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Cyclotron Invented - History

Cyclotron Invented - History

The Cyclotron, otherwise known as the atom smasher, was invented by Ernest Lawrence, an American physicist at the University of California at Berkely. The particle accelerator, as it was also known, allowed advanced research in the areas of biology and physics. In 1939, Lawrence received the Nobel Prize for Physics for his work.


The University of Chicago was one of the first universities to have an academically installed cyclotron (1968). That machine, pictured above, and the program it supported enjoyed a long and storied history in radiochemistry and instrumentation. Investigators such as Katherine Lathrop, Paul Harper, Robert (Bob) Beck, and others provided a rich palette of research interests. Most history of the early days of the Department of Radiology at the University of Chicago can be found at this link.

Katherine Lathrop, a member of the Manhattan Project, was a key member of the University of Chicago team that introduced 99m Tc into clinical practice in the early 1960s as a radiotracer agent in nuclear medicine. This radioactive substance is now used tens of thousands of times a day in the United States and tens of millions of times a year worldwide in nuclear medicine scans designed to identify tumors or abnormal metabolism. Harper and Lathrop also developed the commercial method for producing 125 I, another commonly used diagnostic radionuclide. She passed away in 2005.

The CS-15 cyclotron was installed in 1968 and ran for 30 years. It was housed inside a vault in the sub-basement of the Frank McLean Institute. Radiochemistry was done on the floor above where there was a PET scanner. The CS-15 was decommissioned in 1997 due to changes in the DOE’s sponsored research focus. Renewed interest in early 2000’s to start a radiochemistry program around a new, state-of-the-art cyclotron.

For images of the new Cyclotron, view the Gallery . To see how the Cyclotron was moved into it’s vault, view Insertion of the Cyclotron video.

Robert R. Wilson, a physics professor at Harvard and designer of Harvard’s cyclotron, was the first to propose using protons to treat cancer.

Robert R. Wilson was an American physicist known for his work on the Manhattan Project during World War II. He was a member of the team that developed the atomic bomb and later headed an immense group of physicists that conceived, designed, built, and operated the Fermi National Accelerator Laboratory (Fermilab) outside of Chicago.

Although Wilson was a dedicated scientist, he was also a committed advocate of human rights and championed the peaceful use of atomic energy he helped to unleash. The Oklahoma Proton Center is an example of that peaceful use.

Robert Wilson’s contribution to proton therapy was made manifest in a paper he published in 1946. Titled “Radiological Use of Fast Protons” (Radiology 1946:47:487-91), the article established the fundamentals and techniques still used today at the Oklahoma Proton Center and proton therapy centers worldwide.

Robert Rathbun Wilson (March 4, 1914 – January 16, 2000)

Berkeley Radiation Laboratory conducted extensive studies on protons and confirmed Wilson’s predictions. In 1954 they treated the first patient with protons. Researchers began to recognize the full potential of isolating protons to treat medical conditions. Advanced understanding of particle acceleration, proton beams, and their radiation treatment application has shown improved outcomes for patients diagnosed with many forms of cancer. Wilson is said to be “the father of proton therapy” for all of his research and efforts to advance proton therapy.

Lawrence’s 60-inch cyclotron, with magnet poles 60 inches in diameter, at the University of California Lawrence Radiation Laboratory (1939) the most powerful accelerator in the world at the time. Image of a modern-day cyclotron at the Oklahoma Proton Center used to accelerate protons to more than two-thirds the speed of light and utilized in the treatment of human cancers.

Cyclotron Invented - History

Lawrence invents the cyclotron

Photo: Four-inch copper-encased cyclotron, one of Ernest Lawrence's ealiest models

When Ernest Orlando Lawrence (1901-1958) got his PhD in physics, the hottest topic was bombarding the atom's nucleus to see what new particles it might produce. Ernest Rutherford had only recently shown that striking the atom of one element could make it emit electrons and turn into a different element.

Lawrence joined the physics faculty of the University of California (Berkeley) in 1928 and got intrigued with this new physics. So far, people had used alpha particles (the product of natural radioactivity) and protons (hydrogen atoms, containing a positive charge of 1) to bombard other atoms. But they had about exhausted that field of research. To learn more, they needed an artificial way to accelerate these particles to greater energy. Several accelerators were invented to give the bombarding particle a huge "kick" of electric potential. But it seemed that you'd need a kick of about 1 million volts to get the required acceleration, and making a machine to withstand that power was nearly impossible.

