Neutron Kerma values derived from neutron energy spectra

In the European neutron dosimetry intercomparison (ENDIP) conducted at Rijswijk, dose measurements were performed with TE ionisation chambers at positions ''free-in-air'' and in phantom for collimated beams of 5.3 MeV and 14.8 MeV neutrons produced by d(2.3) + D and d(0.5) + T reactions. In addition, for the different positions and conditions, the spectral neutron fluence distributions of the mixed neutron/gamma ray beams were measured with an organic scintillator (NE213) proton-recoil spectrometer. Discrimination between neutrons and gamma rays was provided by the time difference in the zero crossing of the double differentiated detector pulses. The neutron spectra were derived from these proton-recoil spectra by conversion, applying a set of two polynomials for the nonlinear response function of the scintillator to protons. Kerma values calculated from these spectral neutron fluence distributions are in acceptable agreement with kerma values measured with TE chambers, the discrepancy being equal to or less than 6%. (author)