Comparison between measurements of the poloidal distribution of magnetic fluctuations and predictions of theoretical models during TAE activity

Heidbrink, W. W.; Jaun, A.; Holties, H. A.

doi:10.1088/0029-5515/37/10/i07

Cited by 8 publications

(7 citation statements)

References 27 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The data show an eigenfunction with a strongly peaked amplitude in the center, similar to the structure implied by measurements from a poloidal array of Mirnov coils. 23 The gyrokinetic prediction compares well with the data qualitatively but quantitative discrepancies exist, although these may by accounted for by uncertainties in the modeling.…”

Section: Introductionmentioning

confidence: 69%

“…22 In DIII-D, a poloidal array of magnetic probes was used to measure fluctuations during TAE activity. 23 Although the amplitude of the fluctuations did not agree with predictions from ideal and resistive MHD models, it compared fairly well with the predictions of a model retaining Landau damping and finite Larmor radius ͑FLR͒ effects. For this model, the comparison yielded reduced 2 's of 1.2 and 1.6, respectively, for two different toroidal mode numbers.…”

Section: Introductionmentioning

confidence: 73%

“…Although rough consistency between theoretical eigenfunctions and measurements have been reported, [20][21][22]57 the most detailed comparisons found discrepancies. 21,23 An earlier study of discharge 71524 concluded that the predictions of the MHD model disagree in both amplitude and phase with the poloidal distribution of edge magnetic fluctuations, while the gyrokinetic model gives satisfactory agreement for the amplitude but not the phase. 23 Thus, three sets of data-soft x-ray, beam-ion loss, and poloidal magnetic-are all inconsistent with the theoretical predictions for this discharge.…”

Section: A Origin Of the Discrepancymentioning

confidence: 99%

See 2 more Smart Citations

The toroidicity-induced Alfvén eigenmode structure in DIII-D: Implications of soft x-ray and beam-ion loss data

et al. 2001

View full text Add to dashboard Cite

The internal structure of the toroidicity-induced Alfvén eigenmode (TAE) is studied by comparing soft x-ray profile and beam ion loss data taken during TAE activity in the DIII-D tokamak [W. W. Heidbrink et al., Nucl. Fusion 37, 1411 (1997)] with predictions from theories based on ideal magnetohydrodynamic (MHD), gyrofluid, and gyrokinetic models. The soft x-ray measurements indicate a centrally peaked eigenfunction, a feature which is closest to the gyrokinetic model’s prediction. The beam ion losses are simulated using a guiding center code. In the simulations, the TAE eigenfunction calculated using the ideal MHD model acts as a perturbation to the equilibrium field. The predicted beam ion losses are an order of magnitude less than the observed ∼6%–8% losses at the peak experimental amplitude of δBr/B0≃2–5×10−4.

show abstract

Section: Introductionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 73%

Section: A Origin Of the Discrepancymentioning

confidence: 99%

See 1 more Smart Citation

The toroidicity-induced Alfvén eigenmode structure in DIII-D: Implications of soft x-ray and beam-ion loss data

et al. 2001

View full text Add to dashboard Cite

show abstract

“…The measured frequency agrees well with the expected frequency in many devices. 32 The spatial structure is in rough qualitative agreement with theory for some modes in TFTR 33,34 but agrees rather poorly with theory in DIII-D. 35,36 There have been several notable successes of linear TAE stability theory, particularly for alpha-driven TAEs in TFTR 34 and comparisons of JET antenna measurements with calculations by the gyrokinetic PENN code. 21 The only attempt to compare theoretical predictions of fastion transport with measurements failed.…”

mentioning

confidence: 91%

Alpha particle physics in a tokamak burning plasma experiment

Heidbrink

2002

Physics of Plasmas

View full text Add to dashboard Cite

Much is known about the behavior of energetic ions in tokamak devices but much remains to be understood. Single-particle effects are well understood and provide a firm basis for extrapolation to a burning plasma. In contrast, collective effects involving fast ions are more poorly understood and extrapolations are unreliable. Collective modes of concern include toroidicity-induced and ellipticity-induced Alfvén eigenmodes, kinetic ballooning modes, and internal kink modes. In addition to these magnetohydrodynamic normal modes, there are also energetic particle modes characterized by strong dependence on the fast-ion distribution function. Although many issues are important areas of study in current experiments, five issues distinguish burning plasma experiments. First, the energetic alphas are not the dominant source of free energy for the instabilities unless the fusion power exceeds the heating power by a factor of 10. Second, the damping of the instabilities depends sensitively on mode coupling to other heavily-damped waves. The magnitude of this coupling is expected to depend on the normalized thermal gyroradius, which is much smaller in a reactor. Third, in a reactor, both the radial extent of the instabilities and the fast-ion orbit contract relative to current experiments, so the fast-ion transport will change. Fourth, when instability occurs, a larger number of modes are unstable, so the mechanism of nonlinear saturation could shift from fast-ion transport to mode coupling. Fifth, because of the extreme sensitivity of energetic particle modes to the distribution function, an isotropic alpha particle distribution function differs from anisotropic fast-ion populations.

show abstract

“…51,61 This finding suggests that many modes will be excited in a large burning plasma experiment with the consequence that mode overlap may play a more important role in mode saturation than in current experiments. 62 In a study of the poloidal structure, 63 the data from a poloidal array of magnetic probes were compared with the wavefields predicted by two models: an ideal MHD calculation and a gyrokinetic plasma model that includes coupling to drift-kinetic waves. The phases of the probes disagreed with both theoretical predictions, while the amplitudes agree best with the gyrokinetic model.…”

Section: Iva Toroidicity Induced Alfvén Eigenmodementioning

confidence: 99%