Magnetic Shields for HTc SQUIDs (Special Issue on High-Temperature Superconducting Electronics)

概要

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Bi_2Sr_2Ca_1Cu_2O_x thick film superconducting shields have been fabricated for use with HTc SQUIDs. Shielding factors and internal noise levels of the shields were measured using a DC SQUID magnetometer. A sample in which BSCCO was coated on the outside of a cylindrical Ag substrate exhibited larger noise levels than that with a sample in which BSCCO was coated on the inside of the Ag cylinder. The difference is explained by the thermally driven (Johnson) noise from the Ag substrate. A sample with the Ag cylinder outside the superconductor and samples with MgO substrates inside the superconductor showed good performance with a shielding factors of 10^<-8> and internal noise levels which did not exceed the DC SQUID magnetometer resolution (〜5 fTrms / √<Hz>) at 4.2 K. In addition, the flux relaxation noise of BSCCO superconducting shields was estimated from the relaxation behavior of BSCCO.
社団法人電子情報通信学会の論文
1993-08-25