Functional study of a system of magnetic multilayer shields

Abstract

A multilayer shielding system with five concentric cylinders of P-80 high-permeability material has been design and constructed in the Magnetometry Laboratory of our institute. The paper presents the results of the functional study of the shielding system. The P‐80 annealed alloy was especially elaborated for this application. The d.c. shielding effectiveness of the system is 3\times 10^{3} along the longitudinal axis and 5\times 10^{4} for the transversal direction. The a.c. shielding factor is studied for different frequencies. The remanent magnetic field inside the inner cylinder is in the order of units of nT, as a function of the deperming procedures. A mechanical device situated inside the shields allows the determination of the offset and magnetic noise of the fluxgate sensors, even in urban magnetically polluted conditions.