A 61-channel SQUID system for MEG measurement cooled by a GM/JT cryocooler

Author

Sata, K. ; Fujimoto, S. ; Fukui, N. ; Haraguchi, E. ; Kido, T. ; Nishiguchi, K. ; Kang, Y.M.

Author_Institution

MEC Lab., Daikin Ind. Ltd., Tsukuba, Japan

Volume

7

Issue

2

fYear

1997

fDate

6/1/1997 12:00:00 AM

Firstpage

2526

Lastpage

2529

Abstract

A SQUID-based MEG measurement system cooled by a GM/JT cryocooler have been developed. The system consists of 61 channels of axial gradiometers arranged on a spherical surface, and thus can conform to a human head. The white noise level of the system is in a range between 12 and 18 fT/Hz/sup 1/2/. The noise from the cryocooler controlled to a level of 15 pT by several improvements to the cryostat (e.g., using low electrical conductivity material). Since the latter noise have a periodic characteristics, it can be reduced by using a "noise template" (i.e., a digital process using a computer). The system is described here, and its performance demonstrated by using it to measuring the faint biomagnetic fields from a human brain.

Keywords

SQUID magnetometers; cooling; magnetoencephalography; superconducting device noise; white noise; Gifford-McMahon/Joule-Thompson cryocooler; MEG measurement; axial gradiometer; biomagnetic field; brain; computerised digital process; cryostat; human head; multi-channel SQUID; noise template; white noise; Coils; Copper; Magnetic materials; Magnetic noise; Magnetization; SQUIDs; Superconducting device noise; White noise; Wires; Wiring;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.621753

Filename

621753