Beam distribution modification by Alfv́n modes

Modification of a deuterium beam distribution in the presence of low amplitude toroidal Alfv́n eigenmodes and reversed shear Alfv́n eigenmodes in a toroidal magnetic confinement device is examined. Comparison to experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam transport, and that the experimental amplitudes are only slightly above this threshold. The modes produce a substantial central flattening of the beam distribution.