The effects of collisions on the plasma presheath

Koch, Daniel; Hitchon, W. N. G.

doi:10.1063/1.859040

Cited by 27 publications

(23 citation statements)

References 5 publications

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“…This temperature is also consistent with the theoretical results of Kock and Huchon for a presheath with this degree of collisionality. 27 Charge exchange collisions have approximately the same cross section as elastic collisions 26 and will tend to equilibrate the ion temperature with that of the more numerous neutral atoms. Because the neutral gas temperature is unknown, and is almost certainly not room temperature everywhere, 10 the contribution of charge exchange collisions to the ion temperature is uncertain.…”

Section: Discussionmentioning

confidence: 99%

Laser-induced fluorescence characterization of ions in a magnetron plasma

Goeckner¹,

Goree²,

Sheridan³

1990

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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We report for the first time laser-induced fluorescence measurements of a sputtering magnetron plasma. From these measurements we determined the density, average velocity, and temperature of the ions. The ion density profile is peaked at the same location as the electron density profile, which was measured with a Langmuir probe. The average ion velocity parallel to the cathode surface is less than our detection limit of 93 m/s. The ions at the edge of the discharge are room temperature, while in the center of the discharge they reach a temperature of 0.64 eV. These temperatures are attributed to acceleration of the ions by the electric field in the plasma, together with collisional scattering.

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Section: Discussionmentioning

confidence: 99%

Laser-induced fluorescence characterization of ions in a magnetron plasma

Goeckner¹,

Goree²,

Sheridan³

1990

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…For each time step ⌬t, each cell will move "ballistically" (i.e., collisionlessly) first, then a fraction ⌬t Ӷ 1 of the par-ticles in the cell will be scattered [7][8][9]. The handling of the scattered particles will be discussed in the next section.…”

Section: A Mesh Structure For the Convective Scheme And The Ballistimentioning

confidence: 99%

“…Broadly speaking, particle methods suffer from statistical noise, whereas a solution of the BE will usually have some amount of inaccuracy due to numerical diffusion. The method we present here, which is a version of the method of characteristics which we call a "convective scheme" (CS), minimizes numerical diffusion in a variety of ways [7][8][9] but cannot eliminate it entirely. The CS was originally developed for use in plasma simulation.…”

Section: Introductionmentioning

confidence: 99%

Boltzmann equation description of flows at long mean free paths

Feng

Hitchon

2004

Phys. Rev. E

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The flow of a gas around a rectangular object is simulated by solving the Boltzmann equation for the gas. The Boltzmann equation is solved by means of a method of characteristics which we refer to as a convective scheme (CS). This paper focuses, first, on two computational issues. We describe how the CS which is presented here is implemented so as to handle reflecting boundary conditions very accurately. Next, a collision operator for the self-collisions of the neutral gas has been developed which conserves momentum and energy "exactly" and which also preserves higher moments of the distribution so as to correctly calculate quantities such as viscosity. Finally, the method is illustrated briefly by calculating flow patterns and drag coefficients for a low Mach-number flow around a rectangular obstacle, over a range of Knudsen numbers which spans the transitional regime, and very accurate values of the drag coefficient are obtained across the whole range.

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“…If ionization is not neglected, (9) holds but is defined as in . The effect of retaining the convective derivative is to add the factor in (8). This means that the ion velocity begins to deviate from the usual expression for mobility limited when exceeds 0.3.…”

Section: Theoretical Considerations For Single Ion Presheathmentioning

confidence: 99%

“…A continuum of solutions exists for (1) and (2) depending on the relative sizes of the mean free path for collisions, the mean free path for ionization, and the chamber dimensions [5]- [8].…”

Section: Theoretical Considerations For Single Ion Presheathmentioning

confidence: 99%

Presheath environment in weakly ionized single and multispecies plasmas

Hershkowitz

Wang

et al. 2005

IEEE Trans. Plasma Sci.

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Abstract-The presheath located near boundaries in weakly ionized plasmas is a rich environment in which charge exchange, and ion-ion streaming instabilities combine to establish the electric fields that accelerate ions to close to the Bohm velocity at the sheath/presheath boundary. Charge exchange sets the presheath scale length in weakly collisional plasma, in which ionization can be neglected. The transition of mobility limited ion flow near the bulk plasma to free fall motion close to the plate for single species plasmas is explored. Measurements in argon-helium multidipole plasmas of plasma potential with emissive probes and ion energy distribution functions with laser induced fluorescence are presented. These data show that the argon ions are speeded up by the presheath electric fields, argon ions are heated, and ion-ion instability is present as ions approach the boundary.Index Terms-Bohm velocity, charge exchange, free fall motion, ion-ion streaming instability, ion velocity, mobility limited flow, presheath, sheath, weakly ionized plasma.

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The effects of collisions on the plasma presheath

Cited by 27 publications

References 5 publications

Laser-induced fluorescence characterization of ions in a magnetron plasma

Laser-induced fluorescence characterization of ions in a magnetron plasma

Boltzmann equation description of flows at long mean free paths

Presheath environment in weakly ionized single and multispecies plasmas

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