Array of neutral particle analyzers at DIII-D

Carolipio, E. M.; Heidbrink, W. W.

doi:10.1063/1.1147855

Cited by 12 publications

(8 citation statements)

References 1 publication

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“…The data are obtained by a horizontally scanning neutral particle analyzer with a sightline that intersects two of the heating beams. 35 As the Alfvén activity increases in strength, the central density of beam ions decreases ͓Figs. 10͑b͒ and 10͑c͔͒.…”

Section: A Scans and Representative Dischargesmentioning

confidence: 99%

What is the “beta-induced Alfvén eigenmode?”

et al. 1999

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An instability with a lower frequency than the toroidicity-induced Alfvén eigenmode was initially identified as a beta-induced Alfvén eigenmode ͑BAE͒. Instabilities with the characteristic spectral features of this ''BAE'' are observed in a wide variety of tokamak plasmas, including plasmas with negative magnetic shear. These modes are destabilized by circulating beam ions and they transport circulating beam ions from the plasma core. The frequency scalings of these ''BAEs'' are compared to theoretical predictions for Alfvén modes, kinetic ballooning modes, ion thermal velocity modes, and energetic particle modes. None of these simple theories match the data.

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Section: A Scans and Representative Dischargesmentioning

confidence: 99%

What is the “beta-induced Alfvén eigenmode?”

et al. 1999

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“…To minimize perturbations in the beam population, the combined beam waveform never turns off for more than 10 ms, which is much less than the beam ion slowing down time of τ s 75 ms. The 60 MHz system couples ∼1 MW of power between 1.8 and 3.0 s. With the application of RF power, the stored energy, d-d neutron emission [18] and flux of energetic perpendicular neutrals [19] increase on a τ s timescale. ECE measurements with a heterodyne radiometer [20] indicate that the central electron temperature increases during RF heating and that the sawtooth cycle is modified.…”

Section: Experimental Observationsmentioning

confidence: 99%

High harmonic ion cyclotron heating in DIII-D: Beam ion absorption and sawtooth stabilization

et al. 1999

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Abstract. Combined neutral beam injection and fast wave heating at the fourth cyclotron harmonic produce an energetic deuterium beam ion tail in the DIII-D tokamak. When the concentration of thermal hydrogen exceeds ∼5%, the beam ion absorption is suppressed in favour of second harmonic hydrogen absorption. As theoretically expected, the beam absorption increases with beam ion gyroradius; also, central absorption at the fifth harmonic is weaker than central absorption at the fourth harmonic. For central heating at the fourth harmonic, an energetic, perpendicular, beam population forms inside the q = 1 surface. The beam ion tail transiently stabilizes the sawtooth instability but destabilizes toroidicity induced Alfvén eigenmodes (TAEs). Saturation of the central heating correlates with the onset of the TAEs. Continued expansion of the q = 1 radius eventually precipitates a sawtooth crash; complete magnetic reconnection is observed.

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“…Spatially resolved measurements of the fast ions are obtained three ways. A compact electrostatic neutral particle analyser (NPA) measures the active charge exchange signal at R = 1.95 m [35]; the analyser detects perpendicular 50 keV neutrals from a vertical volume that is determined by the vertical extent of the modulated neutral beam (figure 1). The second spatially resolved diagnostic relies on motional Stark effect (MSE) [36] measurements of the internal magnetic field.…”

Section: Plasma and Fast-ion Diagnosticsmentioning

confidence: 99%

Measurements of fast-ion acceleration at cyclotron harmonics using Balmer-alpha spectroscopy

Heidbrink

Luo

Burrell

et al. 2007

Plasma Phys. Control. Fusion

105

196

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Combined neutral beam injection and fast wave heating at the fourth and fifth cyclotron harmonics accelerate fast ions in the DIII-D tokamak. Measurements with a nine-channel fast-ion D-alpha (FIDA) diagnostic indicate the formation of a fast-ion tail above the injection energy. Tail formation correlates with enhancement of the d-d neutron rate above the value that is expected in the absence of fast-wave acceleration. FIDA spatial profiles and fast-ion pressure profiles inferred from the equilibrium both indicate that the acceleration is near the magnetic axis for a centrally located resonance layer. The enhancement is largest 8-10 cm beyond the radius where the wave frequency equals the cyclotron harmonic, probably due to a combination of Doppler-shift and orbital effects. The fast-ion distribution function calculated by the CQL3D FokkerPlanck code is fairly consistent with the data.

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Array of neutral particle analyzers at DIII-D

Cited by 12 publications

References 1 publication

What is the “beta-induced Alfvén eigenmode?”

What is the “beta-induced Alfvén eigenmode?”

High harmonic ion cyclotron heating in DIII-D: Beam ion absorption and sawtooth stabilization

Measurements of fast-ion acceleration at cyclotron harmonics using Balmer-alpha spectroscopy

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