INTERACTION OF ALFVEN WAVES WITH BIASED H-MODE PLASMAS IN PHAEDRUS-T

Data are presented showing the first demonstration that Il mode plasma s can be produced with a biased electrode in the presence of substanti al auxiliary power (the Alfven wave power was roughly twice the corres ponding ohmic power). The data also show the first demonstration of Al fven wave heating of electrons during an Il mode. Although the H mode has been produced in some tokamaks (without the use of a biased electr ode) by auxiliary heating greater than a threshold value dependent on plasma conditions and the auxiliary heating method, for the first time , measurements presented here Show that subthreshold Alfven wave power increases the edge particle transport (in both ohmic and Il mode plas mas) and that this auxiliary power degrades rather than enhances the b iased electrode H mode. In addition, for the first time, it is shown t hat Alfven waves generated by +pi/2 (as compared with pi) phasing resu lt in greater RF fuelling in H mode plasmas.