Abstract
Experimental observations from TFTR of fast ion losses resulting from the toroidicity induced Alfven eigenmode (TAE) and the Alfven frequency mode (AFM) are presented. The AFM was driven by neutral beam ions, at low BT, and the TAE was excited by hydrogen minority ion cyclotron range of frequencies (ICRF) tail ions at higher BT. The measurements indicate that the loss rate varies linearly with the mode amplitude for both modes, and that the fast ion losses during the mode activity can be significant, with tens of per cent of the input power lost in the worst cases