Aneutronic Fusion Study in Large Helical Device

Abstract A study of aneutronic fusion, which refers to fusion reactions that do not produce neutrons, has been conducted on the Large Helical Device (LHD). For the D–³He study, feasibility investigations of detecting charged fusion products have been performed. High-energy neutral beams, lost proton detectors, and gamma-ray detectors were planned for installation to validate the D–³He fusion reactions. Numerical calculations show that the expected D–³He fusion rate is 2.7 × 10 16 s -1 with most of the protons being lost immediately from the plasma. For the p–¹¹B study, the total alpha particle emission rate was estimated to be 10 14 s -1 , and the loss points of alpha particle distribution were calculated. Based on these numerical simulations, we installed an alpha particle detector on a manipulator and positioned it at the bottom of the LHD. The time evolution of the alpha particle detection rate, measured by the detector, was found to be consistent with the predictions from the numerical simulations, demonstrating the first successful observation of the p–¹¹B reaction in a magnetic confinement system.