EFDA-JET-CP(07)03/02

Toroidal Field Ripple and the Formation of Internal Transport Barriers

The Toroidal Field (TF) ripple of ITER will differ from JET due to a lower number of TF coils, with 18 and 32 coils in these devices, respectively. Ferrite material will be mounted between the ITER coils in order to reduce the ripple. Nevertheless, the estimated TF ripple in ITER is in the order of d~0.5% (the maximum toroidal variation of the magnetic field at the separatrix) which is higher than that at JET (d~0.08%). The question arises if a larger TF ripple may affect the formation and performance of Internal Transport Barriers (ITBs). Firstly, because a larger TF ripple is expected to reduce the toroidal rotation and consequently affecting the rotational shear. Secondly, the TF ripple may act on the H-mode pedestal and Edge Localised Modes (ELMs) which have been found to degrade ITBs. Internal Transport Barriers are an important feature of advance tokamak scenarios, which provide the possibility of steady state, non-inductive tokamak operations with improved confinement. Before, extrapolating such scenarios to ITER, the effects of an enhanced TF ripple on ITBs should be understood.
Name Size  
EFDC070302 137.10 Kb