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Cedric J Powell - One of the best experts on this subject based on the ideXlab platform.
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elsepa dirac partial wave calculation of elastic scattering of electrons and positrons by atoms Positive Ions and molecules new version announcement
Computer Physics Communications, 2021Co-Authors: F Salvat, A Jablonski, Cedric J PowellAbstract:Abstract A new version of the Fortran program elsepa , which calculates differential and integrated cross sectIons for elastic scattering of electrons and positrons, is presented. Details of the program and its applicatIons are given in the original paper [Comput. Phys. Commun. 165 (2005) 157–190]. Dirac phase shifts are now calculated by using the recently published subroutine package radial (Salvat and Fernandez-Varea, 2019), which solves the radial wave equation for real or complex central potentials by means of a robust and accurate power-series method. In addition, elastic collisIons with atoms in elemental solids are described by using the muffin-tin optical model potential proposed by Bote et al., (2009), which is somewhat more elaborate and flexible than that in the original elsepa code and allows adjusting the absorption potential to give inelastic cross sectIons in close agreement with empirical data. With the use of the radial subroutines, the work of elsepa is reduced to (1) the definition of the interaction potential and (2) the summation of the partial-wave series of the scattering amplitudes. The structure of the new code has been simplified and stricter criteria for the convergence of the partial-wave series have been adopted. The distribution package includes gnuplot scripts for easy visualization of the calculation results. Program summary Program Title: elsepa CPC Library link to program files: https://doi.org/10.17632/w4hm5vymym.1 Licensing provisIons: CC BY NC 3.0 Programming language: Fortran 90 Journal reference of previous version: Comput. Phys. Commun. 165 (2005) 157–190 Does the new version supersede the previous version?: Yes Reasons for the new version: This new version offers increased accuracy, and a more flexible modeling of elastic collisIons of electrons and positrons with atoms in elemental solids. Summary of revisIons: The calculation of phase shifts is now performed by the generic subroutines of the radial package [1]. A more flexible optical-model potential for scattering in solids is included [2]. Stricter criteria for convergence of the partial-wave series are applied. The distribution package has been reorganized, with the numerical database files now placed in a separate directory; scripts for direct visualization of the calculation results with the plotting program gnuplot ( http://www.gnuplot.info ) are also included. Nature of problem: The code calculates differential cross sectIons, total cross sectIons and transport cross sectIons for single elastic scattering of electrons and positrons by neutral atoms, Positive Ions and randomly oriented molecules. When the energy of the projectile is less than about 5 MeV, the programs also compute scattering amplitudes and spin polarization functIons. Solution method: The effective interaction between the projectile and the target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less that about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used. The programs only admit kinetic energies higher than 5 eV, a practical lower limit that may be changed by editing the source files. Additional comments including restrictIons and unusual features: The calculatIons are based on the static-field approximation. The optional correlation-polarization and inelastic absorption correctIons are obtained from approximate, semi-empirical models. elsepa allows considering an absorption potential only for projectiles with energies less than about 1 MeV; for higher energies, the absorption potential is set to zero to prevent the occurrence of numerical instabilities. CalculatIons for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by Ions, the electron density of the ion must be supplied by the user; it can be generated, e.g., by running the program dhfs of the radial package [1]. Acknowledgments We are indebted to Dr John Villarrubia for pointing out various cases of incomplete convergence of the original code. Financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades / Agencia Estatal de Investigacion, Spain / European Regional Development Fund , European Union, (project no. RTI2018-098117-B-C22) is gratefully aknowledged. References: [1] F. Salvat, J.M. Fernandez-Varea, Comput. Phys. Commun. 240 (2019) 165–177. [2] D. Bote, F. Salvat, A. Jablonski, C.J. Powell, J. Electron. Spectrosc. Rel. Phenom. 175 (2009) 41—54.
