Magnetic Shielding Effects and PINN Mapping for the Nab Experiment

The Nab experiment at the Spallation Neutron Source, Oak Ridge National Laboratory, will measure the electron-neutrino correlation coefficient with precision Δa/a=0.001 in free neutron β-decay. Achieving this goal requires precise characterization of the magnetic field that guides decay charged particles to the detectors. We compare analytical and finite-element calculations, as well as previous and current field measurements to analyze the influence of the spectrometer's magnetic shielding. We also describe progress on a physics-informed neural network (PINN) framework designed to provide fast, accurate 3D field interpolation for Monte-Carlo simulations used in Nab data analysis.