Sheath Criterion for an Electronegative Plasma Sheath in an Oblique Magnetic Field

Liu, Huiping; Xiu, Zou; Qiu, Minghui

doi:10.1088/1009-0630/16/7/01

Cited by 8 publications

(4 citation statements)

References 27 publications

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“…In the past few decades, the study of plasma-surface transition in an electronegative plasma has become an area of interest both experimentally and theoretically [15][16][17][18][19][20]. The electrostatic potential distribution is a monotonic function in the sheath region.…”

Section: Introductionmentioning

confidence: 99%

Kinetic simulation of an electronegative plasma with a cut-off distribution and modified Bohm criterion

Basnet¹,

Khanal²

2019

Plasma Sci. Technol.

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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.

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Section: Introductionmentioning

confidence: 99%

Kinetic simulation of an electronegative plasma with a cut-off distribution and modified Bohm criterion

Basnet¹,

Khanal²

2019

Plasma Sci. Technol.

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“…A reduction in U 0z Min with increasing N N0 reveals that the negative ions help positive ions to enter the sheath region. Since a magnetized electronegative warm plasma has been visualized under the collisional environment, the values of U 0z Min are less than 1 for all the set of controlling parameters, consistent with [24,31], whereas U 0z Min takes values ⩾1 for collision-less plasmas consistent with [23,27].…”

Section: Resultsmentioning

confidence: 99%

“…The impact of an oblique magnetic field on the sheath structure in view of the positive ion Bohm speed has been investigated by several researchers [23][24][25][26][27] using the Sagdeev potential approach. However, they have neglected several imperative controlling parameters, such as those identified by Asserghine et al [23] in their model where they neglected the impact of collisions, ionization and adiabatic approximation, Yasserian and Aslaninejad [24] who neglected the impact of ionization, positive ion temperature, adiabatic approximation and non-extensivity of the system, Safa et al [25] who neglected the impact of collisions, ionization, adiabatic approximation, positive ion temperature and negative ions, Zou et al [26] who neglected the impact of collisions, ionization, positive ion temperature, adiabatic approximation, negative ions and non-extensivity of the system, and Huiping et al [27] who neglected the collisions, ionization, positive ion temperature, adiabatic approximation and non-extensivity of the system.…”

Section: Introductionmentioning

confidence: 99%

Are the oscillations found in magnetized collisional electronegative warm plasma artifact during plasma-surface interaction?

Dhawan,

Malik

2023

J. Phys. D: Appl. Phys.

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Formation of sheath and its characteristics are investigated in an electronegative plasma under the impact of an oblique and constant magnetic field. Specifically, the role of magnetic field and initial conditions of positive ion velocity on the sheath characteristics is uncovered by adopting Sagdeev potential approach for the determination of modified Bohm’s criterion. At the sheath edge, the upper and lower components of the positive ion velocity perpendicular to the probe/wall are determined and examined in greater details. The sheath structure is found to be modified considerably by the initial conditions. If the magnetic field is strong near the sheath edge, then the profile of the positive-ion density shows a pulse-like structure for the case when we neglect the x-component (parallel to the wall) of positive ion velocity at the sheath edge. This pulse-like structure disappears when all the components of positive ion velocity at the sheath edge are included, i.e., ions are considered to move in any direction but toward the probe. The occurrence or disappearance of pulse-like structure or oscillations completely depend upon the initial conditions. Since in real situations the ions are expected to move in any direction (carrying all their velocity components) and are not aligned only in the direction perpendicular to the wall, these oscillations are artifact in nature. The sheath thickness is observed to be reduced with increasing magnetic field strength and its inclination. In order to better understand the phenomenon, isothermal and adiabatic cases are also discussed.

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“…Besides these, it is crucial in the understanding of the Earthʼs ionosphere [16] and astrophysical plasmas [17]. In the past few decades, many works have been devoted to the study of plasma-sheath characteristics with two or more populations of negatively charged particles (e.g., two groups of electrons, or those containing negative ions) and this is still an attractive subject in plasma physics [18][19][20][21][22]. Sheridan et al [10] experimentally observed the existence of two-temperature groups: hot and cold electrons in magnetron sputtering plasma.…”

Section: Introductionmentioning

confidence: 99%

Kinetic-theory-based investigation of electronegative plasma–wall transition with two populations of electrons

Basnet¹,

Deuja²,

Khanal³

2021

Plasma Sci. Technol.

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Kinetic theory has been employed to investigate the magnetized plasma-sheath structure and its characteristics in the presence of more than one species of negatively charged particles: hot electrons, cold electrons, and negative ions. The cold electrons and negative ions are considered to obey a Maxwellian distribution, whereas the hot electrons follow a truncated Maxwellian distribution. The Bohm sheath condition has been extended for the case of more than one species of negatively charged particles, in which the concentration of hot electrons has a crucial role in achieving the Bohm velocity. The thermal motion of hot electrons is much higher compared to cold electrons and negative ions, such that the variation of hot electron concentrations and the temperature ratio of hot to cold electrons play a key role in the determination of the plasma-sheath parameters: particle densities, electrostatic potential, the flow of positive ions towards the wall, and sheath thickness. We have estimated the deviation of the resultant drift velocity of positive ions on the plane perpendicular to the wall from the parallel component at the presheath–sheath interface. It is found that the deviation between the two velocity components increases with an increase in the obliqueness of the magnetic field. Furthermore, the results obtained from the kinetic trajectory simulation model are compared with the results obtained using a fluid model; the results are qualitatively similar, although the potential varies by less than 4% in terms of the magnitude at the wall.

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Sheath Criterion for an Electronegative Plasma Sheath in an Oblique Magnetic Field

Cited by 8 publications

References 27 publications

Kinetic simulation of an electronegative plasma with a cut-off distribution and modified Bohm criterion

Kinetic simulation of an electronegative plasma with a cut-off distribution and modified Bohm criterion

Are the oscillations found in magnetized collisional electronegative warm plasma artifact during plasma-surface interaction?

Kinetic-theory-based investigation of electronegative plasma–wall transition with two populations of electrons

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