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elsepa dirac partial wave calculation of elastic scattering of electrons and positrons by atoms Positive Ions and molecules
Computer Physics Communications, 2005Co-Authors: F Salvat, A Jablonski, Cedric J PowellAbstract:The fortran 77 code system elsepa for the calculation of elastic scattering of electrons and positrons by atoms, Positive Ions and molecules is presented. These codes perform relativistic (Dirac) partial-wave calculatIons for scattering by a local central interaction potential V(r)V(r). For atoms and Ions, the static-field approximation is adopted, with the potential set equal to the electrostatic interaction energy between the projectile and the target, plus an approximate local exchange interaction when the projectile is an electron. For projectiles with kinetic energies up to 10 keV, the potential may optionally include a semiempirical correlation–polarization potential to describe the effect of the target charge polarizability. Also, for projectiles with energies less than 1 MeV, an imaginary absorptive potential can be introduced to account for the depletion of the projectile wave function caused by open inelastic channels. Molecular cross sectIons are calculated by means of a single-scattering independent-atom approximation in which the electron density of a bound atom is approximated by that of the free neutral atom. Elastic scattering by individual atoms in solids is described by means of a muffin-tin model potential. Partial-wave calculatIons are feasible on modest personal computers for energies up to about 5 MeV. The elsepa code also implements approximate factorization methods that allow the fast calculation of elastic cross sectIons for much higher energies. The interaction model adopted in the calculatIons is defined by the user by combining the different optIons offered by the code. The nuclear charge distribution can be selected among four analytical models (point nucleus, uniformly charged sphere, Fermi's distribution and Helm's uniform–uniform distribution). The atomic electron density is handled in numerical form. The distribution package includes data files with electronic densities of neutral atoms of the elements hydrogen to lawrencium (Z=1Z=1–103) obtained from multiconfiguration Dirac–Fock self-consistent calculatIons. For comparison purposes, three simple analytical approximatIons to the electron density of neutral atoms (corresponding to the Thomas–Fermi, the Thomas–Fermi–Dirac and the Dirac–Hartree–Fock–Slater models) are also included. For calculatIons of elastic scattering by Ions, the electron density should be provided by the user. The exchange potential for electron scattering can be selected among three different analytical approximatIons (Thomas–Fermi, Furness–McCarthy, Riley–Truhlar). The offered optIons for the correlation–polarization potential are based on the empirical Buckingham potential. The imaginary absorption potential is calculated from the local-density approximation proposed by Salvat [Phys. Rev. A 68 (2003) 012708]. Program summary Title of program:ELSEPA Catalogue identifier: ADUS Program summary URL:http://cpc.cs.qub.ac.uk/cpc/summaries/ADUS Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland License provisIons: none Computer for which the program is designed and others in which it is operable: Any computer with a FORTRAN 77 compiler Operating systems under which the program has been tested: Windows XP, Windows 2000, Debian GNU/Linux 3.0r0 (sarge) Compilers: 1Compaq Visual Fortran v6.5 (Windows); GNU FORTRAN, g77 (Windows and Linux) Programming language used: FORTRAN 77 No. of bits in a word: 32 Memory required to execute with typical data: 0.6 Mb No. of lines in distributed program, including test data, etc.:135 489 No. of bytes in distributed program, including test data, etc.: 1 280 006 Distribution format: tar.gz Keywords: Dirac partial-wave analysis, electron elastic scattering, positron elastic scattering, differential cross sectIons, momentum transfer cross sectIons, transport cross sectIons, scattering amplitudes, spin polarization, scattering by complex potentials, high-energy atomic screening functIons Nature of the physical problem: The code calculates differential cross sectIons, total cross sectIons and transport cross sectIons for single elastic scattering of electrons and positrons by neutral atoms, Positive Ions and randomly oriented molecules. For projectiles with kinetic energies less than about 5 MeV, the programs can also compute scattering amplitudes and spin polarization functIons. Method of solution: The effective interaction between the projectile and a target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less that about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used. RestrictIons on the complexity of the program: The calculatIons are based on the static-field approximation. The optional correlation–polarization and inelastic absorption correctIons are obtained from approximate, semiempirical models. CalculatIons for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by Ions, the electron density of the ion must be supplied by the user. Typical running time: on a 2.8 GHz Pentium 4, 1 the calculation of elastic scattering by atoms and Ions takes between a few seconds and about two minutes, depending on the atomic number of the target, the adopted potential model and the kinetic energy of the projectile. Unusual features of the program: The program calculates elastic cross sectIons for electrons and positrons with kinetic energies in a wide range, from a few tens of eV up to about 1 GeV. CalculatIons can be performed for neutral atoms of all elements, from hydrogen to lawrencium (Z=1Z=1–103), Ions and simple molecules.
F Salvat - One of the best experts on this subject based on the ideXlab platform.
