Studies of Alfven Eigenmodes Driven by RF-Heated Fast Ions at JET

Alfvén Eigenmodes (AEs) are destabilized by RF-heated fast ions in many JET plasma configurations (H modes, L modes, Optimised Shear) with various plasma species mixtures (H, D, T, and ^3He) and ICRH schemes, provided there is a sufficiently strong ion tail. The AEs are observed for up to 4 sec at 1 MHz via Mirnov coils, reflectometry, and soft X-ray emission. Roughly 1/3 of the 4000+ JET pulses in 1997-1998 had P_ICRH > 1 MW during the observation interval, creating a large AE excitation database which is now being systematically analyzed. The ICRH power threshold for AE instability ranges from < 1 MW to ≈ 10 MW depending on the plasma conditions and ICRH scheme used. Typical TAE modes have edge amplitude δ B/B ≈ 10^-6 and toroidal mode number n = 5 to 12. ``Standard'' results for the various configurations as well as a variety of unusual AE phenomena are reported.