A weakly magnetized sheath for a collisionless, electronegative plasma comprising positive ions,electrons, and negative ions is investigated numerically using the fluid approach. The electrons are considered to be non...A weakly magnetized sheath for a collisionless, electronegative plasma comprising positive ions,electrons, and negative ions is investigated numerically using the fluid approach. The electrons are considered to be non-Maxwellian in nature and are described by Tsalli's distribution. Such electrons have a substantial effect on the sheath properties. The study also reveals that non-Maxwellian distribution is the most realistic description for negative ions in the presence of an oblique magnetic field. In addition to the negative ion temperature, the sheath potential is also affected by the nonextensive parameters. The present research finds application in the plasma processing and semiconductor industry as well as in space plasmas.展开更多
A hydrodynamic model is used to investigate the characteristics of positive ions in the sheath region of a low-pressure magnetized electronegative discharge. Positive ions are modeled as a cold fluid, while the electr...A hydrodynamic model is used to investigate the characteristics of positive ions in the sheath region of a low-pressure magnetized electronegative discharge. Positive ions are modeled as a cold fluid, while the electron and negative ion density distributions obey the Boltzmann distribution with two different temperatures. By taking into account the ion-neutral collision effect in the sheath region and assuming that the momentum transfer cross section has a power law dependence on the velocity of positive ions, the sheath formation criterion （modified Bohm＇s criterion） is derived and it is shown that there are specified maximum and minimum limits for the ion Mach number M. Considering these two limits of M, the behaviors of electrostatic potential, charged particle density distributions and positive ion velocities in the sheath region are studied for different values of ion-neutral collision frequency.展开更多
A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and...A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.展开更多
The characteristics of dust plasma sheath in an oblique magnetic field are investigated with a fluid model. Hot electrons, cold ions, neutral particles, and dust grains are taken into account in this system. We perfor...The characteristics of dust plasma sheath in an oblique magnetic field are investigated with a fluid model. Hot electrons, cold ions, neutral particles, and dust grains are taken into account in this system. We perform a numerical simulation of the sheath. The results reveal that the magnetic field has significant effects on the sheath structure, and it also makes the suspension position of dust shift away from the wall.展开更多
In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Bolt...In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.展开更多
Determination of the negative ion number density of O2 and O in a DC discharge of oxygen plasma was made employing Langmuir probe in conjunction with eclipse laser photo- detachment technique. The temporal evolution o...Determination of the negative ion number density of O2 and O in a DC discharge of oxygen plasma was made employing Langmuir probe in conjunction with eclipse laser photo- detachment technique. The temporal evolution of the extra electrons resulting from the photo- detachment of O2- and O- were used to evaluate the negative ion number density. The ratio of O2 number density to O varied from 0.03 to 0.22. Number density of both O~ and O increased with increasing power and decreased as the pressure was increased. Electron number density was evaluated from the electron energy distribution function （EEDF） using the I-V recorded characteristic curves. Electron temperature between 2 and 2.7 eV were obtained. Influence of the 02（al△g） metastable state is discussed.展开更多
A kinetic simulation model has been employed to study the properties of an electronegative magnetized plasma sheath assuming the cut-off distribution of electrons and negative ions.The fundamental kinetic Bohm conditi...A kinetic simulation model has been employed to study the properties of an electronegative magnetized plasma sheath assuming the cut-off distribution of electrons and negative ions.The fundamental kinetic Bohm condition for the electronegative magnetized plasma has paramount importance for the formation of a stationary plasma sheath near the material wall.The presence of an oblique magnetic field in an electronegative plasma affects the ion distribution at the plasma injection side and at the wall.The temperature profile of negative charged particles has a non-uniform distribution,which determines the energy flow towards the wall.展开更多
In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,firs...In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,first,the intrinsic connection between the electropositive plasma transport equation and spring oscillator dynamic equation is established.Inspired by this similarity,reformed“spring oscillator”equation with dispersing instead of restoring force that gives quasi-delta solution is devised according to the math embodied in the anion equation,which is of potential significance to the disciplines of atomic physics and astronomy as well.For solving the“diffusion confusion”the physics that determines the delta profile within the continuity equation is explored on the basis that recombination loss source term plays the role of drift flux,which is applicable for fluid model of low temperature plasma,but not the ordinary fluid dynamics.Besides,the math and physics revealed in this work predict that the ratio of recombination or attachment(for electrons)frequency versus the species diffusion coefficient is a very important parameter in determining the delta distribution,as it acts as the acceleration of object,according to the reformed oscillator equation.With this theory,the analogous delta profile of electrons density in the famous drift and ambi-polar diffusion heating mechanism of electronegative capacitively coupled plasma is interpreted.展开更多
This paper presents the evolution of the electronegativity with the applied power during the E to H mode transition in a radio frequency(rf)inductively coupled plasma(ICP)in a mixture of Ar and O2.The densities of the...This paper presents the evolution of the electronegativity with the applied power during the E to H mode transition in a radio frequency(rf)inductively coupled plasma(ICP)in a mixture of Ar and O2.The densities of the negative ion and the electron,as well as their ratio,i.e.,the electronegativity,are measured as a function of the applied power by laser photo-detachment combined with a microwave resonance probe,under different pressures and O2 contents.Meanwhile,the optical emission intensities at Ar 750.4 nm and O 844.6 nm are monitored via a spectrograph.It was found that by increasing the applied power,the electron density and the optical emission intensity show a similar trench,i.e.,they increase abruptly at a threshold power,suggesting that the E to H mode transition occurs.With the increase of the pressure,the negative ion density presents opposite trends in the E-mode and the H-mode,which is related to the difference of the electron density and energy for the two modes.The emission intensities of Ar 750.4 nm and O 844.6 nm monotonously decrease with increasing the pressure or the O2 content,indicating that the density of high-energy electrons,which can excite atoms,is monotonically decreased.This leads to an increase of the negative ion density in the H-mode with increasing the pressure.Besides,as the applied power is increased,the electronegativity shows an abrupt drop during the E-to H-mode transition.展开更多
文摘A weakly magnetized sheath for a collisionless, electronegative plasma comprising positive ions,electrons, and negative ions is investigated numerically using the fluid approach. The electrons are considered to be non-Maxwellian in nature and are described by Tsalli's distribution. Such electrons have a substantial effect on the sheath properties. The study also reveals that non-Maxwellian distribution is the most realistic description for negative ions in the presence of an oblique magnetic field. In addition to the negative ion temperature, the sheath potential is also affected by the nonextensive parameters. The present research finds application in the plasma processing and semiconductor industry as well as in space plasmas.
