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Open AccessArticle

Influence of Resonances on the Noise Performance of SQUID Susceptometers

by Samantha I. Davis 1,2,*,†, John R. Kirtley 3,† and Kathryn A. Moler 1,3,4,5
1
Department of Physics, Stanford University, Stanford, CA 94305-4045, USA
2
California Institute of Technology—The Division of Physics, Mathematics and Astronomy, 1200 E California Blvd, Pasadena, CA 91125, USA
3
Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA
4
Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
5
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Sensors 2020, 20(1), 204; https://doi.org/10.3390/s20010204
Received: 4 November 2019 / Revised: 23 December 2019 / Accepted: 27 December 2019 / Published: 30 December 2019
(This article belongs to the Special Issue Advanced Magnetic Sensors and Their Applications)
Scanning Superconducting Quantum Interference Device (SQUID) Susceptometry simultaneously images the local magnetic fields and susceptibilities above a sample with sub-micron spatial resolution. Further development of this technique requires a thorough understanding of the current, voltage, and flux ( I V Φ ) characteristics of scanning SQUID susceptometers. These sensors often have striking anomalies in their current–voltage characteristics, which we believe to be due to electromagnetic resonances. The effect of these resonances on the performance of these SQUIDs is unknown. To explore the origin and impact of the resonances, we develop a model that qualitatively reproduces the experimentally-determined I V Φ characteristics of our scanning SQUID susceptometers. We use this model to calculate the noise characteristics of SQUIDs of different designs. We find that the calculated ultimate flux noise is better in susceptometers with damping resistors that diminish the resonances than in susceptometers without damping resistors. Such calculations will enable the optimization of the signal-to-noise characteristics of scanning SQUID susceptometers. View Full-Text
Keywords: SQUID; susceptometers; noise; scanning SQUID; susceptometers; noise; scanning
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Davis, S.I.; Kirtley, J.R.; Moler, K.A. Influence of Resonances on the Noise Performance of SQUID Susceptometers. Sensors 2020, 20, 204.

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