Applications of high-temperature SQUIDs

Abstract

Using examples from our recent work, we describe the progress toward three types of applications of SQUID magnetometers and gradiometers operating at the temperature of liquid nitrogen, and using high temperature superconductor (HTS) YBa 2 Cu 3 O 7 thin-film sensors. First, we demonstrated usefulness of our magnetocardiographic data for diagnosis of cardiac arrhythmia and determination of risk of sudden cardiac death by means of a new method. This was achieved in a shielded room using our sensitive HTS magnetometer, in a back-to-back comparison with a state-of-theart low-temperature (LTS) magnetometer. Second, using an eddy-current technique in conjunction with our HTS gradiometer in unshielded environment, we demonstrated detection of flaws located very deep, e.g. 36 mm, below the surfaces of stacks of aluminium sheets. This indicated a high potential for nondestructive material evaluation (NDE) of, e.g. aging airplane structures. Third, we showed the applicability of an HTS magnetometer for electromagnetic geological prospecting. A successful field test was conducted using the controlled-source audio magnetotellurics method, with reference to a commercial induction coil system. In these three areas of applications, HTS SQUID systems are expected to soon gain user and market acceptance.