Integrated SQUID gradiometers for measurement in disturbed environments

Abstract

Planar dc SQUID gradiometers with integrated antenna were designed and investigated. With low-T, superconductors they were realized as washer type and as transformer type SQUID gradiometers. With high-T, superconductors we tested galvanometer SQUIDs. Field gradient sensitivities of 32 ff/(cmdHz) could be achieved with low-T, SQUIDs and of 520 ff/(emdHz) with high-T, SQUIDs, respectively. All types of gradiometers could work stable in disturbed environments. The influence of the SQUID gradiometer layout and the construction of the sample holder on the degree of disturbance suppression is shown.

High-transition-temperature superconducting quantum interference devices

“…This configuration has the disadvantage that large supercurrents are induced around the perimeter when the device is rotated in an ambient field. Knappe et al (1992), Zakosarenko et al (1994), Daalmans et al (1995), Schultze, Stolz et al (1997), have all made single-layer, first-derivative gradiometers of this kind, using dc SQUIDs with either step-edge or bicrystal junctions. The baselines are limited by the size of the substrate to about 5 mm, and the best gradient sensitivities are about 50 pT m Ϫ1 Hz Ϫ1/2 .…”

A signal-to-noise chart for designing planar high-TcSQUID gradiometers for magnetocardiographs

“…Many planar-type high-T c SQUID gradiometers have been previously reported [4][5][6][7][8][9][10][11][12][13][14][15][16]. The gradient field noise and baseline lengths, which are given in these references, have been collected (figure 2).…”

“…Many planar-type high-T c SQUID gradiometers have recently been developed [4][5][6][7][8][9][10][11][12][13][14][15][16], because they can be operated in liquid nitrogen without adjustments of gradiometric balance. However, their feasibility for detecting P-waves has not been sufficiently evaluated.…”

HTS SQUID gradiometer for application without shielding

“…Such a tilt would exist if there was a bending of the substrate. However, as former investigations show [10], such a bending can be excluded for the rigid SrTiO 3 substrate. Hence, we assume a slightly inclined gluing of the flux transformer onto the SQUID to be the cause.…”