A NEW MEASUREMENT OF THE NEUTRON MULTIPLICITY EMITTED IN 252Cf SPONTANEOUS FISSION

Abstract

The Precision Reactor Oscillation and SPECTrum (PROSPECT) experiment was designed to probe short baseline oscillations of electron antineutrinos in search of eV-scale sterile neutrinos and precisely measure the 235U reactor antineutrino spectrum from the High Flux Isotope Reactor (HFIR) at Oak Ridge national Laboratory (ORNL). The PROSPECT antineutrino detector (AD) provided excellent background rejection due to its segmented design and use of 6Li-loaded liquid scintillator for a neutron capture target. By tracking the neutron capture lifetime from cosmogenic neutrons and a 252Cf neutron source, we suspect the 6Li content of our scintillator changed over time. We look at this evolution and uncertainty in the PROSPECT oscillation and spectrum analyses. Additionally, the 252Cf source data taken with the PROSPECT AD for detector calibrations are used to make a new measurement on the neutron multiplicity probability distribution emitted during spontaneous fissions, with an average multiplicity of 3.81 ± 0.05 neutrons per fission.