Gamma-ray emission from radio frequency heating experiments with the three-ion schemes at the Joint European Torus

In so called ‘three-ion’ Ion Cyclotron Resonance Heating (ICRH) experiments a third, mi- nority species is efficiently accelerated in plasmas made by two main ions. This is achieved in the vicinity of the ion-ion hybrid layer, where the wave polarization is entirely left handed [1]. At the Joint European Torus (JET) the scheme has so far been demonstrated in H-(DNBI )-D, H-(3He)-D and D-(DNBI )-3He plasmas [2], (DNBI ) and (3He) being the minority species. In the latter scheme, fast deuterons injected by Neutral Beam Injection (NBI) are further accelerated by ICRH up to energies in the MeV range [3]. High D+D neutron rates (between 1015 and 1016 s-1) have been achieved at moderate external heating power [4]. Reversed Shear Alfven Eigenmodes (RSAEs) have also been systematically observed, which is indicative of a non monotonic q-profile induced by an non-inductive current driven by an intrinsic mechanism [4].