3. Oppenheimer and the Radiation Lab


n 1939, while Germans were smashing Polish borders and Japanese armed forces were smashing Chinese defense lines in Manchuria, Berkeley physicists were smashing atoms. By 1941, as a result of research done at the Rad Lab and elsewhere, the United States began to pursue the creation of a nuclear weapon. Brought into the project by Lawrence, Oppenheimer was assigned the task of calculating fast neutron reactions, a job key to the construction of an atomic weapon.

The scientific principles of nuclear fission were clear enough by this point. Far less clear was the technical feasibility of constructing a deliverable weapon in time to be useful. One challenge overshadowed all others – they needed fissionable material, either highly enriched uranium or the mysterious element plutonium, a man-made radioactive material created thus far only in cyclotrons.

In 1941, in gargantuan facilities above the campus in the Berkeley foothills, from ideas originally conceived in the modest Rad Lab, Berkeley scientists squeezed out plutonium from grudging nature, dime-sized radioactive pellets of uranium.

Scale Used to Measure Early Radioactive Pellets
Scale Used to Measure Early Radioactive Pellets

J. Robert Oppenheimer

J. Robert Oppenheimer
J. Robert Oppenheimer


Lawrence sent an urgent message to Arthur Compton, head of S-1, the Office for Scientific Research and Development’s secret committee in charge of the development of fission weapons, urging that Oppenheimer be invited to a conference in Schenectady, N. Y. Unknown to Compton, Lawrence had already told Oppenheimer about S-1’s work, which was to become the Manhattan Project.

Compton replied that Lawrence could bring Oppenheimer, but suggested that Lawrence consider simply passing on Oppenheimer’s ideas himself, “to avoid duplication of travel cost.” It is amusing to reflect that the expenses costs of the man who would become the head of Los Alamos would be considered unnecessary.

Lawrence was adamant; he offered to let the University of California pay Oppenheimer’s expenses. He wrote,

"I have a great deal of confidence in Oppenheimer, and, when I see you, I will tell you why I am anxious to have the benefit of his judgment in our deliberations."

The Atomic Bomb Conceived


ithin a few months of the Schenectady conference, Oppenheimer’s quick theoretical rigor and his reliability proved indispensable to the project. In a letter to Compton, Oppenheimer outlined some estimates on the efficiency of a device which “could shoot the two halves of the uranium mass together,” a weapon that became the atomic bomb.

In summer 1942, Oppenheimer convened at Berkeley a conference of theorist “luminaries” for a series of secret discussions on the design of an atomic bomb. On the top floor of LeConte Hall, Hans Bethe, Edward Teller, John Van Vleck, Robert Serber, Felix Bloch, and Emil Konopski spent a month going over theoretical data. They also discussed Teller’s pet project: the idea of using a fission bomb as a trigger for an even larger weapon, the hydrogen bomb, christened the “Super.”

When General Leslie R. Groves took over the secret atomic bomb effort – code named the Manhattan Engineering District, or Manhattan Project – in September of that year, he decided to create a centralized scientific laboratory for reasons of speed, security, and logistics. Much to Lawrence's frustration and the surprise of many, Groves appointed Oppenheimer as the scientific director of this still non-existent site, despite knowing of his past political affiliations and his lack of administrative experience.

Oppenheimer developed into a competent and inspiring director. His trademark ability to understand concepts as quickly as they were put in front of him, and his prowess in keeping the various disparate details of the project active in his mind at all times, allowed him to expertly coordinate the many hundreds of scientific experts who poured in at all times to work on the project.

Oppenheimer at Los Alamos


erkeley physics was intimately linked to the building of the bomb at Los Alamos. Behind a high steel fence topped with a triple course of barbed wire, an elaborate communication system was set up to monitor virtually everything, from casual communication carried by the postal service to scientific reading and experimental materials.

Tapped as the ideal candidate to lead a group of scientists through a myriad of scientific and ordnance problems of bomb design, Oppenheimer constantly pressed the military brass to ease regulations, housing restrictions, and isolation. Despite demands for greater security, Oppenheimer often had confidential mail sent to his office at Berkeley and opened weekly progress reviews to any interested scientist on staff.

His mystique and exceptional brilliance inspired the staff at Los Alamos to remarkable scientific achievements. But he also incited suspicion among some federal officials that he was not trustworthy. For instance, Oppenheimer occasionally ignored military orders -- and even the personal requests of his friend and colleague Lawrence – refusing to expand the facility that produced radioactive material.

“A few good men … would make all the difference in the world to us …. …physicists with intermediate training, electrical engineers, and technicians …. … we have always been short on all sorts of engineering talent …."

Telegram from Lawrence to Oppenheimer, May 17, 1944
Telegram from Lawrence to Oppenheimer, May 17, 1944

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“’It has been repeated to me here that you personally are responsible for the fact that the electro-magnet plant is not to be expanded.’”

Lawrence sent this telegram to Oppenheimer at “Site Y, Santa Fe, New Mexico,” to express his disappointment – and perhaps anger – that his suggestions weren’t being followed. It may have been because Oppenheimer suspected there was a better way to separate uranium than Lawrence’s design.

Rad Lab in the Spotlight


fter the war, the Rad Lab’s tenacious growth, and especially its power to command resources on a scale far greater than any other academic program, aggravated a few public critics. But far more people celebrated the lab’s scientific achievements and its contribution to victory in World War II. Popular interest, something physicists so rarely court, became an uncharacteristic obsession. Virtually every mid-20th century U. S. President passed through Berkeley’s physics labs, and celebrity artists and writers also clamored for attention.

Sinclair Lewis and Herbert M. Evans at the Rad Lab, ca. 1950
Sinclair Lewis and Herbert M. Evans at the Rad Lab, ca. 1950

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Lawrence and Mexican Artist Diego Rivera at the Rad Lab, ca. 1948
Lawrence and Mexican Artist Diego Rivera at the Rad Lab, ca. 1948

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