Abstract:
Background Extremely weak magnetic field measurements in life science require near-zero magnetic environments, typically provided by magnetically shielded rooms (MSRs) constructed of high permeability materials. The shielding performance can be improved by demagnetization technologies.
Purpose Conventional AC attenuation demagnetization does not allow for rapid determination and optimization of demagnetization parameters through magnetization state assessment. In contrast, pulse demagnetization can directly reflect the magnetization state through measuring and controlling the magnetic flux linkage. Therefore, this study proposes a flux-controlled pulse demagnetization method for MSR demagnetization equilibrium to regulate the demagnetization process precisely.
Methods The equivalent circuit model is established by considering the losses and the ambient magnetic field, and the flux linkage offset is introduced to correct the control parameters. On this basis, the magnetic properties of the material are measured, and a finite element model of the MSR is established to analyze its theoretical performance limit.
Results By testing the residual magnetic field inside the MSR, it has been demonstrated that this method can achieve an average residual magnetic field as low as 3.1 nT in the central area of the double-layer MSR.
Conclusions The comparison with the conventional demagnetization can illustrate the improvement of pulse demagnetization in static magnetic shielding performance. The average residual magnetic field is improved by 46.6% for 120 complete demagnetization cycles.
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