A dedicated system for in situ testing of gamma ray induced optical absorption and emission in optical materials

Serious radiation damage due to the high energy neutron/gamma fluxes is expected for optical materials such as scintillators, windows, and lenses which will be part of the plasma diagnostics in future fusion devices. Radiation induced absorption represents a major concern for these components for which experimental validation under as near as possible reactor conditions becomes essential. A new experimental system has been developed at the CIEMAT Nayade ⁶⁰Co gamma irradiation facility for in situ radiation induced optical absorption measurements, covering a spectral range between 370 and 730 nm. This setup consists in a rotating sample holder which allows one to collect incident light (reference signal) and transmitted light through the material to be tested as a function of irradiation dose. This is an advanced and robust system which overcomes the important experimental difficulties that radiation involves providing a valuable testing capability for transmission components and scintillators under realistic fusion conditions. A detailed description of the experimental arrangement, together with preliminary tests carried out for system validation is given in this paper.