Cathode Ray Tube

An electron gun consists of three major parts. The first is the cathode, a piece of metal which, when heated, gives off electrons. One of the most common cathodes in use is made of cesium metal, a member of the alkali family that loses electrons very easily. When a cesium cathode is heated to a temperature of about 1,750°F (954°C), it begins to release a stream of electrons. These electrons are then accelerated by an anode (a positively charged electrode) placed a short distance away from the cathode. As the electrons are accelerated, they pass through a small hole in the anode into the center of the cathode ray tube.

The intensity of the electron beam entering the anode is controlled by the grid. The grid may consist of a cylindrical piece of metal to which a variable electrical charge can be applied. The amount of charge placed on the control grid determines the intensity of the electron beam that passes through it.