We attempt a comprehensive review of all published research in nondestructive evaluation (NDE) performed with the superconducting quantum interference device (SQUID) magnetometer since the first work was reported in the mid-1980s. The SQUID is the most sensitive detector of magnetic flux known. The energy sensitivity of the SQUID may make it the most sensitive detector of any kind. The research on SQUIDs for NDE is based on the promise of that sensitivity and on the various other desirable properties developed for SQUID instrumentation in biomagnetism and other fields. The sensitivity of SQUID instruments down to very low frequencies allows them to function as eddy-current sensors with unparalleled depth resolution, and to image the static magnetization of paramagnetic materials and the flow of near-dc corrosion currents. The wide dynamic range of the SQUID makes it possible to image defects in steel structures and to measure the magnetomechanical behaviour of ferromagnetic materials with high sensitivity. In the last decade SQUID instrumentation designed specifically for NDE has appeared and improved the spatial resolution of most work to roughly 1 mm, with promise of another order of magnitude improvement within the next five years. Algorithms for flaw detection and image deconvolution have begun to flourish. With many talented, industrious people in the field, the future of SQUID NDE looks bright, provided the crucial first niche can be found.

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Candling, the traditional means of detecting parasites during fish fillet processing, is time consuming and labor intensive. This method is a major factor in reducing the quality and increasing the cost of fish brought to market. The difference in electrical conductivity between fish and an embedded parasite was hypothesized to be a practical basis for an instrument which would have potential for automated parasite detection. A small electrical current was passed through a parasite-containing fillet and the magnetic field above the fillet was recorded by a Superconducting Quantum Interference Device magnetometer. Results indicate potentially successful detection of parasites by the device.

We examined the potential of an electromagnetic parasite detection technique to become the basis of an automated commercial system. The effects of parasite orientation and position, presence of fish bone, and applied signal strength and frequency on resultant magnetic field strength were determined by scanning a conducting cell containing fish fillet and parasite below a SQUID magnetometer. The parasite orientation affected peak-to-peak voltage of the magnetic dipole. The parasite position with respect to myotome structure seemed to affect the orientation of the dipolar signal. A fish bone was readily detected. The magnetic field strength was independent of the frequency of the injected current and scaled with amplitude=.