Toroidal charge exchange recombination spectroscopy measurements on MST

Magee, Richard; Hartog, D. J. Den; Fiksel, G.; Kumar, S. T. A.; Craig, D.

doi:10.1063/1.3478665

Cited by 4 publications

(4 citation statements)

References 7 publications

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“…and T jj in the core of MST during the reconnection heating event. A simultaneous background measurement allows radial spatial resolution of 1-2 cm and temporal resolution of 100 s [23,24]. The temperatures as a function of time from many similar events are averaged together, aligned such that t ¼ 0 is the maximum rate of change of magnetic flux during reconnection, and grouped into 3 density ranges.…”

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confidence: 99%

Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

et al. 2011

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Complementary measurements of ion energy distributions in a magnetically confined high-temperature plasma show that magnetic reconnection results in both anisotropic ion heating and the generation of suprathermal ions. The anisotropy, observed in the C(+6) impurity ions, is such that the temperature perpendicular to the magnetic field is larger than the temperature parallel to the magnetic field. The suprathermal tail appears in the majority ion distribution and is well described by a power law to energies 10 times the thermal energy. These observations may offer insight into the energization process.

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Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

et al. 2011

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“…All impurity ion velocity measurements in this paper were made with the CHERS diagnostic. 33,35,38 A 50 keV diagnostic neutral hydrogen beam stimulates charge exchange with C þ6 ions. The resulting C þ5 ions emit light that is Doppler shifted and Doppler broadened.…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

“…Toroidal viewing chords emanate from a single porthole displaced by a toroidal angle of 42 from the plane containing the beam and all poloidal viewing chords. 35 The toroidal viewing chord that intersects the beam on-axis is perpendicular to the beam while off-axis chords intersect the beam at angles that are slightly less than 90 . Since radial flows are very small, specifically near the plasma axis, and the projection of any radial flow onto the line of sight is even smaller, all toroidal viewing chords measure predominantly toroidal flow.…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

“…A diagnostic neutral beam 32 and custom highthroughput spectrometer 33 are used to make fast time-resolved measurements of carbon flows during periods of improved confinement in MST. The CHERS system on MST has been used in the past to measure impurity ion temperature, 34,35 impurity ion densities, 36 and ion velocity fluctuations associated with the tearing modes. 37 Recent improvements in absolute wavelength calibration have enabled equilibrium impurity ion flow profile measurements for the first time.…”

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confidence: 99%

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Intrinsic flow and tearing mode rotation in the RFP during improved confinement

et al. 2019

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We use charge exchange recombination spectroscopy to make the first localized measurements of impurity ion flow velocity profiles in the reversed field pinch. Measurements in improved confinement plasmas reveal an intrinsic flow profile that is peaked on the axis and mostly parallel to the equilibrium magnetic field. The toroidal flow decreases in time at off-axis locations where tearing modes are resonant, giving rise to a highly sheared flow profile near the axis. The tearing mode phase velocity correlates strongly with toroidal flow near the resonant surface and weakly with flow in other locations, providing an opportunity to verify the commonly held assumption that the plasma and mode move together at the resonant surface. Mechanisms for the observed momentum loss during the improved confinement period are evaluated, and it is found that eddy currents in the conducting shell caused by the rotation of the dominant tearing mode dominate over other losses.

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Direct measurements of the 3D plasma velocity in single-helical-axis RFP plasmas

et al. 2021

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The first local velocity measurements of helical equilibrium plasmas in the Reversed Field Pinch (RFP) Single Helical Axis (SHAx) state using a Charge Exchange Recombination Spectroscopy (CHERS) diagnostic are presented. Measurements show strong axisymmetric and non-axisymmetric flow, with n = 5 components of flow related to the (m,n)=(1,5) dominant magnetic mode on the order of the axisymmetric flow in certain regions of the plasma, as well as significant n > 5 flow. Flow measurements are compared with NIMROD simulations of visco-resistive, single-fluid MHD in toroidal and cylindrical geometries with limited axial periodicity. Both measurements and the simulation with toroidal geometry show stronger inboard flows relative to the outboard flows, which is attributed to the toroidal geometry of the device. In the experiment, the n = 5 component of flow is phase shifted from the reconnection-like flow pattern observed in the single-fluid simulations, possibly due to decoupling of the ion and electron fluids over much of the plasma. Finally, the strength of the helical angular flow shear relative to the critical shear necessary to disrupt nonlinear coupling between tearing modes is calculated around the helical magnetic axis. The shear in the measured flow is on the order of the theoretical critical threshold needed to nonlinearly decouple modes, but the measurement uncertainty in the gradient of the flow is large.

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Toroidal charge exchange recombination spectroscopy measurements on MST

Cited by 4 publications

References 7 publications

Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

Intrinsic flow and tearing mode rotation in the RFP during improved confinement

Direct measurements of the 3D plasma velocity in single-helical-axis RFP plasmas

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