Investigating flow patterns and related dynamics in multi-instability turbulent plasmas using a three-point cross-phase time delay estimation velocimetry scheme

Brandt, C.; Thakur, Saikat Chakraborty; Tynan, G. R.

doi:10.1063/1.4945629

Cited by 6 publications

(1 citation statement)

References 43 publications

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“…High speed imaging in linear plasma devices allow to gain insight on the ion dynamics 15 , the transition to drift wave turbulence 16 or the generation of zonal flows 17 . It can also be used for the comparison with simulations 18 , or as a complement to other diagnostics 19,20 . However, since the light radiated from a plasma depends in a very non-trivial way on the plasma parameters, extracting physical information from camera imaging is seldom very quantitative.…”

Section: Introductionmentioning

confidence: 99%

High-speed imaging of magnetized plasmas: when electron temperature matters

Vincent,

Dolique,

Plihon

2021

Preprint

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High speed camera imaging is a powerful tool to probe the spatiotemporal features of unsteady processes in plasmas, usually assuming light fluctuations to be a proxy for the plasma density fluctuations. In this article, we systematically compare high speed camera imaging with simultaneous measurements of the plasma parameters -plasma density, electron temperature, floating potential -in a modestly magnetized Argon plasma column at low pressure (1 mTorr, magnetic fields ranging from 160 to 640 G). The light emission was filtered around 488 ± 5 nm, 750 ± 5 nm, 810 ± 5 nm. We show that the light intensity cannot be interpreted as a proxy for the plasma density and that the electron temperature cannot be ignored when interpreting high speed imaging, both for the time-averaged profiles and for the fluctuations. The features of plasma parameter fluctuations are investigated, with a focus on ion acoustic waves (at frequency around 70 kHz) at low magnetic field and low-frequency azimuthal waves (around a few kHz) at larger magnetic fields. An excellent match is found between the high speed images fluctuations and an Arrhenius law functional form which incorporates fluctuations of the plasma density and of the electron temperature. These results explain the discrepancies between ion saturation current and narrow-band imaging measurements previously reported in the literature.

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Section: Introductionmentioning

confidence: 99%

High-speed imaging of magnetized plasmas: when electron temperature matters

Vincent,

Dolique,

Plihon

2021

Preprint

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Collisional considerations in axial-collection plasma mass filters

et al. 2017

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The chemical inhomogeneity of nuclear waste makes chemical separations difficult, while the correlation between radioactivity and nuclear mass makes mass-based separation, and in particular plasma-based separation, an attractive alternative. Here, we examine a particular class of plasma mass filters, namely filters in which (a) species of different masses are collected along magnetic field lines at opposite ends of an open-field-line plasma device and (b) gyro-drift effects are important for the separation process. Using an idealized cylindrical model, we derive a set of dimensionless parameters which provide minimum necessary conditions for an effective mass filter function in the presence of ion-ion and ion-neutral collisions. Through simulations of the constant-density profile, turbulence-free devices, we find that these parameters accurately describe the mass filter performance in more general magnetic geometries. We then use these parameters to study the design and upgrade of current experiments, as well as to derive general scalings for the throughput of production mass filters. Importantly, we find that ion temperatures above 3 eV and magnetic fields above 104 G are critical to ensure a feasible mass filter function when operating at an ion density of 1013 cm–3.

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Comparison of probe and narrow-band imaging measurements in a magnetized cylindrical plasma

2019

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We analyze similarities and differences between electrostatic probe measurements and high-speed visible light imaging measurements in a low-temperature argon helicon plasma. Electrostatic probes are the usual diagnostics for making fluctuation measurements in low-temperature plasmas, although fast-imaging of visible emission is becoming increasingly common. The two diagnostics are highly complementary, and typical analysis takes fluctuations in both ion saturation current and visible light intensity to be proxies for plasma density fluctuations. The observations presented here indicate that care is needed in applying this approximation. The plasma is produced with a helicon antenna, and we measure fluctuations in ion saturation current, floating potential, and visible emission near wavelengths of 488 nm (argon ions) and 750 nm (argon neutrals). Simultaneous measurements show relatively low correlation values between ion saturation current and ion line emission and an anti-correlation between floating potential and ion line emission. Variations in cross-coherence between ion emission and probe quantities indicate the frequency dependence in the relationship between the measurements. For various frequency bands where probe/imaging coherence is relatively high, fluctuation intensity profiles differ significantly and coherent fluctuations are observed in ion light which are not apparent in the probe measurements. A sensitivity analysis indicates that electron temperature fluctuations, although nearly always neglected when analyzing data from low-temperature plasma experiments, may play a role in the discrepancy between probe and narrow-band imaging measurements.

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Investigating flow patterns and related dynamics in multi-instability turbulent plasmas using a three-point cross-phase time delay estimation velocimetry scheme

Cited by 6 publications

References 43 publications

High-speed imaging of magnetized plasmas: when electron temperature matters

High-speed imaging of magnetized plasmas: when electron temperature matters

Collisional considerations in axial-collection plasma mass filters

Comparison of probe and narrow-band imaging measurements in a magnetized cylindrical plasma

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