure argon system （i.e., an argon plasma discharging into an argon environment）, operated in a turbulent mode. An important finding of this work is that the external axial magnetic field （AMF） may have a significant effect on the behavior of arc plasma and thus affects the resulting plume. The AMF impels the plasma to retract axially and expand radially. As a result, the plasma intensity distribution on the cross section of torch seems to be more uniform. Numerical results also show that with AMF, the highest plasma temperature decreases and the anode arc root moves upstream significantly, while the current density distribution at the anode is more concentrated with a higher peak value. In addition, the use of AMF then induces a strong backflow at the torch spout and its magnitude increases with the AMF strength but decreases with the inlet gas velocity.展开更多
The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with th...The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%.Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.展开更多
The inner surface modification process by plasma-based low-energy ion implantation（PBLEII）with an electron cyclotron resonance（ECR）microwave plasma source located at the central axis of a cylindrical tube is model...The inner surface modification process by plasma-based low-energy ion implantation（PBLEII）with an electron cyclotron resonance（ECR）microwave plasma source located at the central axis of a cylindrical tube is modeled to optimize the low-energy ion implantation parameters for industrial applications.In this paper,a magnetized plasma diffusion fluid model has been established to describe the plasma nonuniformity caused by plasma diffusion under an axial magnetic field during the pulse-off time of low pulsed negative bias.Using this plasma density distribution as the initial condition,a sheath collisional fluid model is built up to describe the sheath evolution and ion implantation during the pulse-on time.The plasma nonuniformity at the end of the pulse-off time is more apparent along the radial direction compared with that in the axial direction due to the geometry of the linear plasma source in the center and the difference between perpendicular and parallel plasma diffusion coefficients with respect to the magnetic field.The normalized nitrogen plasma densities on the inner and outer surfaces of the tube are observed to be about 0.39 and 0.24,respectively,of which the value is 1 at the central plasma source.After a 5μs pulse-on time,in the area less than 2 cm from the end of the tube,the nitrogen ion implantation energy decreases from 1.5 keV to 1.3 keV and the ion implantation angle increases from several degrees to more than 40°;both variations reduce the nitrogen ion implantation depth.However,the nitrogen ion implantation dose peaks of about 2×10^（10）-7×10^（10）ions/cm^2 in this area are 2-4 times higher than that of 1.18×10^（10）ions/cm^2 and 1.63×10^（10）ions/cm^2 on the inner and outer surfaces of the tube.The sufficient ion implantation dose ensures an acceptable modification effect near the end of the tube under the low energy and large angle conditions for nitrogen ion implantation,because the modification effect is mainly determined by the ion implantation dose,just as the mass transfer process in PBLEII is dominated by low-energy ion implantation and thermal diffusion.Therefore,a comparatively uniform surface modification by the low-energy nitrogen ion implantation is achieved along the cylindrical tube on both the inner and outer surfaces.展开更多
A two-dimensional mathematical model was developed to describe the heat transfer and fluid flow in an AC arc zone of a ferrosilicon submerged arc furnace. In this model, the time-dependent conservation equations of ma...A two-dimensional mathematical model was developed to describe the heat transfer and fluid flow in an AC arc zone of a ferrosilicon submerged arc furnace. In this model, the time-dependent conservation equations of mass, momentum, and energy in the specified domain of plasma zone were numerically solved by coupling with the Maxwell and Laplace equations for magnetic filed and electric potential, respectively. A control volume-based finite difference method was used to solve the governing equations in cylindrical coordinates. The reliability of the developed model was checked by experimental data from the previous available literature. The results of present model were in good agreement with the given data comparing with other models, because of solving the Maxwell and Laplace equations simul- taneously in order to calculate current density. In addition, parametric studies were carried out to evaluate the effects of electrical current and arc length on flow field and temperature distribution within the arc. According to the computed results, a lower power input led to a higher arc efficiency.展开更多
Plasma-neutral gas dynamics is computationally investigated in a miniaturized mi- crothruster~ that encloses Ar and contains dielectric material sandwiched between two metal plates using a two-dimensional plasma mode....Plasma-neutral gas dynamics is computationally investigated in a miniaturized mi- crothruster~ that encloses Ar and contains dielectric material sandwiched between two metal plates using a two-dimensional plasma mode. Spatial and temporal plasma properties are investigated by solving the Poisson equation with the conservation equations of charged and excited neutral plasma species using the COMSOL Multiphysics 4.2b. The microthruster property is found to depend on the secondary electron emission coefficient. The electrohydrodynamic force （EHD） is calculated and found to be significant in the sheath area near the dielectric layer and is found to affect gas flow dynamics including the Ar excimer formation and density. The effects of pressure and secondary emission coefficient are discussed. The plasma characteristics are affected by small changes in the secondary electron emission coefficient, which could result from the dielec- tric erosion and aging, and is found to affect the electrohydrodynamic force produced when the microthruster is used to produce thrust for a small spacecraft.展开更多
