Confined alpha distribution measurements in a deuterium-tritium tokamak plasma

Fusion-produced alpha particles with energy 0.7 MeV have been spectroscopically observed in the core of a deuterium-tritium plasma in the TFTR tokamak at alpha densities of 3×1016 m-3. During a sawtooth-free discharge, the measured energy spectra at r/a=0.3 are in good agreement with those predicted on the basis of collisional transport. Time-resolved measurements during the alpha thermalization after alpha source turn-off show decay of the distribution function to lower energies consistent with the classical slowing-down time of 0.5 s.