How does an X-ray tube operate?
An X-ray tube is an evacuated glass or metal-ceramic housing into which is placed an anode and a cathode. The cathode is generally a thermionic emitter of electrons, a tungsten filament or indirectly heated cathode. The anode is a large cylinder of copper into which a tungsten plate has been fitted, generally at an angle. The filament or heater is powered up, and then a high DC voltage is applied between the cathode (-) and anode (+). During operation electrons are emitted from the cathode and accelerated towards the anode where they strike the tungsten plate at high velocity. When this happens, electrons within the tungsten atoms are dislodged from their orbits, take on the extra energy of the impacting electrons, and move into higher energy shells. When they once again collapse back into their normal electron shells, photons of X-radiation are produced. This process is called Bremstrallung, or “breaking radiation”. The X-rays pass through the wall of the tube (sometimes a special win
