Recent upgrades to the FIDA (fast-ion D-alpha) diagnostic at ASDEX Upgrade are discussed. The diagnostic has been extended from three to five line of sight arrays with different angles to the magnetic field, and a spectrometer redesign allows the simultaneous measurement of red- and blue-shifted parts of the Doppler spectrum. These improvements make it possible to reconstruct the 2D fast-ion velocity distribution from the FIDA measurements by tomographic inversion under a wide range of plasma parameters. Two applications of the tomography are presented: a comparison between the distributions resulting from 60 keV and 93 keV neutral beam injection and a velocity-space resolved study of fast-ion redistribution induced by a sawtooth crash inside and outside the sawtooth inversion radius.
Weiland, M., Geiger, B., Jacobsen, A. S., Reich, M., Salewski, M., & Odstrčil, T. (2016). Enhancement of the FIDA diagnostic at ASDEX Upgrade for velocity space tomography. Plasma Physics and Controlled Fusion, 58(2), . https://doi.org/10.1088/0741-3335/58/2/025012