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elsepa dirac partial wave calculation of elastic scattering of electrons and positrons by atoms Positive Ions and molecules new version announcement
Computer Physics Communications, 2021Co-Authors: F Salvat, A Jablonski, Cedric J PowellAbstract:Abstract A new version of the Fortran program elsepa , which calculates differential and integrated cross sectIons for elastic scattering of electrons and positrons, is presented. Details of the program and its applicatIons are given in the original paper [Comput. Phys. Commun. 165 (2005) 157–190]. Dirac phase shifts are now calculated by using the recently published subroutine package radial (Salvat and Fernandez-Varea, 2019), which solves the radial wave equation for real or complex central potentials by means of a robust and accurate power-series method. In addition, elastic collisIons with atoms in elemental solids are described by using the muffin-tin optical model potential proposed by Bote et al., (2009), which is somewhat more elaborate and flexible than that in the original elsepa code and allows adjusting the absorption potential to give inelastic cross sectIons in close agreement with empirical data. With the use of the radial subroutines, the work of elsepa is reduced to (1) the definition of the interaction potential and (2) the summation of the partial-wave series of the scattering amplitudes. The structure of the new code has been simplified and stricter criteria for the convergence of the partial-wave series have been adopted. The distribution package includes gnuplot scripts for easy visualization of the calculation results. Program summary Program Title: elsepa CPC Library link to program files: https://doi.org/10.17632/w4hm5vymym.1 Licensing provisIons: CC BY NC 3.0 Programming language: Fortran 90 Journal reference of previous version: Comput. Phys. Commun. 165 (2005) 157–190 Does the new version supersede the previous version?: Yes Reasons for the new version: This new version offers increased accuracy, and a more flexible modeling of elastic collisIons of electrons and positrons with atoms in elemental solids. Summary of revisIons: The calculation of phase shifts is now performed by the generic subroutines of the radial package [1]. A more flexible optical-model potential for scattering in solids is included [2]. Stricter criteria for convergence of the partial-wave series are applied. The distribution package has been reorganized, with the numerical database files now placed in a separate directory; scripts for direct visualization of the calculation results with the plotting program gnuplot ( http://www.gnuplot.info ) are also included. Nature of problem: The code calculates differential cross sectIons, total cross sectIons and transport cross sectIons for single elastic scattering of electrons and positrons by neutral atoms, Positive Ions and randomly oriented molecules. When the energy of the projectile is less than about 5 MeV, the programs also compute scattering amplitudes and spin polarization functIons. Solution method: The effective interaction between the projectile and the target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less that about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used. The programs only admit kinetic energies higher than 5 eV, a practical lower limit that may be changed by editing the source files. Additional comments including restrictIons and unusual features: The calculatIons are based on the static-field approximation. The optional correlation-polarization and inelastic absorption correctIons are obtained from approximate, semi-empirical models. elsepa allows considering an absorption potential only for projectiles with energies less than about 1 MeV; for higher energies, the absorption potential is set to zero to prevent the occurrence of numerical instabilities. CalculatIons for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by Ions, the electron density of the ion must be supplied by the user; it can be generated, e.g., by running the program dhfs of the radial package [1]. Acknowledgments We are indebted to Dr John Villarrubia for pointing out various cases of incomplete convergence of the original code. Financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades / Agencia Estatal de Investigacion, Spain / European Regional Development Fund , European Union, (project no. RTI2018-098117-B-C22) is gratefully aknowledged. References: [1] F. Salvat, J.M. Fernandez-Varea, Comput. Phys. Commun. 240 (2019) 165–177. [2] D. Bote, F. Salvat, A. Jablonski, C.J. Powell, J. Electron. Spectrosc. Rel. Phenom. 175 (2009) 41—54.