Around this time, Lawrence happened to read a German paper describing a linear accelerator that boosted a particle's energy in steps using alternating electric fields. This did increase the particle's speed but to really get it up to the desired energy, the accelerator would have had to be impractically long. Lawrence knew that a magnetic field would deflect the charged particles into a curved path. By making the particles go in a spiral, he could boost their energy bit by bit each time they circled an electrode. The circular machine could fit in one room. The particles would spiral outward as they gained more energy, and when they were moving fast enough, they'd shoot out of the device with amazing force into a collector.

The university gave Lawrence the go-ahead to build what he called the cyclotron in 1930. With some graduate students, he tried a number of different set-ups. They had success using electrodes, a radio frequency oscillator producing 10 watts, a vacuum, hydrogen ions, and a 10 cm electromagnet. The whole contraption was quite small. With a larger magnet, Lawrence's team was able to produce 80,000 electron volts in 1931, and later the same year, with a 25 cm cyclotron, 1 million electron volts. Cyclotrons got successively larger, with new and different capacities. A 69 cm cyclotron could accelerate ions containing both protons and neutrons. With this, researchers produced artificial radioisotopes like technicium and carbon-14 used in medicine and tracer research. In 1939, a 152 cm device was being used for medical purposes, and Lawrence won the Nobel Prize in physics. Work was begun on a 467 cm machine in 1940, but World War II interrupted its development. Lawrence's team turned its attention to producing the uranium-235 needed for the atomic bomb.

The development of the cyclotron and the growth of Lawrence's Radiation Laboratory had tremendous implications for science and the way it's done. This new tool could probe the atom's nucleus and offered applications in medicine and chemical research. It launched the modern era of high-energy physics. But it also launched the era of "big science"-- a new way of organizing scientific work. To feed and care for these increasingly large, complex, and expensive tools required more staff and above all, more money. Governments and corporations saw they had a stake in such research and stepped in as funders.

Ernest Lawrence died in 1958. In 1961, element 103 was discovered and named "lawrencium" in his honor.

Cyclotron Invented - History

J ohn D. Cockcroft and Ernest Walton at the Cavendish Laboratory in Cambridge, England, sought a way into the nucleus through a prediction of quantum mechanics. George Gamow had suggested that a particle with too little energy to overcome the electrical repulsion of the nucleus through the barrier. (The trick was that the energy of the particle was not actually well-defined, according to Heisenberg's Uncertainty Principle). In 1930 Cockcroft and Walton used a 200-kilovolt transformer to accelerate protons down a straight discharge tube, but they concluded that Gamow's tunnelling did not work and decided to seek higher energies.

To penetrate the nucleus, Cockcroft and Walton built a voltage multiplier that used an intricate stack of capacitors connected by rectifying diodes as switches. By opening and closing switches in proper sequence they could build up a potential of 800 kilovolts from a transformer of 200 kilovolts. They used the potential to accelerate protons down an evacuated tube eight feet long. In 1932 they put a lithium target at the end of the tube and found that protons disintegrated a lithium nucleus into two alpha particles. A Soviet team in Kharkov found the same result several months later.

Robert Van de Graaff.

Cockcroft-Walton accelerator.

Scientists working on a
Van de Graaff generator.

The Van de Graaff Generator

R obert Van de Graaff worked as an engineer for the Alabama Power Company before obtaining his Ph.D. in physics at Oxford. While a postdoctoral fellow at Princeton he conceived a device to build up a high voltage using simple principles of electrostatics. A belt of insulating material carries electricity from a point source to a large insulated spherical conductor. Another belt likewise delivers electricity of the opposite charge to another sphere. The spheres build up a potential until the electric field breaks down the air and a huge spark "arcs" across. By 1931 Van de Graaff could charge a sphere to 750 kilovolts, giving 1.5 megavolts differences between two oppositely charged spheres.

By increasing the radius of the spheres, Van de Graaff could reach higher voltages without arcing. The maximum voltage in theory, in megavolts, roughly equalled the radius of the sphere in feet. He was soon planning a pair of spheres 15 feet across.

Lawrence's notes on Wideröe's paper.

The Linear Accelerator

T he difficulties of maintaining high voltages led several physicists to propose accelerating particles by using a lower voltage more than once. Lawrence learned of one such scheme in the spring of 1929, while browsing through an issue of Archiv für Elektrotechnik, a German journal for electrical engineers. Lawrence read German only with great difficulty, but he was rewarded for his diligence: he found an article by a Norwegian engineer, Rolf Wideröe, the title of which he could translate as "On a new principle for the production of higher voltages." The diagrams explained the principle and Lawrence skipped the text.