In this paper,a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted.In the present technological approach,the employment of air poses a significant challeng...In this paper,a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted.In the present technological approach,the employment of air poses a significant challenge.The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime.The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient.In this way,the electron density and in turn the density of reactive species is increased.In addition,the plasma jet assembly is equipped with a short electrode.This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species.The plasma jet is formed within and emitted by a small conical nozzle.A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle.In the jet the concentration of toxic and unwanted neutral plasma species like O3 or NOx is significantly reduced because of the shorter residence time within the plasma.The range of short-lived active plasma species is in turn considerably enhanced.The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment.Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume.展开更多
The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the ...The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the behavior in plasma.In this paper,a glass vacuum chamber and a pair of plate electrodes were designed and fabricated,using 13.56 MHz radio frequency（RF）discharge technology to ionize the working gas of Ar.This discharge was mathematically described with equivalent circuit model.The discharge voltage and current of the plasma were measured atdifferent pressures and different powers.Based on the capacitively coupled homogeneous discharge model,the equivalent circuit and the analytical formula were established.The plasma density and temperature were calculated by using the equivalent impedance principle and energy balance equation.The experimental results show that when RF discharge power is 50–300 W and pressure is 25–250 Pa,the average electron temperature is about 1.7–2.1 e V and the average electron density is about 0.5？×10^17–3.6？×10^17m^-3.Agreement was found when the results were compared to those given by optical emission spectroscopy and COMSOL simulation.展开更多
In previous studies on plasma-particle interaction, as far as we know, the rf plasma flow and temperature fields are all simulated by the non-self-consistent one-dimensional electromagnetic (1-D EM) field model. In th...In previous studies on plasma-particle interaction, as far as we know, the rf plasma flow and temperature fields are all simulated by the non-self-consistent one-dimensional electromagnetic (1-D EM) field model. In the present paper, the complete self-consistent two-dimensional electromagnetic (2-D EM) field model in- corporating the axial Lorentz force component, which is neglected in the 1-D model, is firstly adopted to calculate the aluminium particle trajectory and thermal history in atmospheric rf Ar plasma with the particle evaporation effect included. The cru- cial effect of reverse flow within the coil region on the particle trajectory is discovered and the results show that the 2-D EM field model must be adopted instead of the 1-D model when the plasma-particle interaction is studied. The effect of carrier gas flux on the particle movement and heating are also studied, resulting in some useful conclusions for both plasma theory and application.展开更多
The isentropic exponent of single-ionized mono-atomic plasmas in thermal equilib- rium is studied. Its behavior as a function of the ionization degree and temperature is examined for argon and zinc plasmas at two pres...The isentropic exponent of single-ionized mono-atomic plasmas in thermal equilib- rium is studied. Its behavior as a function of the ionization degree and temperature is examined for argon and zinc plasmas at two pressures （1 bar and 1 mbar, 1 mPa and 1 Pa）, respectively. The results show that for the two sorts of plasma the isentropic exponent equals typically about 1.1-1.2 within a considerably wide range of the ionization degree （5%-80%）.展开更多
Radio frequency capacitively coupled plasmas(RF CCPs)play a pivotal role in various applications in etching and deposition processes on a microscopic scale in semiconductor manufacturing.In the discharge process,the p...Radio frequency capacitively coupled plasmas(RF CCPs)play a pivotal role in various applications in etching and deposition processes on a microscopic scale in semiconductor manufacturing.In the discharge process,the plasma series resonance(PSR)effect is easily observed in electrically asymmetric and geometrically asymmetric discharges,which could largely influence the power absorption,ionization rate,etc.In this work,the PSR effect arising from geometrically and electrically asymmetric discharge in argon-oxygen mixture gas is mainly investigated by using a plasma equivalent circuit model coupled with a global model.At relatively low pressures,as Ar content(α)increases,the inductance of the bulk is weakened,which leads to a more obvious PSR phenomenon and a higher resonance frequency(ω_(psr)).When the Ar content is fixed,varying the pressure and gap distance could also have different effects on the PSR effect.With the increase of the pressure,the PSR frequency shifts towards the higher order,but in the case of much higher pressure,the PSR oscillation would be strongly damped by frequent electron-neutral collisions.With the increase of the gap distance,the PSR frequency becomes lower.In addition,electrically asymmetric waveforms applied to a geometrically asymmetric chamber may weaken or enhance the asymmetry of the discharge and regulate the PSR effect.In this work,the Ar/O_(2) electronegative mixture gas is introduced in a capacitive discharge to study the PSR effect under geometric asymmetry effect and electrical asymmetry effect,which can provide necessary guidance in laboratory research and current applications.展开更多
