In a rotating anode tube, the anode target disc rotates on a highly specialized ball bearing system. The target is subjected to a focused stream of electrons emitting from the cathode and accelerated by a high potential difference between the target disc and the cathode. When the electron beam hits the anode, it produces the X-ray beam. The cathode provides a controlled source of electrons and the filament is a constructed tungsten wire coil of precise pitch and length. A motor rotates the anode disc at a high speed up to 10,000 rpm and to temperatures of 2000° C. The anode assembly is mounted on bearings and actually forms the rotor of the electric motor. The disc has a tungsten rhenium target area and faced onto a molybdenum disc. The disc is cooled by radiation to the glass then oil.
The advantage of using a rotating anode tube is it permits selection of higher electrical load without the risk of overheating. It can be used in almost every radiography application. Constant advances are being made to the rotating anode tube and recent discoveries have led to the use of new anode material, reduced target angle, increased speed of anode rotation, and new styles of tubes including the grid controlled X-ray tube and metal/ceramic X-ray tube.