The TF ripple experiment modification of the JET toroidal field system

The interleaved structure of the TF coils allows to obtain a programmable TF ripple field by feeding the two sub-sets of the TF coils with different currents. This would allow to vary the ripple field within one JET pulse and allow a direct assessment of the increased ripple on confinement time, fast particle losses, plasma rotation and H-mode. The TF ripple experiment (RIPPLE 2) was carried out in the pumped divertor configuration in conditions relevant to ITER. In this configuration, the normal field ripple at the plasma edge is about 0.1%. In the experiment, the ripple field was varied up to 2% at the plasma edge, the plasma current was typically 2-3 MA and the TF field 2-2.5 T.