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

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

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
Volume89
Issue number10
Number of pages5
ISSN0034-6748
DOIs
Publication statusPublished - 2018

Keywords

  • Optical Spectroscopy

Cite this

Madsen, B. ; Salewski, Mirko ; Huang, J. ; Jacobsen, A.S. ; Jones, O. ; McClements, K. G. / Velocity-space tomography using prior information at MAST. In: Review of Scientific Instruments. 2018 ; Vol. 89, No. 10.
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Velocity-space tomography using prior information at MAST. / Madsen, B.; Salewski, Mirko; Huang, J.; Jacobsen, A.S.; Jones, O.; McClements, K. G.

In: Review of Scientific Instruments, Vol. 89, No. 10, 10D125, 2018.

Research output: Contribution to journalJournal articleResearchpeer-review

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AU - Madsen, B.

AU - Salewski, Mirko

AU - Huang, J.

AU - Jacobsen, A.S.

AU - Jones, O.

AU - McClements, K. G.

PY - 2018

Y1 - 2018

N2 - 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.

AB - 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.

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