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elsepa dirac partial wave calculation of elastic scattering of electrons and positrons by atoms Positive Ions and molecules
Computer Physics Communications, 2005Co-Authors: F Salvat, A Jablonski, Cedric J PowellAbstract:The fortran 77 code system elsepa for the calculation of elastic scattering of electrons and positrons by atoms, Positive Ions and molecules is presented. These codes perform relativistic (Dirac) partial-wave calculatIons for scattering by a local central interaction potential V(r)V(r). For atoms and Ions, the static-field approximation is adopted, with the potential set equal to the electrostatic interaction energy between the projectile and the target, plus an approximate local exchange interaction when the projectile is an electron. For projectiles with kinetic energies up to 10 keV, the potential may optionally include a semiempirical correlation–polarization potential to describe the effect of the target charge polarizability. Also, for projectiles with energies less than 1 MeV, an imaginary absorptive potential can be introduced to account for the depletion of the projectile wave function caused by open inelastic channels. Molecular cross sectIons are calculated by means of a single-scattering independent-atom approximation in which the electron density of a bound atom is approximated by that of the free neutral atom. Elastic scattering by individual atoms in solids is described by means of a muffin-tin model potential. Partial-wave calculatIons are feasible on modest personal computers for energies up to about 5 MeV. The elsepa code also implements approximate factorization methods that allow the fast calculation of elastic cross sectIons for much higher energies. The interaction model adopted in the calculatIons is defined by the user by combining the different optIons offered by the code. The nuclear charge distribution can be selected among four analytical models (point nucleus, uniformly charged sphere, Fermi's distribution and Helm's uniform–uniform distribution). The atomic electron density is handled in numerical form. The distribution package includes data files with electronic densities of neutral atoms of the elements hydrogen to lawrencium (Z=1Z=1–103) obtained from multiconfiguration Dirac–Fock self-consistent calculatIons. For comparison purposes, three simple analytical approximatIons to the electron density of neutral atoms (corresponding to the Thomas–Fermi, the Thomas–Fermi–Dirac and the Dirac–Hartree–Fock–Slater models) are also included. For calculatIons of elastic scattering by Ions, the electron density should be provided by the user. The exchange potential for electron scattering can be selected among three different analytical approximatIons (Thomas–Fermi, Furness–McCarthy, Riley–Truhlar). The offered optIons for the correlation–polarization potential are based on the empirical Buckingham potential. The imaginary absorption potential is calculated from the local-density approximation proposed by Salvat [Phys. Rev. A 68 (2003) 012708]. Program summary Title of program:ELSEPA Catalogue identifier: ADUS Program summary URL:http://cpc.cs.qub.ac.uk/cpc/summaries/ADUS Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland License provisIons: none Computer for which the program is designed and others in which it is operable: Any computer with a FORTRAN 77 compiler Operating systems under which the program has been tested: Windows XP, Windows 2000, Debian GNU/Linux 3.0r0 (sarge) Compilers: 1Compaq Visual Fortran v6.5 (Windows); GNU FORTRAN, g77 (Windows and Linux) Programming language used: FORTRAN 77 No. of bits in a word: 32 Memory required to execute with typical data: 0.6 Mb No. of lines in distributed program, including test data, etc.:135 489 No. of bytes in distributed program, including test data, etc.: 1 280 006 Distribution format: tar.gz Keywords: Dirac partial-wave analysis, electron elastic scattering, positron elastic scattering, differential cross sectIons, momentum transfer cross sectIons, transport cross sectIons, scattering amplitudes, spin polarization, scattering by complex potentials, high-energy atomic screening functIons Nature of the physical problem: The code calculates differential cross sectIons, total cross sectIons and transport cross sectIons for single elastic scattering of electrons and positrons by neutral atoms, Positive Ions and randomly oriented molecules. For projectiles with kinetic energies less than about 5 MeV, the programs can also compute scattering amplitudes and spin polarization functIons. Method of solution: The effective interaction between the projectile and a target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less that about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used. RestrictIons on the complexity of the program: The calculatIons are based on the static-field approximation. The optional correlation–polarization and inelastic absorption correctIons are obtained from approximate, semiempirical models. CalculatIons for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by Ions, the electron density of the ion must be supplied by the user. Typical running time: on a 2.8 GHz Pentium 4, 1 the calculation of elastic scattering by atoms and Ions takes between a few seconds and about two minutes, depending on the atomic number of the target, the adopted potential model and the kinetic energy of the projectile. Unusual features of the program: The program calculates elastic cross sectIons for electrons and positrons with kinetic energies in a wide range, from a few tens of eV up to about 1 GeV. CalculatIons can be performed for neutral atoms of all elements, from hydrogen to lawrencium (Z=1Z=1–103), Ions and simple molecules.
