Forging a National Laboratory System in a Time of Peril
by Paul Preuss
On September 1, 1939, Germany invaded Poland. On September 3, France and Great Britain declared war on Germany; on the same day a German submarine torpedoed and sank the passenger liner Athenia off the coast of Scotland, with the loss of 118 lives. Ernest Lawrence’s brother John, returning from Europe, was the last person into a lifeboat after saving others.
There were rumors from Stockholm that no Nobel Prizes would be presented in 1939. But on November 9 the Associated Press announced that Lawrence had won “for the invention and development of the cyclotron and for results obtained with it, especially with regard to artificial radioactive elements.” Eventually his medal and certificate arrived at the Swedish consulate in San Francisco, to be presented at a University of California ceremony on February 29, 1940.
The Palomar of the Infinitesimal
Lawrence used the occasion to promote his dream of a cyclotron that could accelerate protons to 100 million electron volts (100 MeV). Its vacuum chamber would be wider than Mount Palomar’s 200-inch mirror, and its magnet would weigh 3,000 tons — or maybe 4,000 tons, or maybe more — and cost three-quarters of a million dollars. Or maybe one-and-a-quarter million. Or maybe more. The university would have to raise the money from private sources, but a Nobel Prize made that seem possible.
Some scoffers objected that nothing very significant had been done with Lawrence’s cyclotrons, an objection put firmly to rest in the summer of 1939 when Luis Alvarez and Robert Cornog, using the 60-inch cyclotron, discovered stable helium-3 — which every scientist believed should be radioactive — and a few days later used the 37-inch cyclotron to make radioactive hydrogen-3, better known as tritium — which every scientist thought should be stable.
Close on these discoveries came Martin Kamen’s work with carbon isotopes with both the 37-inch and 60-inch cyclotrons, leading to his discovery of radioactive carbon-14 on February 27, 1940 — two days before Lawrence’s Nobel Prize ceremony, at which the discovery was announced.
More significant than sour grapes about the cyclotron’s worth were scientific warnings about its physical limitations. Because its speed increases as its orbit widens, a particle spiraling in a cyclotron’s magnetic field stays in sync with the alternating electric field that accelerates it. But as it approaches the speed of light, the particle’s mass also increases, eventually throwing the beam out of focus.
Hans Bethe was the first to raise the specter of a cyclotron’s “relativistic limit,” which James Chadwick estimated at “about 10 million volts for protons, 15 million volts for deuterons and alpha particles.” This pessimistic guess was left in the dust as Robert Wilson, Edwin McMillan, Donald Cooksey and others among Lawrence’s boys continually came up with clever ways to shape magnetic fields and keep cyclotron beams focused.
Still, a 100-MeV cyclotron seemed to defy the laws of nature. Historians J.L. Heilbron and Robert W. Seidel write that Lawrence “bruited a solution in the style of the Old West: put a million or two volts on the dees and drive the beam home before it knows it has been defocused.”
Lawrence’s confidence was enough to persuade his fans, who included, among many others, Warren Weaver, director of the Rockefeller Foundation’s Division of Natural Sciences. In the spring of 1940 the Rockefeller Foundation agreed to fund the new machine to the tune of $1.4 million. It would be a 184-inch cyclotron, to be built on Charter Hill overlooking the Berkeley campus; its magnet would weight 4,500 tons, and for safety its controls would be located 150 feet away.
To house it, distinguished architect Arthur Brown, whose works included San Francisco’s City Hall, Opera House, and Coit Tower, designed a 90-foot-high dome. This was an aesthetic advance over Lawrence’s original inspiration. While entertaining visitors at the Folies Bergère during the Golden Gate International Exposition on Treasure Island, Lawrence had become distracted by the steel-framed dance hall and inquired whether the university might acquire it to house his new cyclotron when the Exposition closed.
The Uranium Problem
In the spring of 1940 construction of the giant cyclotron began in earnest; meanwhile Lawrence became increasingly worried about the war. His reasons went deeper than the Wehrmacht’s conquests in Europe. Back in January 1939, Luis Alvarez had been sitting in a barber’s chair reading the San Francisco Chronicle when, buried deep inside it, he found an article reporting Niels Bohr’s announcement that German chemists had split the uranium nucleus.
“I stopped the barber in mid-snip and ran all the way to the Radiation Laboratory to spread the word,” Alvarez recalled. A year and a half later Ed McMillan and Philip Abelson used the 60-inch cyclotron to bombard uranium with neutrons, creating element 93, which McMillan named neptunium. By February, 1941, Glenn Seaborg, J.W. Kennedy, and graduate student Arthur Wahl, continuing McMillan’s work and aided by Emilio Segrè, had made and purified element 94. A year later Seaborg named it plutonium; he intended the symbol Pu as a comment — pee-yew — but nobody got the dark humor.
