As part of the development of a low-Tc SQUID-based magnetometer system for measuring fetal heart activity, the means of cooling is evaluated. To lower the threshold for the clin. application of this fetal heart monitor, it should be simple to operate. It is, therefore, deemed necessary to replace the liq. helium by a closed-cycle refrigerator. In this paper, the requirements with respect to the cryogenic system are defined. These include operating temp. (4 K), temp. stability (0.1 W) and requirements on magnetic and mech. interference. The paper also reviews the most relevant options for the realization of the cryogenic system. After comparison, we selected a 4-K mech. cooler. To reduce the interference, it is placed at several meters from the magnetometer. The cooling power is to be transferred by circulation of helium.
|Title of host publication||Advances In Cryogenic Engeineering: Transactions of the Cryogenic Engineering Conference (CEC),|
|Publication status||Published - 2004|
|Name||AIP Conference Proceedings|