Spectroscopic Diagnostics for ITER

Abstract

The main plasma regions of ITER - the core, the edge, the scrape-off layer, and the divertor - will be probed by an extensive array of spectroscopic diagnostics covering the visible to X-ray wavelength range. Plasma parameters will be determined including impurity species/density/input-flux, ion temperature, helium density, fueling ratio, plasma rotation, effective ionic charge and safety factor q. The measurements will be used for plasma control and in studies to understand and improve the performance of ITER. Both passive and active techniques will be employed. A diagnostic neutral beam (DNB) (˜100 keV) will be installed for Charge Exchange Recombination Spectroscopy. Motional Stark Effect measurements (for q profile) can in principle be made using both the heating neutral beam (1 MeV) and the DNB and both possibilities are under consideration. Diagnostic components, such as mirrors, windows, and optical fibers etc, mounted close to the plasma will experience higher levels of radiation due to neutron, gamma ray and particle irradiations than in present devices. Potentially their performance characteristics can be degraded and so the materials of the components have to be carefully selected and mitigating methods adopted where possible. This paper presents an overview of the ITER spectroscopic diagnostic systems and the details of some of the individual systems.