Influence of negative ions on the plasma boundary sheath

In this work, we have considered the formation of warm plasma sheath in the vicinity of a wall in a plasma with considerable presence of dust particles. As an example, we have used the parameters relevant in case of lunar plasma sheath, though the results obtained in this work can be applied to any other physical situation such as laboratory plasma. In the ion-acoustic time scale, we neglect the dust dynamics. The dust particles affect the sheath dynamics by affecting the Poisson equation which determines the plasma potential in the sheath region. We have assumed the current to a dust particle to be balanced throughout the analysis. This makes the grain potential dependent on plasma potential, which is then incorporated into the Poisson equation. The resultant numerical model becomes an initial value problem, which is described by a 1-D integro-differential equation, which is then solved self-consistently by incorporating the change in plasma potential caused by inclusion of the dust potential in the Poisson equation.

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“…Note that we must have M > 1 for σ > 0 in a warm sheath with γ = 5/3 for real solution of Eq. (16). The allowed region is given by V < 0.…”

Section: Sheath Equationsmentioning

confidence: 99%

Revisiting the plasma sheath—dust in plasma sheath

2016

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“…However, Coulomb collisions between positive and negative ions may play a role. Using expressions from Huba (2011) and Deutsch and Rauchle (1992), we obtain ν + ∼ 1.4 × 10 3 s −1 , assuming that the K + ions are fast test ions colliding with the negative ions, and ν − ∼ 110 s −1 , assuming the negative ions are slow test ions colliding with the K + ions. We consider ion density gradients of magnitude L n ∼ 2 cm.…”

Section: Numerical Resultsmentioning

confidence: 84%

Drift instability in a positive ion–negative ion plasma

Rosenberg

Merlino

2013

J. Plasma Phys.

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Drift wave instability in a magnetized plasma composed of positive ions and negative ions is considered using linear kinetic theory in the local approximation. We consider the case where the mass (temperature) of the negative ions is much larger (smaller) than that of the positive ions, and where the gyroradii of the two ion species are comparable. Weak collisional effects are taken into account. Application to possible laboratory parameters is discussed.

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“…The space potential of the target plasma as well as the sheath thickness is found to increase with the increase of negative grid bias voltage V g . 3), but only the threshold value of V g for energy resonance conditions is more for increasing r. The whole phenomenon can be explained that for a small value of rϽ0.26 (r c ϭcritical negative ion density͒, the hump becomes steeper towards the grid ͑see Fig. This clearly indicates that in this region much more ions are accumulated by the sheath and hence the space charge distribution over this region is much higher than the other region of the sheath on the target side.…”

Section: Resultsmentioning

confidence: 99%

“…3,4 The ion sheath oscillations induced by a negatively biased grid in double plasma device have been studied for two component plasma by few authors. By analyzing the fluid model and the particle motion in the sheath, the traditional theory of boundary sheath 1,2 for plasma containing only positive ions and electrons has been extended for plasma with negative ions.…”

Section: Introductionmentioning

confidence: 99%

Ion dynamics in the sheath in multicomponent plasma with negative ions

Prakash

Sarma

Chutia

2000

Review of Scientific Instruments

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The plasma-vacuum transition in rf sources for negative hydrogen ions Rev. Sci. Instrum. 73, 900 (2002); 10.1063/1.1427670Ion energy distributions and sheath voltages in a radio-frequency-biased, inductively coupled, high-density plasma reactorObservations on steady state ion-rich sheath around a negatively biased grid in a double plasma device have been made in multicomponent plasma with negative ions. A hump in the potential profile is found to occur at the sheath edge. The characteristics of the hump depend on the grid voltage, source biasing voltage, density difference in the two chambers, and the negative to positive ion concentration ratio. It is argued that resonance which is coupled with the beam ions and background ions is associated in the excitation mechanism to create the nonsymmetrical structures in the plasma potential profile. Below the critical concentration ratio, the hump grows in height and above the critical ratio, the width of the hump increases but the height decreases and ultimately it vanishes. The variation in the hump potential profile due to the injection of negative ions can be explained by the ion momentum exchange and by their dynamics.

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Influence of negative ions on the plasma boundary sheath

Cited by 36 publications

References 12 publications

Revisiting the plasma sheath—dust in plasma sheath

Revisiting the plasma sheath—dust in plasma sheath

Drift instability in a positive ion–negative ion plasma

Ion dynamics in the sheath in multicomponent plasma with negative ions

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