Angular Momentum Studies with NBI Modulation in JET

In this work we apply the neutral beam modulation technique to a set of JET discharges in order to obtain information on the radial transport of the toroidal angular momentum. This perturbative technique allows one to separate possible pinch terms from the momentum diffusivity, otherwise impossible to decouple with a steady-state momentum balance analysis alone. In this paper a model based on the ion temperature gradient turbulence, which consists of a constant and uniform Prandtl number of the order unity combined with an inward Coriolis pinch term predicted by the gyro-kinetic theory, is validated against data from the JET experiment. The machine size and the good space and time resolution of the charge exchange system make JET particularly suitable for this study. The experimental data are matched with good accuracy, both the steady-state and the transient propagation of the momentum perturbation, choosing a Prandtl number slightly above one, provided the Coriolis pinch is included. Sensitivity studies assess the accuracy range of our predictive modelling