By Lynn Yarris, LCYarris@LBL.gov
The Nobel Prize is an accolade to achievement and the highest award in science. Nine Lawrence Berkeley National Laboratory scientists have been awarded the Nobel Prize. The laureates -- five in physics, four in chemistry -- include the Laboratory's founder Ernest O. Lawrence, plus Luis Alvarez, Melvin Calvin, Owen Chamberlain, Donald Glaser, Edwin McMillan, Glenn Seaborg, Emilio Segre, and Yuan T. Lee.
The story of Berkeley Lab's Nobel laureates begins with the discovery of uranium in 1879. Uranium was assigned number 92 on the periodic table, and was declared by many scientists to be the table's upper limit. In 1934, however, the great Italian physicist Enrico Fermi announced that bombarding an element with neutrons could transmute or convert that element to the next higher number. Fermi and his group then proceeded to blast uranium with neutrons in an effort to create element 93. They thought they had done so, naming their creation "uranium X," but subsequent efforts by others to repeat their experiments revealed that what the Fermi group had actually done was split the uranium atom in two -- a process called "nuclear fission."
A multitude of experiments blossomed from this revelation and in 1940, Edwin McMillan and UC Berkeley chemist Philip Abelson, sifting through the swarm of radioactive species that fission produced, were able to identify -- via the nature of its radioactivity -- element 93. Since uranium had been named after the planet Uranus, element 93 was named neptunium for the next planet out from the sun.
Continuing his work, McMillan found evidence that mixed in with the neptunium he produced was element 94, but his studies were interrupted when he was called to MIT to help develop radar as part of the war effort. Glenn Seaborg picked up where McMillan left off and in 1941, he, along with Joseph Kennedy and Arthur Wahl, confirmed the discovery of plutonium (for the farthest planet from the sun). A month later, they discovered that plutonium was fissionable. The world learned of their findings when the plutonium-fueled "atomic" bomb dropped on Nagasaki to end World War II.
In 1951, McMillan and Seaborg shared the Nobel Prize in chemistry for their discoveries in the transuranium elements, those beyond uranium on the periodic table.
Following his work with the transuranic elements, McMillan returned to accelerator research here and went on to discover the "phase stability principle," which enabled physicists to overcome the energy limitations of cyclotrons. McMillan's findings led to the invention of a new type of accelerator, which he named the "synchrotron." The giant circular accelerators used by physicists today are synchrotrons. For this work, McMillan shared the 1963 Atoms for Peace Prize with Soviet physicist Vladimir Veksler.
Seaborg, meanwhile, working with Albert Ghiorso, used plutonium as a stepping stone to the creation of a train of transuranium elements, including americium (95), curium (96), berkelium (97), californium (98), and mendelevium (101). In 1961 he was appointed chairman of the Atomic Energy Commission by President John F. Kennedy. He served in the post for 10 years, under Presidents Lyndon B. Johnson and Richard M. Nixon, before returning to his research at Berkeley.
Compared to the sky-shattering fire and thunder of fissioning plutonium, the energy conversion process of a green plant would seem to be quite trivial. And yet, all life on this planet depends on the ability of green plants to convert sunlight energy into chemical energy -- a process called photosynthesis. Each year, through photosynthesis, green plants extract about 150 billion tons of carbon from carbon dioxide in the air, and about 25 billion tons of hydrogen from water to produce about 400 billion tons of oxygen. It is estimated that plants utilize the light energy they absorb with an efficiency of at least 30 percent, and possibly as much as 100 percent. Scientists have long maintained that duplicating the success of plants would be a major advance towards ending chronic food and energy shortages. The first step, however, was to find out exactly how photosynthesis worked.
The effort to learn the secret of photosynthesis had been going on since the process was first identified by the German physicist Julius Robert von Mayer in 1845. But up until the 1930s, all scientists really knew for certain was that carbon dioxide and water went into a plant, and that oxygen came out. New information began to emerge, starting at the end of that decade when radioactive "tracers" were put into use. Tracers are detectable elements, usually radioactive isotopes, that can be tagged to organic molecules and used to follow the fate of those molecules through different stages of a chemical process. The early radioisotope tracers used were too "short-lived" to unlock all of the mysteries of photosynthesis, particularly the crucial path of carbon. In 1940, however, carbon 14, with a half-life of 5,000 years was discovered.
