Magnetic Field Monitoring in the SNS Neutron EDM Experiment

A central problem to all neutron EDM experiments is the generation of a highly uniform and stable magnetic field. Because the suppression of systematic effects that arise from magnetic field nonuniformities and temporal drifts is vital to the success of these experiments, it is important to have the ability to precisely control and monitor the magnetic field gradients inside of the experimental volume. However, it is not always possible to measure the field gradients within the region of interest directly. To remedy this issue in the Spallation Neutron Source neutron EDM experiment, we have designed a field monitoring system that will allow us to reconstruct the field gradients inside of the fiducial volume using noninvasive measurements of the field components at discrete locations external to this volume. Studies of a prototype probe array consisting of ~30 cryogenic-compatible, single-axis fluxgate magnetometer sensors will be presented in this talk along with the characterization of these sensors at cryogenic temperatures.