Dual-electrode capacitively coupled plasma discharges are investigated here to lower the non-uniformity of plasma density. The dual-electrode structure proposed by Jung splits the electrode region and increases the fl...Dual-electrode capacitively coupled plasma discharges are investigated here to lower the non-uniformity of plasma density. The dual-electrode structure proposed by Jung splits the electrode region and increases the flexibility of fine tuning non-uniformity. Different RF voltages,frequencies, phase-shifts and electrode areas are simulated and the influences are discussed. RF voltage and electrode area have a non-monotonic effect on non-uniformity, while frequency has a monotonic effect. Phase-shift has a cyclical influence on non-uniformity. A special combination of 224 V voltage and 11% area ratio with 10 MHz lowers the non-uniformity of the original set（200 V voltage and 0% area ratio with 10 MHz） by 46.5%. The position of the plasma density peak at the probe line has been tracked and properly tuning the phase-shift can obtain the same trace as tuning frequency or voltage.展开更多
In this study, we consider three main collisions in dusty plasmas and investigate the effects of dust grains on the propagation of electromagnetic（EM） waves through uniform, unmagnetized and weakly ionized dusty pla...In this study, we consider three main collisions in dusty plasmas and investigate the effects of dust grains on the propagation of electromagnetic（EM） waves through uniform, unmagnetized and weakly ionized dusty plasma. The Drude model is improved to describe the dielectric property of dusty plasmas, which accounts for collisions including electron–molecule, electron–ion, and electron–dust particles. Based on the improved Drude model, the propagation characteristics of microwaves in dusty plasmas have been numerically calculated and studied.The results show that the propagation characteristics of microwaves through dusty plasmas are different from those through normal plasmas. The effects of dust density and size are mainly studied. Numerical results indicate that the momentum transfer between electrons and dust grains makes more energy loss. The dust density and dust size have a similar influence on EM wave propagation, resulting in less transmission and more absorption.展开更多
A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to ...A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to calculate scattering cross-sections and transport properties.The applicability of the proposed plasma screening model is demonstrated using the example of the temperature relaxation rate in dense hydrogen and warm dense aluminum.Additionally,the conductivity of warm dense aluminum is computed in the regime where collisions are dominated by electron-ion scattering.The results obtained are compared with available theoretical results and simulation data.展开更多
An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical mode...An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical model are considered. The numerical simulation is carried out for parallel-plate geometry with a separation of 0.06 cm. The results show that Ar＊ plays a major role in the discharge, which is mainly produced by ground state excitation reaction. The electron temperature reaches its maximum in the cathode sheath but maintains a low value （0.23 eV） in bulk plasma. Elastic collision is the dominant volumetric electron energy loss in atmosphere argon glow discharge, which is negligible in low pressure argon glow discharge. The metastable step-wise ionization is the main mechanism for electron production to sustain the discharge. However, the highest contribution to electron production rate is ground state ionization reaction. The bremsstrahlung power density is related to electric voltage. With the increase of the electric voltage, the bremsstrahlung power density increases, namely, the strength of ultraviolet radiation spectrum enhances in the cathode sheath.展开更多
The industrial application of the Kaufman ion thruster in its arc stage is limited owing to the instability of the discharge pulse.Presently,a complete prediction model that can predict the discharge pulse in the high...The industrial application of the Kaufman ion thruster in its arc stage is limited owing to the instability of the discharge pulse.Presently,a complete prediction model that can predict the discharge pulse in the high-current stage does not exist.In this study,a complete prediction model for the pulse in the ion thruster is established using the zero-dimensional plasma discharge model and equivalent circuit model.The zero-dimensional plasma discharge model is used to obtain the corresponding plasma parameters by calculating the beam current,discharge current,voltage,and gas flow under actual working conditions.The input parameters of the equivalent circuit model are calculated using empirical formulae to acquire the estimated discharge waveforms.The pulse waveforms obtained using the model are found to be consistent with the experimental results.The model is used to evaluate the process of rapid changes in plasma density.Additionally,this model is employed to predict changes in the pulse waveforms when the volume of the discharge chamber and grid plate transmittance are changed.展开更多
In order to measure controllability of vertical instability in EAST,the calculation of model-based vertical growth rate,called rt-gamma,has been successfully carried out in real time.The numerical computing method is ...In order to measure controllability of vertical instability in EAST,the calculation of model-based vertical growth rate,called rt-gamma,has been successfully carried out in real time.The numerical computing method is adapted from rigid plasma response model in TokSys,which is a widely-used analysis tool for tokamak devices in Matlab environment,but the code is rewritten by taking advantage of GPU parallel computing capability to accelerate the computation.The calculation of rt-gamma is validated by comparing it with the corresponding result generated by TokSys for totally 3508 cases.It is shown that the average absolute value of relative errors is about 0.85%.In addition,the calculation program of rt-gamma has been successfully applied during 2019 EAST campaign.The comparison with experimental results is discussed in this paper.The real-time calculation tool is well able to calculate model-based vertical growth rate,which is convenient for fast and continuous evaluations of EAST control system stability performances.展开更多
