15 MeV Proton Emission from JET Plasmas Exhibiting Sawtooth Behaviour: Results and Interpretation

A proton spectrometer has been installed and operated on JET with the objective of measuring the energy spectrum of 15 MeV protons produced in 3 He-d reactions under conditions of ICRF heating. The proton emission is observed to be briefly but strongly enhanced at the moment of a sawtooth collapse. A convincing explanation is proposed for the proton energy spectrum recorded between sawtooth collapses. The interpretation of the spectra recorded at the collapse itself is more contentious, nevertheless it is clear that a momentary radial drift for the energetic particles is required as well as a significant alteration in pitch angle.