A multichannel SQUID magnetometer system based on double relaxation oscillation SQUIDs
Yong-Ho Lee
Hyukchan Kwon
Jin-Mok Kim
Chan-Seok Kang
Kiwoong Kim
In-Seon Kim
Yong-Ki Park
Soon-Gul Lee
Korea Res. Inst. of Stand. & Sci., Daejeon, South Korea;
This paper appears in: Applied Superconductivity, IEEE Transactions on
Publication Date: June 2003
Volume: 13,
Issue: 2, Part 1
On page(s): 755- 758
ISSN: 1051-8223
INSPEC Accession Number: 7715461
Digital Object Identifier: 10.1109/TASC.2003.814031
Current Version Published: 2003-07-15
Abstract
We constructed a multichannel superconducting quantum interference device (SQUID) magnetometer system for magnetoencephalogram measurements. The SQUID is based on the double relaxation oscillation SQUID (DROS), which consists of a hysteretic signal SQUID and a reference junction, and shunted by a relaxation circuit of a resistor and an inductor. With the high flux-to-voltage transfers, usually larger than 1 mV/Φ0, simple flux-locked loop circuits could be used for SQUID operation. The SQUID system consists of 37 integrated magnetometers, distributed on a hemispherical surface, and external feedback scheme was used to eliminate magnetic coupling with the adjacent channels. In addition to the 37 signal channels, 8 reference channels were installed to pickup background noise and to apply software gradiometer. The average noise level of the magnetometers is about 3 fT/√Hz at 100 Hz, operated inside a magnetically shielded room. The magnetometer system was applied to measure auditory-evoked fields.
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