We propose a numerical methodology for the simultaneous numerical simulation of four states of matter:gas,liquid,elastoplastic solids,and plasma.The distinct,interacting physical processes are described by a combinati...We propose a numerical methodology for the simultaneous numerical simulation of four states of matter:gas,liquid,elastoplastic solids,and plasma.The distinct,interacting physical processes are described by a combination of compressible,inert,and reactive forms of the Euler equations,multi-phase equations,elastoplastic equations,and resistive MHD equations.Combinations of systems of equations are usually solved by coupling finite element for solid modelling and CFD models for fluid modelling or including material effects through boundary conditions rather than full material discretisation.Our simultaneous solution methodology lies on the recasting of all the equations in the same,hyperbolic form allowing their solution on the same grid with the same finite volume numerical schemes.We use a combination of sharp-and diffuse-interface methods to track or capture material interfaces,depending on the application.The communication between the distinct systems of equations(i.e.,materials separated by sharp interfaces)is facilitated by means of mixed-material Riemann solvers at the boundaries of the systems,which represent physical material boundaries.To this end,we derive approximate mixed-material Riemann solvers for each pair of the above models based on characteristic equations.To demonstrate the applicability of the new methodology,we consider a case study,where we investigate the possibility of ignition of a combustible gas that lies over a liquid in a metal container that is struck by a plasma arc akin to a lightning strike.We study the effect of the metal container material and its conductivity on the ignition of the combustible gas,as well as the effects of an additional dielectric coating,the sensitivity of the gas,and differences between scenarios with sealed and pre-damaged metal surfaces.展开更多
Radial equilibrium of the KTX plasma column is maintained by the vertical field which is produced by the equilibrium field coils.The equilibrium is also affected by the eddy current,which is generated by the coupling ...Radial equilibrium of the KTX plasma column is maintained by the vertical field which is produced by the equilibrium field coils.The equilibrium is also affected by the eddy current,which is generated by the coupling of copper shell,plasma and poloidal field coils.An equivalent circuit model is developed to analyze the dynamic performance of equilibrium field coils,without auxiliary power input to equilibrium field coils and passive conductors.Considering the coupling of poloidal field coils,copper shell and plasma,the evolution of spatial distribution of the eddy current density on the copper shell is estimated by finite element to analyze the effect of shell to balance.The simulation results show that the copper shell and equilibrium field coils can provide enough vertical field to balance 1 MA plasma current in phase 1 of a KTX discharge.Auxiliary power supply on the EQ coils is necessary to control the horizontal displacement of KTX due to the finite resistance effect of the shell.展开更多
A model coupling the plasma with a cathode body is applied in the simulation of the diffuse state of a magnetically rotating arc.Four parametric studies are performed：on the external axial magnetic field（AMF）,on th...A model coupling the plasma with a cathode body is applied in the simulation of the diffuse state of a magnetically rotating arc.Four parametric studies are performed：on the external axial magnetic field（AMF）,on the cathode shape,on the total current and on the inlet gas velocity.The numerical results show that：the cathode attachment focuses in the center of the cathode tip with zero AMF and gradually shifts off the axis with the increase of AMF;a larger cathode conical angle corresponds to a cathode arc attachment farther away off axis;the maximum values of plasma temperature increase with the total current;the plasma column in front of the cathode tip expands more severely in the axial direction,with a higher inlet speed;the cathode arc attachment shrinks towards the tip as the inlet speed increases.The various results are supposed to be explained by the joint effect of coupled cathode surface heating and plasma rotating flow.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0118700)the National Natural Science Foundation of China(Grant No.62375101)the Fundamental Research Funds for the Central Universities(Grant No.YCJJ20230216).
文摘Spectroscopy,especially for plasma spectroscopy,provides a powerful platform for biological and material analysis with its elemental and molecular fingerprinting capability.Artificial intelligence(AI)has the tremendous potential to build a universal quantitative framework covering all branches of plasma spectroscopy based on its unmatched representation and generalization ability.Herein,we introduce an AI-based unified method called self-supervised image-spectrum twin information fusion detection(SISTIFD)to collect twin co-occurrence signals of the plasma and to intelligently predict the physical parameters for improving the performances of all plasma spectroscopic techniques.It can fuse the spectra and plasma images in synchronization,derive the plasma parameters(total number density,plasma temperature,electron density,and other implicit factors),and provide accurate results.The experimental data demonstrate their excellent utility and capacity,with a reduction of 98%in evaluation indices(root mean square error,relative standard deviation,etc.)and an analysis frequency of 143 Hz(much faster than the mainstream detection frame rate of 1 Hz).In addition,as a completely end-to-end and self-supervised framework,the SISTIFD enables automatic detection without manual preprocessing or intervention.With these advantages,it has remarkably enhanced various plasma spectroscopic techniques with state-of-the-art performance and unsealed their possibility in industry,especially in the regions that require both capability and efficiency.This scheme brings new inspiration to the whole field of plasma spectroscopy and enables in situ analysis with a real-world scenario of high throughput,cross-interference,various analyte complexity,and diverse applications.
