Cryogenic design of a high-T, SQUID-based heart scanner cooled by small Stirling cryocoolers

A heart scanner based on high-T, SQUIDS is currently under development at the University of Twente. It is intended to be used in standard clinical environments without a magnetically shielded room. In order to make the application simple to use, the SQUIDS will be cooled by small cryocoolers, thus realizing a turnkey apparatus. The aimed field resolution is 50 ffRMs HZ-‘/~ in a measuring band of 0.1-100 Hz. The mechanical cooler interference is reduced by incorporating two coolers and operating them in counter phase. The magnetic cooler interference is reduced by positioning the coolers and the SQUIDS in a coplanar arrangement, and by separating the SQUIDS from the cold tips with a solid conducting thermal interface. A design is presented in which a temperature of 55 K is expected with a cool-down time of less than 1 h.