RADIOLUMINESCENCE PROBLEMS FOR DIAGNOSTIC WINDOWS

Radioluminescence from 200 to 800 nm has been measured in UV grade sap phire at ionizing dose rates and temperatures of relevance for ITER op tical diagnostic windows. The intensity has been quantified in terms o f photon emission and has been found to be comparable to present day t okamak plasma emission intensities. Furthermore the light emission sho ws a complex dose, dose rate, and temperature dependence. It is conclu ded that without careful design it will prove extremely difficult to s eparate out the plasma emission from the window emission, High-tempera ture operation which in general produces thermal quenching, is seen no t to be a complete answer. While emission from about 200 to 500 nm is significantly reduced, over the range 600 to 800 nm it markedly increa ses due to the broadening chromium emission. However, despite the high intensity and complex behaviour, a possible operational wavelength re gion from 500 to 600 nm has been identified.