基金National Natural Science Foundation of China(Nos.10375065,10675122)
文摘A theoretical model is presented to describe the electromagnetic, heat transfer and fluid flow phenomena within a magnetron plasma torch and in the resultant plume, by using a commercial computational fluid dynamics （CFD） code FLUENT. Specific calculations are pre- sented for a pure argon system （i.e., an argon plasma discharging into an argon environment）, operated in a turbulent mode. An important finding of this work is that the external axial magnetic field （AMF） may have a significant effect on the behavior of arc plasma and thus affects the resulting plume. The AMF impels the plasma to retract axially and expand radially. As a result, the plasma intensity distribution on the cross section of torch seems to be more uniform. Numerical results also show that with AMF, the highest plasma temperature decreases and the anode arc root moves upstream significantly, while the current density distribution at the anode is more concentrated with a higher peak value. In addition, the use of AMF then induces a strong backflow at the torch spout and its magnitude increases with the AMF strength but decreases with the inlet gas velocity.
基金Supported by the Fund of Science and Technology on Vacuum Technology and Physics Laboratory of Lanzhou Institute of Physics under Grant No YSC0715the National Natural Science Foundation of China under Grant No 62601210the Civil Aerospace Technology Research Project under Grant No D010509
文摘The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%.Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.
基金supported by National Natural Science Foundation of China(Nos.50725519,51271048,51321004)
文摘The inner surface modification process by plasma-based low-energy ion implantation（PBLEII）with an electron cyclotron resonance（ECR）microwave plasma source located at the central axis of a cylindrical tube is modeled to optimize the low-energy ion implantation parameters for industrial applications.In this paper,a magnetized plasma diffusion fluid model has been established to describe the plasma nonuniformity caused by plasma diffusion under an axial magnetic field during the pulse-off time of low pulsed negative bias.Using this plasma density distribution as the initial condition,a sheath collisional fluid model is built up to describe the sheath evolution and ion implantation during the pulse-on time.The plasma nonuniformity at the end of the pulse-off time is more apparent along the radial direction compared with that in the axial direction due to the geometry of the linear plasma source in the center and the difference between perpendicular and parallel plasma diffusion coefficients with respect to the magnetic field.The normalized nitrogen plasma densities on the inner and outer surfaces of the tube are observed to be about 0.39 and 0.24,respectively,of which the value is 1 at the central plasma source.After a 5μs pulse-on time,in the area less than 2 cm from the end of the tube,the nitrogen ion implantation energy decreases from 1.5 keV to 1.3 keV and the ion implantation angle increases from several degrees to more than 40°;both variations reduce the nitrogen ion implantation depth.However,the nitrogen ion implantation dose peaks of about 2×10^（10）-7×10^（10）ions/cm^2 in this area are 2-4 times higher than that of 1.18×10^（10）ions/cm^2 and 1.63×10^（10）ions/cm^2 on the inner and outer surfaces of the tube.The sufficient ion implantation dose ensures an acceptable modification effect near the end of the tube under the low energy and large angle conditions for nitrogen ion implantation,because the modification effect is mainly determined by the ion implantation dose,just as the mass transfer process in PBLEII is dominated by low-energy ion implantation and thermal diffusion.Therefore,a comparatively uniform surface modification by the low-energy nitrogen ion implantation is achieved along the cylindrical tube on both the inner and outer surfaces.
文摘A two-dimensional mathematical model was developed to describe the heat transfer and fluid flow in an AC arc zone of a ferrosilicon submerged arc furnace. In this model, the time-dependent conservation equations of mass, momentum, and energy in the specified domain of plasma zone were numerically solved by coupling with the Maxwell and Laplace equations for magnetic filed and electric potential, respectively. A control volume-based finite difference method was used to solve the governing equations in cylindrical coordinates. The reliability of the developed model was checked by experimental data from the previous available literature. The results of present model were in good agreement with the given data comparing with other models, because of solving the Maxwell and Laplace equations simul- taneously in order to calculate current density. In addition, parametric studies were carried out to evaluate the effects of electrical current and arc length on flow field and temperature distribution within the arc. According to the computed results, a lower power input led to a higher arc efficiency.
