Ernest Lawrence(1901 — 1958)
Ernest Orlando Lawrence
États-Unis
8 min read
American physicist (1901–1958), inventor of the cyclotron, the first circular particle accelerator. Winner of the 1939 Nobel Prize in Physics, he paved the way for modern nuclear physics and contributed to the Manhattan Project.
Frequently asked questions
Key Facts
- 1929: invention of the cyclotron principle
- 1930: construction of the first cyclotron at the University of California, Berkeley
- 1939: Nobel Prize in Physics for the invention and development of the cyclotron
- 1941–1945: participation in the Manhattan Project for the separation of uranium-235
- 1952: founding of the Lawrence Livermore National Laboratory
Works & Achievements
A revolutionary invention that made it possible to accelerate charged particles to unprecedented energies without resorting to dangerous electrical voltages. The cyclotron paved the way for all of modern experimental nuclear physics.
An improved version capable of accelerating protons to 4.8 million electron volts. This device was used to produce the first artificial radioisotopes at Berkeley and demonstrated the power of the design.
A machine capable of accelerating deuterons to 20 million electron volts, it enabled major advances in nuclear physics and the production of medical radioisotopes, including for the first therapies against leukemia.
Lawrence established this university laboratory, which became a worldwide model for "Big Science": a mode of research that mobilizes large teams, heavy infrastructure, and massive funding — a sharp departure from the small-scale physics of the nineteenth century.
Lawrence adapted the principle of the cyclotron to create large-scale isotope separators for producing the uranium-235 needed for the atomic bomb. The Y-12 plant at Oak Ridge housed hundreds of calutrons operating simultaneously.
A national laboratory co-founded by Lawrence during the Cold War to develop the American hydrogen bomb. It remains to this day one of the most important nuclear physics research centers in the world.
Anecdotes
In 1929, Lawrence stumbled upon an article by Norwegian physicist Rolf Wideröe on the acceleration of charged particles. Unable to read German, he focused on the diagrams and mathematical formulas, and intuitively understood how to make particles travel in circles to accelerate them indefinitely. From this improvised reading, the idea of the cyclotron was born.
His first cyclotron, built in 1930 at Berkeley, fit in the palm of a hand: it measured barely 10 centimeters in diameter and was largely assembled from salvaged materials, including copper wire and glass plates. Despite its rudimentary appearance, it accelerated protons to 80,000 electron volts, proving the concept worked.
Lawrence received the Nobel Prize in Physics in December 1939, just as World War II had broken out in Europe. The ceremony in Stockholm was one of the last to be held normally for years to come. Lawrence, only 38 years old at the time, was the youngest Nobel laureate in physics in decades.
During the Manhattan Project, Lawrence developed “calutrons,” giant electromagnetic separators derived from the cyclotron, to isolate uranium-235 from uranium-238. Thousands of young women from the Oak Ridge area operated these machines without knowing they were helping build an atomic bomb.
Ernest’s brother, John Lawrence, a physician, used the Berkeley cyclotron to produce radioisotopes and treat leukemia patients as early as 1937. Their mother was among the first patients treated with these new techniques. This collaboration between fundamental physics and medicine ushered in the era of nuclear medicine.
Primary Sources
By applying an oscillating potential difference between two D-shaped electrodes placed within a magnetic field, it is possible to accelerate ions along successive circular trajectories, reaching very high energies without resorting to dangerous voltages.
The cyclotron, in its design, rests on the principle of magnetic resonance: the frequency of rotation of an ion in a uniform magnetic field is independent of its velocity, which allows cumulative acceleration through synchronized electrical impulses.
I am convinced that if we concentrate our efforts on electromagnetic separation, we can obtain sufficient quantities of uranium-235 within the timescales required by the program.
The 60-inch cyclotron made it possible to accelerate heavy nuclei to energies sufficient to induce a variety of artificial nuclear reactions, opening new prospects in experimental nuclear physics.
Key Places
Ernest Lawrence's birthplace, born on August 8, 1901. The son of a school superintendent, he grew up in the American Midwest in a modest but intellectually stimulating environment.
The site of Lawrence's entire scientific career from 1928 onward. It was here that he conceived, built, and refined the cyclotron, and where he founded the Radiation Laboratory (today known as Lawrence Berkeley National Laboratory).
The secret Manhattan Project site where Lawrence oversaw the installation of calutrons at the Y-12 plant. Thousands of workers there carried out the separation of fissile uranium, unaware of the true nature of their mission.
The city where Ernest Lawrence received his Nobel Prize in Physics on December 11, 1939, in the midst of World War II. The ceremony marked international recognition of the cyclotron's importance to modern physics.
The city where Lawrence co-founded the Lawrence Livermore National Laboratory in 1952, dedicated to thermonuclear weapons research during the Cold War. The laboratory still bears his name today.
