Neutron induced fission fragment angular distributions and momentum transfer measured with the NIFFTE fission time projection chamber

Abstract

Nuclear fission is the process by which a large nucleus splits into two heavy fragments and is often induced by an incident neutron. Understanding the probability by which an incident neutron will cause fission, i.e. the neutron induced fission cross section, is an important input into fission applications such as nuclear energy and stockpile stewardship. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) Collaboration built a fission time projection chamber (fissionTPC) to study the fission process in a novel way in the hopes of achieving unprecedented precision on fission cross section measurements. With the fissionTPC’s ability to do three-dimensional tracking of fission fragments and other ionizing radiation, systematics of previous cross section measurements using fission chambers can be further explored. Because the fissionTPC records a wealth of data for every fission event, other physics can be measured concurrently with the cross section. In particular, fission fragment angular distributions and the linear momentum transferred from the incident neutron to the target nucleus as a function of incident neutron energy from 130 keV to 250 MeV will be the focus of this work. Angular anisotropy values for 235U and 238U and neutron linear momentum transfer for 235U, 238U, and 239Pu will be presented.