Overview of the R&D activities for the ITER bolometer diagnostic

The detailed development of the ITER bolometer diagnostic has recently been started. The aim is to reach a level from which on built-To-print drawings for the diagnostic components can be produced. Based on the challenges and corresponding requirements a review of the development status reveals that for some issues solutions are available. Among them are the damping of ECRH stray radiation, precise definition of the geometry of narrow lines-of-sight and their in-situ measurement, first prototype components for operation at high temperatures as well as detector prototypes with thick absorbers to detect photon energies up to 20 keV and which are potentially radiation resistant. However, there are also several issues still to be solved. Prominent among those discussed is the mechanical stability of the detector prototypes at high operating temperatures, but also the detailed definition of bolometer camera components suited for the integration in ITER and capable to withstand the operating conditions, in particular the effects of neutrons. A development path is proposed which focuses on the open issues and includes proposals for crucial prototype tests to validate design concepts.