On the operational specifications and associated R/D for the VIS/IR diagnostic for ITER

The measurement requirements which have been defined for ITER are being associated to specific diagnostics for which they are guidelines for the development - not technical specifications. As intermediate step we consider the definition of operational specifications and the associated research and development (R/D). This step is elucidated here for the example of the Visible and Infrared diagnostic at the equatorial plane of ITER. The measurement requirements are given in terms of temperature and spectral luminance ranges, spatial coverage and temporal and spatial resolution. The operational specifications have to take the harsh environment, the difficulties of the measurements and the operational role of the diagnostic into account. We find three distinct levels of operational performances in ascending order of difficulty to realize but arguably descending order of indispensability for operational purposes: qualitative imaging, quantitative imaging and the deliverance of precise temperature and flux data. This ordering helps us to prioritize the R/D work and the degree of required robustness and availability for certain functions of the diagnostic. The R/D ranges from first mirror and radiation hardness investigations of refractive optical material which is elaborated in some detail here and the development of cognitive image processing for the first level over the development of a multi-color approach and advanced calibration and maintenance methods for the second level to in situ measurements of optical and thermal properties and complex image processing including the use of data from other diagnostics for the third level. Photon-flux modeling and tokamak testing is important for all stages. It seems desirable that the diagnostic should comply from the onset with the second performance level. The third level could be reached later. (authors)