Velocity-space tomography using prior information at MAST

B. Madsen*, Mirko Salewski, J. Huang, A.S. Jacobsen, O. Jones, K. G. McClements

*Corresponding author for this work

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Velocity-space tomography provides a way of diagnosing fast ions in a fusion plasma by combining measurements from multiple instruments. We use a toroidally viewing and a vertically viewing fast-ion D-alpha diagnostic installed on the mega-amp spherical tokamak (before the upgrade) to perform velocity-space tomography of the fast-ion distribution function. To make up for the scarce amount of data, prior information is included in the inversions. We impose a non-negativity constraint, suppress the distribution in the velocity-space region associated with null-measurements, and encode the belief that the distribution function does not extend to energies significantly higher than those expected neoclassically. This allows us to study the fast-ion velocity distributions and the derived fast-ion densities before and after a sawtooth crash.
Original languageEnglish
Article number10D125
JournalReview of Scientific Instruments
Issue number10
Number of pages5
Publication statusPublished - 2018


  • Optical Spectroscopy


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