Active Spectroscopy on JET and ITER

Ion temperature and velocity distribution functions, ion densities, plasma rotation velocities and magnetic fields have been identified by the ITER design team as key parameters1, for which spatially-resolved profiles with medium time resolution are of vital importance in three major areas. These are: machine protection and plasma control, evaluation and optimisation of plasma performance, and investigation of the physical phenomena which might limit ITER’s performance. Only a diagnostic based on active-charge-exchange (CXRS) and beam-emission spectroscopy (BES), using a dedicated neutral beam, can provide all these data with the accuracy and resolution required (table 1).