Gamma-ray imaging of D and 4He ions accelerated by ion-cyclotron- resonance heating in JET plasmas

Gamma-ray images of fast D- and He-4-ions accelerated with third-harmonic ion-cyclotron-resonance heating of He-4-beam were simultaneously recorded for the first time in JET tokamak experiments dedicated to the investigation of burning plasmas with 3.5 MeV fusion alpha (a) particles. Gamma (gamma) rays, born as a result of nuclear reactions, Be-9(He-4, n gamma)C-12 and C-12(D, p gamma)C-13, between the fast ions and the main plasma impurities, are measured using a two-dimensional multicollimator spectrometer array, which distinguishes the gamma-rays from accelerated D- and He-4-ions. Tomographic reconstruction of the gamma-ray emission profiles gives images of the fast-ion population in the poloidal cross-section. The potential of this technique to visualize several energetic ion species and to determine their behaviour in different plasma scenarios is demonstrated.