what did robert j. graaff discover?
» Robert Jemison Van de Graaff Biography - World Famous Biographies- Biographies of famous people : Famous People biography
American physicist and inventor of the Van de Graaff generator, a type of high-voltage electrostatic generator that serves as a type of particle accelerator. This device has found widespread use not only in atomic research but also in medicine and industry.
Robert Jemison Van de Graaff was born on December 20, 1901 in Tuscaloosa, Alabama. His mother was Minnie Cherokee Hargrove and his father was Adrian Sebastian Van de Graaff. Robert attended the Tuscaloosa public schools and then attended the University of Alabama where he received a BS degree in 1922 and an MS degree in 1923. Both degrees were in mechanical engineering.
Van de Graaff
After graduating from college he worked for the Alabama Power Company for a year as a research assistant. He studied at the Sorbonne in Paris from 1924 to 1925 and while there, attended lectures by Marie Curie on radiation. In 1925 he went to Oxford University in England as a Rhodes Scholar. At Oxford he received a BS in physics in 1926 and a Ph.D. in physics in 1928.
While at Oxford, he became aware of the hope of nuclear experimenters such as Ernest Rutherford, that particles could someday be accelerated to speeds sufficient to disintegrate nuclei. By disintegrating atomic nuclei much could be learned about the nature of individual atoms. It is from these ideas that Robert Van de Graaff saw the need for a particle accelerator.
In 1929 Van de Graaff returned to the United States to join the Palmer Physics Laboratory at Princeton University as a National Research Fellow. In the fall of that year he constructed the first working model of his electrostatic accelerator which developed 80,000 volts. Improvements were made to the basic design and in November, 1931 at the inaugural dinner of the American Institute of Physics, a demonstration model was exhibited that produced over 1,000,000 volts. The invention was reported at a meeting of the American Physical Society in 1931.
In 1931, when Karl T. Compton became president of Massachusetts Institute of Technology, Van de Graaff was invited to come to MIT as a research associate. In 1931 Van de Graaff constructed his first large machine in an unused aircraft hangar at Round Hill, the estate of Colonel E.H.R. Green, in South Dartmouth, Massachusetts. The machine used two polished aluminum spheres, each 15 feet in diameter mounted on 25 foot high insulating columns, which were 6 feet in diameter.
The columns were mounted on railway trucks that boosted the spheres to 43 feet above ground level. The machine had its debut on November 28, 1933 and was able to produce 7,000,000 volts. This accomplishment was reported in the New York Times for November 29, 1933 in a story titled "Man Hurls Bolt of 7,000,000 Volts". In 1937 the machine was moved to a pressurized enclosure at MIT.
