Edwin Mattison McMillan, one of the brilliant scientists who helped lead t he Laboratory to its fame, died September 7, 1991, at the age of 83. Nobel laure ate, former director of LBL, and professor emeritus of physics at the University of California, Berkeley.
McMillan received the last of many honors just a year before his death: the N ational Medal of Science. McMillan's "important and versatile scientific contrib utions spanning physics, chemistry, and engineering, and his great human qualiti es, form an important chapter in the history of science," said Glenn Seaborg, wi th whom McMillan shared the 1951 Nobel Prize in Chemistry.
This tribute is adapted from a talk by Edward Lofgren, McMillan's longtime friend and colleague, at a memorial service in Berkeley on September 14, 1991.< /B>
In January 1932, Ernest Lawrence wrote to Edwin M. McMillan at Princeton University: "We all would welcome your coming to California on a National Resea rch Fellowship next year. We are busy installing equipment in our new Radiation Laboratory. If you wish to join in OD the work, we would be only too glad."
Who was this young man who was so cordially invited to the new Laborator y? He was the schoolboy whose toys were mechanical and electrical gadgetry, chem icals, rocks, minerals, and botanical oddities. He was the eager high- school st udent who lived in the shadow of Caltech, walked its hallways, attended lectures , and glimpsed the fabulous world of science.
He was the graduate of Caltech, greatly influenced by close association with Linus Pauling. He was the new Princeton Ph.D. and a holder of the most soug ht-after prize: a two-year National Research Council Fellowship.
Ed accepted the invitation of Lawrence to come to Berkeley but chose to do his research in the Physics Department on his own projects in molecular beams and hyperfine structure rather than in the new Radiation Laboratory. However, h e was a close observer of the Radiation Laboratory and felt the excitement as La wrence and his co-workers struggled with the powerful but temperamental cyclotro n to make it work and to produce solid physics results. The attraction was irres istible; his interested observer status grew first to a part-time and then, in 1 934, to a full-time commitment to the Radiation Laboratory that was destined to be his intellectual home for the rest of his life.
In those earliest days, Ed brought to the Laboratory a technique of meti culous experimentation combined with a mastery of nuclear theory that it did not have before. He discovered new isotopes-oxygen15 with Stanley Livingston and be ryllium-10 with Samuel Ruben, and he provided the first unambiguous verification of electron pair production by gamma-ray absorption. He also took a keen interest in the operation and improvement of the cyclotron and was responsible for substantial improvements in ion sources, magnetic-field shaping, beam extraction, and power and control systems. He played an especially valuable role in the construction and initial operation of the 60-inch cyclotron.
As the decade of the 1930s drew to a close, momentous events in the worl d had their repercussions at the Laboratory. In the first days after January 29, 1939, when the discovery of fission became known, a number of verifying experim ents were carried out at the Laboratory. Ed chose, he said, "to do an experiment of a very simple kind"-a measurement of the range of the fission fragments usin g a foil technique. Ed, ever the careful observer, noticed that the residue in a thin layer of uranium compound showed "something very interesting." The somethi ng-after a long series of exacting experiments in collaboration with Philip Abel son-was proven to be an isotope of element 93, the first element beyond uranium.
Ed named the element neptunium and had ready the name plutonium for the next element. Indeed, he prepared a sample of element 94, but the final chemical proof of its identify eluded him, as he was called away to help organize a new laboratory at MIT for research in radar. The chemical identification of element 94
was carried forward by a team including Glenn Seaborg, Joseph Kennedy, and Ar thur Wahl. A paper co-authored by these three, along with McMillan, recorded the result in 1940, but wartime secrecy held up the announcement until 1946. Five y ears later, the Nobel Prize was awarded jointly to McMillan and Seaborg "for the ir discoveries in the chemistry of the transuranium elements."
Ed's mastery of physics-both theory and experiment-was such that he coul d contribute to almost any line of research. When Robert Oppenheimer was designa ted to head what became the Los Alamos Laboratory, the first person he called on , in November 1942, to help organize the laboratory was Ed McMillan. He assumed major responsibilities both in weapons development and in testing and instrument ation.
In the summer of 1945, activity at Los Alamos reached a climax in the te st shot at Alamogordo. With the end of the war in sight, Ed's thoughts reverted to the central problem of cyclotrons: the energy limit imposed by the relativist ic increase of mass of the ions as they gain energy. The highest energy accelera tor at this time was the 60-inch cyclotron in Berkeley, with a beam of 16 MeV. T he next projected cyclotron was to produce beams of 100 MeV.
Although the huge magnet had been built, the machine's operation was dou btful. Unless there was a new idea, further progress would be absolutely blocked .
McMillan had such a new idea. His principle of phase stability was as st artling in its elegant simplicity as it turned out to be far-reaching in practic e. He showed that under certain conditions, ions in cyclotron orbits collect in stable, zero- energy-gain bunches. The frequency of the accelerating field and t he strength of the magnetic field may then be slowly altered to increase the ene rgy of the stable bunches without limit. This is the principle of phase stabilit y, which, together with strong focusing, provides the basis for the design of al l the great high-energy accelerators today.
The principle of phase stability had also been determined by Vladimir Ve ksler in Russia, but due to the breakdown of communication during the war, the w ork of the two scientists was entirely independent. In 1963 McMillan and Veksler shared the Atoms for Peace Award for their contribution.
Returning to Berkeley when the war ended, Ed had a leading role in the p rogram of the Laboratory to build new accelerators based on the principle of pha se stability: the 184-inch cyclotron, the 300-MeV synchrotron, and the Bevatron.
In parallel with his remarkably productive career in research and in acc elerator development, McMillan taught as a faculty member of the UC Berkeley Phy sics Department, becoming a full professor in 1946. He was chosen Faculty Resear ch Lecturer in 1954, with the citation: "His teaching is notable for the clarity and simplicity with which he presents even the most complex scientific facts an d theories."
McMillan was named associate director of the Laboratory and head of the Physics Division that same year. With the untimely death of Lawrence in 1958, he was appointed director of the newly named Ernest O. Lawrence Radiation Laborato ry. Few scientists could have managed such a large and diverse scientific enterp rise at all; McMillan did it well. He directed with a light touch, giving scope to individuals and making it possible for persons of great talent, but with some times very different styles, to work side by side. The years were very productiv e ones for the Laboratory.
McMillan held this position with distinction until his retirement in 197 3. In retirement, he was an active participant in an experiment at CERN in Genev a, Switzerland; he maintained an interest in Laboratory affairs; and he contribu ted several important papers on aspects of the history of science.
Ed McMillan was one of the great scientists of the century. His colleagu e and fellow Nobel laureate, Luis Alvarez-a tough judge of scientific worth-summ arized Ed's stature this way:
"Many people agree with me that Ed McMillan certainly earned two or thre e Nobel Prizes in physics, but only got one."
Great scientist and scholar, superb teacher, fine gentlemen. . . it was a privilege to have Ed McMillan as a friend.