War work initially had nothing to do with transuranic elements or nuclear fission, however. “I am puzzled as to what, if anything, ought to be done in this country in connection with it,” Vannevar Bush wrote in May 1940, shortly before Roosevelt commissioned him to head the National Defense Research Committee to work on war problems. The first act of the committee was to recruit “cyclotroneers,” thought to be “ideal for crash programs,” of which the most urgent was radar.
In November of 1940 Lawrence sent some of his best people, including Alvarez and McMillan, to MIT’s Radiation Laboratory — so named partly to honor Lawrence and partly to “confuse the enemy” — where they would help perfect radar in many forms. But when NDRC asked Lawrence to jump-start a parallel effort, the Navy’s Anti-Submarine Warfare Unit in San Diego, he did so chiefly by persuading McMillan to leave the MIT Rad Lab; McMillan’s contributions were to prove crucial to the development of sonar.
In early 1941 the war had not yet completely engulfed Berkeley’s Rad Lab. Steel executive William H. Donner, whose son had died of cancer, gave $165,000 to fund the Joseph W. Donner Laboratory, initially intended for John Lawrence’s research in nuclear medicine; ground was broken in June. But Lawrence’s worries about fission soon found a focus. “It will not be a calamity if, when we get the answers to the uranium problem, they turn out to be negative from the military point of view,” he said, but if positive, “and we fail to get them first, the results for our country may well be tragic disaster.”
Lawrence had the 37-inch cyclotron converted into a mass spectrograph to see how well it could magnetically separate fissile U-235 from chemically identical U-238. He suggested that plutonium, then made only in the 60-inch cyclotron, would also be fissile and could be produced in a nuclear reactor, provided one were ever built.
On December 6, 1941, one day before the Japanese attacked Pearl Harbor, the 37-inch cyclotron succeeded in separating a few micrograms of fissionable U-235 from heavier U-238. Two weeks later the government gave Lawrence’s lab $400,000 to investigate magnetic separation. Lawrence also wanted a contract to build an atomic pile, but that went to the University of Chicago. Within a short time the conversion of the Rad Lab to a wartime footing was complete.
In mid-February, 1942, the 37-inch cyclotron produced 75 micrograms of 30-percent U-235 for research purposes. In March, Seaborg left for Chicago’s Metallurgical Labora-tory to head the plutonium separation program, taking Al Ghiorso and others with him. In May, the magnet on Charter Hill was first turned on; instead of a cyclotron, Lawrence hoped it would accommodate up to 10 magnetic separators.
The big magnet’s separators didn’t work dependably until the end of 1942 — when a Rad Lab administrator suggested they be dubbed Calutrons — but a site for a pilot separation plant had already been chosen in Tennessee. In the spring of 1943 Lawrence and his boys descended on Oak Ridge to energize the construction of racetrack-shaped assemblies of Calutrons; Ed Lofgren designed a second-stage process for further purification of U-235.
By now all bomb work was under the aegis of the Manhattan Engineering District, headed by General Leslie Groves, previously noted for overseeing the construction of the Pentagon. Late in 1942, at Lawrence’s urging, Groves chose Caltech and UC Berkeley theorist Robert Oppenheimer to head a secret laboratory in New Mexico.
Long before Hiroshima and Nagasaki, the Berkeley Rad Lab’s active role in the war effort came to an end. In July 1944 the 60-inch cyclotron finished testing the stability of graphite rods destined for the giant plutonium-producing reactors at Hanford; it was time to return the machine to basic research. And it was also time, at last, to finish the 184-inch cyclotron — this time with government support. General Groves kicked in $170,000.
Whether the 184-inch would run afoul of the relativistic limit was a question the peripatetic Ed McMillan rendered moot when he returned from Los Alamos — where Lawrence had sent him early in 1943 — with a new idea for focusing accelerators. Instead of a continuous beam, particles would be emitted in pulses. As each bunch approached the speed of light, the accelerating frequency slowed to stay in sync with their ponderous mass.
At 12 minutes past midnight on November 1, 1946, Ernest Lawrence and “half the Lab” — its total staff had declined from a wartime high of 1,200 to fewer than 500 people — watched as the 184-inch “synchrocyclotron” produced deuterons at 200 MeV, equivalent to the 100 MeV proton energy Lawrence had dreamed of more than six years earlier.
Two months later the Manhattan District ceased to exist. The Atomic Energy Commission inherited its network of laboratories, which included Los Alamos and Argonne, Oak Ridge and Hanford, and, reluctantly at first, UC’s Radiation Laboratory, which had played a key role in establishing the others. From now on, big science would depend on government funds.