Development of Active Magnetic Shielding for the Neutron Electric Dipole Moment Experiment at TRIUMF

Active magnetic shielding has been proposed to provide low-frequency magnetic field stability in the neutron electric dipole moment (nEDM) experiment planned for TRIUMF. A prototype active magnetic shielding system was constructed and tested at the University of Winnipeg. The system is capable of providing RMS shielding factors > 1000 for magnetic field perturbation frequencies ≤ 20 mHz, and > 100 for frequencies ≤ 0.5 Hz, and can reduce magnetic field variations on the order of tens of muT to the level of tens of nT. The achievable shielding factor was limited by the field sampling rate limit of ~400 Hz, and by the background fi eld noise floor of the laboratory. This represents good progress towards the eventual system for nEDM experiments, where low-frequency field drifts on the order of 100 nT require active shielding to the order of 1 nT.