Neutron emission spectroscopy results for internal transport barrier and mode conversion ion cyclotron resonance heating experiments at JET

The effect of ion cyclotron resonance heating (ICRH) on (H3 e) D plasmas at JET was studied with the time of flight optimized rate (TOFOR) spectrometer dedicated to 2.5 MeV dd neutron measurements. In internal transport barrier (ITB) plasma experiments with large H3 e concentrations (X (H3 e) >15%) an increase in neutron yield was observed after the ITB disappeared but with the auxiliary neutral beam injection and ICRH power still applied. The analysis of the TOFOR data revealed the formation of a high energy (fast) D population in this regime. The results were compared to other mode conversion experiments with similar X (H3 e) but slightly different heating conditions. In this study we report on the high energy neutron tails originating from the fast D ions and their correlation with X (H3 e) and discuss the light it can shed on ICRH-plasma power coupling mechanisms. © 2008 American Institute of Physics.