Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array

Schubert, M.; Endler, M.; Thomsen, H.; Team, W As

doi:10.1063/1.2740785

Cited by 19 publications

(14 citation statements)

References 26 publications

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“…It has recently been demonstrated that the inflection point in the limit of zero emission technique can be used to make time-resolved plasma potential measurements [124]. It is possible to obtain timeresolved I-V traces by sweeping the probe bias faster than the plasma potential fluctuation, which is known as the fast-sweep method [40,125]. This method, however, requires carefully designed electronics and the measurements can be difficult to make.…”

Section: Temporal Resolutionmentioning

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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Section: Temporal Resolutionmentioning

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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“…see [15]) full sweep and data collection frequencies of 100 kHz or faster would be needed to resolve detail with in a spoke. Such single probe systems have been employed to observe plasma parameter instabilities and fluctuations in fusion device edge regions [33] but are not routinely available in most HiPIMS laboratories.…”

Section: Introductionmentioning

confidence: 99%

Triple probe interrogation of spokes in a HiPIMS discharge

Estrin

Karkari

Bradley

2017

J. Phys. D: Appl. Phys.

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Using a triple probe situated above the racetrack and inside the magnetic trap of a magnetron, rotating spokes-like structures have been clearly identified in a single HiPIMS pulse as periodic modulations in the electron temperature T e , electron density n e , ion saturation current I isat , floating potential V f and plasma potential V p. The spokes rotate in the E x B direction with a velocity of ~ 8.8 km/s. Defining the spoke shape from the footprint of ion current they deliver to flush mounted probes embedded in the target, each spoke can be characterised by a dense but cool leading edge (n e ~ 2.0 x 10 19 m-3 , T e ~ 2.1 eV) and relatively hotter but more rarefied trailing edge (n e ~ 1 x 10 19 m-3 , T e ~ 3.9 eV). Measurements of V p show a potential hump towards the rear of spoke, separated from regions of highest density, with plasma potentials up to 8 V more positive than the inter-spoke regions. Azimuthal electric fields of ~1kV/m associated with these structures are calculated.

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“…The simplifying assumption that temperature fluctuations are negligible has been proven valid in a toroidally confined low-temperature plasma [11]. However, in the boundary of several high-temperature plasmas, significant temperature fluctuations have been found by fast sweeping Langmuir probes [12][13][14][15], triple probes [14,16,17], swept double probes [18], a harmonic probe technique [3,19,20] and Thomson scattering [3,21].…”

Section: Introductionmentioning

confidence: 99%

Influence of temperature fluctuations on plasma turbulence investigations with Langmuir probes

et al. 2012

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The reliability of Langmuir probe measurements for plasmaturbulence investigations is studied on GEMR gyro-fluid simulations and compared with the results from conditionally sampled I -V characteristics as well as electron-emitting probe measurements close to the last closed flux surface of the tokamak ASDEX Upgrade. In this region, simulation and experiment consistently show coherent in-phase fluctuations in density, plasma potential and also electron temperature. Ion-saturation current measurements turn out to reproduce density fluctuations quite well. Fluctuations in the floating potential, however, are strongly influenced by temperature fluctuations and, hence, are strongly distorted compared to the actual plasma potential. These results suggest that interpreting floating as plasma-potential fluctuations while disregarding temperature effects is not justified near the separatrix of hot fusion plasmas. Here, floating potential measurements led to corrupted results on the E × B dynamics of turbulent structures in the context of, e.g., turbulent particle and momentum transport or turbulence characterization on the basis of density-potential phase relations.

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Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array

Cited by 19 publications

References 26 publications

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

Triple probe interrogation of spokes in a HiPIMS discharge

Influence of temperature fluctuations on plasma turbulence investigations with Langmuir probes

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