Theory of sheath in a multicomponent plasma

Mahanta, M. K.; Goswami, K. S.

doi:10.1063/1.873767

Cited by 7 publications

(6 citation statements)

References 11 publications

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“…It is important to stress that numerical results of many authors [11][12][13][14][15][16][17][18][19] have clearly shown that under collisional conditions a space charge sheath can exist when v i < v B . The physical interpretation and the mathematical description of these results by analytical expressions [19][20][21][22][23][24][25] has led to different views [21][22][23]. This is mainly because of the use of incompletely defined terms, a few simple errors and insufficient attention to the numerical results.…”

Section: Introductionmentioning

confidence: 99%

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Sheath formation in low-pressure discharges

Valentini

2000

Plasma Sources Sci. Technol.

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Sheath formation is studied for slightly ionized plasmas, i.e. for many typical low-pressure discharges. A sheath adjacent to an insulating wall is a space charge region where the electron flux to the wall is reduced to the corresponding ion flux. Numerical and analytical results show that no lower bound of the ion drift speed v i exists to form a sheath under collisional conditions. The product of the ambipolar ion speed v B and the square root of the ratio of the number density of the ions to that of the electrons occurs as a characteristic ion drift speed v c for the sheath formation. In the interval 0 < v i < v c the collisions promote the sheath formation, whereas the electric field inhibits it. The effect of the collisions dominates. In the interval v i > v c both the electric field and the collisions support the sheath formation. The effect of the electric field alone can form the sheath. When the electron density is relatively small under collision-dominated conditions the space charge density can become relatively large in the neighbourhood of the point where v i = v B , and then the difference between v c and v B is significant. It is also possible that such a point does not exist. At low collisionality, in the centre of the plasma and close to the wall v i < v c can hold, whereas in an intermediate region v i > v c can be satisfied. When the collisionality is high v i < v c everywhere. This relation can also hold when v i > v B occurs close to the wall. The sheath formation can be dominated by collisions in a larger range of parameters than recognized to date. The application of the Bohm criterion is inappropriate when the collisionality is high and the electron density is relative low. Multi-component plasmas are discussed briefly. The concept of a sheath edge is examined critically.

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Section: Introductionmentioning

confidence: 99%

“…Furthermore, to date, the papers deriving analytical expressions for the sheath formation under collisional conditions [4,6,7,[20][21][22][23][24][25] assume a very small space charge density near v i = v B . This assumption is correct only when the effect of the collisions is small and the electron density is high.…”

Section: Introductionmentioning

confidence: 99%

Sheath formation in low-pressure discharges

Valentini

2000

Plasma Sources Sci. Technol.

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“…The quantity of dust particles and the velocity of the electron beam were discovered to be significant factors in the development of wave instability in the plasma [26]. Mahanta and Goswami looked into the effect of the electron beam on the sheath structure in a dusty plasma in the past [27]. They came to the conclusion that the presence of an electron beam reduces the negative floating potential [27].…”

Section: Introductionmentioning

confidence: 99%

Effects of a static and an magnetic field electron beam on the linear propagation of dust acoustic mode

El-Shorbagy,

Mahassen,

Elbendary

2024

Preprint

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Dusty plasma consist of electron, ions, electron beam as a separate component and charged dust grains observed in several astrophysical and space environments such as nebulas, planetary rings, and planetary ionosphere. The physical and optical properties of plasma are depend on dynamic of species in the discharge volume, then the presence of an electron beam and external static magnetic field in a dusty plasma can modify the plasma structure. In this study, we proved the linear propagation in the non-collision dusty plasma. The results revealed that the propagation of acoustic waves in the dusty plasma can be controlled by adjusting the electron number density of the electron beam and the external magnetic field.

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“…A number of approaches have been used to model the boundary layer in multi-component plasma. For instance, one-dimensional (1D) fluid models have been used to describe the plasma pre-sheath containing directional beamlike electrons [3], while full space-charge fluid models have been developed for plasmas containing fast isotropic electrons [1] and collimated beam electrons [4]. It is a feature of these models that significant secondary electron densities can persist in the sheath, which give rise to oscillatory or periodic solutions in the sheath potential.…”

Section: Introductionmentioning

confidence: 99%

The plasma boundary containing fast isotropic electrons: a comparison between kinetic and fluid ion models

Bradley

2001

J. Phys. D: Appl. Phys.

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The behaviour of a boundary layer containing fast isotropic primary electrons has been investigated using a modified Tonks-Langmuir model for the one-dimensional collisionless plasma, both using the full space-charge description and the quasi-neutral approximation. The plasma solutions are compared directly to those obtained from a fluid model of the same system developed by Schott in 1987 (Phys. Fluids 30 1795). In the kinetic ion model a single double-layer structure is observed to form for all primary electron densities, with a two-stage rise in the boundary potential approaching the wall. This single double-layer exists at a point corresponding to the initiation of oscillatory solutions (periodic double layers) in the potential, particle concentrations and space charge in the fluid model. In the quasi-neutral approximation of the kinetic model, for primary to thermal electron densities above a ratio of about 0.3 the sheath-edge potential jumps from a value close to the voltage equivalent of the electron temperature to a value just under the isotropic electron energy. This is in very close agreement with the previously obtained fluid quasi-neutral solutions.

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Theory of sheath in a multicomponent plasma

Cited by 7 publications

References 11 publications

Sheath formation in low-pressure discharges

Sheath formation in low-pressure discharges

Effects of a static and an magnetic field electron beam on the linear propagation of dust acoustic mode

The plasma boundary containing fast isotropic electrons: a comparison between kinetic and fluid ion models

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