Multiplicity and energy of neutrons from 235U(n th,f) fission fragments

Abstract

The correlation between fission fragments and prompt neutrons from the reaction 235U(n th,f) was measured with improved accuracy. The results determined the neutron multiplicity and emission energy as a function of fragment mass and/or total kinetic energy. The average multiplicity as a function of fragment mass followed a saw-tooth distribution and the distribution of average energy with mass had a bell-shaped distribution centered about the equal-mass split. The slope of the neutron multiplicity with kinetic energy had a saw-tooth distribution with a minimum at m ∗ ≈ 130 . The total excitation energy implied by the measurements was consistent with energy conservation and had a concave distribution with heavy-fragment mass, with a flat minimum between m ∗ ≈ 132 and 152 , suggesting that fragment pairs are preferentially formed in a compact configuration at the scission point.