Emissive probe current bias method of measuring dc vacuum potential

Diebold, D.; Hershkowitz, N.; Bailey, Andrew D.; Cho, M. H.; Intrator, T.

doi:10.1063/1.1140239

Cited by 47 publications

(29 citation statements)

References 7 publications

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“…The Langmuir probe is used to determine n 0 , T e , and φ p . The emissive probe is used to measure the local potential as a function of position in the chamber [ Diebold et al , 1988]. These measurements provide the vertical potential profile in the sheath, φ s ( z ).…”

Section: Resultsmentioning

confidence: 99%

Experimental levitation of dust grains in a plasma sheath

et al. 2002

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[1] Dust grains have been observed to levitate above the surface of the Moon and as spokes in Saturn's rings. In order to gain a better understanding of these observations, we have performed levitation experiments on dust grains in a low-density plasma. Plasma sheath potential profiles, measured by an emissive probe, are used to determine the spatial dependence of the electric force on a grain in the sheath. The observed levitation height agrees with the values calculated using orbital-motion-limited charging theory and force balance equations. Levitating grains were also exposed to an ultraviolet light source to induce photoemission. Three types of dust were investigated: polystyrene divinylbenzene microspheres 10.0 ± 0.5 mm in diameter, glass microballoons <38 mm in diameter, and JSC-1 (lunar regolith simulant) <25 mm in diameter. Our experimental results show that (1) various types and sizes of grains can levitate in a plasma sheath above a conducting surface; (2) levitating grains of a standard size float at a height corresponding to that predicted by theory; (3) exposure to UV light causes the grain levitation height to decrease slightly as a result of less negative charge; and (4) a mechanism to inject grains into the sheath is not necessary if the electric field is sufficiently strong.

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Section: Resultsmentioning

confidence: 99%

Experimental levitation of dust grains in a plasma sheath

et al. 2002

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“…Standard references for the construction and operation of these probes suggest a probe radius of 12.7 μm, a probe length of 5 mm, and an emission current of 50 μA [14], [15]. If an operating temperature of 2000 K is assumed, the electron density at the probe surface is 1.1 × 10 10 cm −3 when the virtual cathode returns all the emitted electrons.…”

Section: Introductionmentioning

confidence: 99%

The Electron Sheath Around an Emissive Wire in Vacuum

Robertson

2012

IEEE Trans. Plasma Sci.

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An orbit-motion-limited (OML) theory is developed for the electron sheath and the virtual cathode that forms around an emissive wire in vacuum. The electron cloud above the wire surface is assumed to be described by a 2-D Maxwellian distribution function. A comparison is made with a 1-D theory having only radial velocities for the electrons. The OML theory gives a greater electron density and a more negative virtual cathode because of differences between the 1-D and 2-D distribution functions. Expressions are derived for the current from the cathode to the anode.

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“…The plate was 25 cm in diameter and 60 cm from the filament. The potential profiles in the sheaths were measured with an emissive probe [ Diebold et al , ], which was made of a thoriated tungsten wire 3 mm long and 0.025 mm in diameter. The electron emission from the emissive probe was small to avoid the influence to the sheath potentials.…”

Section: Methodsmentioning

confidence: 99%

Plasma potential in the sheaths of electron‐emitting surfaces in space

Wang

Pilewskie

Hsu

et al. 2016

Geophysical Research Letters

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Sheaths are formed around the surfaces of airless bodies, which both collect and emit electrons. Depending on the ratio of the emitted to collected electron fluxes Γ, the sheath potential structure can be quite different. We present the first experimental measurements of all the three types of the sheath potentials: classical, space‐charge‐limited (SCL), and inverse. A solid surface immersed in plasmas emits secondary electrons. The potential structure changes from a monotonic classical to a nonmonotonic SCL sheath as Γ increases. At the critical electron emission with zero electric field at the surface, the sheath potential is determined by the plasma electron temperature, and Γ approaches but remains smaller than 1, in agreement with the theoretical expectation. The nonmonotonic SCL sheath persists steadily for Γ > 1. When the emitted electron density becomes larger than the plasma electron density, a monotonic inverse sheath forms with a positive surface potential relative to the ambient.

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Emissive probe current bias method of measuring dc vacuum potential

Abstract: Effective electric field in dc magnetization measurements: Comparing magnetization to transport critical currents

Cited by 47 publications

References 7 publications

Experimental levitation of dust grains in a plasma sheath

Experimental levitation of dust grains in a plasma sheath

The Electron Sheath Around an Emissive Wire in Vacuum

Plasma potential in the sheaths of electron‐emitting surfaces in space

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