Low noise YBa2Cu3O7−x SQUID magnetometers operated with additional positive feedback
- 25 March 1996
- journal article
- conference paper
- Published by AIP Publishing in Applied Physics Letters
- Vol. 68 (13) , 1856-1858
- https://doi.org/10.1063/1.116036
Abstract
Three magnetometers based on dc superconducting quantum interference devices (SQUIDs) fabricated from YBa2Cu3O7−x have been operated in a magnetically shielded room using a flux‐locked loop involving additional positive feedback with bias current reversal. Two of these devices, integrated multiloop dc SQUIDs with outer diameters of 7 mm, achieved white noise levels of 10 fT/√Hz for bicrystal junctions and 30 fT/√Hz for step‐edge junctions. The third magnetometer involved a flux transformer with a 10×10 mm2 pickup coil connected to a 16‐turn input coil which was inductively coupled to a bicrystal SQUID. This device achieved a white noise of 16.2 fT/√Hz. High quality magnetocardiograms were obtained without signal averaging.Keywords
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