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

•A novel hybrid optical design for the In-Vessel Viewing system is proposed, using both FM and AM LIDAR.•3D range precisions of 2–400 μm are estimated based on line-of-sight ranging measurements in a full-size prototype.•An IVVS simulator was developed, and reflectivity of an ITER component was measured to assess IVVS coverage.•A target of measurement of up to 65° incidence angle and up to 8 m distance is set to achieve coverage of 85% of in-vessel plasma facing surfaces. 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