Internal mode oscillations as a diagnostic for the plasma rotation in JT-60

Characteristics of the internal mode frequency associated with the plasma rotation have been investigated for unidirectional neutral beam injection experiments into the JT-60 divertor plasma. The phase velocity inferred from the mode frequency as observed on the soft X-ray signals reached 1.2x105m·s-1 for counter-injection with 9 MW. The dependence of the velocity on the electron density and beam power is studied. Simple modelling calculations based on the incremental phase velocity show that the obtained toroidal momentum confinement time of ∼ 100 ms is of the order of the energy confinement time. (author). Letter-to-the-editor. 22 refs, 7 figs, 1 tab