Characterizing Cold Neutron Beam Intensity on the CG-2 Beamline at the High Flux Isotope Reactor

In 2024 the University of Tennesse and Oak Ridge National Laboratory NN' Collaboration conducted a fundamental neutron physics experiment at the High Flux Isotope Reactor to search for the transformation of neutrons to hidden-sector neutrons. Given the subtety of the effect under study, precise intensity characterization was crucial to this experiment. My analysis is focused on instrumentation simulations and intensity-monitoring of experimental detector data, where I identified several problems complicating the intensity measurements. These included potential backward Bragg Scattering effects, detector deadtime issues, and accurate determination of the transmission factors in simulations using the McStas neutron-raytracing software. Through examination of these factors, I developed a final intensity correction that accounts for the identified problems. Cold neutron beam intensity was determined with its errors, and it will be used by the Collaboration in the final characterization of the effect being searched for.