Alfvén Laboratory, Teknikringen 31, KTH, SE-100 44 Stockholm, Sweden
+) PSFC-MIT, Cambridge MA 02139, USA and
JET, Abingdon, Oxfordshire OX14 3EA, United Kingdom
*) CRPP, EPFL, CH-1015 Lausanne, Switzerland
The modeling of Alfvénic instabilities is discussed from the point of view of mode-conversion, showing how the development of the theory affects the predictions as the limitations of the models are gradually relaxed. Conventional tokamak plasmas are relatively well understood and are used for the case of a kinetic Alfvén eigenmode to assess the resonant wave-particle interactions along the magnetic field. The large safety factor in the core of deeply reversed shear plasmas and the low magnetic field of spherical tokamaks, however, bring the Alfvén Eigenmodes down into the drift-frequency range; modifications of the spectrum through toroidal mode-conversion then creates a new class of drift-kinetic Alfvén eigenmodes that could affect the fast particle confinement. Experiments have been carried out to verify these predictions in JET. They confirm the presence of weakly damped modes, which do not follow the usual Alfvén Eigenmodes scaling.
On-line document ( browse html, download ps, download pdf), back to the list of publications.