Title: The applicability of high-frequency ultrasonic testing for the inspection of the bonded interface between a divertor’s mono-block and screw pipe
Abstract: This study investigated the applicability of high-frequency ultrasonic testing to inspect the tungsten-copper bonded interface between a divertor's mono-block and a cooling pipe called the “screw pipe.” Mock-up samples simulating the interface were fabricated by diffusion bonding of a 2.5 mm thick oxygen-free copper plate to a 12 mm thick tungsten block that satisfied the ITER material specifications. After making the bond, grooves were machined on the oxygen-free copper side of the samples. High-frequency ultrasonic tests were performed before and after machining the grooves using an ultrasonic scanner with a 30 MHz probe in the immersion pulse-echo setting. The testing results showed that the original screw pipe has a low capability for inspection with high-frequency ultrasonic testing. The visibility of a defect at the interface decreased because of the reflection of ultrasonic waves from the slope of the grooves and interference by the echoes from the interface and the grooves' surfaces. These issues were addressed by proposing geometrical modifications for the grooves and testing with high-frequency ultrasonic testing. The proposed modifications considerably increased the visibility of a defect at the interface and improved detectability by high-frequency ultrasonic tests.
This project whose basic results were presented as a poster in ISEM2023, started more than a year ago. Now the full paper is accepted for publication and we are working on getting more results. Professor Yusa once told me that a paper is not just a name in our CV; now I can say that I truly believe what he said. Setting aside the uncountable things I learned in the whole journey of writing and revising this paper; what I want to emphasize here is the value of receiving productive comments from the reviewers. The detailed comments we received not only improved the quality of the final paper, but also, gave us interesting ideas for our future steps in this project. I want to thank the reviewers who reviewed our manuscript and every hard-working reviewer who selflessly give ideas just to promote science. If I get the chance to review journal papers in the future, I would definitely like to be such a reviewer.