A. K. Kamra - One of the best experts on this subject based on the ideXlab platform.
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measurements of Positive Ions and air earth current density at maitri antarctica
Journal of Geophysical Research, 2007Co-Authors: Devendraa Siingh, Vimlesh Pant, A. K. KamraAbstract:[1] Simultaneous measurements of the small, intermediate and large Positive Ions and air-Earth current density made at a coastal station, Maitri (70°45′52″S, 11°44′03″E, 130 m above sea level), at Antarctica during January–February 2005, are reported. Although small and large Positive ion concentratIons do not show any systematic diurnal variatIons, variatIons in them are almost similar to each other. On the other hand, variatIons in intermediate Positive ion concentratIons are independent of variatIons in the small/large Positive Ions and exhibit a diurnal variation which is similar to that in atmospheric temperature on fair weather days with a maximum during the day and minimum during the night hours. No such diurnal variation in intermediate Positive ion concentration is observed on cloudy days when variatIons in them are also similar to those in small/large Positive ion concentratIons. Magnitude of diurnal variation in intermediate Positive ion concentration on fair weather days increases with the lowering of atmospheric temperature in this season. Scavenging of Ions by snowfall and trapping of α-rays from the ground radioactivity by a thin layer of snow on ground is demonstrated from observatIons. VariatIons in intermediate Positive ion concentration are explained on the basis of the formation of new particles by the photolytic nucleation process.
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Measurements of Positive Ions and air-earth current density at Maitri, Antarctica
Journal of Geophysical Research: Atmospheres, 2007Co-Authors: Devendraa Siingh, Pant, A. K. KamraAbstract:Simultaneous measurements of the small-, intermediate- and large- Positive Ions and air earth current density made at a coastal station, Maitri at Antarctica during January to February 2005, are reported. Although, small and large Positive ion concentratIons do not show any systematic diurnal variatIons, variatIons in them are almost similar to each other. On the other hand, variatIons in intermediate Positive ion concentratIons are independent of variatIons in the small/large Positive Ions and exhibit a diurnal variation which is similar to that in atmospheric temperature on fair weather days with a maximum during the day and minimum during the night hours. No such diurnal variation in intermediate Positive ion concentration is observed on cloudy days when variatIons in them are also similar to those insmall/large Positive ion concentratIons. Magnitude of diurnal variation in intermediate Positive ion concentration on fair weather days increases with the lowering of atmospheric temperature in this season. Scavenging of Ions by snowfall and trapping of Alha - rays from the ground radioactivity by a thin layer of snow on ground, is demonstrated from observatIons. VariatIons in intermediate Positive ion concentration are explained on the basis of the formation of new particles by the photolytic nucleation process.
Devendraa Siingh - One of the best experts on this subject based on the ideXlab platform.
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measurements of Positive Ions and air earth current density at maitri antarctica
Journal of Geophysical Research, 2007Co-Authors: Devendraa Siingh, Vimlesh Pant, A. K. KamraAbstract:[1] Simultaneous measurements of the small, intermediate and large Positive Ions and air-Earth current density made at a coastal station, Maitri (70°45′52″S, 11°44′03″E, 130 m above sea level), at Antarctica during January–February 2005, are reported. Although small and large Positive ion concentratIons do not show any systematic diurnal variatIons, variatIons in them are almost similar to each other. On the other hand, variatIons in intermediate Positive ion concentratIons are independent of variatIons in the small/large Positive Ions and exhibit a diurnal variation which is similar to that in atmospheric temperature on fair weather days with a maximum during the day and minimum during the night hours. No such diurnal variation in intermediate Positive ion concentration is observed on cloudy days when variatIons in them are also similar to those in small/large Positive ion concentratIons. Magnitude of diurnal variation in intermediate Positive ion concentration on fair weather days increases with the lowering of atmospheric temperature in this season. Scavenging of Ions by snowfall and trapping of α-rays from the ground radioactivity by a thin layer of snow on ground is demonstrated from observatIons. VariatIons in intermediate Positive ion concentration are explained on the basis of the formation of new particles by the photolytic nucleation process.
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Measurements of Positive Ions and air-earth current density at Maitri, Antarctica
Journal of Geophysical Research: Atmospheres, 2007Co-Authors: Devendraa Siingh, Pant, A. K. KamraAbstract:Simultaneous measurements of the small-, intermediate- and large- Positive Ions and air earth current density made at a coastal station, Maitri at Antarctica during January to February 2005, are reported. Although, small and large Positive ion concentratIons do not show any systematic diurnal variatIons, variatIons in them are almost similar to each other. On the other hand, variatIons in intermediate Positive ion concentratIons are independent of variatIons in the small/large Positive Ions and exhibit a diurnal variation which is similar to that in atmospheric temperature on fair weather days with a maximum during the day and minimum during the night hours. No such diurnal variation in intermediate Positive ion concentration is observed on cloudy days when variatIons in them are also similar to those insmall/large Positive ion concentratIons. Magnitude of diurnal variation in intermediate Positive ion concentration on fair weather days increases with the lowering of atmospheric temperature in this season. Scavenging of Ions by snowfall and trapping of Alha - rays from the ground radioactivity by a thin layer of snow on ground, is demonstrated from observatIons. VariatIons in intermediate Positive ion concentration are explained on the basis of the formation of new particles by the photolytic nucleation process.
