Journal article · Preprint article
Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra
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 Dα (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.
Language: | English |
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Publisher: | IOP Publishing |
Year: | 2014 |
Pages: | 023005 |
ISSN: | 17414326 , 00295515 and 10185577 |
Types: | Journal article and Preprint article |
DOI: | 10.1088/0029-5515/54/2/023005 |
ORCIDs: | Salewski, Mirko , Korsholm, Søren Bang , Leipold, Frank , Madsen, Jens , Nielsen, Stefan Kragh , Rasmussen, Jesper and Stejner Pedersen, Morten |