Temperature dependence of the effective sensing area of high- dc SQUIDs
H J M ter Brake; W A M Aarnink; P J van den Bosch; J W M Hilgenkamp; J Flokstra; H Rogalla; H J M ter Brake; Low Temperature Division, Faculty of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands; W A M Aarnink; Low Temperature Division, Faculty of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands; P J van den Bosch; Low Temperature Division, Faculty of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands; J W M Hilgenkamp; Low Temperature Division, Faculty of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands; J Flokstra; Low Temperature Division, Faculty of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands; H Rogalla; Low Temperature Division, Faculty of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
Журнал:
Superconductor Science and Technology
Дата:
1997-07-01
Аннотация:
The effective sensing area of a high- dc SQUID depends on temperature. As a consequence, fluctuations in the operating temperature result in apparent magnetic field noise if the SQUID is placed in a background magnetic field. An analysis of this effect for two SQUID types, the square-washer `Ketchen' type and the inductively shunted type, is performed. For magnetocardiography, the temperature fluctuations (peak to peak) of the latter SQUID type should be below w0.3 mK at 77 K, and below 2 mK at 55 K, with an earth's field suppression of 40 dB. For the square-washer SQUID the requirements are about 8 times less stringent.
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