Design of a high-tc SQUID based heart scanner cooled by small stirling coolers

A heart scanner based on high-Tc SQUIDs is under development. It should be used in standard clinical environments without magnetically shielded room. Because the scanner should be simple to use, the SQUIDs will be cooled by small cryocoolers thus realizing a turn-key apparatus. The aimed field resolution is 0.05 pT/√Hz, requiring an extremely stable temperature (fluctuations in the mK-range and drift below 0.1 mK/s). 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 hour.