Stable TAE n Discrimination with Plasma Rotation J. A. Snipes, A. Fasoli*, J. E. Rice, J. A. Sears MIT Plasma Science and Fusion Center, Cambridge, MA USA *CRPP-EPFL Association Euratom, Lausanne, Switzerland J A Snipes, Alcator C-Mod Ideas Forum, MIT PSFC, Cambridge, MA 13 – 15 December 2006

Improved Toroidal Mode Number Measurements New pick-up coil limiters at four toroidal locations will improve low n resolution for all MHD modes  If multiple n’s are simultaneously excited by the TAE antennas, a large plasma rotation should separate the modes in frequency J A Snipes, Alcator C-Mod Ideas Forum, MIT PSFC, Cambridge, MA 13 – 15 December 2006

Plasma Rotation in Ohmic H-mode Reaches 40 km/s ~ 9.5 kHz Motivation: Actively excited TAE measured phases often show no clear n number. The broad antenna spectrum may excite multiple n’s simultaneously. Knowing n is essential to compare with theory. Goals: Excite stable TAEs with the active MHD antennas during high plasma rotation • Look for closely frequency spaced multiple n modes with spacing proportional to plasma rotation • Attempt to discriminate the various n values and determine the damping rate as a function of n • Compare high n damping rate with theoretical expectation of increased radiative damping at high n Plan of execution: In Ohmic H-mode plasmas: • Sweep active MHD antenna frequency through the real-time TAE frequency and look for resonances • Attempt to maximize plasma rotation in H-mode • Look for frequency splitting of each resonance • Sweep through frequencies associated with high n>10 to attempt to drive higher n modes J E Rice, et al, 2004 Phys Plasmas 11, 2427 J A Snipes, Alcator C-Mod Ideas Forum, MIT PSFC, Cambridge, MA 13 – 15 December 2006