An
X-ray tube is a
vacuum tube that converts electrical input power into the intensity of
X-rays. X-ray tubes evolved from experimental
Crookes tubes with which X-rays were first discovered on November 8th, 1895, by the German physicist
Wilhelm Conrad Röntgen. The availability of this controllable source of X-rays created the field of
radiography, the imaging of partly opaque objects with penetrating
radiation. In contrast to other sources of ionizing radiation, X-rays are only produced as long as the X-ray tube is energized. X-ray tubes are also used in
CAT scanners, airport luggage scanners,
X-ray crystallography, material and structure analysis, and for industrial inspection.