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arXiv · 0707.4457

Long-time stable HTSC DC-SQUID gradiometers with silicon dioxide passivation for measurements with superconducting flux transformers

P Seidel·C Becker·A Steppke·M Buettner·H Schneidewind·V Grosse·G Zieger·F Schmidl
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Abstract

In applications for high-Tc superconducting DC-SQUIDs such as biomagnetism, nondestructive evaluation and the relaxation of magnetic nanoparticles, it is important to maintain reliable sensor performance over an extended time period. We designed and produced DC-SQUID gradiometers based on YBCO thin films which are inductively coupled to a flux transformer to achieve a higher sensitivity. The gradiometers are protected against ambient atmosphere and humidity by SiO2 and amorphous YBCO layers. The noise properties of the sensor in flip-chip configuration, especially in unshielded environments, are shown. We present a comparison of TBCCO thin films on buffered sapphire or LaAlO3 substrates for the flux transformer in shielded and unshielded environments. We reach a low white field gradient noise of 72 fT/(cm sqrt(Hz)) with the TBCCO on LaAlO3 flux transformer. The electric properties of the gradiometers (critical current IC, normal state resistance RN and the transfer function VPhi) were measured over a period of one year and do not show significant signs of degradation.

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P Seidel, C Becker, A Steppke, M Buettner, H Schneidewind, V Grosse, G Zieger, F Schmidl. 2007-07-30. Long-time stable HTSC DC-SQUID gradiometers with silicon dioxide passivation for measurements with superconducting flux transformers. https://doi.org/10.1088/0953-2048%2F20%2F11%2Fs15

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