Experimental Investigation of the Plasma-Wall Transition

Lunt, T.; Fußmann, G.; Waldmann, O.

doi:10.1103/physrevlett.100.175004

Cited by 25 publications

(22 citation statements)

References 10 publications

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“…This is a common situation because it applies to floating boundaries and electrodes biased negatively with respect to the wall. However, it is often not satisfied for positively biased electrodes [153]. Even if the electrode is large enough that current balance demands that the plasma potential is more positive than it (ion sheath regime), the sheath potential drop may be small.…”

Section: Weak Ion Sheaths and The Transition To Electron Sheathmentioning

confidence: 99%

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

Baalrud

Scheiner

Yee

et al. 2020

Plasma Sources Sci. Technol.

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Biased electrodes are common components of plasma sources and diagnostics. The plasma-electrode interaction is mediated by an intervening sheath structure that influences properties of the electrons and ions contacting the electrode surface, as well as how the electrode influences properties of the bulk plasma. A rich variety of sheath structures have been observed, including ion sheaths, electron sheaths, double sheaths, double layers, anode glow, and fireballs. These represent complex self-organized responses of the plasma that depend not only on the local influence of the electrode, but also on the global properties of the plasma and the other boundaries that it is in contact with. This review summarizes recent advances in understanding the conditions under which each type of sheath forms, what the basic stability criteria and steady-state properties of each are, and the ways in which each can influence plasma-boundary interactions and bulk plasma properties. These results may be of interest to a number of application areas where biased electrodes are used, including diagnostics, plasma modification of materials, plasma sources, electric propulsion, and the interaction of plasmas with objects in space.

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Section: Weak Ion Sheaths and The Transition To Electron Sheathmentioning

confidence: 99%

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

Baalrud

Scheiner

Yee

et al. 2020

Plasma Sources Sci. Technol.

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“…[5][6][7][8][9]). Only recently has their detailed experimental investigation become possible [10][11][12]. Sheaths are present in the edge of magnetically confined fusion plasmas, at the interface between spacecrafts and space plasmas, in the fabrication of semiconductor devices, and wherever a plasma interacts with a solid surface.…”

Section: Introductionmentioning

confidence: 99%

Existence of subsonic plasma sheaths

2011

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The location of the plasma sheath edge, where quasineutrality is broken, is rigorously derived by using a kinetic description of the plasma. It is shown that sheaths can exist with arbitrarily small ion velocity at the sheath edge, thus violating the Bohm criterion, V i = c s at the sheath edge. Bohm's criterion is recovered in the case of large enough ion current through the wall, and it is found to be a reasonable approximation in floating potential conditions. However, in the case of a predominant electron current through the wall, Bohm's criterion is not able to describe the sheath-edge transition. The analytical results are supported by numerical simulations performed with a fully kinetic particle-in-cell code modeling a source-driven, weakly collisional plasma, bound between two absorbing walls.

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“…For an example measurement with a clearer signal at v z = 0 see Fig. 3 of [24]. 38,39] that there is no useful sheath-related information in Eq.…”

mentioning

confidence: 99%

Reply to comment on ‘Kinetic theory of the presheath and the Bohm criterion’

Hegna

2012

Plasma Sources Sci. Technol.

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In his comment, Riemann defends the conventional kinetic Bohm criterion on the basis that the underlying approximations become rigorous in the limit λ D /l → 0, where λ D is the Deybe length and l is a collision length scale for the dominant collision process. Here, we expand on our previous arguments showing that the basic assumptions for the justified use of the conventional kinetic Bohm criterion are typically not satisfied in laboratory plasmas. We corroborate our argument with experimental data, as well as data from numerical simulations, showing that the conventional criterion is violated in common situations. In contrast, a formulation based on positive velocity moments of the kinetic equation provides a criterion that both agrees with the experimental data and reduces to the traditional expectations from fluid theory in the appropriate limit.

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Experimental Investigation of the Plasma-Wall Transition

Cited by 25 publications

References 10 publications

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

Existence of subsonic plasma sheaths

Reply to comment on ‘Kinetic theory of the presheath and the Bohm criterion’

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