Axial high-temperature superconducting gradiometer with a flexibleflux transformer

Abstract

An axial first-order gradiometer is formed by coupling the input coil of a flexible high-temperature superconducting flux transformer inductively to a directly coupled superconducting quantum interference device magnetometer. The transformer is patterned in a single-layer YBa2Cu3O7−x film on a flexible Hastelloy tape. The tape is bent such that the two outer pickup loops of the transformer are facing each other while perpendicular to the magnetometer plane resulting in a gradiometer baseline of 35mm. A superconducting shield is mechanically adjusted to reduce the gradiometer response to uniform fields applied perpendicularly to both the magnetometer plane and the plane of the transformer pickup loops, by a factor of typically 7000.

Highly Balanced Long-Baseline Axial Gradiometer Based on High-<tex>$rm T_rm c$</tex>Superconducting Tape

“…It consists of a dc-SQUID magnetometer which is inductively coupled 1051-8223/$20.00 © 2005 IEEE to the input coil of a flexible flux transformer and a superconducting shield. Details on the working principle can be found elsewhere [10], [12]. In summary, the transformer is bent in a way that the two pickup loops are facing each other ( Fig.…”

“…The improving quality of HTS tapes [6]- [8], with critical current densities larger than 1 , creates the possibility to construct high-quality flexible flux transformers operating at liquid nitrogen temperature [9], [10]. In earlier work, we reported the use of a flexible HTS flux transformer coupled to a single HTS dc-SQUID magnetometer to form an axial firstorder gradiometer [11], [12]. A superconducting shield, based on a gradiometric structure described in [13], was used to reject magnetic fields applied perpendicular to the magnetometer plane.…”

HTS Josephson junction devices for microwave and terahertz applications

“…Using this technology we have developed many electronic devices and complex systems, e.g. HTS SQUID LANDTEM system for geophysics applications [4], for airborne mineral exploration [5], under water magnetic sensing [6], a novel rotating SQUID gradiometer [7] and a planar SQUID gradiometer [8] system to enable magnetic tensor gradient measurements from a mobile platform. An overview of the CSIRO research activities in HTS superconducting electronics since 1987, outlining the HTS junction and device technology as well as various application systems developed by the group can be found elsewhere [9].…”

Flux transformers made of commercial high critical temperature superconducting wires

“…1 Furthermore, nonplanar gradiometers and flux transformers are hard to produce using thin film technology. 4 All these constraints can be overcome using high-T c superconducting wires. The progress in the industrial fabrication of high-T c superconductors for the past years has led to the production of reliable and cheap wires made of high-T c superconductors embedded in a silver alloy matrix.…”

“…The flux transfer should not be affected by Joule losses or extra noise. For this reason, flux transformers made of low-T c superconducting wires 3 or high-T c superconductors deposited on substrates 1,4 are commonly used. The use of high-T c flux transformers deposited on substrates with a base line limited to a few centimeters may be adequate for magnetocardiography but is not sufficient for applications with a longer source-tomagnetometer separation.…”