As what we have seen from above picture, molybdenum disc is used. Rotating anode came into use in 1929, but the first construction of rotating anode tube was done by Wood in 1897. The modern rotating anode tube with disk-shaped, normally made of molybdenum. Molybdenum disk is used as main material, because it has twice the heat capacity of a pure tungsten disk with the same mass.
Molybdenum discis also used in other products, as a small but important part.