On the day of the Japanese surrender, Ernest Lawrence, the Director of UC Berkeley's Radiation Laboratory, told his colleague, biochemist Melvin Calvin, that it was "time to do something useful with radioactive carbon." Organizing a team of researchers from Lawrence's "Rad Lab," Calvin attacked the photosynthesis question. Using the carbon 14 tracer, he and his team mapped the complete route that carbon travels through a plant during photosynthesis, starting from its absorption as atmospheric carbon dioxide to its conversion into carbohydrates and other organic compounds. In doing so, Calvin and his team also showed that sunlight acts on the chlorophyll in a plant to fuel the manufacturing of organic compounds, rather than on carbon dioxide as was previously believed. The chlorophyll uses radiant energy to split water molecules into hydrogen and oxygen. Separated, hydrogen and oxygen contain more chemical energy than they do when combined as water.
For deciphering the photosynthetic process, Calvin received the 1961 Nobel Prize in chemistry. He went on to establish Berkeley Lab's Chemical Biodynamics division, which he directed for 20 years. Upon his retirement in 1980, the unique, doughnut-shaped three-story laboratory on the UC Berkeley campus, which houses scientists in that division, was renamed the Melvin Calvin Laboratory.
Understanding the hows and whys in the transformation of matter has been a driving force in the study of chemistry ever since ancient alchemists tried turning lead into gold. In the 1980s, Berkeley Lab chemist Yuan T. Lee attempted to understand what occurs during a chemical reaction at the atomic scale. Lee and colleagues sought to examine the forces operating between atoms and molecules during chemical reactions in order to find out exactly how, and at what rate, these reactions take place.
To follow the motion of atoms and molecules as they collide and react to form new products and to observe the flow of energy between them, Lee used a technique called "crossed molecular beams." Two beams of selected molecules were accelerated at supersonic speeds, then sent on a collision course in a vacuum. When the beams hit, the angles at which the resulting products are scattered and the amount of energy released during the collision are recorded. By controlling the content and velocity of the beams, and the angle at which they approach one another, Lee and his research team were able, in essence, to "view" chemical reactions as they occur.
In 1986, this achievement was recognized when Lee was awarded the Nobel Prize in chemistry. Also sharing the prize were Dudley Herschbach of Harvard and John Polanyi of the University of Toronto.
With sufficient knowledge of the dynamics of chemical reactions, ultimately it may be possible to manipulate molecules to promote specific reactions from a given combination. For example, combustion -- the process wherein oxygen and hydrocarbon atoms slam together and release heat -- remains the backbone of energy production and a major source of air pollution in the world today. The problem is that the elementary chemical reactions involved in combustion are still pretty much of a mystery. Better understanding of combustion should bring about more efficient energy production and less air pollution.
The most recent Berkeley Lab scientist to win the Nobel Prize in physics, was Luis Alvarez in 1968. Even a cursory review of the accomplishments of this scientific maverick and iconoclast is a breath-taking endeavor. A member of the National Inventor's Hall of Fame, Alvarez held the patents for more than 30 inventions, including three types of radar systems still in use today. In 1948, he designed a linear accelerator that produced proton beams of unprecedented intensity and served as the prototype for today's "linacs." He was the co-discoverer of tritium, the hydrogen isotope that offers the best possibility of fuel for fusion energy. He designed the complex detonator for the plutonium bomb that brought World War II to a close, and in fact, was aboard the trailing aircraft for both the Hiroshima and Nagasaki missions to observe the blast effects.
It was Alvarez who first proposed that a large extraterrestrial object, such as a comet or a giant meteor, crashed into the earth approximately 65 million years, setting off a chain of ecological catastrophes that killed off the dinosaurs. Initially met with considerable skepticism in the scientific community, this theory since has withstood all challenges and has come to be widely accepted. In his "spare time," Alvarez used cosmic rays to search for hidden chambers in an Egyptian pyramid, devised an indoor golf trainer, and analyzed the famous Zapruder film of the assassination of President Kennedy to determine how many shots had actually been fired.
The work for which Alvarez received his Nobel prize was his discovery of a slew of resonance states -- particles from within the nucleus of atom which were so short-lived that their existence had to be deduced from the appearance of the particles spawned by their decay. Alvarez' discoveries parted the gates to the sub-atomic zoo and let loose a sub-atomic particle stampede. So numerous were these resonance states (there are more than 150 different kinds now), that physicists became convinced of the existence of a more basic particle of matter than protons, neutrons, or other members of the hadron family. This desire for a simpler universe led to the discovery of quarks.
