Overview of Alfven eigenmode experiments in JET

Fasoli, A.; Lister, J.B.; Sharapov, S. E.; Ali-Arshad, S.; Bosia, G.; Borba, D.; Campbell, D.J.; Deliyanakis, N.; Dobbing, John; Gormezano, C.; Holties, H. A.; Huysmans, G. T. A.; Jacquinot, J.; Jaun, A.; Kerner, W.; Lavanchy, P.; Moret, J.M.; Porte, L.; Santagiustina, A.; Villard, L.

doi:10.1088/0029-5515/35/12/i09

Cited by 54 publications

(49 citation statements)

References 27 publications

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“…The TAE resonances are observed to coincide with the TAE frequency at the q=1.5 surface, as also observed in JET. 4 This is expected theoretically, as long as the antennas couple to this resonance, since the least stable TAE is at the q=1.5 surface for a monotonic q profile, halfway between the m=1 and m=2 continua. 29 To observe multiple resonances in a single discharge and follow the resonance in time, the antenna frequency can be swept up and down through the expected TAE resonant frequency in the plasma (Figure 2).…”

Section: Stable Alfvén Eigenmode Experimentsmentioning

confidence: 82%

“…[1][2][3][4][5] Calculations indicate that fusion generated α particles may destabilize these modes in next step devices such as the International Thermonuclear Experimental Reactor (ITER) 6 and if the modes are large enough to transport substantial amounts of hot α particles from the core of the plasma, they could quench the fusion burn or lead to damage to the first wall. The energetic ions that destabilize Alfvén eigenmodes in present devices are produced by neutral beam injection or ion cyclotron radio frequency (ICRF) heating.…”

Section: Introductionmentioning

confidence: 99%

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Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

et al. 2005

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Section: Stable Alfvén Eigenmode Experimentsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

et al. 2005

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“…While such synchronous detection was performed with hardware electronic circuits on JET [14], we chose to fast sample the data and perform synchronous detection with software to allow more flexibility in the analysis of the data.…”

Section: Software Synchronous Detectionmentioning

confidence: 99%

Initial active MHD spectroscopy experiments exciting stable Alfvén eigenmodes in Alcator C-Mod

Snipes¹,

Schmittdiel²,

Fasoli³

et al. 2004

Plasma Phys. Control. Fusion

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A pair of toroidally localised in-vessel antennas in Alcator C-Mod were used to excite and detect stable Toroidal Alfvén Eigenmode (TAE) resonances in the frequency range of 400 -500 kHz. By ramping the toroidal field, the plasma TAE frequency was swept through the constant antenna excitation frequency to find a resonance and the width of the resonance was measured to determine the effective damping rate of the mode. The toroidal field and density at the resonances were observed to scale as , as expected for Alfvén eigenmodes. TAE damping rates were measured in both inner wall limited and diverted discharges. The inner wall limited damping rates for these discharges were in the range of 1% < |γ/ω| < 4%. Diverted plasmas, on the other hand, required a very small outer gap between the last closed flux surface (LCFS) and the outboard limiter of less than 1 cm to observe the resonances and the damping rates were then very low with |γ/ω| < 1%.

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“…Indeed, many of these modes have been studied with an internal antenna in ohmically heated plasmas. 12 However, there is another class of fast-ion driven instabilities, the energetic particle modes 13 ͑Table I͒. In contrast to the MHD modes, these only exist in plasmas with a significant energetic ion population.…”

Section: Fast-ion Physics In Current Devicesmentioning

confidence: 99%

Alpha particle physics in a tokamak burning plasma experiment

Heidbrink

2002

Physics of Plasmas

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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.

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Overview of Alfven eigenmode experiments in JET

Cited by 54 publications

References 27 publications

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

Initial active MHD spectroscopy experiments exciting stable Alfvén eigenmodes in Alcator C-Mod

Alpha particle physics in a tokamak burning plasma experiment

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