Probe measurements of low-frequency plasma potential and electric field fluctuations in a magnetized plasma

Ratynskaia, S.; Demidov, V. I.; Rypdal, Kristoffer

doi:10.1063/1.1505846

Cited by 25 publications

(52 citation statements)

References 23 publications

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“…(3) has been justified in the case of a plug probe in which only electron temperature oscillations were considered [14]. Indirect confirmation that µ e and µ i are constants for a definite value of I sat e /I sat i is the absence of harmonics on measured spectra (see, for instance, Fig.…”

Section: Methodsmentioning

confidence: 98%

Utility of a Baffled Probe for Measurements of Oscillations in Magnetized Plasma

Demidov

Finnegan

Koepke

et al. 2004

Contrib. Plasma Phys.

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Key words Electric probe, magnetized plasma, space potential and temperature oscillations. PACS 52.70.-m A baffled probe for distinguishing the oscillations of space potential and temperature in magnetized plasma is tested. The probe consists of a tungsten wire tip, oriented perpendicular to the magnetic field, that is partially shielded by ceramic baffles (masks). The probe works under the condition that the electron Larmor radius is much smaller than the probe radius, and the ion Larmor radius is comparable to or larger than the probe radius. The probe uses the same principles as Katsumata and plug probes, but has the advantage of convenient, realtime controllability of the ratio between electron and ion current while electrically floating, and insensitivity to uncertainties in the orientation of the probe tip relative to the direction of the magnetic field. By rotating the baffle configuration around the probe tip, the ratio between electron and ion probe current and consequently the relative sensitivity of the probe to oscillations of space potential and electron/ion temperature, can be adjusted. Thus, measurements of ac floating potential with different ratio of electron and ion currents allow us to distinguish oscillations of space potential from electron/ion temperature fluctuations. Experiments have been conducted in a fully ionized, barium plasma in the West Virginia University Q-machine.

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Section: Methodsmentioning

confidence: 98%

Utility of a Baffled Probe for Measurements of Oscillations in Magnetized Plasma

Demidov

Finnegan

Koepke

et al. 2004

Contrib. Plasma Phys.

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“…27,44,48 Before and after pellet injection, when long time records of turbulence are measured, the ensemble power spectrum, ensemble cross coherence, and ensemble cross phase can be accurately calculated using standard methods (e.g., Refs. 27 and 48).…”

Section: Low-frequency Turbulent Fluctuationsmentioning

confidence: 99%

Turbulent fluctuations during pellet injection into a dipole confined plasma torus

et al. 2017

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We report measurements of the turbulent evolution of the plasma density profile following the fast injection of lithium pellets into the Levitated Dipole Experiment (LDX) [Boxer et al., Nat. Phys. 6, 207 (2010)]. As the pellet passes through the plasma, it provides a significant internal particle source and allows investigation of density profile evolution, turbulent relaxation, and turbulent fluctuations. The total electron number within the dipole plasma torus increases by more than a factor of three, and the central density increases by more than a factor of five. During these large changes in density, the shape of the density profile is nearly “stationary” such that the gradient of the particle number within tubes of equal magnetic flux vanishes. In comparison to the usual case, when the particle source is neutral gas at the plasma edge, the internal source from the pellet causes the toroidal phase velocity of the fluctuations to reverse and changes the average particle flux at the plasma edge. An edge particle source creates an inward turbulent pinch, but an internal particle source increases the outward turbulent particle flux. Statistical properties of the turbulence are measured by multiple microwave interferometers and by an array of probes at the edge. The spatial structures of the largest amplitude modes have long radial and toroidal wavelengths. Estimates of the local and toroidally averaged turbulent particle flux show intermittency and a non-Gaussian probability distribution function. The measured fluctuations, both before and during pellet injection, have frequency and wavenumber dispersion consistent with theoretical expectations for interchange and entropy modes excited within a dipole plasma torus having warm electrons and cool ions.

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“…This is not consistent with the fact that the gradients of the density and the magnetic field are opposite at most of the radial positions in this shot. This inconsistency comes from the unsuitable neglect of the gradients of electron temperature T e , as was done in many of other magnetically confined devices [22,23]. Using the relation of:…”

Section: Resultsmentioning

confidence: 97%

“…This result is different from Refs. [22,23], in which the conclusion of a dominant flute mode is drawn. This difference reveals the fact that the fluctuation and the gradient of electron temperature are not neglectable even in a low temperature plasma.…”

Section: Resultsmentioning

confidence: 99%

Statistical properties of turbulence in a toroidal magnetized ECR plasma

Yu¹,

Lu²,

Wang³

et al. 2008

Physics Letters A

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Probe measurements of low-frequency plasma potential and electric field fluctuations in a magnetized plasma

Cited by 25 publications

References 23 publications

Utility of a Baffled Probe for Measurements of Oscillations in Magnetized Plasma

Utility of a Baffled Probe for Measurements of Oscillations in Magnetized Plasma

Turbulent fluctuations during pellet injection into a dipole confined plasma torus

Statistical properties of turbulence in a toroidal magnetized ECR plasma

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