Robert Jemison Van de Graaff (December 20, 1901 – January 16, 1967) was an American physicist and inventor. He is best known for developing the Van de Graaff generator, a high-voltage electrostatic machine that became a fundamental tool in nuclear physics research.
Raised in Tuscaloosa, Alabama, Van de Graaff earned his DPhil degree at Oxford as a Rhodes Scholar. In Europe, lectures by Marie Curie and Ernest Rutherford encouraged him to develop methods for accelerating particles to nuclear energies. He built his first electrostatic generator at Princeton University in 1929 and demonstrated a 1.5-million-volt model in 1931, more than twice the highest direct current voltage previously achieved. After joining the Massachusetts Institute of Technology he constructed the 5-megavolt Round Hill generator. He collaborated with John G. Trump, his former student, on creating compact, gas-insulated machines, which became the first accelerators used in clinical medicine. During World War II, he directed development of high-voltage X-ray equipment for the U.S. Navy.
A high school football injury, aggravated by wartime overwork and later accidents, left Van de Graaff with chronic health problems in his later career. Nevertheless, in 1946 he joined Trump and Denis M. Robinson in organizing the High Voltage Engineering Corporation (HVEC), the first company to manufacture particle accelerators. As Chief Scientist, he guided development of commercial accelerators. In the 1950s, he invented the insulating-core transformer and was instrumental in commercializing HVEC's tandem accelerators. By 1967, more than 500 high-voltage Van de Graaff generators were operating worldwide, and HVEC had installed accelerators in hospitals and labs in 30 countries. He received the Tom W. Bonner Prize in 1966 for his contributions to electrostatic accelerator development.
Robert Jemison Van de Graaff was born on December 20, 1901, at the Jemison–Van de Graaff Mansion in Tuscaloosa, Alabama, the youngest of four sons of Minnie Cherokee (née Jemison) and Adrian Sebastian Van de Graaff. The family had deep roots in Alabama: his great-grandfather was Robert Jemison Jr., a slaveholder planter and former state senator, and his father, a circuit judge, had been a substitute on Yale's first 11-man football team. The elder Van de Graaff became a professor of law at the University of Alabama in 1891.
Van de Graaff's three older brothers—Adrian, Hargrove, and William—became celebrated football players for the Alabama Crimson Tide, and William became Alabama's first All-American player in 1915. Robert intended to follow them: as a sophomore at Tuscaloosa High School, he played quarterback on the team coached by his brother Adrian. However, in the fall of 1917, during his senior year, he suffered a severe injury while playing, breaking his femur and severely injuring his back. He spent the rest of his senior year recuperating in the mansion, reading books about engines to pass the time, and never graduated from high school.
Despite his injuries, Van de Graaff enrolled at the University of Alabama in the fall of 1918, remaining on crutches for much of his freshman year. He joined the "Scrubs" (reserve team), coached by his brothers Adrian and Hargrove after their return from World War I, and played left end in games against Georgia Tech and Mississippi A&M. But he came to realize he would not match his brothers' athletic achievements. Years later, he recalled that a young woman asked how football was going, he replied, "It's not my game." She asked, "Well, Robert, what is your game?" He later recounted this as a life-changing moment that redirected him toward science.
In February 1921, Van de Graaff petitioned with eleven other students to become charter members of the University of Alabama's Theta Tau engineering fraternity. He became studious and made the honor roll for the first time. His lifelong nickname, "Tee," derived from his habit of drinking tea to stay alert while studying all night before exams. During summers, he worked on steamboats navigating the Black Warrior River, cultivating an interest in engines.
Van de Graaff received a Bachelor of Science (1922) and a Master of Science (1923) in Mechanical Engineering from the University of Alabama. For his master's degree thesis, he developed an improved system for mining lower grades of iron ore, in which ore moved on a conveyor belt and the more ferromagnetic components were extracted by a high magnetic field at a sharp metallic tip—a concept that anticipated aspects of his later inventions. After graduation, he worked for a year at the Alabama Power Company as a research assistant, where he observed that hydroelectric generators could operate with much larger gaps in their magnetic circuits than he had believed possible. This observation that would later inform his invention of the insulating core transformer.
With a grant from the state of Alabama, Van de Graaff traveled to Paris in 1924 to study at the Sorbonne. There he attended lectures by Marie Curie on radioactivity and became fascinated by the clicks of individual alpha particles detected by a Geiger counter—an experience he later cited as inspiring his life's work. At the Sorbonne, Van de Graaff realized that atomic nuclei are electrically charged, therefore electrostatic high voltages could accelerate particles over the nuclear potential barrier and into the nucleus.
In 1925, Van de Graaff won a Rhodes Scholarship to The Queen's College at the University of Oxford. At Oxford, Van de Graaff studied under J. S. E. Townsend and felt intimidated by the erudition of his colleagues, who typically spoke three languages fluently. He continued to participate in sports despite his leg injury, playing lacrosse and receiving a "blue" in rowing. He earned a second Bachelor of Science in Physics in 1926 and a Doctor of Philosophy in 1928.
While at Oxford, Van de Graaff had his first extended opportunity to discuss accelerator physics with a peer. In 1926, he shared a room for a week at Leiden University with J. Robert Oppenheimer, then also a graduate student. The two talked late into the night, Oppenheimer about theoretical aspects of proton scattering and Van de Graaff about possibilities for electrostatic accelerators.
Van de Graaff later read Ernest Rutherford's 1927 anniversary address to the Royal Society, in which Rutherford expressed his ambition "to have available... a copious supply of atoms and electrons... transcending in energy the alpha and beta particles from radioactive substances." According to Van de Graaff, this address increased his conviction that an approach to generating high voltages was needed for progress in nuclear research.
In September 1929, Van de Graaff returned to the United States as a National Research Fellow at Princeton University, expressly to develop a high-voltage source. That fall, he built a rudimentary proof-of-concept from "a tin can, a silk ribbon, and a small motor, at no expense." This simple model could sustain 80 kV, limited by discharge from the can's edges. With encouragement from Karl Compton, head of the physics department, he developed this concept further.
On March 20, 1931, after a sleepless night and many preliminary drafts, Van de Graaff wrote to Compton outlining his vision for the scientific applications of his generator. He predicted that proton bombardment of uranium might precipitate disintegration or that "the proton would be captured by the nucleus, thus opening up the possibility of creating new elements of atomic number greater than 92"—eight years before the first transuranium element was synthesized. In the same letter, he predicted the nuclear reaction that would result from proton bombardment of lithium. One year later, John Cockcroft and Ernest Walton demonstrated this reaction, for which they received the 1951 Nobel Prize in Physics.
Van de Graaff built a larger demonstration model with $100 (equivalent to $2,117 in 2025) in department funds. By November 1931, the model was producing more than 1.5 million volts—more than twice the highest direct current voltage previously achieved. He publicly demonstrated this device at the inaugural dinner of the American Institute of Physics, with Compton at his side as he "nervously explained the principles of his invention." Van de Graaff observed that, paired with a discharge tube yet to be designed, his device offered a "powerful means for the investigation of the atomic nucleus and other fundamental problems."