Right: Rolf Wideröe's diagrams describing a method for accelerating ions inspired Ernest Lawrence's invention of the cyclotron.

Particles with a positive electric charge are drawn into the first cylindrical electrode by a negative potential by the time they emerge from the tube the potential has switched to positive, which propels them away from the electrode with a second boost. Adding gaps and electrodes can extend the scheme to higher energies.

The Cyclotron

T he linear accelerator proved useful for heavy ions like mercury, but lighter projectiles (such as alpha particles) required a vacuum tube many meters long. Lawrence judged that impractical. Instead he thought of bending the particles into a circular path, using a magnetic field, in order to send them through the same electrode repeatedly.

A few quick calculations showed that such a device might capitalize on the laws of electrodynamics. The centripetal acceleration of a charged particle in a perpendicular magnetic field B is evB/c, where e is the charge, v the particle's velocity, and c the velocity of light. The mechanical centrifugal force on the particle is mv 2 /r, where m is the mass and r the radius of its orbit. Balancing the two forces for a stable orbit yields what is now known as the cyclotron equation: v/r = eB/mc.

Lawrence was surprised to find that the frequency of rotation of a particle is independent of the radius of the orbit: f = v/2 r = eB/2mc, with r disappearing from the equation. The circular method would thus allow an electric field alternating at a constant frequency to kick particles to ever higher energies. As their velocities increased so did the radius of their orbit. Each rotation would take the same amount of time, keeping the particles in step with the alternating field as they spiralled outward.

A n electric field with a frequency of about four million cycles per second lay in the realm of short radio waves. Lawrence's experience with these waves would come in handy, and recent advances in high-power vacuum-tube oscillators would be indispensable. Combined with a reasonable magnetic field, a potential on the electrodes of only ten thousand volts could accelerate an alpha particle to one million electron volts. Bigger magnets promised higher energies. In theory, the scheme offered the long-sought route to study the nucleus. Lawrence pressed students and professors to confirm his calculations and sketched out a device.

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 &mdash including the one used in a recent PLOS ONE study &mdash 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&rsquos first laureate was Lawrence, the inventor of the cyclotron.

Figure 1. Diagram of a cyclotron. Picture obtained through Wikimedia Commons. Picture is in the public domain. Author unknown.

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 &ldquobig science,&rdquo 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 &ldquoproton-merry-go-round&rdquo (Ernest Lawrence&rsquos Cyclotron) at the time.

The cyclotron

Figure 2. The prototype cyclotrons built by Lawrence. On display at the Lawrence Hall of Science. Picture by Deb McCaffrey.

Lawrence&rsquos 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 &ldquowire and sealing wax and probably cost $25 in all.&rdquo (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&rsquot play nice with others, specifically the Nobel committee.) Lewis also discovered deuterons, a crucial particle in the cyclotron&rsquos 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 &ldquoRad Lab&rdquo once stood.

Figure 3. The 37inch cyclotron on display at the Lawrence Hall of Science. Photo by Deb McCaffrey.

Nuclear science is born

With the Rad Lab operational, Lawrence and &ldquo[his] boys&rdquo (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&rsquot 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&rsquos contribution to physics was artificial mesons, but Lawrence&rsquos brother John also used it to make significant medical advancements. In 1958, Ernest Lawrence passed away, leaving a tremendous legacy behind.

Figure 4. A view of the Advanced Light Source from the Doe Library patio. Photo by Deb McCaffrey.

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&rsquos 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&rsquos well-kept secrets.

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 (1993) Bright Beams: The Advanced Light Source.

Linear Accelerators


“Installation of the first clinical linear accelerator began in June 1952 in the Medical Research Council (MRC) Radiotherapeutic Research Unit at the Hammersmith Hospital, London. It was handed over for physics and other testing in February 1953 and began to treat patients on 7 September that year.”

“Today – Thousands of Medical linear accelerators are used in hospitals around the world and have been effective in treating millions of cancer patients. Researchers continue to further improve the effectiveness of medical linear accelerators in the fight against cancer.”


1931—A Close Second: The First Cyclotron

1937 – First clinical Van de Graaff generator treatment at Harvard Medical School.
1932-1940—The Decade of the Cyclotron
1940—The Betatron
1945—New Ideas: Synchronous Acceleration Leads to the Microtron
1947—More Synchronicity: The Electron Synchrotron

1947 – First linear accelerator built at Stanford by William Hansen and the Varian brothers.
1952—Even Higher Energies: The Proton Synchrotron
1952—A Strong Leap Ahead: Focusing the Beam
1953—Synchrotrons Become Stronger

1953 – Patient treated with the first medical linear accelerator at Hammersmith Hospital in London.

