The ITER VIS/IR wide angle viewing system: Challenges and on-going R and D
The ITER tokamak is the next generation fusion device which will allow studying burning plasma obtained by a Deuterium-Tritium (D-T) fusion reaction during hundreds of seconds. ITER vacuum vessel real-time protection will be mandatory during plasma operation to avoid water leaks and critical plasma facing components degradation. The protection system will be based on a wide angle viewing system (WAVS) composed with 18 visible (VIS) and 18 infrared (IR) cameras covering 80 % of the vacuum vessel which will be one of the major imaging systems of ITER. Compared to protection systems routinely used on current tokamaks and based on imaging (VIS and/or IR), new constraints must be taken into account because of their influence on the system performance: the harsh environment (high neutron flux) and the metallic plasma facing components (both first wall and divertor). In this new demanding context, we have achieved three mandatory R and D studies starting from the understanding of the source of signals by using realistic photonic simulation up to real-time processing strategy taken into account first order optical design constraints to define what type of performance could be reached for ITER vacuum vessel protection. (authors)