Construction and tests of a heart scanner based on superconducting sensors cooled by small stirling cryocoolers |
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| Authors: | A P Rijpma C J H A Blom A P Balena E de Vries H J Holland H J M ter Brake H Rogalla |
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| Affiliation: | a Low Temperature Division, Department of Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands;b Philips Medical Systems Nederland B.V., Afd. MR Scan Software, P.O. Box 10000, 5680 DA Best, Netherlands;c Hollandse Signaalapparaten B.V., P.O. Box 42, 7550 GD Hengelo, Netherlands |
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| Abstract: | At the University of Twente, a heart scanner has been designed and constructed that uses superconducting devices (superconducting quantum interference devices (SQUIDs)) to measure the magnetic field of the heart. A key feature is the elimination of liquid cryogens by incorporating cryocoolers. In the design, two coolers are operated in counter-phase to reduce the mechanical interference. In addition to the application of ferromagnetic shields around the compressors, the magnetic cooler interference is reduced by placing the SQUID magnetometers coplanar with respect to the coolers. In this way, the cooler noise was reduced to a level below the intrinsic sensor noise: 0.16 pT/√Hz. A temperature of 60 K was realised with a cool-down time of about 2 h. The corresponding heat load to the coolers is roughly 0.9 W. Magnetocardiograms were recorded inside a magnetically shielded room. |
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| Keywords: | Cryocooler SQUID Magnetic interference Stirling cooler Superconductivity |
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