Open Access
Sheaths: More complicated than you think
Noah Hershkowitz
- Vol. 46
TLDR
In this article, a range of sheaths and presheaths in weakly collisional plasmas are described and a key diagnostic is emissive probes operated in the limit of zero emission.Abstract:
Sheaths in low temperature collisionless and weakly collisional plasmas are often viewed as simple examples of nonlinear physics. How well do we understand them? Closer examination indicates that they are far from simple. Moreover, many predicted sheath properties have not been experimentally verified and even the appropriate “Bohm velocity” for often encountered two-ion species plasma is unknown. In addition, a variety of sheathlike structures, e.g., double layers, can exist, and many two- and three-dimensional sheath effects have not been considered. Experimental studies of sheaths and presheaths in weakly collisional plasmas are described. A key diagnostic is emissive probes operated in the “limit of zero emission.” Emissive probes provide a sensitive diagnostic of plasma potential with a resolution approaching 0.1V and a spatial resolution of 0.1cm. Combined with planar Langmuir probes and laser-induced fluorescence, they have been used to investigate a wide variety of sheath, presheath, and sheathlike structures. Our experiments have provided some answers but have also raised more questions.read more
Citations
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Journal Article
100 Years of the Physics of Diodes
TL;DR: The Child-Langmuir Law (CL) as mentioned in this paper gives the maximum current that can be transported across a planar diode in the steady state, which is central to the studies of high current diodes, such as high power microwave sources, vacuum microelectronics, electron and ion sources, and high current drivers used in high energy density physics experiments.
Dissertation
Increasing the Extracted Beam Current Density in Ion Thrusters
TL;DR: In this article, the authors aim to address the low thrust conception, whereby improving ion thrusters performance and thrust density will lead to expanded mission capabilities for ion thruster technology, which poses a challenge because the mechanism for accelerating ions, the ion optics, is space charge limited according to the Child-Langmuir law.
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Influence of Neutral Pressure on Instability Enhanced Friction and Ion Velocities at the Sheath Edge of Two-Ion-Species Plasmas
TL;DR: In this article, the instability-enhanced friction theory is extended to account for the influence of neutral pressure in predicting the flow speed of each ion species at the sheath edge of plasmas containing two ion species.
DissertationDOI
Theory and Simulation of Electron Sheaths and Anode Spots in Low Pressure Laboratory Plasmas
TL;DR: In this article, a 1D model for the electron sheath and presheath was developed based on electron velocity distribution functions (EVDFs) observed in particle-in-cell (PIC) simulations.
Journal ArticleDOI
Characteristics of plasma sheath in multi-component plasmas with three-ion species
M. M. Hatami,Ioannis Kourakis +1 more
TL;DR: In this article , the plasma sheath of a three ion species plasma is studied numerically, relying on the results of the experiment by Yip et al. (2016) to measure the positive ion velocities at the sheath edge.
References
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Andrew Guthrie,R. K. Wakerling +1 more
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The Interaction of Electron and Positive Ion Space Charges in Cathode Sheaths
TL;DR: In this paper, the potential distribution in the plasma and near the sheath edge of a double-sheath was studied and the effect of the initial velocities of the ions and electrons that entered a double sheath from the gas is to decrease the electron current by an amount that varies with the voltage drop in the sheaths.
Journal ArticleDOI
Experimental astrophysics with high power lasers and Z pinches
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Magnetic Multipole Containment of Large Uniform Collisionless Quiescent Plasmas
TL;DR: In this paper, over 1200 Alnico magnets are used to contain a conventional discharge plasma produced by 1-20 A of emission from 6-48 small filaments at − 60 V.