Fusion product diagnostics based on four commercially
available single-crystal chemical vapor deposition (s-CVD) diamond
detectors are installed in the Large Helical Device (LHD) in order
to understand energetic ion confinement. Characteristics of s-CVD
diamonds were surveyed using alpha and D-T neutron sources. It is
found that the energy resolutions of s-CVD diamonds for ∼ 5 MeV
alpha particles and 14 MeV neutrons are 1%–3% and ∼ 1.7%,
respectively. Moreover, the response of four s-CVD diamond detectors
to alpha particles and D-T neutrons is almost identical. The
installation positions of the diamond detectors in the vacuum vessel
are searched for, based on the loss points of charged fusion
products reckoned by Lorentz orbit calculations. Energy- and
time-resolved measurement of fusion product flux will progress in
further understanding of energetic ion confinement in LHD.