The first subatomic beast released by Alvarez was the "Y-particle", which he discovered in 1960. The Y-particle is a combination of an alpha particle and a meson that holds together for a trillionth of a trillionth second before breaking down into smaller, less energetic particles. Its discovery established that new states of matter could be created in collisions of sufficient energy. To explore this unseen world, Alvarez bombarded hydrogen nuclei in Berkeley Lab's Bevatron with k-mesons, particles about half the size of a proton that interact strongly with atomic nuclei. To "see" any resonance particles he might unleash, Alvarez coupled the Bevatron to a detection device he designed: the hydrogen bubble chamber.
Legend has it that bubble chambers were conceived in 1952, in a saloon near the campus of the University of Michigan. The story is that Berkeley Lab physicist Donald Glaser was admiring the smooth, clean lines formed by the stream of bubbles in a glass of beer which he was in the process of imbibing. A companion remarked that the bubbles made a nice track and it suddenly struck Glaser that such a track could be used to follow the path of charged particles.
At that time, physicists were better prepared to bust open atomic nuclei than they were to see what was inside. Scintillation counters were only good for detecting single particles, and cloud chambers contained too few ions to be of value for fast-moving, short-lived particles. Glaser overcame these obstacles by filling a glass chamber with liquid which he would heat, under pressure to just below boiling. Particles blasted out of a nucleus cleave through this superheated sea like tiny torpedoes, leaving in their wake tiny trails of bubbles that can be photographed. Analysis of a particle's bubble chamber tracks can tell physicists much about the particle's physical properties and history.
His invention of the bubble chamber won for Glaser, at the tender age of 34, the 1960 Nobel prize for physics. Glaser first reported his invention at a meeting of the American Physical Society in 1953. Alvarez attended that meeting and he was soon taking his colleague's creation to the next stage of development.
Particles speed through a bubble chamber until they either loose energy and decay into something else, or until they hit another particle. Glaser filled his bubble chambers with diethyl ether, but Alvarez replaced this with liquid hydrogen because the single-proton nucleus of hydrogen atom minimized any interference with the particles being tracked. Glaser's original bubble chamber was all glass because it was believed that smooth walls were necessary to prevent the formation of unwanted bubbles. This all glass composition promised to keep bubble chambers small: Glaser's original was only a few inches in diameter.
Alvarez proved that good tracks and accurate photos could be obtained despite any accidental bubbles. His bubble chambers were made from metal and featured glass windows through which the particle tracks could be seen and recorded. These "dirty chambers" -- so called to distinguish them from the all-glass "clean chambers" -- quickly grew in size, from 2.5 inches to 72 inches within a decade. The 72-inch bubble chamber, plus computerized methods of track analysis, which he devised, enabled Alvarez to detect the Y-particle and the parade that followed it.
Before there was the Y-particle, there was the proton, the neutron and the electron. And there was antimatter. Or was there? This question was first raised in 1930, when theoretical physicist Paul Dirac mathematically analyzed the properties of the known subatomic particles and concluded that for each particle, there should be an antiparticle. Though scientists generally love symmetry as much as simplicity, few seemed very interested in Dirac's proposal until two years later when Carl Anderson and Robert Millikan found the antielectron. Identical to the electron in every way except that it carried a positive charge, the new particle was called a positron. The discovery of the positron ignited the imaginations of scientists and science fiction writers everywhere, for its existence made feasible antimatter -- a world of positive electrons and negative protons, the mirror image of our own. All that was needed was an antiproton.
The antiproton quest got off to a slow start. Since the energy required to produce a particle is proportional to its mass, the creation of an antiproton would take 1,836 times as much energy as the creation of a positron. Not until Berkeley Lab's Bevatron went on line in 1954 were such energies available. A group of Berkeley Lab scientists immediately joined the hunt. In this group were physicists Emilio Segre and Owen Chamberlain.
