Comparison of the filtered-neutron beams at the NBS and PTB reactors by calibrating a spherical rem meter

Two filtered-neutron beam facilities at the NBS and at the PTB providing quasi-monoenergetic beams of 2 keV, 24.5 keV and 144 keV are in use for radiation protection instrument calibration. Measurements are described which were performed to investigate the properties, and compare the calibrations, of these beams at both installations. A 20.8 cm diameter spherical rem counter and an 11 cm diameter sphere served as transfer instruments. The neutron current in the beams was determined with the respective methods in use at either facility. A filter-difference method was used to determine the contribution of high-energy neutron contamination to the count rate of the instruments. The responses of the instruments to the quasi-monoenergetic neutrons at both institutes are compared