Lawrence and the Cyclotron: the Birth of Big Science

An official announcement from the International Union of Pure and Applied Chemistry that came out on December 30, 2015 still has scientists buzzing with excitement. The seventh row of the periodic table is officially complete, thanks to the addition of elements 113, 115, 117, and 118 (with temporary names ununtritium, ununpentium, ununseptium, and ununoctium respectively). It took many experiments using various particle accelerators from several different countries, but all that work has finally paid off. But what did that work entail? Since uranium is the last naturally occurring element, all the ones after it are man-made. Synthesizing these elements requires smashing one atom into another and monitoring the fission products. The trick to creating a synthetic element is giving the collision enough energy. Today, we have many advanced accelerators of all shapes and sizes to help achieve this — including the one used in a recent PLOS ONE study — and it all started with a man named Ernest Orlando Lawrence.

Lawrence and the Radiation Laboratory

On the eastern shore of the San Francisco Bay is a city known for its food, activism, and science, Berkeley, California. In fact, the University of California, Berkeley (UC Berkeley) has produced so many Nobel Laureates that they have reserved parking on campus. UC Berkeley claims 22 Nobel Prize winning faculty and 29 Nobel Prize winning alumni. UC Berkeley’s first laureate was Lawrence, the inventor of the cyclotron.

In 1928, Lawrence, a South Dakota native with a PhD from Yale University, was hired as an assistant professor of physics at UC Berkeley. He entered a world where physics, chemistry, and engineering departments were completely separate and their members never mixed. But one day, he scrawled an idea on a napkin that would change history. This idea would not only pave the way for elemental discovery, it would bring about multidisciplinary collaboration and what Lawrence called “big science,” a term that he would use to describe projects like the Large Hadron Collider and the Laser Interferometer Gravitational-wave Observatory.

His idea was all about how to provide energy to a particle without the use of high voltages. In those days, to accelerate a particle, you needed a linear accelerator. However, linear accelerators require high voltages because the electric field can only transfer energy to the particle once. This limits the acceleration that can be achieved in a linear configuration. Lawrence realized that using a circular accelerator could solve this problem. The same electric field could be used to accelerate particles more than once. Lawrence came up with a device that he called the “proton-merry-go-round” (Ernest Lawrence’s Cyclotron) at the time.

The cyclotron

Lawrence’s idea was simple (relatively speaking). He used powerful magnets to create a perpendicular magnetic field that would drive particles in a circular path. He contained the particles in two metal dees, which are two pieces of metal fashioned as if to enclose a disc. The dees, however, were separated by a crucial gap. When the dees were polarized by an RF current, they provided the particle with energy every time it crossed the gap. This would cause the circular path to become an outward spiraling path, the particle accelerating along the way. Eventually, the particle would slam into its target and various nuclear processes could occur. His first device was made of “wire and sealing wax and probably cost $25 in all.” (About: Lawrence Hall of Science.) His next model, which was the first functional device, is on display at the Lawrence Hall of Science in Berkeley. The device would become known as the cyclotron.

Every time Lawrence created a functional cyclotron, he immediately set his sights on a bigger cyclotron. However, to begin upscaling his bench-sized devices, he would need help from engineers. He befriended an electrical engineer at UC Berkeley named Leonard Fuller, who would provide him with the magnets he needed. He also befriended Gilbert Lewis. Lewis was to the UC Berkeley chemistry department what Lawrence was to the physics department, except that Lewis never received the Nobel Prize. (According to Coffey, this is because Lewis didn’t play nice with others, specifically the Nobel committee.) Lewis also discovered deuterons, a crucial particle in the cyclotron’s discoveries. With the help of Fuller and Lewis, Lawrence was able to build a 27-inch cyclotron. This device was so large that it no longer fit in the lab. Lawrence founded the Radiation Laboratory in another building in order to house his cyclotrons. Latimer Hall stands today where the “Rad Lab” once stood.

Nuclear science is born

With the Rad Lab operational, Lawrence and “[his] boys” (Ernest Lawrence Exhibit) quickly set about making discoveries. The 27-inch cyclotron was redesigned as a 37-inch cyclotron. This 37-inch device provided the first artificial element: technetium. It was also a key part of the Manhattan Project; the Rad Lab was able to separate uranium-235 magnetically, thus paving the way for the bomb dropped on Hiroshima. The 37-inch cyclotron can still be seen in front of the Lawrence Hall of Science.

Of course, 37 inches still wasn’t big enough for Lawrence. He helped his brother create a 60-inch cyclotron that would go on to discover carbon-14 and synthesize neptunium and plutonium. His masterpiece, though, was the 184-inch cyclotron he built after receiving the Nobel Prize. Unsurprisingly, this device would require an even larger facility. A building with a distinctive dome roof was built on the hill above campus to house it. Another wrinkle was that speeds would approach the limit where special relativity must be taken into account. The device had to be converted to a synchrocyclotron. The two major modifications were to vary the RF frequency and replace one dee with an open version of the dee (see figure 1 for a reminder of what a dee looks like). This scientific behemoth’s contribution to physics was artificial mesons, but Lawrence’s brother John also used it to make significant medical advancements. In 1958, Ernest Lawrence passed away, leaving a tremendous legacy behind.

On the shoulders of a giant

While the 184-inch cyclotron no longer exists, the distinctive dome roof still marks the ridge where it once stood. The Berkeley Radiation Laboratory became the Ernest Orlando Lawrence Berkeley National Laboratory and the cyclotron was replaced with a synchrotron light source that is still in use today.

Further up the hill, the Lawrence Hall of Science entertains families with its exhibits and influences students across the country with its curriculum development. On the other side of the ridges, the Lawrence Livermore National Laboratory pursues fusion. These institutions stand as a testament to Lawrence’s scientific achievements. More importantly, he led the way for a new paradigm of science, one where multidisciplinary teams would come together to build colossal experiments in search of the universe’s well-kept secrets.

References

Coffey, P. (2008) Cathedrals of Science: The Personalities and Rivalries That Made Modern Chemistry. Oxford University Press.

Ernest Lawrence Exhibit (n.d.) Lawrence Hall of Science

Hiltzik, M. (2015). Big Science: Ernest Lawrence and the Invention That Launched the Military-Industrial Complex. Simon & Schuster.

Lawrence Berkeley National Laboratory (n.d.) Berkeley Lab History: 75 Years of World Class Science.

Lawrence Berkeley National Laboratory (1993) Bright Beams: The Advanced Light Source.

Lawrence Hall of Science (2016) About: Lawrence Hall of Science, popup History.

Nafee SS, Shaheen SA, Al-Ramady AM (2016) Nuclear Data Evaluation for Mass Chain A=217:Odd-Proton Nuclei. PLoS ONE 11(1): e0146182. doi:10.1371/journal.pone.0146182

Wikipedia (2016) Cyclotron.

Wikipedia (2016) Ernest Lawrence.

Wikipedia (2016) Synchrocyclotron.

Yarris, L. (n.d.) Ernest Lawrence’s Cyclotron: Invention for the Ages.

Yarris, L. (2001) Ernest Orlando Lawrence – The Man, His Lab, His Legacy.