Neutron spectra from californium-252 wire sources

Abstract

Neutron spectra from four types of 2s2 Cf wire sources were measured with commercially available 3He and 6 Li "sandwich" spectrometers. The sources all emitted essentially pure fission neutron spectra. The presence of non-radioactive cationic impurities at concentrations up to the accepted limit of four times the californium content produced insignificant amounts of additional neutrons. Spectra from the four so~rce types were obtained between 0.5 and 4.7 MeV with the 3 He spectrometer and between 0.2 and 5.0 MeV with the 6 Li spectrometer with no detectable variation from the fission spectrum obtained from an electroplated source containing high-purity 2s2 Cf . The neutron spectrum from a wire source containing samarium and terbium did not differ significantly from the 2s2 Cf fission spectrum between 0.5 and 8.6 MeV as measured with the 3 He spectrometer.The instrumentation 'and techniques for fissile neutron detection and counting are described. Spectrometer response to neutrons of different energies was verified by resolving the energy groups from a plutonium-beryllium neutron source.