Angular Anisotropy of Correlated Neutrons in Lab Frame of Reference and Application to Detection and Verification

摘要

It has been shown that neutrons emitted from the same Cf-252 fission event are preferentially emitted within small angles of each other and at angles around 180°. Inorder to reach this conclusion, a Cf-252 source was placed in an array of liquid scintillators and data was taken in list-mode. Previous work has mainly focused on neutron angular distribution relative to the fission fragments. By considering the angular distribution between neutrons from the same fission event, information about potential preferential emission of neutrons from the same or opposite fission fragments is captured. After finding through simulation the extent to which neutron double scattering should occur in the system for a Cf-252 source, the effects of neutron double scattering for various angles were accounted for. It was found that for Cf-252 neutrons, there is no preferential emission of neutrons from the same or opposite fission fragments. Since different fissioning radioisotopes have different distributions of fission fragments, there should be differences in the distributions of angles between neutrons from the same fission event for different isotopes. It is this uniqueness that makes knowledge of the distribution of the angles between neutrons from the same fission event useful for detection and verification of radioisotopes. Furthermore, the mere knowledge that the angles between neutrons emitted from a certain radioisotope are preferentially detected within small angles of each other and at angles around 180° allows one to know that the radioisotope is undergoing fission.