Measurement of LHCD Effects on q(r) Through Stable Alfvén Eigenmodes in the Current Rise

1. Measurement of LHCD Effects on q(r) Through Stable Alfvén Eigenmodes in the Current Rise MIT Plasma Science and Fusion Center, Cambridge, MA USA *Princeton Plasma Physics Laboratory, Princeton, NJ USA †University of Texas at Austin, Fusion Research Center, Austin, TX USA J. A. Snipes, E. Edlund, N. Gorelenkov*, R. R. Parker, P. Phillips†, M. Porkolab, S. Scott*, J. A. Sears, S. Wukitch J A Snipes, Alcator C-Mod Ideas Forum, MIT PSFC, Cambridge, MA 13 – 15 December 2006

2. Can we Excite Stable Alfvén Eigenmodes in the Current Rise? In the current rise with and without ICRF driven fast particlesSweep the active MHD antenna frequency over the AC & TAE range Use LHCD to flatten q(r) and look for changes in TAE resonances J A Snipes, Alcator C-Mod Ideas Forum, MIT PSFC, Cambridge, MA 13 – 15 December 2006

3. LHCD Effects on q(r) Through Stable Alfvén Eigenmodes Motivation: To gain physics understanding of Alfvén eigenmodes and clarify the differences between Alfvén Cascades and TAEs. Even small changes in q(r) induced by LHCD will affect the excited AEs so that they can be used as a sensitive measure of q(r) changes. Goals:Excite stable Alfvén Eigenmodes with active MHD antennas • Measure small changes in q(r) through the effects on AEs • Measure n and / of AEs to compare with NOVA-K modeling Plan of execution: Use Ohmic+LHCD inner wall limited plasmas • Sweep active MHD antenna frequency over the Alfvén cascade and TAE range in the current rise and look for resonances vs frequency • Add LHCD to modify q(r) and maintain or extend low shear • Use DNB to measure q(r) with MSE • Compare measured modes with NOVA-K to estimate changes in q(r) and compare measured damping rates with calculated damping • Add ICRF to drive unstable AEs to compare J A Snipes, Alcator C-Mod Ideas Forum, MIT PSFC, Cambridge, MA 13 – 15 December 2006