Cathode Ray Tubes

Abstract The cathode‐ray‐tube (CRT) is best known as the display for television and computer monitors. It is a vacuum tube in which electrons move in a beam. A cut‐away diagram of the interior of a CRT for color television display is shown. Inside the tube, the large, nearly flat, area, called the screen, is covered with phosphor materials that convert the electron‐beam energy into light. The beam is rapidly swept over this area, and its intensity is varied, so a display appears to the viewer, who visually integrates the light. When the display is rapidly changed, the viewer sees motion, as in television. The CRT is described in this article. In particular, the parts of the CRT, such as the cathode, electron gun, phosphors, deflection system, and shadow mask, are explained. The electrons come from the negative electrode, called the cathode, and form a beam, or ray, inside a vacuum tube, leading to the name cathode‐ray‐tube. Much interesting physics is associated with the beam formation and direction and its conversion to light, as well as with the manufacture of CRTs. CRTs have been used in other display applications, such as oscilloscopes, radar, and photorecording tubes. Some history of the tube, which extends during the last century, is presented.