1953 – Dr. Henry Kaplan and physicist Edward Ginzton developed the first medical linear accelerator in the Western hemisphere. The 6MV unit was installed at Stanford-Lane Hospital in San Francisco.
1946-1954—The Linac Grows Up: An Electron and Proton Linac

1960 – Varian Clinac ®6/100 introduced, the first fully rotational radiotherapy linear accelerator.
1966—Stanford Gets Serious About the Linac: SLAC
1960—The Storage Ring Collider
1969—CERN Enters the Collider Age
1970—Germany Joins the Collider Age
1981—The First Proton-Antiproton Colliders: CERN and FNAL

1981 – Introduction of the Varian Clinac® 2500, the first dual energy medical linear accelerator.

1985 – Philips introduces the SL25®, the first fully digitally controlled medical linear accelerator.

1988 – Varian introduces the Varian Clinac ® 2100C, Varian’s first computer controlled accelerator.

1997 – Stanford continues its research, using intensity-modulated radiation therapy, which combines imaging with linear accelerators that deliver hundreds of thin beams of radiation from any angle.

2004 – Four-dimensional radiotherapy is implemented, which accounts for the motion of breathing during imaging and radiation therapy.


In 1958, Karl Brown was the first to use matrix algebra to calculate magnetic-optical aberrations in charged particle spectrometers, used by physicists for the precise analysis of nuclear and subnuclear structure. He developed a computer code called TRANSPORT to facilitate the equipment design process

Henry Kaplan and Ed Ginzton, PhD, professor of electrical engineering and of physics, developed the first medical linear accelerator in the Western Hemisphere, installed at Stanford-Lane Hospital in San Francisco.

1972 – Dr. Peter Fessenden arrives at Stanford and begins to develop a linear accelerator that combats tumor cells using two types of radiation. Working with Varian Medical Systems, Inc., Dr. Fessenden’s team creates the first linear accelerator that combined both X-ray and electron treatment.

Ernest Lawrence and the Invention of the Cyclotron

On August 8 , 1901 , pioneering American nuclear scientist Ernest Orlando Lawrence was born. He was awarded the 1939 Nobel Prize in Physics for his invention of the cyclotron . He is also known for his work on uranium-isotope separation for the Manhattan Project , and for founding the Lawrence Berkeley Laboratory and the Lawrence Livermore Laboratory .

“I am mindful that scientific achievement is rooted in the past, is cultivated to full stature by many contemporaries and flourishes only in favorable environment. No individual is alone responsible for a single stepping stone along the path of progress, and where the path is smooth progress is most rapid. In my own work this has been particularly true.”
— Ernest Orlando Lawrence, Nobel Prize banquet speech (29 Feb 1940)

Growing Up in South Dakota

Ernest Lawrence grew up in South Dakota . His parents were offsprings of Norwegian immigrants and taught at the high school in Canton, South Dakota . His mother, Gunda, remembered his enormous curiosity when he was still a child. Apparently, the two-year-old Lawrence managed to light a fire with matches and burn down all of his clothes. His mother further remembered that “ Ernest was always of a happy disposition and life to him seemed to be one thrill after another, but he was also always persistent and insistent!“. With his high school friends, Lawrence built a very early short-wave radio transmitting station and later applied his experiences to the acceleration of protons [1,2].

Academic Career

Lawrence enrolled at the University of South Dakota and sold kitchenware to farming households in order to finance his education. This training was later helpful, when Lawrence had to sell scientific projects to government officials and funding agencies. After earning his Bachelor degree , the young physicist enrolled at the University of Minnesota in order to finish his master studies and he moved to Yale , where Lawrence received his Ph.D . in 1925 . Before even turning 27 years old, Lawrence accepted an associate professor position at Berkeley , where he became the institution’s youngest full professor three years later [1]. In 1936 he became Director of the University’s Radiation Laboratory as well, remaining in these posts until his death [3].

The Cyclotron

It is assumed that while reading a scientific paper by Rolf Widerøe about a device that produced high-energy particles, he was inspired to work on a more compact accelerator that would fit into the Berkeley laboratories . After initial work on the ionization potential of metal vapors, Lawrence invented the cyclotron in 1929. The very first cyclotron he constructed was apparently only 10cm in diameter and consisted of brass, wire, and sealing wax.In this period, Lawrence and his research group built a bigger machine, which he used to bombard various elements with accelerated particles. In rare cases, completely new elements and hundreds of previously unknown radioactive isotopes of known elements were generated by the particle bombardment. He applied for patent protection for his invention in the USA on January 26, 1932, which was granted to him on February 20, 1934.

