Ferromagnetic high-permeability alloy alone can provide sufficient low-frequency and eddy-current shieldings for biomagnetic measurements

Author

Okada, Yoshio C. ; Shah, Bharat ; Huang, Jin-Chu

Author_Institution

Dept. of Neurology and Physiol., New Mexico Univ., Albuquerque, NM, USA

Volume

41

Issue

7

fYear

1994

fDate

7/1/1994 12:00:00 AM

Firstpage

688

Lastpage

697

Abstract

A low cost, two-shell ferromagnetic shielded room large enough for a person to enter and prepare experiments was constructed for biomagnetic measurements. No aluminium or copper shell was used for eddy-current shielding. A high-permeability nickel-iron-molybdenum alloy (1.57 mm thick) was used for both ferromagnetic and eddy-current shieldings. The shielding factor was 60 dB at DC and 40 dB between 0.1 Hz and about 3 Hz. The eddy-current shielding due to the alloy alone provided a shielding factor of 55 dB at 30 Hz and 66 dB at 60 Hz. The shielding factor was sufficiently high in all the frequency range for biomagnetic measurements with a first-order superconducting gradiometer.

Keywords

biological techniques and instruments; biomagnetism; eddy currents; ferromagnetism; iron alloys; magnetic shielding; molybdenum alloys; nickel alloys; 0 to 60 Hz; 40 to 66 dB; NiFeMo; biomagnetic measurements; biomagnetism research; eddy-current shielding; ferromagnetic high-permeability alloy; first-order superconducting gradiometer; high-permeability Ni-Fe-Mo alloy; low-frequency shielding; shielded room; shielding factor; Aluminum; Biological materials; Biomagnetics; Costs; Frequency; Geophysical measurements; Iron alloys; Magnetic materials; Magnetic noise; Magnetic shielding; Alloys; Environment, Controlled; Equipment Design; Facility Design and Construction; Magnetics; Permeability;

fLanguage

English

Journal_Title

Biomedical Engineering, IEEE Transactions on

Publisher

ieee

ISSN

0018-9294

Type

jour

DOI

10.1109/10.301736

Filename

301736