Van de Graaff Generator

Van de Graaff Generator, an electrostatic machine used in nuclear physics for the generation of extremely high voltages (see Electricity; Physics: Developments Since 1930). It was developed in 1931 by the American physicist Robert Jemison Van de Graaff. The generator consists of a high-voltage terminal in the form of a metal sphere, mounted at the top of an insulating column. A continuous belt of dielectric material such as rubber-impregnated cotton runs from a pulley at the base of the column to a pulley within the sphere. An electric potential of approximately 50,000 volts sprays electrons from a metal comb, which has sharply pointed teeth and is mounted parallel to the moving belt. As the belt carries its charge up into the sphere, the charges are removed by other combs and applied to the body of the sphere. As the belt continuously picks up charges and delivers them to the sphere, a potential difference of as much as 5 million volts is built up. The Van de Graaff generator is used to accelerate a beam of electrons, protons, or ions to bombard the nuclei in a small target. See Particle Accelerators.

See also Atom; Nuclear Energy.