Demobilized Physics

The military service of the Laboratory and the reputation and resourcefulness of its director insured that Lawrence would be a leader in the new compact between science and government struck during the war. We have a measure of the effect of the success of the Manhattan Engineering District on these arrangements in the form of plans for the future that Lawrence drew up in 1944 and revised in 1945. In the earlier plan he assumed that the Laboratory would continue as a division of the University's physics department and proposed the establishment of a second division for medical physics to accommodate John Lawrence and his colleagues in the Crocker and Donner laboratories. He expected to have a small permanent staff of scientists and technicians, and to reimplement the frugal policy of allowing visitors and students to do much of the work. As for expenses, he thought to make do with $85,000 a year and some war surplus: "a considerable proportion of the [wartime] laboratory equipment, particularly supplies and machine tools, [might] be kept available either through gift from the Federal Government or purchase by the University."
The magnet yoke for the 184-inch cyclotron was set in place and the building erected around it.

By the time of the plan of 1945, however, Lawrence knew that science would be both honorably discharged and held in ready reserve for the national defense and welfare. The increasing production of uranium-235 and plutonium meant that high status in national councils rather than unending Congressional investigations would reward the Manhattan Project. Four months before Trinity, Lawrence wrote the MED offering to accept $7 to $10 million for the Laboratory's first year of postwar operation, a hundred-fold increase over the budget he had estimated the year before. After Trinity, which confirmed his confidence in dealing with Groves as it did Truman's in negotiating with Stalin, he set the postwar laboratory staff at 239, including 66 scientists. Alvarez and McMillan, returning from Los Alamos, had plans for new accelerators that would exploit wartime technology and surplus materiel worth millions. The entrepreneurs who had attracted the nation's philanthropic wealth to nuclear science before the war turned to the new public provider.

Groves admired Lawrence's drive and confidence, and the MED generously supported the Rad Lab's conversion to peace-time research. "[It is] in the best interest of the government," Groves said, and authorized the completion of the 184-inch synchrocyclotron and the construction of an electron synchrotron, both of which used a concept that McMillan had developed towards the war's end. The completion of the 184-inch synchrocyclotron cost the District $170,000, the construction of the electron synchrotron $230,000 in cash plus $203,000 in surplus capacitors from Oak Ridge. Alvarez got support for preliminary work on a linear accelerator designed to produce 2,000 MeV protons and estimated to cost $5.5 million in all, including 750 surplus radar generators valued at $1.5 million. Seaborg, returning from Chicago to direct nuclear chemistry, had $75,000 for a "Hot Lab" for research on radioactive isotopes. The staff exceeded Lawrence's highest estimates. In February 1946 it numbered 479, with a monthly payroll of $194,000; the semiannual budget from the MED amounted to $1,370,000. When University Regent John Francis Neylan complained that local contributions to the atomic bomb had not been adequately appreciated, Lawrence showed him Groves' gift of radar apparatus as an indication of the kind and quantity of credit the Laboratory was getting.
Nuclear chemistry prospered in the postwar era, with the discovery of several new elements by the team including Seaborg (left) and Albert Ghiorso.

Groves could not guarantee support of the Laboratory after January 1, 1947, when the Atomic Energy Commission (AEC) took charge of the nuclear energy program. Lawrence had supported the May-Johnson bill, which would have created a Commission dominated by the friendly military. He withdrew from the debate when many nuclear scientists lined up behind the McMahon bill, which provided instead for a civilian commission under Presidential control. Once the McMahon bill was approved and the Commission appointed, Lawrence took steps to insure that the agency would favor the kind of research he thought important.

The AEC formulated its research policy in 1947 in a series of meetings, the most important of which Lawrence arranged at Bohemian Grove in August. There Oppenheimer, chairman of the AEC's General Advisory Committee, called for broad and strong support for basic scientific research. Lawrence, better at personal negotiation than at speech-making, took AEC Chairman David Lilienthal on a four-day trip in the coastal mountains before the meeting. Congressional rejection of Vannevar Bush's plan for a National Science Foundation had already inclined the commissioners to support fundamental research under the AEC; and after the meeting and eating at the Grove, the one strong opponent, the Commission's director of research James Fisk, who had opposed the financing of accelerators by the agency, conceded the necessity. In October 1947 the AEC appropriated $15 million for atom smashers. Prohibited by the Atomic Energy Act of 1947 from giving grants for research, the agency developed a system of contracts with universities and set up an independent Division of Research to administer them. To complete the loop, Kenneth Pitzer, professor of chemistry at Berkeley, succeeded Fisk. By the end of 1948 AEC research policy had been shaped to assure the future of fundamental nuclear science.

