Accurate determination of the fast-neutron detection efficiency for organic scintillators using a collimated neutron beam

A practical method is described for an accurate determination of the fast-neutron detection efficiency of organic scintillators. The procedure is based on the associated-particle technique, using n–p scattering with a collimated, continuous-energy neutron beam. The central efficiency of two NE213 detectors has been measured for energies between 2 and 11 MeV with an accuracy of 0.9% from which, by use of a Monte-Carlo program, the average efficiency was determined to ±1.4%.