A high-Tc SQUID-based sensor head cooled by a Joule–Thomson cryocooler

Rijpma, A.P. and Brake ter, H.J.M. and Vries de, E. and Nijhof, N. and Holland, H.J. and Rogalla, H. (2002) A high-Tc SQUID-based sensor head cooled by a Joule–Thomson cryocooler. Physica C: Superconductivity, 372-37 (Part 1). pp. 209-212. ISSN 0921-4534

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Abstract:	The goal of the so-called FHARMON project is to develop a high-Tc SQUID-based magnetometer system for the measurement of fetal heart activity in standard clinical environments. To lower the threshold for the application of this fetal heart monitor, it should be simple to operate. It is, therefore, advantageous to replace the liquid cryogen bath by a closed-cycle refrigerator. For this purpose, we selected a mixed-gas Joule–Thomson cooler; the APD Cryotiger©. Because of its magnetic interference, the compressor of this closed-cycle cooler will be placed at a distance of ≈2 m from the actual sensor, which is an axial second order gradiometer. The gradiometer is formed by three magnetometers placed on an alumina cylinder, which is connected to the cold head of the cooler. This paper describes the sensor head in detail and reports on test experiments.
Item Type:	Article
Copyright:	© 2002 Elsevier
Faculty:	Science and Technology (TNW)
Research Group:	Energy, Materials and Systems (EMS) Low Temperatures - Biomagnetism (LT)
Link to this item:	http://purl.utwente.nl/publications/74859
Official URL:	http://dx.doi.org/10.1016/S0921-4534(02)00672-X
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