AbstractThe standard irradiation field for DT neutrons has been developed by using an associated α-particle technique. Special attention has been paid to establish the DT neutron standard for fusion diagnostics at neutron energies from 14.0 MeV to 14.10 MeV by using special emission angles between 90° and 100° to the direction of an accelerated deuteron beam. The sharp distributions with the energy spread less than 10 keV at 96°–98° provide the standard energy points of DT neutrons at energies from 13.98 MeV to 14.00 MeV. A new technique with a 3He proportional detector has been applied to determine the energy spread as well as the precise mean energy of a DT neutron distribution after calibrating the detector at the reference energy point of 14.00 MeV.