Energetic Ions and MHD Diagnosis through Alfven Eigenmodes Detection in JET

摘要

Unstable Alfven Eigenmodes (AEs) driven by ICRF-acceleratedenergetic ions are routinely observed in JET plasmas. The stable AE spectrum is also measured in JET plasmas with the use of external saddle-coil antennae [1]. These AE measurements can be compared with models in order to obtain important information on the energetic particles and plasma characteristics [2]. the first determination of plasma parameters from measurements of the stable AEs on JET was performed in [3]. These studies are extended here, with emphasis on the measurement of unstable AEs driven by ICRF-heated ions. In contrast to the case of linearly stable AEs [3], the accuracy of the measurements of unstable AEs depends on the non-linear behaviour of AE amplitudes, which can vary from a saturated state to a chaotic regime as the aE drive increases [4].