August 8, 1901 - Birth of Ernest Lawrence, Nobel Prize winner and inventor of the cyclotron

Ernest Orlando Lawrence graduated in chemistry from the University of South Dakota in 1922 and his master's degree in physics from the University of Minnesota in 1923. He received his PhD in physics from Yale in 1925 with his thesis on the photoelectric effect of potassium vapour.

He remained at Yale as a researcher and continued to investigate the photoelectric effect. He showed that photoelectrons appeared 2 x 10^-9 seconds after the collision of photons against the photoelectric surface, near the limiting moment of measurement. The reduction of the emission time by an interruption of the light source (with rapid switching on and off) made the spectrum of emitted energy broader, by the Heisenberg uncertainty principle.

In 1928, he was hired as an associate professor of physics at UC Berkeley in California and, two years later, became the youngest full professor.

Lawrence conceived the idea of the cyclotron in 1929. His invention began as a sketch on a piece of paper napkin while in the library, he glanced at an article written by Rolf Widerøe and was intrigued by one of his diagrams. It depicted a device with a series of electrodes of different lengths, producing high-energy particles by a succession of small ‘pulses’. One of his students, M. Stanley Livingstone, took up his idea and built a device capable of accelerating protons to an energy of 13,000 electron volts (eV). Encouraged by his student's success, Lawrence designed another cyclotron, capable of communicating to subatomic particles an energy of up to 1,200,000 eV, enough energy to cause the atomic nucleus to disintegrate.

In those years, physicists were beginning to explore the atomic nucleus. In 1919, Ernest Rutherford bombarded nitrogen atoms with alpha particles and succeeded in extracting protons from some of their nuclei. Little did they know that nuclei have a positive charge that repels other nuclei with the same electric charge, and are held together by a force that they were only beginning to understand. To separate or disintegrate them, higher energies, of the order of millions of volts, were required.

To do this, he realised that a particle accelerator would be too large and difficult to manipulate for his university laboratory. Looking for a way to build a more compact one, he decided to create a circular acceleration chamber between the poles of an electromagnet. The magnetic field would keep the charged protons in a sperila trajectory as they accelerated between two semicircular electrodes connected to an alternating potential. After a hundred or so turns, the protons could impact a target, such as a high-energy particle beam.

Over the next few years, he built a series of increasingly large and expensive cyclotrons. His Radiation Laboratory became the official laboratory of the University of California in 1936, with Lawrence as director supporting the use of the cyclotron for both physics and medical radioisotope research. In one of his cyclotrons, he succeeded for the first time in isolating technetium, the first non-naturally occurring element obtained artificially. With the cyclotron he also obtained radioactive phosphorus and other isotopes for medical use; he also discovered the usefulness of neutron beams in the treatment of cancerous diseases.

In 1939 he received the Nobel Prize in Physics for his research.

During World War II he developed electromagnetic isotope separation in his laboratory using a device known as a calutron, a hybrid between a standard mass spectrometer and the cyclotron. This led to the construction of a huge electromagnetic separation plant at Oak Ridge, which became known as ‘Y-12’. His process was inefficient, but it worked.

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