基金the support provided by the Deanship of Scientific Research (DSR) at the King Fahd University of Petroleum and Minerals (KFUPM) for funding this work through project No. IN111026
文摘Plasma-neutral gas dynamics is computationally investigated in a miniaturized mi- crothruster~ that encloses Ar and contains dielectric material sandwiched between two metal plates using a two-dimensional plasma mode. Spatial and temporal plasma properties are investigated by solving the Poisson equation with the conservation equations of charged and excited neutral plasma species using the COMSOL Multiphysics 4.2b. The microthruster property is found to depend on the secondary electron emission coefficient. The electrohydrodynamic force （EHD） is calculated and found to be significant in the sheath area near the dielectric layer and is found to affect gas flow dynamics including the Ar excimer formation and density. The effects of pressure and secondary emission coefficient are discussed. The plasma characteristics are affected by small changes in the secondary electron emission coefficient, which could result from the dielec- tric erosion and aging, and is found to affect the electrohydrodynamic force produced when the microthruster is used to produce thrust for a small spacecraft.
文摘In this paper,a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted.In the present technological approach,the employment of air poses a significant challenge.The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime.The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient.In this way,the electron density and in turn the density of reactive species is increased.In addition,the plasma jet assembly is equipped with a short electrode.This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species.The plasma jet is formed within and emitted by a small conical nozzle.A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle.In the jet the concentration of toxic and unwanted neutral plasma species like O3 or NOx is significantly reduced because of the shorter residence time within the plasma.The range of short-lived active plasma species is in turn considerably enhanced.The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment.Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume.
基金supported by National Natural Science Foundation of China(Grant No.61378037)the Fundamental Research Funds for the Central Universities(Nos.2013B33614,2017B15214)+1 种基金the Research Funds of Innovation and Entrepreneurship Education Reform for Chinese Universities(No.16CCJG01Z004)the Changzhou Science and Technology Program(No.CJ20160027)
文摘The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the behavior in plasma.In this paper,a glass vacuum chamber and a pair of plate electrodes were designed and fabricated,using 13.56 MHz radio frequency（RF）discharge technology to ionize the working gas of Ar.This discharge was mathematically described with equivalent circuit model.The discharge voltage and current of the plasma were measured atdifferent pressures and different powers.Based on the capacitively coupled homogeneous discharge model,the equivalent circuit and the analytical formula were established.The plasma density and temperature were calculated by using the equivalent impedance principle and energy balance equation.The experimental results show that when RF discharge power is 50–300 W and pressure is 25–250 Pa,the average electron temperature is about 1.7–2.1 e V and the average electron density is about 0.5？×10^17–3.6？×10^17m^-3.Agreement was found when the results were compared to those given by optical emission spectroscopy and COMSOL simulation.
文摘In previous studies on plasma-particle interaction, as far as we know, the rf plasma flow and temperature fields are all simulated by the non-self-consistent one-dimensional electromagnetic (1-D EM) field model. In the present paper, the complete self-consistent two-dimensional electromagnetic (2-D EM) field model in- corporating the axial Lorentz force component, which is neglected in the 1-D model, is firstly adopted to calculate the aluminium particle trajectory and thermal history in atmospheric rf Ar plasma with the particle evaporation effect included. The cru- cial effect of reverse flow within the coil region on the particle trajectory is discovered and the results show that the 2-D EM field model must be adopted instead of the 1-D model when the plasma-particle interaction is studied. The effect of carrier gas flux on the particle movement and heating are also studied, resulting in some useful conclusions for both plasma theory and application.
文摘The isentropic exponent of single-ionized mono-atomic plasmas in thermal equilib- rium is studied. Its behavior as a function of the ionization degree and temperature is examined for argon and zinc plasmas at two pressures （1 bar and 1 mbar, 1 mPa and 1 Pa）, respectively. The results show that for the two sorts of plasma the isentropic exponent equals typically about 1.1-1.2 within a considerably wide range of the ionization degree （5%-80%）.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12020101005 and 11975067)。
文摘Radio frequency capacitively coupled plasmas(RF CCPs)play a pivotal role in various applications in etching and deposition processes on a microscopic scale in semiconductor manufacturing.In the discharge process,the plasma series resonance(PSR)effect is easily observed in electrically asymmetric and geometrically asymmetric discharges,which could largely influence the power absorption,ionization rate,etc.In this work,the PSR effect arising from geometrically and electrically asymmetric discharge in argon-oxygen mixture gas is mainly investigated by using a plasma equivalent circuit model coupled with a global model.At relatively low pressures,as Ar content(α)increases,the inductance of the bulk is weakened,which leads to a more obvious PSR phenomenon and a higher resonance frequency(ω_(psr)).When the Ar content is fixed,varying the pressure and gap distance could also have different effects on the PSR effect.With the increase of the pressure,the PSR frequency shifts towards the higher order,but in the case of much higher pressure,the PSR oscillation would be strongly damped by frequent electron-neutral collisions.With the increase of the gap distance,the PSR frequency becomes lower.In addition,electrically asymmetric waveforms applied to a geometrically asymmetric chamber may weaken or enhance the asymmetry of the discharge and regulate the PSR effect.In this work,the Ar/O_(2) electronegative mixture gas is introduced in a capacitive discharge to study the PSR effect under geometric asymmetry effect and electrical asymmetry effect,which can provide necessary guidance in laboratory research and current applications.
