Recent Progress in Fast-Ion Physics on JET

This paper presents recent results on fast-ion studies in JET. The unique diagnostic set for confined and lost particle studies was utilised to investigate the response of fast ions to MHD modes and Toroidal Field (TF) ripple, and of fast 3He-ions behaviour in shear-reversed plasmas. A dependence of the loss intensity versus the MHD mode amplitude was derived from the experiments. A study of various plasma scenarios has shown that a significant redistribution of the fast ions happens during the change in the profile of the safety factor from strongly shear-reversed to monotonic. It was found that significant changes in the losses of ICRH accelerated protons are associated with confinement transitions in plasmas. After an L-H transition, an abrupt decrease in the ICRH proton losses was observed. In plasmas with an internal transport barrier, the loss of ICRH-accelerated ions increases as the barrier forms. Further results concerning fast ion losses were obtained during JET experiments in which the magnitude of the TF ripple was varied. The ripple losses of fusion products in high triangularity plasmas appear similar to classical losses, and are in agreement with modelling.
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