The X-ray tube is a vacuum diode working at a high voltage. Contains two electrodes: one is a filament for transmitting electrons, as a cathode, and the other is a target for receiving an electron bombardment, as an anode. The two level is sealed in a high vacuum glass or ceramic enclosure.
A vacuum electronic device which produces x-rays by using high-speed electrons to hit a metal target. The X-ray tube can be divided into two types: inflatable tube and vacuum tube according to the way of producing electrons.
An inflatable X-ray tube is an early X-ray tube. In 1895, W. C. Roentgen discovered X-rays during the Crookes tube experiment. The Crookes tube is the first gas-filled X-ray tube. After the tube is connected with high pressure, the gas is ionized in the tube, and electrons are escaping from the cathode under the positive ion bombardment, and the X-rays are produced by accelerating the impact of the target surface. The gas-filled X-ray tube has little power, short life and difficult control. In 1913, W. D. Kuligi invented the vacuum X-ray tube.