Purpose of the ex-p: localization of LH current S. Bernabei, J. Hosea, C. Phillips, J. R. Wilson In order to learn how to localize the current driven by LH waves, it is necessary to have diagnostics which show us where the waves damp. The hard X-ray camera is the best way to see where the fast electrons are created. Hard X-ray picture PBX-M time evolution diameter

How to localize damping If a simple phase scan does’nt produce the desired localization of the damping, we should try to launch two different spectra, one “fast” from either the two top arrays or lower arrays, the other “slower”. The slower one should produce an electron tail which will damp the faster spectrum and produce the current needed. n|| (PBX-M)

MSE Naturally, MSE will ultimately show that the current is in the desired radial position and the current has the desired profile. A problem would arise if LH waves will be damped (partially) be the fast ions of the beam: this has to studied by using available codes. One possible solution could be to reach stady state, then fire a beam blip: before the current will have time to change we should be able to obtain the current profile. Once we are confident that we have the desired current profile, during the experiment we could avoid using MSE.