基金supported by National Natural Science Foundation of China(No.51405261)
文摘Dual-electrode capacitively coupled plasma discharges are investigated here to lower the non-uniformity of plasma density. The dual-electrode structure proposed by Jung splits the electrode region and increases the flexibility of fine tuning non-uniformity. Different RF voltages,frequencies, phase-shifts and electrode areas are simulated and the influences are discussed. RF voltage and electrode area have a non-monotonic effect on non-uniformity, while frequency has a monotonic effect. Phase-shift has a cyclical influence on non-uniformity. A special combination of 224 V voltage and 11% area ratio with 10 MHz lowers the non-uniformity of the original set（200 V voltage and 0% area ratio with 10 MHz） by 46.5%. The position of the plasma density peak at the probe line has been tracked and properly tuning the phase-shift can obtain the same trace as tuning frequency or voltage.
基金supported by National Natural Science Foundation of China under Grant Nos.61205093 and 61601419the Fundamental Research Funds for the Central Universities under Grant No.HIT.MKSTISP.2016 11
文摘In this study, we consider three main collisions in dusty plasmas and investigate the effects of dust grains on the propagation of electromagnetic（EM） waves through uniform, unmagnetized and weakly ionized dusty plasma. The Drude model is improved to describe the dielectric property of dusty plasmas, which accounts for collisions including electron–molecule, electron–ion, and electron–dust particles. Based on the improved Drude model, the propagation characteristics of microwaves in dusty plasmas have been numerically calculated and studied.The results show that the propagation characteristics of microwaves through dusty plasmas are different from those through normal plasmas. The effects of dust density and size are mainly studied. Numerical results indicate that the momentum transfer between electrons and dust grains makes more energy loss. The dust density and dust size have a similar influence on EM wave propagation, resulting in less transmission and more absorption.
基金funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan Grant No.AP19678033“The study of the transport and optical properties of hydrogen at high pressure.”。
文摘A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to calculate scattering cross-sections and transport properties.The applicability of the proposed plasma screening model is demonstrated using the example of the temperature relaxation rate in dense hydrogen and warm dense aluminum.Additionally,the conductivity of warm dense aluminum is computed in the regime where collisions are dominated by electron-ion scattering.The results obtained are compared with available theoretical results and simulation data.
基金supported by the Major State Basic Research Development Program of China (973 Program) (No. 2011CB20941)Scientific Research Foundation of State Key Lab. of Power Transmission Equipment and System Security of China (No. 2007DA10512709102)+1 种基金National Natural Science Foundation of China (No. 51007096)the Fundamental Research Funds for the Central Universities of China(No. CDJZR10150001)
文摘An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical model are considered. The numerical simulation is carried out for parallel-plate geometry with a separation of 0.06 cm. The results show that Ar＊ plays a major role in the discharge, which is mainly produced by ground state excitation reaction. The electron temperature reaches its maximum in the cathode sheath but maintains a low value （0.23 eV） in bulk plasma. Elastic collision is the dominant volumetric electron energy loss in atmosphere argon glow discharge, which is negligible in low pressure argon glow discharge. The metastable step-wise ionization is the main mechanism for electron production to sustain the discharge. However, the highest contribution to electron production rate is ground state ionization reaction. The bremsstrahlung power density is related to electric voltage. With the increase of the electric voltage, the bremsstrahlung power density increases, namely, the strength of ultraviolet radiation spectrum enhances in the cathode sheath.
基金the financial support from National Natural Science Foundation of China(Nos.11402025,11475019,and 11702123)the National Key Laboratory of Science and Technology on Vacuum Technology&Physics(No.ZWK1608)+1 种基金the Advanced Space Propulsion Laboratory of BICEBeijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology(No.Lab ASP-2018-03)。
文摘The industrial application of the Kaufman ion thruster in its arc stage is limited owing to the instability of the discharge pulse.Presently,a complete prediction model that can predict the discharge pulse in the high-current stage does not exist.In this study,a complete prediction model for the pulse in the ion thruster is established using the zero-dimensional plasma discharge model and equivalent circuit model.The zero-dimensional plasma discharge model is used to obtain the corresponding plasma parameters by calculating the beam current,discharge current,voltage,and gas flow under actual working conditions.The input parameters of the equivalent circuit model are calculated using empirical formulae to acquire the estimated discharge waveforms.The pulse waveforms obtained using the model are found to be consistent with the experimental results.The model is used to evaluate the process of rapid changes in plasma density.Additionally,this model is employed to predict changes in the pulse waveforms when the volume of the discharge chamber and grid plate transmittance are changed.
