Technique for high axial shielding factor performance of large-scale, thin, open-ended, cylindrical Metglas magnetic shields

TL;DR

This paper introduces an optimized construction method for large-scale, thin, open-ended cylindrical Metglas magnetic shields that achieve high axial shielding factors comparable to thicker, multi-shell designs without magnetic shaking.

Contribution

The paper presents a novel construction technique for large-scale, thin, open-ended cylindrical Metglas shields that attain high axial shielding factors with minimal material thickness.

Findings

Measured axial shielding factor of 267 in Earth's field

Transverse shielding factor of 1500 achieved

Performance comparable to thicker, multi-shell shields

Abstract

Metglas 2705M is a low-cost commercially-available, high-permeability Cobalt-based magnetic alloy, provided as a 5.08-cm wide and 20.3-$\mu$m thick ribbon foil. We present an optimized construction technique for single-shell, large-scale (human-size), thin, open-ended cylindrical Metglas magnetic shields. The measured DC axial and transverse magnetic shielding factors of our 0.61-m diameter and 1.83-m long shields in the Earth's magnetic field were 267 and 1500, for material thicknesses of only 122 $\mu$m (i.e., 6 foil layers). The axial shielding performance of our single-shell Metglas magnetic shields, obtained without the use of magnetic shaking techniques, is comparable to the performance of significantly thicker, multiple-shell, open-ended Metglas magnetic shields in comparable-magnitude, low-frequency applied external fields reported previously in the literature.