Measurements of the radial structure and poloidal spectra of toroidal Alfvén eigenmodes in the Tokamak Fusion Test Reactor

Durst, R.; Fonck, R. J.; Wong, K. L.; Cheng, C. Z.; Fredrickson, E.; Paul, S. F.

doi:10.1063/1.860326

Cited by 37 publications

(24 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In TFTR, the TAE radial eigenfunction was obtained for the first time using Beam Emission Spectroscopy (BES) and reflectometry. The poloidal mode number was found to be consistent within 50 % of the predictions from an ideal MHD model [10]. Nazikian et al investigated the radial mode structure of a n = 4 TAE using three fixed frequency X-mode reflectometer channels.…”

Section: Introductionmentioning

confidence: 69%

Localization of MHD and fast particle modes using reflectometry in ASDEX Upgrade

Graca¹,

Conway²,

Lauber³

et al. 2007

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Abstract. The radial structure of Toroidal Alfvén Eigenmodes (TAEs) is of great importance for comparison with theoretical predictions. A dual-channel fast frequency hopping millimeter-wave reflectometer installed on the ASDEX Upgrade tokamak is capable of measuring density fluctuations from the plasma edge to core, allowing the radial eigenfunction of n = 4 TAE and edge MHD modes to be obtained using phase perturbation and coherence data analysis techniques. The two techniques reveal similar results, and in particular the radial structure of the n = 4 TAE is found to be in good agreement with numerical predictions from linear gyrokinetic simulations. First results of the radial localization of Alfvén cascades are also presented.

show abstract

Section: Introductionmentioning

confidence: 69%

Localization of MHD and fast particle modes using reflectometry in ASDEX Upgrade

Graca¹,

Conway²,

Lauber³

et al. 2007

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…On the other hand, the experimental plasma displacement has been estimated ϳ5 -10 mm from the density fluctuation. 16 This enables us to estimate the amplitude ␦B/Bϳv/V A ϳ / A Rϳ0.6-1.3ϫ10 Ϫ3 . With this esti- FIG.…”

Section: Discussion and Summarymentioning

confidence: 99%

Simulation of intermittent beam ion loss in a Tokamak Fusion Test Reactor experiment

2003

View full text Add to dashboard Cite

Recurrent bursts of toroidicity-induced Alfvén eigenmodes ͑TAE͒ are studied using a self-consistent simulation model. Bursts of beam ion losses observed in the neutral beam injection experiment at the Tokamak Fusion Test Reactor ͓K. L. Wong et al., Phys. Rev. Lett. 66, 1874 ͑1991͔͒ are reproduced using experimental parameters. It is found that synchronized TAE bursts take place at regular time intervals of 2.9 ms, which is close to the experimental value of 2.2 ms. The stored beam energy saturates at about 40% of that of the classical slowing down distribution. The stored beam energy drop associated with each burst has a modulation depth of 10%, which is also close to the inferred experimental value of 7%. Surface of section plots demonstrate that both the resonance overlap of different eigenmodes and the disappearance of KAM surfaces in phase space due to overlap of higher-order islands created by a single eigenmode lead to particle loss. Only co-injected beam ions build up to a significant stored energy even though their distribution is flattened in the plasma center. However, they are not directly lost, as their orbits extend beyond the outer plasma edge when the core plasma leans on a high field side limiter. The saturation amplitude is ␦B/B ϳ2ϫ10 Ϫ2 , which is larger than would appear to be compatible with experiment. Physical arguments are presented for why the stored energetic particle response observed in the simulation is still plausible.

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: 90%

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

Measurements of the radial structure and poloidal spectra of toroidal Alfvén eigenmodes in the Tokamak Fusion Test Reactor

Cited by 37 publications

References 11 publications

Localization of MHD and fast particle modes using reflectometry in ASDEX Upgrade

Localization of MHD and fast particle modes using reflectometry in ASDEX Upgrade

Simulation of intermittent beam ion loss in a Tokamak Fusion Test Reactor experiment

Alpha particle physics in a tokamak burning plasma experiment

Contact Info

Product

Resources

About