An Efficient Finite-Element Approach for the Modeling of Planar Double-D Excitation Coils and Flaws in SQUID NDE Systems

Incorporating an efficient approach for the finite-element simulation of eddy current superconductive quantum interface device (SQUID) nondestructive evaluation (NDE) systems, an appropriate finite-element method (FEM) has been presented for simulating and analyzing such systems. We have introduced a new model for the planar double-D coils, which are used as the excitation source in eddy current SQUID NDE systems, and also another model for the description of the flaw effect on the induced current. We have also examined our simulation results with their associated measurements. Our system is based on a high-T_C YBCO gradiometer RF-SQUID sensor with a flux noise level below 100 ????₀/ ??Hz at 100 Hz in an unshielded environment while being shielded against external RF electromagnetic interference. The very good agreement between experimental and numerical approaches confirmed our model for the 3-D FEM simulation of the system, which is being done in reasonable time and using reasonable computer resources.