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

A.P. Rijpma, H.J.M. Brake, ter, E. Vries, de, N. Nijhof, H.J. Holland, H. Rogalla

    Research output: Contribution to journalArticleAcademicpeer-review

    6 Citations (Scopus)


    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 std. clin. 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 liq. 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 expts.
    Original languageEnglish
    Pages (from-to)209-212
    Number of pages4
    JournalPhysica C : Superconductivity
    Issue numberPart 1
    Publication statusPublished - 2002


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