Use of the nuclear reaction for diagnostics of energetic particles in burning plasmas

Application of reaction-produced γ -rays to diagnostics of energetic particles in burning plasmas is analyzed. Particularly, we focus on 0.981 MeV γ -rays emitted in the Li 6 ( t , p 1 γ ) Li 8 nuclear reaction solely governed in the plasmas by energetic tritons. It is shown that these γ quanta can serve as a promising tool to diagnose α knock-on tritons and α -particles confined in burning DT plasmas. Key parameters of the α knock-on triton population and the α -particle confinement property can be obtained by comparing the experimental γ -ray yield and spectrum with theoretical slowing-down calculations. Even if the γ -ray spectral shape cannot be acquired, one can monitor densities of these tritons and α -particles at energies of 0.6–1.8 MeV and 2.0–3.5 MeV, respectively, in a nearly steady-state plasma. The 0.981-MeV photons also would help to display time evolution of the α -particle population in experiments of deuterium plasmas with pulsed tritium beam shots.