文摘A hydrodynamic model is used to investigate the characteristics of positive ions in the sheath region of a low-pressure magnetized electronegative discharge. Positive ions are modeled as a cold fluid, while the electron and negative ion density distributions obey the Boltzmann distribution with two different temperatures. By taking into account the ion-neutral collision effect in the sheath region and assuming that the momentum transfer cross section has a power law dependence on the velocity of positive ions, the sheath formation criterion （modified Bohm＇s criterion） is derived and it is shown that there are specified maximum and minimum limits for the ion Mach number M. Considering these two limits of M, the behaviors of electrostatic potential, charged particle density distributions and positive ion velocities in the sheath region are studied for different values of ion-neutral collision frequency.
文摘A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.
文摘The characteristics of dust plasma sheath in an oblique magnetic field are investigated with a fluid model. Hot electrons, cold ions, neutral particles, and dust grains are taken into account in this system. We perform a numerical simulation of the sheath. The results reveal that the magnetic field has significant effects on the sheath structure, and it also makes the suspension position of dust shift away from the wall.
文摘In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.
基金financed by CONACy T with contract#41072-F,PRODEPthe Programa Integral de Fortalecimiento Institucinal-2
文摘Determination of the negative ion number density of O2 and O in a DC discharge of oxygen plasma was made employing Langmuir probe in conjunction with eclipse laser photo- detachment technique. The temporal evolution of the extra electrons resulting from the photo- detachment of O2- and O- were used to evaluate the negative ion number density. The ratio of O2 number density to O varied from 0.03 to 0.22. Number density of both O~ and O increased with increasing power and decreased as the pressure was increased. Electron number density was evaluated from the electron energy distribution function （EEDF） using the I-V recorded characteristic curves. Electron temperature between 2 and 2.7 eV were obtained. Influence of the 02（al△g） metastable state is discussed.
基金Suresh Basnet would like to acknowledge the University Grants Commission,Nepal for the PhD fellowship.
文摘A kinetic simulation model has been employed to study the properties of an electronegative magnetized plasma sheath assuming the cut-off distribution of electrons and negative ions.The fundamental kinetic Bohm condition for the electronegative magnetized plasma has paramount importance for the formation of a stationary plasma sheath near the material wall.The presence of an oblique magnetic field in an electronegative plasma affects the ion distribution at the plasma injection side and at the wall.The temperature profile of negative charged particles has a non-uniform distribution,which determines the energy flow towards the wall.
文摘In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,first,the intrinsic connection between the electropositive plasma transport equation and spring oscillator dynamic equation is established.Inspired by this similarity,reformed“spring oscillator”equation with dispersing instead of restoring force that gives quasi-delta solution is devised according to the math embodied in the anion equation,which is of potential significance to the disciplines of atomic physics and astronomy as well.For solving the“diffusion confusion”the physics that determines the delta profile within the continuity equation is explored on the basis that recombination loss source term plays the role of drift flux,which is applicable for fluid model of low temperature plasma,but not the ordinary fluid dynamics.Besides,the math and physics revealed in this work predict that the ratio of recombination or attachment(for electrons)frequency versus the species diffusion coefficient is a very important parameter in determining the delta distribution,as it acts as the acceleration of object,according to the reformed oscillator equation.With this theory,the analogous delta profile of electrons density in the famous drift and ambi-polar diffusion heating mechanism of electronegative capacitively coupled plasma is interpreted.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11675039,11875101,and 11935005)the Fundamental Research Founds for the Central Universities,China(Grant Nos.DUT18TD06 and DUT20LAB201).
文摘This paper presents the evolution of the electronegativity with the applied power during the E to H mode transition in a radio frequency(rf)inductively coupled plasma(ICP)in a mixture of Ar and O2.The densities of the negative ion and the electron,as well as their ratio,i.e.,the electronegativity,are measured as a function of the applied power by laser photo-detachment combined with a microwave resonance probe,under different pressures and O2 contents.Meanwhile,the optical emission intensities at Ar 750.4 nm and O 844.6 nm are monitored via a spectrograph.It was found that by increasing the applied power,the electron density and the optical emission intensity show a similar trench,i.e.,they increase abruptly at a threshold power,suggesting that the E to H mode transition occurs.With the increase of the pressure,the negative ion density presents opposite trends in the E-mode and the H-mode,which is related to the difference of the electron density and energy for the two modes.The emission intensities of Ar 750.4 nm and O 844.6 nm monotonously decrease with increasing the pressure or the O2 content,indicating that the density of high-energy electrons,which can excite atoms,is monotonically decreased.This leads to an increase of the negative ion density in the H-mode with increasing the pressure.Besides,as the applied power is increased,the electronegativity shows an abrupt drop during the E-to H-mode transition.