M M Hatami - One of the best experts on this subject based on the ideXlab platform.
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the properties of the space charge and net current density in magnetized plasmas
Plasma Science & Technology, 2013Co-Authors: M M HatamiAbstract:A hydrodynamic model is used to investigate the properties of Positive space-charge and net current density in the sheath region of magnetized, collisional plasmas with warm Positive Ions. It is shown that an increase in the ion-neutral collision frequency, as well as the magnitude of the external magnetic field, leads to an increase in the net current density across the sheath region. The results also show that the accumulation of Positive Ions in the sheath region increases by increasing the ion-neutral collision frequency and the magnitude of the magnetic field. In addition, it is seen that an increase in the Positive ion temperatures causes a decrease in the accumulation of Positive Ions and the net current density in the sheath region.
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the properties of the space charge and net current density in
2013Co-Authors: Magnetized Plasmas, M M HatamiAbstract:A hydrodynamic model is used to investigate the properties of Positive space-charge and net current density in the sheath region of magnetized, collisional plasmas with warm Positive Ions. It is shown that an increase in the ion-neutral collision frequency, as well as the magnitude of the external magnetic fleld, leads to an increase in the net current density across the sheath region. The results also show that the accumulation of Positive Ions in the sheath region increases by increasing the ion-neutral collision frequency and the magnitude of the magnetic fleld. In addition, it is seen that an increase in the Positive ion temperatures causes a decrease in the accumulation of Positive Ions and the net current density in the sheath region.
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Collisional effects in magnetized plasma sheath with two species of Positive Ions
Journal of Physics D: Applied Physics, 2008Co-Authors: M M Hatami, B Shokri, A R NiknamAbstract:The effects of ion–neutral collision on the characteristics of a magnetized plasma sheath which consists of two species of Positive Ions are investigated. It is assumed that the Ions have different masses. In contrast to our previous work, the effects of ion–neutral collision frequency are added to the magnetized plasma sheath. Using a three-fluid hydrodynamic model and some dimensionless variables, the dimensionless equatIons are obtained and solved numerically. By taking into account the ion–neutral collision effects on a magnetized three-component plasma sheath, it is shown that apart from the presence of the second ion species, by increasing the collision frequency of two Ions with neutrals, the amplitude of fluctuatIons of ion species density distributIons increases and the position of these fluctuatIons is shifted towards the plasma sheath edge. Also, by increasing the ion–neutral collision frequency these fluctuatIons turn off faster than those in a collisionless case. It is shown that in the collisional magnetized plasma sheath, the effects of the presence of the heavier ion species on the lighter ion density turn off much faster in comparison with what happens in a collisionless magnetized plasma sheath. Furthermore, it is found that in a collisionless plasma sheath by increasing the density of the heavier ion species, the normalized electrostatic potential decreases while in a collisional plasma sheath the presence of the heavier ion species does not have any considerable effect on the normalized electrostatic potential. In addition, it is shown that when the distance of each ion species from the plasma sheath boundary becomes larger than five times the electron Debye length (x > 5λDe) the fluctuatIons of the ion species velocities disappear by increasing the ion–neutral collision frequency. Also, it is found that the electron density distribution decreases by increasing the ion–neutral collision frequency.
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magnetized plasma sheath with two species of Positive Ions
Physics of Plasmas, 2008Co-Authors: M M Hatami, A R Niknam, B Shokri, Hamid GhomiAbstract:The effects of the magnitude and direction of an oblique magnetic field and the effect of the ion densities ratio on a plasma sheath of electrons and two species of Positive Ions are investigated by using a three-fluid hydrodynamics model. These Ions have different masses but the same ionization ratio (Z=1). It is shown that the density distribution and velocity of the lighter and heavier ion species begin to fluctuate under the action of the electrostatic and Lorentz forces when the ratio of electron Debye length to lighter ion species Larmor radius becomes greater than 1 and 3, respectively. Also, it is found that the velocity fluctuatIons of the lighter ion species are much higher than those of the heavier ion species. Furthermore, the obtained results due to the presence of the second ion (the heavier ion) are compared to the reported results of the magnetized plasma sheath including single Positive ion species. In the presence of the second ion, it is shown that the velocity and density distribution ...
