Theoretical Simulations and Quantitative Magnetic Field Measurements for Eddy-Current Testing with an HTS SQUID System

The use of a Superconducting QUantum Interference Device (SQUID) magnetometer for quantitative measurements in eddy-current nondestructive evaluation is presented. The SQUID is used in absolute mode, and the magnetic field measurements are directly compared to theoretical results from both analytical and semi-analytical models. The measurements are taken in an ambient noise environment, and the excitation has the form of a double-rectangle printed-circuit-board coil. The configurations examined involve the coil in air and above aluminum plates with or without defects in the form of notches. Agreement between experimental and theoretical results is very good in all cases, showing that SQUID magnetometers can be used for quantitative magnetic field measurements and that modeling can be readily applied for parametric analysis and optimizations of the measurement configuration including excitation coils´ design and frequency selection.