All the main components of Lawrence's interdisciplinary establishment prospered under the new regime of peacetime financial support for scientific research. In the "Hot Lab," the most prominent locus of nuclear chemistry at the Laboratory, Seaborg, Albert Ghiorso, James Kennedy, B. B. Cunningham, and others elaborated the rich and varied chemical properties of the actinide elements. They continued work begun during the war at Chicago where their identification of americium (element 95) and curium (96) among the products of plutonium bombarded in the Berkeley and St. Louis cyclotrons confirmed the actinide concept, the existence of a series of heavy homologues of the rare earth elements. After their return to Berkeley Seaborg and his associates synthesized additional members of the series, berkelium (97), californium (98), and mendelevium (101), in the 60-inch cyclotron.
Newspaper headlines announced the discovery of another new element, berkelium.

The Donner Laboratory, at first of interest to AEC for its studies of the physiological effects of fissile materials and their products, soon won federal support for continuation of its prewar work in medical diagnosis, instrumentation, and therapy. An example is the treatment of acromegaly and Cushing's disease with beams of charged particles, initiated by John Lawrence and Cornelius Tobias. Other work, like that leading to the discovery of the lipoproteins and their effects on cardiovascular disease by John Gofman, Frank Lindgren, and their collaborators, brought the Laboratory into entirely new areas.

One of the new areas, cultivated both in Donner and the Old Radiation Laboratory, was the study of organic compounds labeled with carbon-14. Melvin Calvin took charge of this work at the end of the war in order to provide raw materials for John Lawrence's researches and for his own study of photosynthesis. Using carbon-14, available in plenty from Hanford reactors, and the new techniques of ion exchange, paper chromatography, and radioautography, Calvin and his many associates mapped the complete path of carbon in photosynthesis. The accomplishment brought him the Nobel prize in chemistry in 1961. About that time his interdisciplinary bio-organic chemistry group became the Division of Chemical Biodynamics and obtained a new building on campus, recently renamed the Melvin Calvin Laboratory, in which to pursue their work.

Similar institutional growth began from Latimer's wartime investigations of the behavior of reactor materials at high temperature. His successor as Dean of the College of Chemistry and head of the Laboratory's general chemistry program, Pitzer, proposed in 1959 to expand these studies to the investigation of novel materials for applications to space exploration and other new technologies. The AEC agreed, and Latimer's old chemistry group became the nucleus around which several other campus programs collected to form the Inorganic Materials Research Division.

Although the bases for major programs in materials research and chemical biodynamics were set soon after the war as nuclear medicine and chemistry resumed their growth, experience and opportunity in physics determined the directions of most Laboratory effort from 1945 to the mid-1960s. Alvarez remarked in 1947 that history had apparently repeated itself. Then, as in the early thirties, the Laboratory was simultaneously investigating several machines: the 184-inch cyclotron, the electron synchrotron, the linear accelerator, and a 10-BeV proton synchrotron. Only the new Brookhaven National Laboratory, organized in the Northeast by fourteen universities to provide a counterweight to Berkeley in nuclear research, had an accelerator program nearly as ambitious.

The research most characteristic of the Laboratory exploited the then unrivaled beam of the synchrotron, as McMillan named machines built on his principle of phase stability. In a conventional cyclotron the relativistic mass increase ultimately shuts off acceleration: the particles fall progressively out of phase with the radiofrequency field until they reach the gap between the dees as the field there drops to zero. Thereafter they will be decelerated. As McMillan (and, independently, the Soviet physicist V. I. Veksler) showed, a net acceleration might be achieved by decreasing the oscillator frequency without changing the magnetic field (the principle of the synchrocyclotron) or by changing both frequency and field so that the accelerated particles describe a path of constant radius (the proton synchroton). In the case of relativistic electrons, only the magnetic field need be altered (the electron synchrotron).
The 184-inch cyclotron operated for the first time on November 1, 1946. In the foreground, left to right, are Thornton, Lawrence, McMillan, and James Vale.

Just before midnight on November 1, 1946 the 184-inch synchrocyclotron gave its first beam. Lawrence arranged a big celebration, a weekend at Del Monte Lodge in Monterey paid for by his old supporter Alfred Loomis. Everyone who had contributed money or influence to the completion of the machine was invited: representatives of the Rockefeller Foundation, the National Academy of Sciences, the International Cancer Research Foundation, the Research Corporation, General Electric, Eastman Kodak, American Cyanamid, the University, the Manhattan Engineering District. A place might also have been found for the Pacific Gas and Electric Company. It was struggling to find the million watts needed to run the newest conspicuous consumer, which doubled the power required on the Hill. After the weekend the guests came to Berkeley to see the dials that registered the arrival of 195 MeV deuterons.

