Confined Alpha Distribution Measurements in a Deuterium-Tritium Tokamak Plasma

Fusion-produced alpha particles with energy $\le$0.7 MeV have been spectroscopically observed in the core of a deuterium-tritium plasma in the TFTR tokamak at alpha densities of $3\times {10}^{16}{\mathrm{m}}^{-3\mathrm{}}$. During a sawtooth-free discharge, the measured energy spectra at $r/a=0.3\mathrm{}$ 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.