HTS scanning SQUID microscope cooled by a closed-cycle refrigerator

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作者：

Univ of Maryland at College Park, College Park, United States ^{[1
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来源：

IEEE Trans Appl Supercond | / 2 III卷 / 3704-3707期

关键词：

High temperature superconductors - Microscopes - White noise - Yttrium barium copper oxides;

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摘要：

We have developed a scanning SQUID microscope which uses a commercially available closed-cycle refrigerator to cool a YBa2Cu3O7 bi-crystal dc SQUID to about 77 K. The system allows magnetic imaging of samples which are at room temperature and pressure with spatial resolutions of 50 μm or better. It is more compact and requires less maintenance than a more conventional liquid-nitrogen cooled system, while delivering equal sensitivity. In order to reduce the SQUID-sample separation while maintaining vacuum thermal isolation of the SQUID, the sensor is separated from the sample by a 25 μm thick, optically transparent window. The noise spectrum of our SQUID shows a 1/f spectrum below 500 Hz with 72 pT/√Hz field sensitivity at 10 Hz, and a white noise level of 20 pT/√Hz.

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