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ST458 - A Magnetoencephalography System Having Superconductively Shielded SQUID Magnetometer

https://snf.ieeecsc.org/sites/ieeecsc.org/files/documents/snf/abstracts/hdrposterLee%2C%20Yong-Ho_Poster-ISEC2015-Nagoya.pdf
A Magnetoencephalography System Having Superconductively Shielded SQUID Magnetometer
 
Y. H. Lee, K. K. Yu, H. Kwon, J. M. Kim, S. K. Lee, S. J. Lee, K. Kim, and M. Y. Kim
 
Center for Biosignals
Korea Research Institute of Standards and Science
Daejeon, Republic of Korea
 
 
Abstract — We fabricated a whole-head SQUID magnetometer system having a superconductive shield to measure magnetoence-phalography (MEG) signals inside a thin magnetic shielding for practical MEG measurements. For a robust magnetometer with a reduced flux trap, compact axial SQUID magnetometers were made using a wire-wound pickup coil with simple connection structure between the pickup coil and the input coil. The white noise of the SQUID system was about 2 fT/√Hz at 100 Hz. The magnetometers have a distance of 30 mm from the superconducting Pb surface, forming gradiometers with a baseline of 60 mm. The superconductive shielding structure showed shielding factors in the range of 20~500, depending on the positions of the magnetometers inside the helmet. Simulation showed that magnetic flux lines are concentrated at the inner corner of the helmet brim, and magnetometers at the brim picked up large environmental noise. To enhance the overall shielding performance, we improved the design by extending the shield plate brim toward the inner side of the helmet, and found that the shielding performance was improved much especially in the brim area. The MEG signals measured with a double-side brim showed much better signal quality than having single-side brim, showing that a thinner magnetically shielded room can be used.

Keywords (Index Terms) — SQUID, magnetoencephalography, magnetic shielding, magnetometer.

IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2015.
Selected August 10, 2015. Reference ST458; Category 4. 
Invited poster SQ-P01-INV presented at ISEC 2015; Nagoya, Japan, July 6 – 9, 2015.