Large magnetic shielding factor measured by nonlinear magneto-optical rotation

A passive magnetic shield was designed and constructed for magnetometer tests for the future neutron electric dipole moment experiment at TRIUMF. The axial shielding factor of the cylindrical magnetic shield was measured using a magnetometer based on non-linear magneto-optical rotation of the plane of polarized laser light upon passage through a paraffin-coated vapor cell containing natural Rb at room temperature. The laser was tuned to the Rb D1 line, near the 85Rb F=2→2,3 transition. The shielding factor was measured by applying an axial field externally and measuring the magnetic field internally using the magnetometer. The axial shielding factor was determined to be (1.3±0.1)×107, from an applied axial field of 1.45μT in the background of Earth׳s magnetic field.