Space potential measurements with a continuously emitting probe

Mravlag, E.; Krumm, Peter

doi:10.1063/1.1141384

Cited by 18 publications

(14 citation statements)

References 7 publications

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“…The electron saturation current should remain unaffected because the emitted electrons are reflected from plasma back to the probe when the probe voltage becomes positive with respect to the plasma potential. However, changes in the electron saturation current of the emissive probe with the variations of the probe heating current, i. e. with the emission current, were frequently observed in experiments -e. g. [5]. This is the reason why our work focuses on this phenomenon which, to our knowledge, has not been systematically studied and explained as yet.…”

Section: Introductionmentioning

confidence: 83%

Experimental investigation of the change of the electron saturation current of a dc-heated emissive probe

et al. 2006

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We report on experimental investigations of the change of the electron saturation current of a dc-heated emissive probe with the probe heating current. According to the simple theory of the emissive probe, the electron saturation current should not be affected by emission. However, in many experiments a variation of the electron saturation current with the emission current was observed. We consider two possible reasons for such variations: (a) the influence of the space charge around the probe shaft, (b) the change of the work function of the probe surface material due to heating. We tried to find sufficient experimental evidence for supporting one or the other (or both) of these two explanations. We used two different types of plasma to validate the results: a cylindrical magnetron plasma and the non-magnetized plasma of a DP machine. From our experiments follows that the electron saturation current of the emissive probe is affected by the space charge effect as well as it depends on the probe wire material. : 52.25.Xz, 52.70.Ds PACS

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Section: Introductionmentioning

confidence: 83%

Experimental investigation of the change of the electron saturation current of a dc-heated emissive probe

et al. 2006

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“…Therefore, the effective bias voltage can be taken as the bias potential at the middle of the probe [62]. Depending on the heating circuit, this could mean that the effective bias potential is the bias potential plus V H ∕2, 0, or −V H ∕2 [66].…”

Section: Heating Methodsmentioning

confidence: 99%

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

Sheehan

Raitses

Hershkowitz

et al. 2017

Journal of Propulsion and Power

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This article provides recommended methods for building, operating, and taking plasma potential measurements from electron-emitting probes in electric propulsion devices, including Hall thrusters, gridded ion engines, and others. The two major techniques, the floating point technique and the inflection point technique, are described in detail as well as calibration and error-reduction methods. The major heating methods are described as well as the various considerations for emissive probe construction. Special considerations for electric propulsion plasmas are addressed, including high-energy densities, ion flows, magnetic fields, and potential fluctuations. Recommendations for probe design and operation are provided.

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“…This voltage drop is undesirably high, typically a few volts. 42 That is, one side of the filament has a potential a few volts higher than the other side. In our previous work we have introduced a pulsed version of an emissive probe that addresses this issue by alternating between heating and measuring intervals.…”

Section: Emissive Probe Techniquesmentioning

confidence: 99%

“…40 Emissive probes have been successfully applied to measure plasma potentials in a wide range of magnetic fields, from tens of mT for a quadrupole device 41 to 0.5 T at the edge of a Tokamak 38 or Q-machine. 42 It should be noted that the emitted electrons have energies of about 0.3 eV, corresponding to a wire temperature of 3000 K w T  . This limits the voltage resolution of the emissive probe to about 0.3 V, which is generally not of concern given the errors of the potential measurements resulting from other factors.…”

Section: Emissive Probe Techniquesmentioning

confidence: 99%

Plasma potential mapping of high power impulse magnetron sputtering discharges

Rauch

Mendelsberg

Sanders

et al. 2012

Journal of Applied Physics

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Pulsed emissive probe techniques have been used to determine the plasma potential distribution of high power impulse magnetron sputtering (HiPIMS) discharges. An unbalanced magnetron with a niobium target in argon was investigated for pulse length of 100 µs at a pulse repetition rate of 100 Hz, giving a peak current of 170 A. The probe data were taken with a time resolution of 20 ns and a spatial resolution of 1 mm. It is shown that the local plasma potential varies greatly in space and time. The lowest potential was found over the target's racetrack, gradually reaching anode potential (ground) several centimeters away from the target. The magnetic pre-sheath exhibits a funnel-shaped plasma potential resulting in an electric field which accelerates ions toward the racetrack. In certain regions and times, the potential exhibits weak local maxima which allow for ion acceleration to the substrate. Knowledge of the local E and static B fields lets us derive the electrons' E × B drift velocity, which is about 10 5 m/s and shows structures in space and time.

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Space potential measurements with a continuously emitting probe

Cited by 18 publications

References 7 publications

Experimental investigation of the change of the electron saturation current of a dc-heated emissive probe

Experimental investigation of the change of the electron saturation current of a dc-heated emissive probe

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

Plasma potential mapping of high power impulse magnetron sputtering discharges

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