The toroidicity-induced Alfven eigenmode structure in DIII-D: Implicationsof soft x-ray and beam-ion loss data

The internal structure of the toroidicity-induced Alfven eigenmode (TAE) is studied by comparing soft x-ray profile and beam ion loss data taken durin g TAE activity in the DIII-D tokamak [W. W. Heidbrink , Nucl. Fusion 37, 14 11 (1997)] with predictions from theories based on ideal magnetohydrodynami c (MHD), gyrofluid, and gyrokinetic models. The soft x-ray measurements ind icate a centrally peaked eigenfunction, a feature which is closest to the g yrokinetic model's prediction. The beam ion losses are simulated using a gu iding center code. In the simulations, the TAE eigenfunction calculated usi ng the ideal MHD model acts as a perturbation to the equilibrium field. The predicted beam ion losses are an order of magnitude less than the observed similar to6%-8% losses at the peak experimental amplitude of deltaB(r)/B(0 )similar or equal to2-5x10(-4). (C) 2001 American Institute of Physics.