Kinetic analysis of γ-ray-generating reactions for fuel ion and energetic particle diagnostics of D-T fusion plasma

In D-T fusion plasma seeded with a small amount of ⁶Li, monochromatic 0.429-, 0.478- and 0.981-MeV γ rays are produced in the ⁶Li + D and ⁶Li + T nuclear reactions. In the present paper we investigate these processes in the appropriate plasma kinetic model. The non-Maxwellian tails of deuteron and triton distribution functions created due to nuclear elastic scattering of D-T α-particles by fuel ions are found to enhance crucially production of the diagnostic γ rays. This result can be considered as the first explicit demonstration that in a fusion plasma the role of suprathermal reaction channels induced by energetic knock-on ions can become comparable with (or even dominate) that of thermal ones. Possibilities of fuel ion and α-particle diagnostics using the reaction-produced γ rays are also discussed. It is pointed out for the first time that the behavior of α-particles during slowing-down could be diagnosed by detecting 0.981-MeV α-rays emitted in a nuclear reaction between knock-on tritons and ⁶Li admixture ions.