AbstractThe diagnostic windows of a machine for thermonuclear fusion experiments are basically subjected to atmospheric pressure and thermal loads due to plasma radiation. The glass or ceramic windows capable of withstanding the expected design loads become critical components if a highly radiative plasma is present near the window, as experienced in RFX during pulses with plasma current in the range of 1 MA. The transient thermal and mechanical analyses of windows having different shapes and made from different materials have been carried out. The results in terms of stress distributions showed that high tensile stresses can be present in the window volume shielded from radiation by the mounting flanges. The calculation of the failure probabilities gave a thorough knowledge of the behaviour and safety margins of the diagnostic windows.