An approach to analyzing magnetically shielded room comprising discontinuous layers considering permeability in low magnetic field

To enable the realization of weak magnetic field at the level of several nanotesla, a magnetically shielded room (MSR) is required to create a space with residual magnetic field below 1 nT. Since the magnetic field shielded by inner shielding shells is very low, the permeability of shielding materials in this range is measured. As the gaps between ferromagnetic material strips in shielding wall lead to considerable reduction of shielding factor, a new numerical model to evaluate the equivalent permeability of discontinuous shielding layers is proposed and demonstrated experimentally. Based on the equivalent magnetic property in lower and normal magnetic field range, the improved approach to predicting the performance of MSR is obtained.