Robert J. Van de Graaff

Robert J. Van de Graaff
File:Robert J. Van de Graaff.jpg
Born	(1901-12-20)December 20, 1901 Tuscaloosa, Alabama, U.S.
Died	Boston, Massachusetts, U.S.
Nationality	American
Fields	Physics
Institutions	Massachusetts Institute of Technology Princeton University
Alma mater	University of Alabama La Sorbonne University of Oxford
Known for	Van de Graaff generator
Notable awards	Elliott Cresson Medal (1936) Duddell Medal and Prize (1947) Tom W. Bonner Prize in Nuclear Physics (1966)

Robert Van de Graaff (left) (Utrecht University, 1966)

Robert Jemison Van de Graaff (December 20, 1901 – January 16, 1967) was an American physicist, noted for his design and construction of high-voltage Van de Graaff generators. He taught at Princeton University and Massachusetts Institute of Technology.

Biography

Robert Jemison Van de Graaff was born at the Jemison-Van de Graaff Mansion in Tuscaloosa, Alabama. His parents were of Dutch descent. His three older brothers Adrian, Hargrove, and William were all All-Southern college football players for the Alabama Crimson Tide. William was known as "Bully" and was Alabama's first All-American. In Tuscaloosa, Robert received his BS and master's degrees from The University of Alabama where he was a member of The Castle Club (later became Mu Chapter of Theta Tau). After a year at the Alabama Power Company, Van de Graaff studied at the Sorbonne. In 1926 he earned a second BS at Oxford University on a Rhodes Scholarship, completing his PhD in 1928.

Van de Graaff was the inventor of the Van de Graaff generator, a device which produces high voltages. In 1929 he developed his first generator, producing 80,000 volts, with help from Nicholas Burke at Princeton University. By 1931 he had constructed a larger generator generating 7 million volts.

Van de Graaff was a National Research Fellow, and from 1931 to 1934 a research associate at the Massachusetts Institute of Technology. He became an associate professor in 1934 (staying there until 1960). He was awarded the Elliott Cresson Medal in 1936.

During WWII Van de Graaff was director of the High Voltage Radiographic Project. After WWII he co-founded the High Voltage Engineering Corporation (HVEC) with John G. Trump, uncle of real estate magnate Donald Trump. During the 1950s he invented the insulating-core transformer, producing high-voltage direct current. He also developed tandem generator technology.

The American Physical Society awarded him the T. Bonner prize (1965) for the development of electrostatic accelerators.

Van de Graaff died on January 16, 1967 in Boston, Massachusetts.

Van de Graaff generator

Main article: Van de Graaff generator

The Van de Graaff generator uses a motorized insulating belt (usually made of rubber) to conduct electrical charges from a high voltage source on one end of the belt to the inside of a metal sphere on the other end. Since electrical charge resides on the outside of the sphere, it builds up to produce an electrical potential much higher than that of the primary high voltage source. Practical limitations restrict the potential produced by large Van de Graaff generators to about 7 million volts. Van de Graaff generators are used primarily as DC power supplies for linear atomic particle accelerators in nuclear physics experiments. Tandem Van de Graaff generators are essentially two generators in series, and can produce about 15 million volts.

The Van de Graaff generator is a simple mechanical device. Small Van de Graaff generators are built by hobbyists and scientific apparatus companies and are used to demonstrate the effects of high DC potentials. Even small hobby machines produce impressive sparks several centimeters long. The largest air insulated Van de Graaff generator in the world, built by Van de Graaff himself, is operational and is on display at the Boston Museum of Science. Demonstrations throughout the day are a popular attraction. More modern Van de Graaff generators are insulated by pressurized dielectric gas, usually freon or sulfur hexafluoride. In recent years, Van de Graaff generators have been slowly replaced by solid-state DC power supplies without moving parts. The energies produced by Van de Graaff atomic particle accelerators are limited to about 30 MeV, even with tandem generators accelerating doubly charged (for example alpha) particles. More modern particle accelerators using different technology produce much higher energies, thus Van de Graaff particle accelerators have become largely obsolete. They are still used to some extent for graduate student research at colleges and universities and as ion sources for high energy bursts.

Education

• B.S. 1922 — University of Alabama
• Master's degree (Mechanical Engineering, 1923) — University of Alabama
• Marie Curie lectures (1925) — La Sorbonne
• Doctorate of Philosophy (Physics, 1928) — Oxford University

Patents

• US1,991,236 — "Electrostatic Generator"
• US2,024,957 — "Electrical Transmission System"
• US2922905 — "Apparatus For Reducing Electron Loading In Positive-Ion Accelerators"
• US3,187,208 — "High Voltage Electromagnetic Apparatus Having An Insulating Magnetic Core"
• US3,323,069 — "High Voltage Electromagnetic Charged-Particle Accelerator Apparatus Having An Insulating Magnetic Core"
• US3239702 — "Multi-Disk Electromagnetic Power Machinery"
• US3,308,323 — "Inclined field High Voltage Vacuum Tubes"

External links

• Short biography at the web-site for the Jemison-Van de Graaff Mansion
• Wiplich, M., "Short Biography Of Robert Jemison Van de Graaff". 2001. [bnl.gov]
• Trump, J.G., Merrill, F.H., and Safford, F.J., "Van de Graaff Generator". Rev. Sci. Instrum., 9 (1938) 398
• "Dr. Van de Graaff's large generator". MIT.
• "VDG for hobbyists and science fairs"
• "History of the Van de Graaff Generator". Museum of Science, Boston. 2004.
• Brenni, Paolo, "The Van de Graaff Generator -- An Electrostatic Machine for the 20th Century". Bulletin of the Scientific Instrument Society No. 63. 1999.
• Photos of Robert J. Van de Graaff at the Emilio Segrè Visual Archives, American Institute of Physics
• Build your own VDG