233U, 235U, 239Pu, and 252Cf fission prompt neutron spectra

Spectra of prompt neutrons produced in induced fission of 233U, 235U, and 239Pu in the range from 0.01 to 4 MeV by thermal neutrons and those from spontaneous fission of 252Cf in the energy range from 0.01 to 10 MeV have been measured. Measurements are conducted by the time-of-flight method with two types of neutron detectors (a gas scintillation chamber and an ionization chamber) using a beam of thermal neutrons from the SM-2 reactor. The two measurement runs have provided similar results within the limits of statistical accuracy. The points are found to fall below the maxwellian distribution in the range from 0.3 to 0.6 MeV (for 239Pu approximately 8%), the spectra of 233U, 235U and 252Cf are found to exceed the maxwellian distribution below 0.4 MeV