Robert J. Van de Graaff

Robert Jemison Van de Graaff (December 20, 1901 – January 16, 1967) was an American applied physicist known for his invention of the Van de Graaff generator. He spent most of his career at the Massachusetts Institute of Technology.

Biography

Robert Jemison Van de Graaff was born on December 20, 1901, at the Jemison–Van de Graaff Mansion in Tuscaloosa, Alabama, the son of Adrian Sebastian "Bass" Van de Graaff and Minnie Cherokee Jemison. His great-grandfather was Robert Jemison Jr. His father, a circuit judge, was of Dutch descent.<ref name=bnl>Template:Cite web</ref><ref name="jemisonmansion">Template:Cite web</ref>

His three older brothers, Adrian, Hargrove and William, were All-Southern college football players for the Alabama Crimson Tide. William was known as "Bully" and was Alabama's first All-American.

Van de Graaff received a B.S. in Mathematics in 1922 and an M.S. in Mechanical Engineering in 1923 from The University of Alabama, where he was a founding member of The Castle Club (later became Mu chapter<ref>Template:Cite web</ref> of Theta Tau).

After a year working for the Alabama Power Company, Van de Graaff attended Marie Curie's lectures at the Sorbonne in France in 1925. The following year, he earned his second B.S. from the University of Oxford in England by a Rhodes Scholarship, and received his Ph.D. under J. S. E. Townsend in 1928.<ref name=AIP>Template:Cite web</ref>

Van de Graaff was the inventor of the Van de Graaff generator, a device that produces high voltages. In 1929, he developed his first such generator, producing 80,000 volts. By 1933, he had constructed a larger generator generating 7 million volts, working together with his doctoral student John Trump. Van de Graaf was granted his first patent in 1935.<ref>Template:Cite news</ref>

In 1929, Van de Graaff became a National Research Fellow at Princeton University. In 1931, he became a Research Associate at the Massachusetts Institute of Technology. In 1934, he was appointed Associate Professor of Physics, a position he held until 1960.<ref name=AIP/>

During World War II, Van de Graaff was director of the High Voltage Radiographic Project. After World War II, he co-initiated the High Voltage Engineering Corporation (HVEC) with John Trump. During the 1950s he invented the insulating-core transformer, producing high-voltage direct current. He also developed tandem generator technology.

Van de Graaff died on January 16, 1967, in Boston, Massachusetts, at the age of 65.<ref name=bnl/>

The year that he died, the progressive rock band Van der Graaf Generator was formed, named after him (notwithstanding the spelling errors). Van de Graaff crater on the far side of the Moon is named after him.

Van de Graaff generator

Template:Main Van de Graaff generators use 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 accumulates to produce an electrical potential much greater than that of the primary high voltage source. Practical limitations restrict the potential produced by large Van de Graaff generators to about 7 MV. Van de Graaff generators are used primarily as DC power supplies for linear atomic particle accelerators used for nuclear physics experiments. Tandem Van de Graaff generators are essentially two generators in series and can produce about 15 MV.

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 in the Boston Museum of Science. Demonstrations during daytimes are a popular attraction. More modern Van de Graaff generators are insulated by pressurized dielectric gas, usually freon or sulfur hexafluoride. During 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 greater 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.

Recognition

Memberships

Country	Year	Institute	Type	Template:Reference column heading
Template:Flag	1934	American Physical Society	Fellow	<ref>Template:Cite web</ref>

Awards

Country	Year	Institute	Award	Citation	Template:Reference column heading
Template:Flag	1936	Franklin Institute	Elliott Cresson Medal	"High voltage electrostatic generator"	<ref>Template:Cite web</ref>
Template:Flag	1947	Institute of Physics	Duddell Medal and Prize		<ref>Template:Cite web</ref>
Template:Flag	1966	American Physical Society	Tom W. Bonner Prize	"For his contributions to and continued development of the electrostatic accelerator"	<ref>Template:Cite web</ref>

Patents

• Template:US patent – "Electrostatic Generator"
• Template:US patent – "Electrical Transmission System"
• US2922905Template:Dead link — "Apparatus For Reducing Electron Loading In Positive-Ion Accelerators"
• Template:US patent – "High Voltage Electromagnetic Apparatus Having An Insulating Magnetic Core"
• Template:US patent – "High Voltage Electromagnetic Charged-Particle Accelerator Apparatus Having An Insulating Magnetic Core"
• US3239702 — "Multi-Disk Electromagnetic Power Machinery"
• Template:US patent – "Inclined field High Voltage Vacuum Tubes"

External links

• Template:Commons category-inline
• Template:MathGenealogy
• Template:Find a Grave