A zero order study of the effect of resonances on fast ions measured by FILD in ASDEX Upgrade.

This work introduces the Resonance Index (RI) technique, a new methodology for exploring MagnetoHydroDynamic (MHD) induced Fast Ion (FI) losses in tokamaks, with applications to cases involving Toroidicity Induced Alfvén Eigenmodes (TAEs) and Neoclassical Tearing Modes (NTMs) in ASDEX Upgrade (AUG). The RI technique focuses on the impact of the FI phase space topology on the mechanisms that drive FI loses and aims at the interpretation of signals from the Fast Ion Loss Detector (FILD). A fresh approach to orbit labeling is presented, linking the FI phase space with the FILD plane. Key findings, such as notable changes in RI and a distinct maximum along the boundary dividing phase space regions emphasize the importance of phase space topology in resonant interactions. The technique provides insights into the synergetic effects and underlying physics of FI losses, offering a computationally efficient tool for analyzing and interpreting experimental data when the MHD mode structure is partially known.