A Novel Method Applicable to Large-Scale Active Magnetic Shielding System which Effectively Compensates Gradient Magnetic Fields Originated from the Surrounding Buildings

We propose the novel magnetic compensation method which is suitable to compensate gradient magnetic fields. The method is to be applied to a conventional large-scale, tri-axial active magnetic shielding system such as spacecraft magnetic testing facility. The essences of this method are adoption of compensation coils which have degrees of freedom in their coil orientations, and their installation position, which is chosen to have certain distances from the center of the shielding area. The method works with at least 4 compensation coils. In this research, we actually demonstrated the method with scaled-down experiment. Disturbance magnetic field (B) at the target zone was suppressed from 21.33nT to -1.54nT and magnetic field uniformity (ΔB) within the test zone was improved from 2.3nT to 0.015nT. In terms of magnetic field gradient, improvement from over 4nT/m to below 0.5 nT/m was achieved.