基金National MCF Energy Research and Development Program of China(Grant No.2018YFE0302100)the National Natural Science Foundation of China(Grant Nos.11705239,11805236,and 11875291).
文摘In order to measure controllability of vertical instability in EAST,the calculation of model-based vertical growth rate,called rt-gamma,has been successfully carried out in real time.The numerical computing method is adapted from rigid plasma response model in TokSys,which is a widely-used analysis tool for tokamak devices in Matlab environment,but the code is rewritten by taking advantage of GPU parallel computing capability to accelerate the computation.The calculation of rt-gamma is validated by comparing it with the corresponding result generated by TokSys for totally 3508 cases.It is shown that the average absolute value of relative errors is about 0.85%.In addition,the calculation program of rt-gamma has been successfully applied during 2019 EAST campaign.The comparison with experimental results is discussed in this paper.The real-time calculation tool is well able to calculate model-based vertical growth rate,which is convenient for fast and continuous evaluations of EAST control system stability performances.
基金This work was supported by Jaguar Land Rover and the UK-EPSRC Grant EP/K014188/1 as part of the jointly funded Programme for Simulation Innovation and Boeing Research&Technology(BR&T)Grant SSOW-BRT-L0516-0569.
文摘We propose a numerical methodology for the simultaneous numerical simulation of four states of matter:gas,liquid,elastoplastic solids,and plasma.The distinct,interacting physical processes are described by a combination of compressible,inert,and reactive forms of the Euler equations,multi-phase equations,elastoplastic equations,and resistive MHD equations.Combinations of systems of equations are usually solved by coupling finite element for solid modelling and CFD models for fluid modelling or including material effects through boundary conditions rather than full material discretisation.Our simultaneous solution methodology lies on the recasting of all the equations in the same,hyperbolic form allowing their solution on the same grid with the same finite volume numerical schemes.We use a combination of sharp-and diffuse-interface methods to track or capture material interfaces,depending on the application.The communication between the distinct systems of equations(i.e.,materials separated by sharp interfaces)is facilitated by means of mixed-material Riemann solvers at the boundaries of the systems,which represent physical material boundaries.To this end,we derive approximate mixed-material Riemann solvers for each pair of the above models based on characteristic equations.To demonstrate the applicability of the new methodology,we consider a case study,where we investigate the possibility of ignition of a combustible gas that lies over a liquid in a metal container that is struck by a plasma arc akin to a lightning strike.We study the effect of the metal container material and its conductivity on the ignition of the combustible gas,as well as the effects of an additional dielectric coating,the sensitivity of the gas,and differences between scenarios with sealed and pre-damaged metal surfaces.
基金supported by the Ministry of Science and Technology of China(No.2011GB106000)
文摘Radial equilibrium of the KTX plasma column is maintained by the vertical field which is produced by the equilibrium field coils.The equilibrium is also affected by the eddy current,which is generated by the coupling of copper shell,plasma and poloidal field coils.An equivalent circuit model is developed to analyze the dynamic performance of equilibrium field coils,without auxiliary power input to equilibrium field coils and passive conductors.Considering the coupling of poloidal field coils,copper shell and plasma,the evolution of spatial distribution of the eddy current density on the copper shell is estimated by finite element to analyze the effect of shell to balance.The simulation results show that the copper shell and equilibrium field coils can provide enough vertical field to balance 1 MA plasma current in phase 1 of a KTX discharge.Auxiliary power supply on the EQ coils is necessary to control the horizontal displacement of KTX due to the finite resistance effect of the shell.
基金supported by National Natural Science Foundation of China(Nos.11475174,11035005 and 50876101)
文摘A model coupling the plasma with a cathode body is applied in the simulation of the diffuse state of a magnetically rotating arc.Four parametric studies are performed：on the external axial magnetic field（AMF）,on the cathode shape,on the total current and on the inlet gas velocity.The numerical results show that：the cathode attachment focuses in the center of the cathode tip with zero AMF and gradually shifts off the axis with the increase of AMF;a larger cathode conical angle corresponds to a cathode arc attachment farther away off axis;the maximum values of plasma temperature increase with the total current;the plasma column in front of the cathode tip expands more severely in the axial direction,with a higher inlet speed;the cathode arc attachment shrinks towards the tip as the inlet speed increases.The various results are supposed to be explained by the joint effect of coupled cathode surface heating and plasma rotating flow.
