The UT 19-channel dc-SQUID based neuromagnetometer

H.J.M. ter Brake, J. Flokstra, W. Jaszczuk, R. Stammis, G.K. van Ancum, A. Martinez, Horst Rogalla

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A l9-channel DC SQUID based neuromagnetometer is under construction at the University of Twente (UT). Except for the cryostat all elements of the system are developed at the UT. It comprises 19 wire-wound first-order gradiometers in a hexagonal configuration. The gradiometers are connected to planar DC SQUIDS fabricated with a Nb/Al, AlOx/Nb technology. For this connection we developed a method to bond a Nb wire to a Nb thin-film. The SQUIDs are placed in compartmentalised Nb modules. Further, external feedback is incorporated in order to eliminate cross talk between the gradiometers. The electronics basically consist of a phase-locked loop operating with a modulation frequency of 100 kHz. Between SQUID and preamplifier a small transformer is used to limit the noise contribution of the preamplifier. In the paper the overall system is described, and special attention is paid to the SQUID module (bonding, compartments, external-feedback setup, output transformer).
Original languageEnglish
Pages (from-to)45-50
Number of pages6
JournalClinical physics and physiological measurement
Issue numberSuppl. B
Publication statusPublished - 1991


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