In Situ Magnetic Field Mapping System for the LANL Neutron EDM Experiment*

The LANL neutron electric dipole moment (LANL-nEDM) experiment requires precise knowledge of the magnetic field within the fiducial volume. In the experiment, a high-uniformity magnetic field coil mounted within a multi-layer magnetic shield house provides for the static $B_0$ magnetic field. We have designed and installed an in situ magnetic field mapping system which permits for automated, remotely-controlled measurements of the $B_0$ magnetic field within the shield house. The system is capable of full three-dimensional motion, and can either carry out measurements of the field within the measurement cell volume (e.g., when the measurement cell is not installed) or can provide for periodic monitoring of the field at a large number of positions external to the measurement cell with the measurement cell in place. In this talk, results from initial testing of the system will be presented.