These particles had about twice the energy called for by the designs of 1940. The doubling had one most significant consequence: it brought particles up to an energy at which they had a good chance of making mesons during collisions with nuclei. And it was the creation and study of mesons, rather than the manufacture of exotic isotopes or the multiplication of information about scattering, that became the prime achievement and justification of the new machine. Once again, however, the key discovery came not from Berkeley or an accelerator laboratory but from study of cosmic rays.

In 1937 Seth Neddermeyer and Anderson found a track that they identified as the trace of a particle with the charge of the electron but a greater mass. The new particle immediately seemed to find its place in theory. Like Dirac's theory of the electron, Yukawa's account of the strong force between nucleons required the existence of a novel particle. Anderson's "mesotron" had about the mass expected of Yukawa's field quantum or "Yukon;" and nuclear physicists, then still parsimonious with theoretical entities, thought the two particles one. After the war a major difficulty in the identification obtruded: as Marcello Conversi, Ettore Pancini, and Oreste Piccioni were the first to show, the negative mesotron escaped capture by matter far longer than theory allowed the Yukon, which, by hypothesis, interacts strongly with nucleons. Physicists began to entertain the idea that two mesons (to use the modern term) exist. Confirmation of this hypothesis came early in 1947 in pictures obtained by C. F. Powell's group in Bristol, England. (See Episode beginning page 54.)

The pictures were tracks of charged particles in a special photographic emulsion designed just after the war on the initiative of G. P. S. Occhialini by C. Waller of the Ilford film company. The tracks in question, found after inspecting a few plates exposed by Occhialini, apparently showed one charged meson (which Powell and his associates called ) giving birth to another (). The turned out to be the Yukon or nuclear-force meson, and the to be Neddermeyer and Anderson's cosmic-ray particle. The mass of the pions as determined by Powell's group put them within the manufacturing capabilities of the new Berkeley machine. The Laboratory already had a film group, headed by Eugene Gardner, struggling to adapt Powell's technique to the great flux of particles from the synchrocyclotron. After months of experiment with exposure and development times, and with the position and orientation of the film in secondary beams from targets struck by deuterons and alpha particles, Gardner's group had not found a trace of a pion. The first detection of artificially created pions came in February 1948, shortly after the arrival at the Laboratory of G. C. M. Lattes, who had worked with Occhialini and Powell.

The first pions found were negatively charged. Soon Gardner's group detected positive pions and daughter muons caught where their parents ended their careers within the films. Accurate values for the masses of both sorts of meson were obtained. At the end of 1948 McMillan's electron synchrotron came to life and made mesons by photoproduction via 335 MeV gamma rays. Perhaps the most elegant experiments in this series concerned the neutral pion, the first elementary particle discovered through the use of a high-energy accelerator.

The output of research papers, over 100 in all through 1949 matched that of the machine, a phenomenal performance in the judgement of Stanley Livingston, then established in the rival fortress at Brookhaven. The only declared rival was the synchrocyclotron at Birmingham, scheduled for completion late in 1949. Its designers hoped to reach 1.3 BeV. It made Lawrence "anxious," or so he wrote in February 1948, responding to Sproul's worry that Columbia's new machine, to go on line by the year's end at 400 MeV, would eclipse the 184-inch. Lawrence expected to outdistance Columbia with modifications to the synchrocyclotron already planned. To beat Birmingham he would need a new accelerator.
"Old Town" -- the site of the 184-inch cyclotron -- during the peaceful days after the war.

On March 8, 1948, representatives of Brookhaven met with Lawrence and his senior staff to fix the design energies for the proton synchrotrons that the AEC had promised to fund at each laboratory. Evidently the bidding would begin above 1.3 BeV. It began at 2 BeV, the amount calculated by Brookhaven for abundant production of pions by proton-proton collisions. Lawrence then revealed that he was about to announce that the 184-inch had made pions plentifully with 380 MeV alpha particles. The Eastern ambassadors quickly recovered: Berkeley's discovery made the need for a 2 or 3 BeV machine even more evident, they said, since only a complicated reaction could produce mesons so near the theoretical threshold. The minutes of the meeting record its consensus that the performance of the synchrocyclotron "raise [d] many questions which cannot be answered without a 2.5 to 3 BeV proton accelerator." That satisfied Lawrence. He preferred to strike into the unknown, into the land where antiprotons might dwell. It was decided that Brookhaven would build to 3.0 BeV and Berkeley to 6 or a little more, just above the threshold for making negative protons as calculated by McMillan and Wolfgang Panofsky.

In the first postwar years the Laboratory took the lead in experimental nuclear physics as well as in accelerator design. The period of productive relaxation ended in 1950. The explosion of the first Soviet atomic bomb in August 1949 called the Rad Lab to the colors once again. This time the particle accelerator would play a direct role in the nation's defense.

EPISODE 3 Machine Made Mesons