Abstract
An international flux density comparison of monoenergetic fast neutrons has been organized by the Bureau International des Poids et Mesures. Nine laboratories carried out measurements which extended from December 1973 to February 1978. The five neutron energies 250 keV, 565 keV, 2.2 MeV, 2.5 MeV and 14.8 MeV were selected. A polyethylene sphere with a small BF3 counter at the center served as a transfer instrument at all energies except for 14.8 MeV. A 3He proportional counter was used at the two lower energies as the second transfer instrument. At 14.8 MeV a fission chamber (238U) and the iron foil activation method based on the 56Fe (n,p) 56Mn reaction were used. The experimental conditions, the neutron flux density determinations and the transfer instrument measurements are described. The results of the intercomparison are summarized in tables and graphs.