The high energy portion of the Cf-252 neutron spectrum deduced from integral experiments

To investigate the validity of the neutron excess in the Cf-252 spectrum above 20 MeV first reported by the Dresden group in 1982, the responses of two (n,3n) reactions were measured in a Cf-252 neutron field. The reactions were 107Ag(n,3n) and 169Tm(n,3n) which are both sensitive to the shape of the spectrum above 20 MeV. In parallel, the (n,2n) spectrum-averaged cross sections of both reactions were also determined. The experimental results were compared with calculated ones based on various assumptions of the shape of the neutron spectrum. Due to low induced radioactivities and close sample-to-detector distances, extensive calculations of cascade-summing corrections were made in the radioactivity analysis process before deriving spectrum-averaged cross section data. The comparison of the corrected experimental results with calculated spectrum-averaged data did not confirm the neutron excess above 20 MeV as quoted. (author)