Detection of interlayer delamination in W monoblock of ITER divertors via electromagnetic acoustic transduction

The W monoblock is one of the key components in divertors of the International Thermonuclear Experimental Reactor (ITER). During fabrication, it is prone to interlayer delamination posing a severe threat to integrity of diverters and safe operation of ITER. This opens up the research of efficient nondestructive evaluation techniques for quality assessment of W monoblock. In this paper, electromagnetic acoustic transduction with full-circumference radial excitation (FREM-EMAT) for detection of interlayer delamination in W monoblock has been intensively investigated via simulations and experiments. The probe parameters including the distance between permanent magnets, magnet type and height of excitation coil, etc and their influence on the transduction efficiency and testing signals are analyzed through semi-analytical modeling. Following this, a series of experiments have been carried out for detection of simulated interlayer delamination in W monoblocks via FREM-EMAT. It can be seen from the results that FREM-EMAT is capable of efficiently detecting the interlayer delamination with the diameter of 1mm in W monoblock, which fulfills the engineering requirement.