Diagnosing RF driven high energy minority tails with γ-ray and neutron spectroscopy

The reactions of energetic, radio frequency heated, hydrogen, deuteron and tritium minority ions with carbon and oxygen impurity ions, are investigated. The experiment is carried out by observing gamma radiation from their excited products. The importance of carbon as the major impurity in JET plasmas is confirmed. An indication of the energy of the minority ions is obtained from a study of reaction thresholds. Equivalent tail temperatures in the MeV range are observed for the minority ions. Sawtoothing of individual γ-ray lines shows the expulsion of fast ions from the middle of the plasma. Inverted sawteeth in the γ-emission provide evidence that these γ-rays were emitted from the plasma. The comparison of the 2.5 MeV neutron peak with the total neutron yield shows that a fraction of the emitted neutrons (50% or more) are of non-thermal origin