Study of fast-ion transport induced by fishbones on JET

Thun, C. Perez von; Salmi, A.; Perona, A.; Sharapov, S. E.; Pinches, S. D.; Popovichev, S.; Conroy, S.; Kiptily, V.; Brix, M.; Cecconello, M.; Johnson, T.

doi:10.1088/0029-5515/52/9/094010

Cited by 14 publications

(19 citation statements)

References 33 publications

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“…In addition to sawtooth events, we highlight that fishbone instabilities also appear in this discharge at times close to some of the sawtooth crashes. These modes represent another manifestation of an (m, n) = (1, 1) perturbation in the plasma and can, under certain conditions, also give rise to significant anomalous fast-ion transport [22,23]. An example is presented in figure 7, showing the burst-like rise and slightly slower decay of magnetic perturbations characteristic of these modes.…”

Section: Resultsmentioning

confidence: 99%

Collective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade

et al. 2016

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Abstract. Sawtooth instabilities can modify heating and current-drive profiles and potentially increase fast-ion losses. Understanding how sawteeth redistribute fast ions as a function of sawtooth parameters and of fast-ion energy and pitch is hence a subject of particular interest for future fusion devices. Here we present the first collective Thomson scattering (CTS) measurements of sawtooth-induced redistribution of fast ions at ASDEX Upgrade. These also represent the first localized fast-ion measurements on the high-field side of this device. The results indicate fast-ion losses in the phasespace measurement volume of about 50% across sawtooth crashes, in good agreement with values predicted with the Kadomtsev sawtooth model implemented in TRANSP and with the sawtooth model in the EBdyna go code. In contrast to the case of sawteeth, we observe no fast-ion redistribution in the presence of fishbone modes. We highlight how CTS measurements can discriminate between different sawtooth models, in particular when aided by multi-diagnostic velocity-space tomography, and briefly discuss our results in light of existing measurements from other fast-ion diagnostics.

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Section: Resultsmentioning

confidence: 99%

Collective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade

et al. 2016

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“…Strong and coherent fast-ion losses observed in the presence of neoclassical tearing modes have shown that these modes selectively redistribute fast particles under resonance conditions [59,78]. Fishbones [72,79] and off-axis fishbones [80] have also been demonstrated to act selectively in velocity space. However, the underlying mechanisms leading to enhanced fast-ion transport in the presence of these MHD instabilities are still not understood well.…”

Section: Discussionmentioning

confidence: 99%

Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra

et al. 2014

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We present the first measurement of a local fast-ion 2D velocity distribution function f (v , v ⊥ ). To this end, we heated a plasma in ASDEX Upgrade by neutral beam injection and measured spectra of fast-ion D α (FIDA) light from the plasma centre in three views simultaneously. The measured spectra agree very well with synthetic spectra calculated from a TRANSP/NUBEAM simulation. Based on the measured FIDA spectra alone, we infer f (v , v ⊥ ) by tomographic inversion. Salient features of our measurement of f (v , v ⊥ ) agree reasonably well with the simulation: the measured as well as the simulated f (v , v ⊥ ) are lopsided towards negative velocities parallel to the magnetic field, and they have similar shapes. Further, the peaks in the simulation of f (v , v ⊥ ) at full and half injection energies of the neutral beam also appear in the measurement at similar velocity-space locations. We expect that we can measure spectra in up to seven views simultaneously in the next ASDEX Upgrade campaign which would further improve measurements of f (v , v ⊥ ) by tomographic inversion.

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“…Note that here we define EPMs to be fast-particle-driven internal kink modes with a dominant poloidal mode number m = 1, and with fundamental toroidal mode number n = 1; higher toroidal harmonics may also be present. Fast-ion transport induced by fishbones has recently been reported on JET, where the observed changes in neutron rate were compared with modelling [7]. Finally, on MAST, the recentlycommissioned collimated neutron camera has been used to detect changes in the radial emissivity profile of neutrons caused by sawteeth and EPMs [8].…”

Section: Introductionmentioning

confidence: 99%

Fast-ion deuterium alpha spectroscopic observations of the effects of fishbones in the Mega-Ampere Spherical Tokamak

Jones

Michael

McClements

et al. 2013

Plasma Phys. Control. Fusion

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Abstract. Using the recently-installed Fast-Ion Deuterium Alpha (FIDA) spectrometer, the effects of low-frequency (20 − 50 kHz) chirping energetic particle modes with toroidal mode number n ≥ 1 on the NBI-driven fast-ion population in MAST plasmas are considered. Results from the FIDA diagnostic are presented and discussed in the light of the present theoretical understanding of these modes, known as fishbones, in plasmas with reversed shear. Measurements of the fast-ion population reveal strong redistribution of fast ions in both real and velocity space as a result of the fishbones. Time-resolved measurements throughout the evolution of a fishbone show radial redistribution of fast ions with energies up to 95% of the primary beam injection energy. Correlations between changes in the FIDA signal and the peak time derivative of the magnetic field perturbation are observed in a limited range of operating scenarios. The transient reduction in signal caused by a fishbone may in some cases reach 50% of the signal intensity before mode onset.

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Study of fast-ion transport induced by fishbones on JET

Cited by 14 publications

References 33 publications

Collective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade

Collective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade

Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra

Fast-ion deuterium alpha spectroscopic observations of the effects of fishbones in the Mega-Ampere Spherical Tokamak

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