Sizing of defects in special shaped coolant pipe of Tokamak magnet based on eddy current testing signals

In this study, quantitative evaluation of defects in an outer-square-inner-round (OSIR), aluminum pipe, which is used as the coolant pipe of Tokamak superconducting magnet, is conducted based on the eddy current testing (ECT) technique. First, numerical simulations to predict ECT signal due to defects in OSIR pipes are performed using a code of A^r method; Second, ECT signal is detected using an Eddyfi ECT instrument with an absolute pancake ECT probe; Finally, the defect profile in OSIR pipe is reconstructed from the experimental ECT signals with the help of a fast-forward ECT solver, the developed multiple databases strategy and the deterministic inversion algorithm.