Measurements and modelling of fast-ion redistribution due to resonant MHD instabilities in MAST
Abstract
The results of a comprehensive investigation into the effects of toroidicity-induced Alfvén eigenmodes (TAE) and energetic particle modes on the NBI-generated fast-ion population in MAST plasmas are reported. Fast-ion redistribution due to frequency-chirping TAE in the range 50 kHz-100 kHz and frequency-chirping energetic particle modes known as fishbones in the range 20 kHz-50 kHz, is observed. TAE and fishbones are also observed to cause losses of fast ions from the plasma. The spatial and temporal evolution of the fast-ion distribution is determined using a fission chamber, a radially-scanning collimated neutron flux monitor, a fast-ion deuterium alpha spectrometer and a charged fusion product detector. Modelling using the global transport analysis code Transp, with ad hoc anomalous diffusion and fishbone loss models introduced, reproduces the coarsest features of the affected fast-ion distribution in the presence of energetic particle-driven modes. The spectrally and spatially resolved measurements show, however, that these models do not fully capture the effects of chirping modes on the fast-ion distribution.
- Publication:
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Plasma Physics and Controlled Fusion
- Pub Date:
- December 2015
- DOI:
- 10.1088/0741-3335/57/12/125009
- arXiv:
- arXiv:1503.06698
- Bibcode:
- 2015PPCF...57l5009J
- Keywords:
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- Physics - Plasma Physics
- E-Print:
- 32 pages, 23 figures, submitted to Plasma Physics and Controlled Fusion