Precise Determination of theU233Fission Neutron Spectrum

Abstract

The ${\mathrm{U}}^{233}$ prompt fission neutron spectrum is measured. Fast time of flight techniques are employed to study the neutron energy distribution from 0.3 to 5.0 Mev. Proton recoil emulsions are utilized for neutron measurements from 1.2 to 7.0 Mev. The experimentally determined fission neutron spectrum is expressed in the form: $N(E)={{a}_{0}+{a}_{1}E+{a}_{2}{E}^{2}}\ensuremath{\varphi}(E),$ where $E$ is the neutron energy in Mev, $N(E)$ is the number of ${\mathrm{U}}^{233}$ fission neutrons per unit energy interval, $\ensuremath{\varphi}(E)$ is the ${\mathrm{U}}^{235}$ prompt fission neutron spectrum, and ${a}_{0}$, ${a}_{1}$, and ${a}_{2}$ are constants normalized to give agreement with the known average number of ${\mathrm{U}}^{233}$ prompt fission neutrons. The average energy of the ${\mathrm{U}}^{233}$ prompt fission neutrons calculated from the experimental results is 1.87 \ifmmode\pm\else\textpm\fi{}0.04 Mev.