Prediction and evaluation of measurement performances of imaging diagnostics for ITER wall protection

Abstract

ITER divertor and first wall protection is primarily based on infrared (IR) thermography system used to measure surface temperatures and power loads of critical machine components. This system consists of 22 lines of sight installed in the equatorial and upper ports to monitor the maximum surface area of the first wall and the divertor with sufficient accuracy to analyze the plasma-wall interaction and optimize the plasma scenarios in safe conditions. Predicting the measurements performance of all these diagnostics is essential during the design phase and in preparation for operations. Particular attention is paid to spatial coverage and resolution in order to quantify operational limits. A new calculation tool, based on a fast ray-surface interaction, has been developed to accurately assess the chamber area within the field of view and evaluate the coverage of all imaging systems of ITER. The useful spatial coverage (i.e. with spatial resolution better than 50 mm/pixel) is estimated to be 77% for the first wall, 80% for the divertor. In addition, a 2D-3D mapping algorithm is used to display the calculated data onto a 3D scene model and onto a 2D representation of the in-vessel components. Such a tool is also applied and tested on WEST experimental data and then supports the preparation of ITER operation by developing adapted tools for machine protection.