Revision as of 21:14, 26 March 2015

Physics

A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we investigate the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments which emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons which impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons was measured using a large acceptance neutron detector array. A comprehensive set of measurements of two neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool for the detection of fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.