Measurements of the T+T neutron energy spectrum from magnetically confined fusion plasmas

Neutron spectroscopy can be used to study fuel composition and velocity distributions in fusion plasmas. To this end, it is necessary to have a good understanding of the nuclear physics processes at play in the fusion reactions between the fuel ions deuterium (D) and tritium (T). The fusion of two tritons, T + T → n + n + ⁴He, is particularly challenging in this regard, as it involves a three-body final state; the neutron energy spectrum is therefore not only determined by the velocity distributions of the reactants, but is also affected by interactions between the three reaction products.



In this contribution we present measurements of the T+T neutron spectrum from JET, and their interpretation in terms of an R-matrix model [1] for the three-body final state. The analysis builds on results presented in [2], now including a more careful investigation of the angular dependence of the neutron energy spectrum, caused by the fact that the majority of the T+T neutrons from these JET plasmas were produced in beam-target reactions.



The results show how neutron spectroscopy measurements of magnetically confined fusion plasmas can contribute to the understanding of the nuclear physics processes involved in the T+T reaction, but also highlights that fusion neutron spectroscopy could benefit from further studies of the T+T fusion reactions in more controlled environments, e.g. accelerator facilities.



[1] C. Brune et al, Phys. Rev. C 92 014003 (2015)

[2] B. Eriksson et al, Phys. Rev. C 109 054620 (2024)