Multichannel SQUID magnetometry using double relaxation oscillation SQUIDs


Duuren, Michiel J. van and Lee, Y.H. and Adelerhof, Derk Jan and Kawai, J. and Kado, H. and Flokstra, J. and Rogalla, H. (1996) Multichannel SQUID magnetometry using double relaxation oscillation SQUIDs. IEEE Transactions on Applied Superconductivity, 6 (1). pp. 38-44. ISSN 1051-8223

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Abstract:A highly sensitive first-order gradiometer based on double relaxation oscillation SQUID's (DROS's) for multichannel use is presented. The white flux noise level of the bare DROS's is 4.5 μΦ0/√Hz (ε=275 h). With wire-wound first-order gradiometers, having a baseline of 40 mm, the white magnetic field noise equals 4 fT/√Hz. As a result of the high flux-to-voltage transfer of the DROS's of about 1 mV/Φ0, this low noise level could be obtained with simple room-temperature flux locked loop electronics based on direct voltage readout. The relaxation frequency of the present DROS's is approximately 1 GHz. No degradation of the DROS characteristics caused by interference between relaxation oscillations in two adjacent channels has been observed, although the gradiometers are spaced by less than 1 mm. This shows that DROS's can be used in multichannel SQUID magnetometers.
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Copyright:©1996 IEEE
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