Multiplexed SQUID array for non-destructive evaluation of aircraft structures

H. Krause, S. Gartner, N. Wolters, R. Hohmann, W. Wolf, J. Schubert, W. Zander, Yi Zhang, M. v. Kreutzbruck, M. Muck
2001 IEEE transactions on applied superconductivity  
SQUID sensors offer a significant advantage for eddy-current (EC) testing of aircraft components for material flaws hidden deeply in the tested structure. However, the requirement to take maps of the magnetic field, usually by meander-shaped scans, leads to unacceptably long measurement times. D u e to their inductive coupling to a tank circuit, several rf SQUID sensors may be read out sequentially by selectively coupling to their tank circuits, using only one electronics with a multiplexer
more » ... h a multiplexer 111. The multiplexed operation of three planar H T S rf SQUID gradiometers with one electronics and one cable is shown, demonstrating the advantage o f lower liquid nitrogen boil-off. Independent operation and switching is confirmed using local coil excitation o f the individual SQUIDs. W e report on the implementation of two multiplexed SQUID sensors in conjunction with an EC excitation and lock-in readout a t unshieltled laboratory environment. Scanning is performed while continuously switching the operating SQUID, thus obtaining two traces simultaneously. T h e applicability to EC testing o f riveted sections of aircraft fuselage is discussed.
doi:10.1109/77.919556 fatcat:jr4soludevbibic4ljskipji24