High-T_c Superconducting Quantum Interference Device with Additional Positive Feedback

概要

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This study shows that using the direct offset integration technique (DOIT) and additional positive feedback (APF) in a high-T_c dc superconducting quantum interference device (SQUID) improves the effective flux-to-voltage transfer function and reduces the flux noise of a magnetometer, thus improving the magnetic field noise. The effective flux-to-voltage transfer function and the flux noise with APF were measured at different values of the positive feedback parameter β_a, which depends on the resistance of the APF circuit. These quantities were also compared between conditions with and without APF. This investigation showed that a β_a condition the most suitable for minimizing the flux noise of a magnetometer with APF exists and that it is β_a=0.77. The effective flux-to-voltage transfer function with APF is about three times what it is without APF (93μV/Φ_0 vs. 32μV/Φ_0). The magnetic field noise of a magnetometer with APF is improved by a factor of about 3(242fT/√ltHzgt vs. 738 fT/√ltHzgt).
社団法人電子情報通信学会の論文
1995-05-25