Plasma disruptions in ITER and the ECH upper port plug design

Abstract

During ITER operation malfunctions of the control system due to excessively large perturbations and for special configurations can lead to vertical displacement events (VDE), where a vertical plasma movement is followed by a fast or slow plasma current quench. As a result during the plasma breakdown induced eddy and halo currents cause severe loads on the in-vessel components. For the upper port plug (UPP) structures in ITER the upward VDEs with the subsequent fast current quench are the most critical disruptions. The upper port design requires a plug length of about 5 m with a spacing of 10 mm at the first wall to the neighboring panels. One of the major challenges in the port plug design is to remain within the 10 mm gap during the disruption. The presented ECH UPP structural design cycle combines numerical analysis with manufacturing and prototype issues such as complex double wall structures and joining qualities.