The Magnetically Shielded Room (MSR) for the Los Alamos National Laboratory Neutron EDM Experiment (LANL nEDM)*

The Los Alamos National Laboratory Neutron Electric Dipole Moment experiment (LANL nEDM) is designed to measure the neutron EDM to a statistical uncertainty of 2×10−27 e·cm with ultracold neutrons (UCN) stored in paired bottles with opposite electric fields. This sensitivity requires controlling and measuring the magnetic fields and magnetic field gradients to achieve the statistical sensitivity and to mitigate systematic effects that couple to motional magnetic fields (vxE). The experiment is mounted inside an MSR with internal dimensions of 2.3 m x 2.3 m x 2.3 m and located at the UCN experimental area at LANL. The MSR consists of four layers of high permeability permalloy (mu-metal) and a copper RF shield to mitigate the effects of external magnetic field and gradient fluctuations. In this talk, we will report on extensive studies of the MSR shielding efficacy, degaussing, stability of the residual fields, and response to environment changes.