TY - JOUR
T1 - Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra
AU - Salewski, Mirko
AU - Geiger, B.
AU - Jacobsen, Asger Schou
AU - García-Muñoz, M.
AU - Heidbrink, W.W.
AU - Korsholm, Søren Bang
AU - Leipold, Frank
AU - Madsen, Jens
AU - Moseev, Dmitry
AU - Nielsen, Stefan Kragh
AU - Rasmussen, Jesper
AU - Stejner Pedersen, Morten
AU - Tardini, G.
AU - Weiland, M.
PY - 2014
Y1 - 2014
N2 - 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.
AB - 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.
KW - Fast-ion velocity distribution function
KW - Tomography
KW - Inverse problems
KW - Fast ions in tokamaks
U2 - 10.1088/0029-5515/54/2/023005
DO - 10.1088/0029-5515/54/2/023005
M3 - Journal article
SN - 0029-5515
VL - 54
SP - 023005
JO - Nuclear Fusion
JF - Nuclear Fusion
IS - 2
ER -