Ernest Lawrence, Nobel Prize winner and inventor of the cyclotron

8 August 1901, in Canton (USA) - 27 August 1958, in Palo Alto (California, USA)

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, under the supervision of William Francis Gray Swan, who encouraged him to obtain his PhD in physics from Yale in 1925 with his thesis on the photoelectric effect of potassium vapour.

On Swann's recommendation, he received a grant from the US National Research Council, and instead of using it for a trip to Europe, as was the custom at the time, he decided to stay at Yale as a researcher with Swann.

With the assistance of Jesse Wakefield Beams, Lawrence continued to investigate the photoelectric effect. They 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 on/off switching) made the spectrum of emitted energy broader, by the Heisenberg uncertainty principle.

In 1928, he was hired as an associate professor of physics at the University of California at Berkeley 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 realised the usefulness of neutron beams in the treatment of cancerous diseases.

In 1932, while at Yale, he married Mary Kimberly ‘Molly’ Blumer, with whom he had six children, one of whom he named after his best friend at Berkeley, Robert Oppenheimer.

Interestingly, in 1941, Molly's sister married Edwin Mattison McMillan, who would go on to win the Nobel Prize in Chemistry in 1951. A few years earlier, in 1933, McMillan had accepted an offer from Lawrence to join the Radiation Laboratory. Together with M. Stanley Livingston, discovered O-15, an isotope of oxygen that emits positrons, and investigated the absorption of gamma rays produced by bombarding fluorine with protons.

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.

After the war, he campaigned for government sponsorship of major scientific programmes and was an advocate of ‘Big Science’, which requires large machinery and heavy investment. It was at this stage that he founded Livermore Laboratory.

After he died in 1958, the Chancellors of the University of California renamed his Radiation Laboratories at Livermore and Berkeley as Lawrence National Laboratory at both locations as a tribute to this great scientist.

In addition to the Nobel Prize, he received a multitude of awards and medals and the chemical element number 103 on the periodic table was named ‘lawrentium’ in his honour.