Research and some applications of high-T_c SQUIDS

In the work, we studied the noise characteristics of electronic gradiometers in unshielded environments. In the off-axis electronic gradiometers for biomagnetic measurements, we optimized low frequency noise and performed two-dimensional magnetic mapping of magnetic signal from human heart. The measured magnetocardiography (MCG) signal was averaged according to the simultaneously recorded electrocardiography signal to further enhance the signal-to-noise ratio. The off-axis configuration in our gradiometer system offers the flexibility for multichannel SQUID-based MCG applications. In the study of the SQUID microscope for circuit detection in unshielded environment, we fabricated SQUIDs, considered the design of cryostat, and used the lock-in technique to examine the circuit board. We also examined the magnetic field pattern from the magnetized magnetic thin film.