Radiation effects on the optical and electrical properties of CVD diamond

CVD diamond is the prime candidate material for use as windows in the ITER ECRH system, and can also be used as transmission component in ECE diagnostics. Hence electrical conductivity, radioluminescence, and optical absorption are important properties for the use of this material. In case of use for ECE diagnostics, the main concerns are absorption and radioluminescence. To address these issues measurements of surface electrical degradation, optical absorption, and radiolumniscence have been made. Intense radioluminescence bands related to nitrogen aggregates and carbon vacancies are observed within the bulk of CVD diamond during electron irradiation. Severe surface degradation occurs in CVD diamond when subjected to ion bombardment, increasing the surface electrical conductivity by many orders of magnitude and drastically reducing the optical transmission.