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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.

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