The influence of collisions on the plasma sheath transition

Riemann, K.‐U.

doi:10.1063/1.872536

Cited by 212 publications

(205 citation statements)

References 24 publications

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“…The possibility of the existence of sheaths with subsonic ions at the edge was widely addressed in the literature, by exploring if the presheath processes (collisions, ionization) or the geometry could influence the transition to the non-neutral region [14,15]. It was concluded that the Bohm criterion, V i = c s , is a ubiquitous property of ion sheaths in the limit T i T e and λ D L [2,16]. In this article we rigorously derive the location of the sheath edge where quasineutrality is broken by using an appropriate kinetic description of the plasma.…”

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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Section: Introductionmentioning

confidence: 99%

Existence of subsonic plasma sheaths

2011

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“…The edge of the visible emission region corresponds to the edge of the quasineutral pre-sheath region from which ions exit with the Bohm speed, (kT e / M) 1/2 (T e : electron temperature, M: ion mass) acquired in the last mean free path [13]. At this point, the field increases monotonically up to the transition region field.…”

Section: Estimation Of Ion Bombardment Energymentioning

confidence: 99%

Environment with reduced ion bombardment energy for levitated particles in an rf plasma

Shimizu

Annaratone

Shimizu

et al. 2008

Plasma Sources Sci. Technol.

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We describe levitation of diamond fine particles in the H 2 rf plasma chamber equipped with an adaptive rf electrode. Since suppression of ion bombardment is essential for crystalline diamond growth, we use an adaptive rf electrode system in a parallel-plate capacitively coupled rf plasma in order to levitate particles in a quasineutral "spot plasma" region. Here the ions energy corresponds only to the floating potential of the particles without the additional energy of the streaming ions as in the sheath. One can expect ion bombardment with greatly reduced ion energy when this technique is applied to diamond deposition on levitated particles.

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“…When a hypersonic vehicle reenters the atmosphere, severe friction between the aircraft and the ambient air results in a dramatic increase in the local temperature and pressure, which leads to intensified air ionization, and a layer of plasma flow is generated around the reentry vehicle [1]. The plasma flow, which consists of numerous free electrons, ions, and neutral particles, is nonmagnetic, lowtemperature, weakly ionized, and quasi-neutral (i.e., electricity neutral on macroscopic-length scales) [2,3].…”

Section: Introductionmentioning

confidence: 99%

Backward Scattering Characteristics of a Reentry Vehicle Enveloped by a Hypersonic Flow Field

Sun

Wang

Han

et al. 2018

International Journal of Antennas and Propagation

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The hypersonic flow field around a reentry vehicle has a significant influence on the ground-vehicle communication as well as on the detection and recognition of the reentry vehicle. Backward scattering characteristics of a reentry vehicle enveloped by a hypersonic flow field are analyzed using a high-order auxiliary differential equation finite difference time-domain (ADE-FDTD) method in this paper. Flow field parameters, including electron density, neutral particle density, and temperature, are obtained by solving the Navier-Stokes (NS) equations numerically. According to the flow field parameters, distributions of the plasma frequency and the collision frequency are then derived. Based on a validity of the physical model and the high-order ADE-FDTD method, backward radar cross sections (RCSs) of a perfect electrical conductor (PEC) sphere enveloped by a hypersonic flow field under different Mach numbers, heights, and incident angles of the electromagnetic (EM) wave are then investigated. Numerical results show that the incident angle of the EM wave exerts noticeable effects on the backward RCS, which is due to an inhomogeneous distribution of the plasma. The flight height and Mach number have significant influences on the distribution of the plasma that they play an important role in the variation of the RCSs. The results presented in this paper provide useful reference data for practical tests in ballistic range or in the high-frequency plasma wind tunnels, where a sphere target is usually used due to its simple shape.

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The influence of collisions on the plasma sheath transition

Cited by 212 publications

References 24 publications

Existence of subsonic plasma sheaths

Existence of subsonic plasma sheaths

Environment with reduced ion bombardment energy for levitated particles in an rf plasma

Backward Scattering Characteristics of a Reentry Vehicle Enveloped by a Hypersonic Flow Field

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