Fusion Meets Nuclear Physics: Quantifying Fusion Power from the Radiative Branches of the DT Reaction

Accurate knowledge of fusion power is critical for evaluating the performance of magnetically confined plasmas. While neutron counting remains the standard method in deuterium-deuterium and deuterium-tritium (DT) plasmas, gamma-ray spectroscopy is emerging as a promising, neutron-independent diagnostic. Recent experiments at the Joint European Torus (JET) have demonstrated that gamma rays from the rare radiative branch of the DT reaction can be used to assess fusion power directly [1,2]. This method enables unique cross-validation of neutron-based techniques and offers access to nuclear processes that are otherwise difficult to probe in plasma conditions.

In this contribution, we present results from JET DT campaigns highlighting the potential of gamma-ray spectroscopy as a fusion power monitor and discuss its extension to aneutronic reactions such as D–³He and p–¹¹B, where gamma-ray diagnostics are uniquely suited. We will also address the interplay between plasma and nuclear physics: extracting quantitative information from gamma-ray spectra requires accurate nuclear models and cross sections, while fusion plasmas offer a novel environment for investigating fundamental nuclear reactions. As a case study, we will present a comparison between plasma-based and accelerator-based measurements of the T(D,γ)⁵He reaction, identifying current challenges and future perspectives for nuclear data needs.

[1] Dal Molin et al., PRL 133(5), 2024

[2] Rebai et al., PRC 110(1), 2024