Interaction of Alfven waves with biased H mode plasmas in Phaedrus-T

Abstract

Data are presented showing the first demonstration that H mode plasmas can be produced with a biased electrode in the presence of substantial auxiliary power (the Alfven wave power was roughly twice the corresponding ohmic power). The data also show the first demonstration of Alfven wave heating of electrons during an H mode. Although the H mode has been produced in some tokamaks (without the use of a biased electrode) 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 H mode plasmas) and that this auxiliary power degrades rather than enhances the biased electrode H mode. In addition, for the first time, it is shown that Alfven waves generated by + pi /2 (as compared with a) phasing result in greater RF fuelling in H mode plasmas