Diagram of cyclotron operation from Lawrence’s 1934 patent

Radioactive Isotopes and Cancer Therapy

He was invited to the 1933 Solvay Conference to give a presentation on the cyclotron and Lawrence extended the apparatus to a 37-inch cyclotron in June 1937 . Two years later, it was used for the first time to bombard iron and produce its first radioactive isotopes . With a more powerful cyclotron he was able to produce the mesons known from cosmic radiation for the first time in 1941, later he extended his studies to antiparticles. In the same year, the first cancer patient received neutron therapy from the cyclotron .

The Nobel Prize in Physics

Ernest Lawrence was awarded the Nobel Prize in physics in 1939 and was the first at Berkeley to become a Nobel Laureate. The scientists was also known as an incredibly prolific writer. Most of his work was published in The Physical Review and the Proceedings of the National Academy of Sciences. He was decorated with numerous awards and prizes including Medal for Merit and he held honorary doctorates of thirteen American and one British University, the University of Glasgow [3].

Later Life

Lawrence was instrumental in the development of the atomic bomb during the Second World War, after the war he campaigned for a nuclear test ban and was a member of the US delegation to the 1958 Geneva conference on the subject. After the war, Lawrence campaigned extensively for government sponsorship of large scientific programs.. The 103rd element of the chemical periodic table, Lawrencium (Lr), was named after him.

Ernest Orlando Lawrence passed away on August 27 , 1958 at age 57.

At yovisto academic video search, you may be interested in a video lecture on Particle Accelerators at Berkeley University by Professor Norman.

Cyclotron Invented - History

This entry contributed by Dana Romero

A device invented by E. O. Lawrence and M. S. Livingston at Berkeley in 1931 that is used to accelerate charged particles by means of a magnetic field. A particle of mass m and charge q moving with a velocity v will interact with a magnetic field of strength B whose direction is perpendicular to the plane of its travel with force

The force of the magnetic field is perpendicular to the particle's direction, resulting in a circular path inside the cyclotron. Equating F with a centripetal force gives

gives the charge-to-mass ratio of the particle in terms of known values for v, B, and R.

Particles in cyclotrons emit radiation called cyclotron radiation.

Livingston, M. S. High-Energy Accelerators. New York: Interscience Publishers, 1954.

Livingston, M. S. and Blewett, J. P. Particle Accelerators. New York: McGraw-Hill, 1962.

Livingston, M. S. Particle Accelerators: A Brief History. Cambridge, MA: Harvard University Press, 1969.

Mann, W. B. The Cyclotron, 2nd ed. New York: Chemical Publishing Co., 1945.

Wilson, R. R. and Littauer, R. Accelerators: Machines of Nuclear Physics. Garden City, NY: Anchor Books, 1960.


The Lab’s legacy began in the summer of 1928, when a 27-year-old physics professor named Ernest O. Lawrence was wooed from his faculty position at Yale University to a job at the University of California’s Berkeley campus. While at Berkeley, Lawrence invented a unique particle accelerator called a cyclotron which would prove his hypothesis: whirling charged particles around to boost their energies, then casting them toward a target is an effective way to smash open atomic nuclei. The cyclotron would go on to win Lawrence the 1939 Nobel Prize in physics and usher in a new era in the study of subatomic particles. Through his work, Lawrence launched the modern era of multidisciplinary, team science. In August of 1931, when he created the Radiation Laboratory in a modest building on the Berkeley campus, Lawrence began recruiting a brilliant circle of colleagues from physics, chemistry, biology, engineering and medicine, whose groundbreaking teamwork would be critical to the laboratory’s legendary success. When his plans for bigger and better atom-smashing cyclotrons required more room, he moved the laboratory off campus and up to its present location in the Berkeley hills, overlooking the San Francisco Bay. After his death in 1959, the Lab was officially renamed the Ernest O. Lawrence Berkeley Laboratory.

The old Radiation Laboratory

Today, Berkeley Lab continues the tradition of multidisciplinary scientific teams working together to solve global problems in human health, technology, energy, and the environment. Thirteen Nobelists have worked here. And countless other researchers have contributed to the Lab’s success as an institution for furthering our nation’s scientific endeavors, whether in fundamental research, science education, or technology transfer.

Go here to view an article written in 2001 to commemorate the 100th anniversary of Lawrence’s birth in 1901.

As a youth, Lawrence was a ham-radio enthusiast and set up South Dakota’s first-ever radio station.