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A susceptometer based on planar DC superconducting quantum interference devices has been designed and constructed. The device is used in examining microcrystallites as a function of temperature from 0.3 K to 4 K in magnetic fields greater than 280G. Large, in-plane static fields can be applied through an external coil while perpendicular fields up to 2G can be applied by using a series-wound on-chip field coil. Paramagnetic, antifferomagnetic and superconducting transitions have been resolved on samples with sizes ranging from 20 to 50 micrometers.

A planar direct current superconducting quantum interference device (SQUID) gradiometer is developed for measuring magnetic field distributions in unshielded environments. The SQUID gradiometer is provided with a pickup antenna and a flux transformer with highly symmetrical layouts. It is very useful for performing nondestructive testing and magnetocardiographic measurements.

Neuromagnetic superconducting quantum interference device (SQUID) measurements were performed on a human brain protected by a helmet-shaped superconducting magnetic shield made from Bi-Sr-Ca-Cu-Ox alloy. The cerebral magnetic fields were generated by electrically stimulating the tibial nerves of the right ancle of a human subject. The measured data show that the presence of the helmet-shaped magnetic shield reduced the low-frequency-noise components of the fields and enhanced the accuracy of the SQUID measurements.

The two-dimensional current and magnetization distribution data obtained by conducting high-resolution superconducting quantum interference device magnetometer studies on superconducting thin films were evaluated using three different algorithms. The deconvolution algorithms were applied to simplify the original magnetic field maps for easier interpretation. Results show that the application of the algorithms to appropriate conditions allows the easier visualization of the magnetic sources.

The design and development of a high resolution magnetic susceptometer for investigating the composition of diamagnetic and paramagnetic materials are discussed. The susceptometer, which is based on the superconducting quantum interference device magnetometer, is capable of measuring local magnetic field variations caused by the distribution of magnetic susceptibility in the samples. Preliminary analyses conducted on several specimens demonstrate the applicability of the proposed susceptometer.

A superconducting quantum interference device (SQUID)-based sensor system for the dynamic alternating current field measurement of current flows in electrically conductive test subjects is presented. The system uses a SQUID component and pick-up coils immersed in LHe to obtain both static and dynamic alternating current field measurements for ferromagnetic materials. Actual tests performed on steel and aluminum plate specimens validate the viability of the proposed sensor system.

The performance of several magnetic field sensors equipped with digital superconducting quantum interference device (SQUID) feedback read-out was evaluated. The interferometers, which were designed with different configurations, were taken in a magnetically shielded room for the experimental measurements. Results indicate that the digital read-out SQUID devices are less sensitive to the effects of resonance than a conventional direct current SQUID.

The Superconducting Quantum Interference Device (SQUID) is a low frequency transducer that detects magnetic field variations. When it is linked to a superconducting coil it could measure small changes in stable DC magnetic fields. This gives the SQUID system a better signal-to-noise ratio than conventional magnetometers used in non-destructive evaluation. SQUID is used in determining the thermal aging of Duplex steel rods by measuring the residual magnetization. The measurements can be done at a distance of 200 mm from the specimen and could also be used in the in-situ non-destructive evaluation of Duplex steel.

A multichannel high-resolution superconducting quantum interference device magnetomer has been developed to measure biomagnetic fields produced by small animals. The magnetocardiogram produced by a rate was measured and topographies of the P wave, QRS wave, and T wave were obtained. Auditory evoked magnetic fields were obtained and differences in the wave forms in both sides of the right ear were observed.