The Neutron Energy Spectrum fromU235Thermal Fission

Abstract

A Ranger measurement of the distribution-in-range of knock-on protons from thin paraffin layers indicates the distribution-in-energy from 0.4 Mev to 7 Mev of the neutrons emitted from uranium bombarded by neutrons from the thermal column of the Argonne Heavy Water Reactor. The spectrum shows a broad maximum near 0.75 Mev and follows closely an exponential drop from 2 Mev to 7 Mev with a relaxation energy of 1.55 Mev. The observed neutron intensity does not go to zero below 16 Mev.