Both men were eminently qualified to take part in the antiproton chase. Segre, the first student to earn his degree in physics at the University of Rome under Fermi, had, with the aid of the new cyclotron at Berkeley, discovered technetium, the first artificially-produced chemical element. He was one of the scientists who determined that a bomb based on plutonium was
feasible, and his experiments on the scattering of neutrons and protons and proton polarization broke new ground on understanding nuclear forces. Chamberlain also studied under Fermi, and Segre as well. He was Segre's assistant on the Manhattan Project at Los Alamos while still a graduate student, and later joined Segre at Berkeley to collaborate on the nuclear forces studies.
Making an antiproton was only half the task. Posing no less formidable a challenge was devising a means of knowing the beast once it had been flushed. For every antiproton created, 40,000 other particles would also come into existence. The time to sort through all of these particles would be brief: within about a 10 millionth of a second after it appears, an antiproton comes into contact with a proton and both particles are annihilated.
In 1955, Segre and Chamberlain, along with Clyde Wiegand and Thomas Ypsilantis, wove an elaborate network of magnets and electronic counters into a detection system that could cull the antiproton out from the surrounding herd. Armed at last with the means of both producing and recognizing an antiproton, Segre and Chamberlain proceeded to bombard copper with protons that had been accelerated to 6.2 billion electron volts of energy. The barrage continued for several hours and when the smoke cleared they had in their bag not one but 60 of the long-sought particles. No hunters ever came away with a more grand trophy: in 1959, Segre and Chamberlain received the 1959 Nobel prize in physics for their discovery.
Fittingly enough, Berkeley Lab's first Nobel laureate was Ernest O. Lawrence. The 1939 Prize in physics was presented to him for "the invention and development of the cyclotron, and for the results thereby attained, especially with regard to artificial radioelements."
Modern physics is based on the ability of scientists to venture inside the atom and explore the elementary particles of force and matter. This takes energy. Energy is the universal container holding everything together. If you want to open any one container to see its contents, you have to overcome that container's energy. Physicists get the energy they need in particle accelerators. Accelerators propel subatomic particles to nearly the speed of light (186,000 miles per second). As a particle's speed climbs, its kinetic energy grows, reaching mammoth proportions when the particle's speed approaches that of light. Smashing these tiny little speeding bullets into target particles shatters the target and releases its contents. Sometimes, the release of energy from the cataclysms triggers the formation of new particles, as was the case when Alvarez created the Y-particle.
Lawrence opened the door to modern physics with the invention of the cyclotron in 1931. The granddaddy of all circular accelerators, the cyclotron soon made possible the attainment of energies few scientists would have thought possible only a few years before.
From out of the laboratory of the English physicist Ernest Rutherford in 1928 had come the voltage multiplier, a device for building up electric potential that could push a proton to energies of about 400,000 electron volts. The ante was quickly upped by the American physicist Robert van de Graff, whose electrostatic generator took protons up to 8 million electron volts. Linear accelerators appeared on the scene, raising the stakes considerably higher, but the requirement of longer and longer accelerating tubes to produce higher energies placed a severe crimp on the use of these machines.
The circular design of Lawrence's accelerator allowed for the production of high energies in a machine relatively compact in size. In its simplest form, a cyclotron is composed of two semicircular electrodes encased in a closed vacuum chamber and sandwiched between the poles of a circular electromagnet. An electric field fills the gap between the electrodes. Particles moving across this gap are given an electrical push forward. The magnet bends the path of the particles so that they travel in a circle. This means that the particles keep crossing through the same accelerating gap over and over again, gaining speed and energy with each crossing.
The first cyclotron was less than a foot in diameter. It was used to boost a handful of protons to about 80,000 electron volts. By 1939, Lawrence had presided over the construction of a cyclotron with magnets nearly five feet across. This cyclotron could boost particles to 20 million electron volts. More machines would follow, each more powerful than its predecessor.
If his invention of the cyclotron opened the door to modern physics, it was Lawrence himself who led everyone through. He believed in doing research on a large-scale and has been called "the father of big science." At the "Radiation Laboratory," which he founded on the UC Berkeley campus and nurtured through its expansion onto the hills above, Lawrence began the concept of doing research with multidisciplinary scientific teams. He was also the first to push for the inclusion of engineers as full partners on such teams, as well as the integration of engineering concepts and designs into basic scientific research equipment.
That Lawrence's approach to scientific research yields rich dividends in basic knowledge and applied technology has been acknowledged by the profusion of awards bestowed over the years upon the scientists and engineers at Berkeley Lab -- including, first and foremost, nine Nobel Prizes.