Simultaneous Spin Analyzers for the LANL nEDM Experiment

The LANL nEDM experiment aims to measure the electric dipole moment (EDM) of the neutron. In the experiment at Los Alamos National Laboratory, polarized neutrons are stored for free precession under a uniform magnetic field and an electric field. The resulting spin state is analyzed using two double-armed spin analyzers (DSAs). In the DSAs, two magnetized iron foils, in conjunction with RF spin flippers, are used to analyze the spin state of the neutrons. High-field seeking neutrons are transmitted through the iron foil of one arm and counted by a neutron detector, which consists of a boron-10 coated scintillating sheet coupled to a silicon photomultiplier (SiPM). The other arm flips the spins of the low-field seeking neutrons and counts them similarly. To ensure optimal performance, we characterized the magnetic fields produced by permanent magnets and electromagnetic coils and tuned the operating parameters to ensure a high spin-flipping efficiency. Results of the field mapping are used to construct a COMSOL magnetic model which provides input to simulate the ultracold neutron spin transport. In this talk, I will present results on testing the DSAs at LANL during the 2025 beam cycle.