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Proceedings Paper

Development and application of magnetic field sensors based on high-temperature superconductors
Author(s): Paul Seidel; Swen Wunderlich; Frank Schmidl; Sven Linzen; Frits Schrey; F. Schmidt; L. Doerrer; C. Steigmeier
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Paper Abstract

Thin films of YBa2Cu3O7-x (YBCO) were prepared on different kinds of substrates (SrTiO3, LaAlO3, sapphire or silicon) with critical current densities jc (77K) > 2 (DOT) 106 A/cm2 and critical temperatures (zero resistance) of up to 90 K. We used laser deposition techniques for film preparation on SrTiO3-substrates with a maximum substrate size of 10 X 10 mm2. Applying bicrystallin substrates made from this material a pronounced RSJ-behavior of the grain boundary Josephson junctions was observed with ICRN-products of 410 (mu) V and critical current density of 1.2(DOT)105 A/cm2 in maximum on 24 degree grain boundaries. On that basis planar galvanically coupled dc-SQUID-gradiometers were patterned on this limited substrate size with a field gradient resolution of 308 fT/(cm(root)Hz) in the white noise level and 2 pT/(cm(root)Hz) at 1 Hz in electrically and magnetically unshielded environment. This extraordinary field gradient resolution even in unshielded environment enables this kind of dc-SQUID sensor for measurements of the magneto-cardiogram (MCG) of the human heart as well as for investigations in non-destructive testing (NDT). The layout of the dc-SQUID as well as the antenna layout of the gradiometer antennas were varied in order to determine their influence on the whole sensor performance. For the dc-SQUID layout itself we present a gradiometric scheme with decreased parasitic area of the dc-SQUID in the gradiometer. Furthermore the additional use of buffer layers to prevent interdiffusion, lattice mismatch and internal stress by different thermal expansion coefficients enables the use of silicon substrates for YBCO thin film deposition. Gradiometric flip-chip- antennas were patterned on 2'-silicon-substrates and combined with dc-SQUID-gradiometers explained above. With this sensor concept the resolution was increased by a factor of 6 in shielded environment thus also the human MCG was measured. By the integration of superconducting antennas with Hall-effect sensors on the same substrate a hybrid sensor concept is introduced having less sensitivity compared to SQUID-based sensors but improved dynamic range enabling their application in a NDT-measurement system in highly disturbed environment.

Paper Details

Date Published: 6 September 2000
PDF: 12 pages
Proc. SPIE 4058, Superconducting and Related Oxides: Physics and Nanoengineering IV, (6 September 2000); doi: 10.1117/12.397843
Show Author Affiliations
Paul Seidel, Friedrich-Schiller-Univ. Jena (Germany)
Swen Wunderlich, Friedrich-Schiller-Univ. Jena (Germany)
Frank Schmidl, Friedrich-Schiller-Univ. Jena (Germany)
Sven Linzen, Friedrich-Schiller-Univ. Jena (Germany)
Frits Schrey, Friedrich-Schiller-Univ. Jena (Germany)
F. Schmidt, Friedrich-Schiller-Univ. Jena (Germany)
L. Doerrer, Friedrich-Schiller-Univ. Jena (Germany)
C. Steigmeier, Friedrich-Schiller-Univ. Jena (Germany)

Published in SPIE Proceedings Vol. 4058:
Superconducting and Related Oxides: Physics and Nanoengineering IV
Davor Pavuna; Ivan Bozovic, Editor(s)

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