Overview of the beam emission spectroscopy diagnostic system on the National Spherical Torus Experiment

Smith, D. R.; Feder, Harvey H.; Feder, R.; Fonck, R. J.; Labik, G.; McKee, G. R.; Schoenbeck, N.L.; Stratton, B.; Uzun-Kaymak, Ilker; Winz, G.R.

doi:10.1063/1.3478660

Cited by 34 publications

(38 citation statements)

References 10 publications

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“…Ion-scale turbulence research has made significant progress in recent years due to the implementation of the beam emission spectroscopy (BES) diagnostic on NSTX and MAST. 171,172 One may note that because of the multiple possible ion transport relevant turbulence modes with a similar range of wavelength and frequency (i.e., ITG, TEM, and KBM), it is often difficult to clearly identify one particular mode responsible for the ion energy transport. In the core region of the MAST plasma, highly non-linear saturated "critically balanced" turbulence behavior was observed.…”

Section: Ion Energy Transportmentioning

confidence: 99%

“…In order to develop a physics-based understanding of the radial transport of heat and particles, there have been extensive edge turbulence transport studies in many fusion devices utilizing visible fast cameras, 267 gas-puff-imaging (GPI) measurements, 268 edge probes, 269,270 and BES, 171,172 together with theory and modeling. [271][272][273][274] The region of interest is outside of the last-closed-flux-surface (LCFS), and it is in the open field line region.…”

Section: Edge Turbulence Studymentioning

confidence: 99%

“…102, a variety of EP modes can be excited simultaneously and their behavior is highly timevarying, particularly during the initial current ramp-up phase where the plasma parameters are rapidly changing. In addition to the magnetic pick-up loops, there are various techniques such as microwave reflectometry 318 and BES 171,172 that can be used to measure the EP mode amplitudes. The observed EP modes were compared with theoretical models and show generally good agreement with linear theory.…”

Section: B Energetic-particle-driven Modesmentioning

confidence: 99%

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Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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Section: Ion Energy Transportmentioning

confidence: 99%

Section: Edge Turbulence Studymentioning

confidence: 99%

Section: B Energetic-particle-driven Modesmentioning

confidence: 99%

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Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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“…The δB r fluctuations are also much stronger on the outboard side with instantaneous values (~25-30 Gauss) approaching 1% of the local equilibrium field (~3.5kG). The recently implemented beam emission spectroscopy (BES) diagnostics [67] is sensitive to density fluctuations at the poloidal wavelengths relevant to microtearing turbulence (k θ ρ s <1). However, typical BES fiber optic views are 2-3 cm wide and it is unknown how sensitive it will be to the narrow density perturbations.…”

Section: Real Space Structure and Measurement Opportunitiesmentioning

confidence: 99%

Simulation Of Microtearing Turbulence In NSTX

Guttenfelder¹,

Kaye²,

Nevins³

et al. 2012

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Thermal energy confinement times in NSTX dimensionless parameter scans increase with decreasing collisionality. While ion thermal transport is neoclassical, the source of anomalous electron thermal transport in these discharges remains unclear, leading to considerable uncertainty when extrapolating to future ST devices at much lower collisionality.Linear gyrokinetic simulations find microtearing modes to be unstable in high collisionality discharges. First non-linear gyrokinetic simulations of microtearing turbulence in NSTX show they can yield experimental levels of transport. Magnetic flutter is responsible for almost all the transport (~98%), perturbed field line trajectories are globally stochastic, and a test particle stochastic transport model agrees to within 25% of the simulated transport. Most significantly, microtearing transport is predicted to increase with electron collisionality, consistent with the observed NSTX confinement scaling. While this suggests microtearing modes may be the source of electron thermal transport, the predictions are also very sensitive to electron temperature gradient, indicating the scaling of the instability threshold is important. In addition, microtearing turbulence is susceptible to suppression via sheared E×B flows as experimental values of E×B shear (comparable to the linear growth rates) dramatically reduce the transport below experimental values. Refinements in numerical resolution and physics model assumptions are expected to minimize the apparent discrepancy. In cases where the predicted transport is strong, calculations suggest that a proposed polarimetry diagnostic may be sensitive to the magnetic perturbations associated with the unique structure of microtearing turbulence.

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“…The DIII-D [5] and National Spherical Torus Experiment (NSTX) [6] BES diagnostics measure Doppler-shifted D α light from injected deuterium neutral beams. Another instrument, the fast-ion D α (FIDA) diagnostic also measures Doppler-shifted D α light [7].…”

Section: Introductionmentioning

confidence: 99%

‘Beam-emission spectroscopy’ diagnostics also measure edge fast-ion light

Heidbrink

McKee

Smith

et al. 2011

Plasma Phys. Control. Fusion

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Beam-emission spectroscopy (BES) diagnostics normally detect fluctuations in the light emitted by an injected neutral beam. Under some circumstances, however, light from fast ions that charge exchange in the high neutral-density region at the edge of the plasma make appreciable contributions to the BES signals. This 'passive' fast-ion D α (FIDA) light appears in BES signals from both the DIII-D tokamak and the National Spherical Torus Experiment (NSTX). One type of passive FIDA light is associated with classical orbits that traverse the edge. Another type is caused by instabilities that expel fast ions from the core; this light can complicate measurement of the instability eigenfunction.

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Overview of the beam emission spectroscopy diagnostic system on the National Spherical Torus Experiment

Cited by 34 publications

References 10 publications

Recent progress on spherical torus research

Recent progress on spherical torus research

Simulation Of Microtearing Turbulence In NSTX

‘Beam-emission spectroscopy’ diagnostics also measure edge fast-ion light

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