The balance and noise properties of directly coupled high-Tc superconducting quantum interference device gradiometers with a serial array

We characterize the balance and noise properties of directly coupled high-Tc superconducting quantum interference device (SQUID) gradiometers with a series array. The gradiometer consisted of symmetrical pickup loops, in which a series of SQUID was symmetrically configured and directly coupled to pi...

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Veröffentlicht in:Applied physics letters 2008-01, Vol.92 (3)
Hauptverfasser: Yang, Hong-Chang, Chen, J. C., Wu, C. H., Chen, K. L., Horng, Herng-Er, Tsai, Yi-Shou, Yang, S. Y.
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Sprache:eng
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Zusammenfassung:We characterize the balance and noise properties of directly coupled high-Tc superconducting quantum interference device (SQUID) gradiometers with a series array. The gradiometer consisted of symmetrical pickup loops, in which a series of SQUID was symmetrically configured and directly coupled to pickup loops. We characterize the balance resolution B from the following formula: B=Aeff,uniformfield∕Aeff,gradientfield, where Aeff,uniformfield and Aeff,gradientfield are the parasitic effective area and the effective area of the gradiometer, respectively. We obtained B=1.25×10−2 which was comparable to the typical balance resolution of ∼10−2 for a gradiometer fabricated onto the 10×10mm2 substrate. This discrepancy was probably due to the many superconducting pads inside the pickup loops which deteriorated the uniformity of applied uniform magnetic fields. The gradient field sensitivity of ∼40fT∕Hz1∕2cm at 1kHz for two-SQUID gradiometers was demonstrated in a magnetically unshielded environment, which was comparable to the best gradient sensitivity of 30fT∕Hz1∕2cm, with gradiometric flip-chip flux transformer with a length of 24mm and a base line of 10mm in shielded environment.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.2835700