Bochum 2015 – scientific programme
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P: Fachverband Plasmaphysik
P 22: Helmholtz Graduate School for Plasma Physics II
P 22.5: Talk
Wednesday, March 4, 2015, 18:10–18:25, HZO 50
Influence of Alfvén eigenmodes and ion cyclotron heating on the fast-ion distribution in the ASDEX Upgrade tokamak — •Markus Weiland, Benedikt Geiger, Roberto Bilato, Philip Schneider, Giovanni Tardini, Philipp Lauber, Francois Ryter, Mirjam Schneller, and ASDEX Upgrade Team — Max-Planck-Institut für Plasmaphysik, Garching
Fast, supra-thermal ions are created in the tokamak ASDEX Upgrade by neutral beam injection and ion cyclotron resonance heating (ICRH) and they are needed for plasma heating and current drive. A possibility to study them is the spectroscopic observation of line radiation (fast-ion D-alpha, FIDA), which emerges from charge exchange reactions. Here, the fast ions can be distinguished from the thermal particles through there strong Doppler-shift, and their radial density profile can be measured and compared to theoretical models.
An analysis of the whole Doppler spectrum yields information about the 2D velocity distribution f(v∥, v⊥). Observation from different viewing angles allows consequently a tomographic reconstruction of f(v∥, v⊥). For this purpose, the FIDA diagnostic at ASDEX Upgrade has been extended from two to five views, and the spectrometer setup was improved to allow a simultaneous measurement of blue and red Doppler shifts. These recently developed diagnostic capabilities are used to study changes in the fast-ion distribution, which are caused by Alfvén eigenmodes. Moreover, the further acceleration of fast ions through 2nd harmonic ICRH is investigated and compared to theoretical predictions.