In-vessel viewing system prototype performance measurements and simulation of measurement quality across the ITER in-vessel components

Abstract The In-Vessel Viewing and Metrology System (IVVS) is a fundamental tool for the ITER machine operations, tasked with inspection of plasma facing surfaces (PFS) of in-vessel components for both damage and erosion. The IVVS design has evolved to include a hybrid viewing and metrology system, using Frequency Modulated (FM) lidar for absolute distance measurements, and amplitude modulated (AM) lidar for surface viewing A full-scale prototype has been built, and has produced line-of-sight range precision of Performance was found to be highly sensitive to received power and surface reflectivity. To parameterize the reflectivity, the Bidirectional Reflectance Distribution Function (BRDF) of a divertor monoblock prototype was measured and an analytic BRDF model was developed. An IVVS simulator was developed and used both to analyse the in-vessel geometry and to predict the coverage of the PFS. We have shown that 85% of the PFS area can be covered if the IVVS meets performance requirements up to incidence angles of 65° and distances of 8 m.