Seth Neddermeyer
In May 1943, while their laboratories were still being equipped and constructed, scientists at Los Alamos planned the research program that would lead to the first atomic bombs. They were helped by consultants and a committee appointed by the Manhattan Engineer District's leadership to review their plans to ensure they would accomplish that goal.
After they had been acquainted with the state of the art by Robert Serber's lectures, the scientists met with I.I. Rabi of Columbia University, the deputy director of the Radiation Laboratory at the Massachusetts Institute of Technology; Enrico Fermi, also of Columbia, who had been detailed to work on nuclear reactors at the Metallurgical Laboratory at the University of Chicago; and Samuel K. Allison of the Metallurgical Laboratory.
In addition to these consultants, who later became heavily involved in the Laboratory's work, a review committee, known as the Lewis Committee, appointed by the commander of the Manhattan Engineer District, Gen. Leslie Groves, helped plan the program. Warren K. Lewis, a chemical engineer from MIT.; John H. Van Vleck, a theoretical physicist from Wisconsin who had participated in the June 1942 summer study at Berkeley and whose theoretical work led to the establishment of Los Alamos; chemist E. Bright Wilson from Harvard; engineer Edwin L. Rose, then director of research for the Jones and Lamson Machine company; and Richard Tolman, a California Institute of Technology physical chemist and the vice president of the National Defense Research Committee, were the members of the committee.
James Bryant Conant, chairman of the NDRC Committee charged with scientific oversight of the nuclear weapons program, persuaded Groves that such a review committee was necessary to ensure the soundness of the research program and assured him that scientists in university and industrial laboratories were accustomed to such review committees.
The Lewis Committee reported to Groves and Conant on May 10, 1943, endorsing much that had been presented in the Serber lectures - recorded in the "Los Alamos Primer" - but recommending that in addition to the basic research to determine the critical mass, efficiency and damage of the weapon, more ordnance and engineering work would be required to actually develop it. Engineering a weapon would more than double the personnel of the Laboratory, require local testing of weapon components and demand more liaison with the military services.
John Manley, the University of Illinois experimental physicist from the Metallurgical Laboratory who had overseen the original program, agreed: "We thought we could just go to the military and buy a gun that would blow a couple of pieces together fast enough to make an explosion. But fast enough turned out to be really very fast. On top of that, the whole business had to be carried by a B-29 and dropped as a ballistic missile, and the Navy or Army just don't make guns for those purposes. All of this put very stringent size and shape and weight requirements on a gun. The upshot was that for the most part the gun was designed and tested at Los Alamos.
" The Lewis Committee also recommended that the Laboratory be made responsible for the purification of the plutonium to be used in the bomb, requiring an increase in personnel and facilities similar to that required by ordnance development.
"That added a considerable extra effort to the Los Alamos activity in terms of people and plant. It was a logical decision though, because the material was never very abundant, and if you did one experiment and a following test had to have a different shape, the material would have to be reworked. It made lots of sense to do it right at Los Alamos. One couldn't really quarrel with that decision."
The Lewis Committee was hardest on the University of California procurement operation. The business office, established in Los Angeles for security reasons, was following "unduly slow and cumbersome" procedures. This, the committee felt, could not be tolerated because the progress of the work and the morale at Los Alamos depended on an efficient procurement organization. As a result of its recommendations, procurement offices were set up in New York and Chicago to obtain supplies and equipment from the Midwest and the East.
Within the broad guidelines established by the Lewis Committee, Oppenheimer permitted his staff to proceed along a number of lines. For example, although the assembly of the nuclear materials, whether uranium-235 or plutonium, into a critical mass seemed most feasible by firing one fraction of it into another, Seth Neddermeyer, who had transferred to Los Alamos from the National Bureau of Standards along with Charles Critchfield and John Streib, heard of implosion in Serber's indoctrination lectures, and suggested that it might produce higher velocities than were available in the gun method. "There was a lot of skepticism," recalled Ed McMillan, an experimental physicist from the University of California Radiation Laboratory who had helped Manley to plan Los Alamos. "But Seth wanted to get on with the job and try it out. So without any particular official recognition from the laboratory he set up to do the early work on his own. He went to Bruceton, Pa., where the Bureau of Mines had an explosives research station, to learn something about explosions, and I went with him, as I was very interested in this idea. ... The first cylindrical implosions were done at Bruceton. É That was the birth of the experimental work on implosion, long before experimental work on the gun method."
Unlike the experimental research program, which required laboratories, accelerators and instruments, the theoretical program could begin immediately. Eldred C. Nelson and Stanley Frankel who had worked with Robert Serber on early calculations of neutron diffusion theory for the project at the Radiation Laboratory of the University of California, Berkeley, had bought mechanical calculators to equip the effort. "Keeping in mind the cost as well as the capability of the calculators, we ordered both economical eight-digit calculators and high-speed 10-digit calculators (Marchants and Fridens) in a mix thought to be balanced. This turned out to be misguided economy, for the high-speed 10-digit calculators were so much more productive than the low-speed eight-digit calculators that the low-priced machines were rarely used."
The calculators were distributed to theorists and a small group of "hand computers" to input calculations were recruited from wives of Los Alamos scientists, including Mary Frankel, Stanley's wife; Mici Teller, the wife of theorist Edward Teller; and Jean Bacher, the wife of experimental physics division leader Robert Bacher.
Richard Feynman, a young postdoctoral physicist from Princeton who had been recruited to help install and repair he calculators, recalled that the machines had substantial competition: "I had a lot of interesting experiences with [Hans] Bethe [the Cornell physicist who was head of the theoretical division]. The first day when he came in, we had a Marchant that you work by hand. The formula he'd been working out involved the pressure squared. 'The pressure is 48; so the square of 48 is--.' I reach for the machine. He says, 'It's about 2,300.' So I plugged it in just to find out. He says, 'You want to know exactly? It's 2,304' and it came out 2,304."
The experimental physicists, meantime, while waiting until their apparatus was ready, planned experiments to determine the average number of neutrons that would be produced in each fission of plutonium or uranium-235, the energy range of those neutrons, and the probability of fission by neutrons over a wide range of neutron energies. The probabilities that the neutrons might be captured or scattered rather than causing fission also had to be determined. They also planned to measure the scattering of neutrons in materials that might be used as tampers and to make a nuclear reactor using uranium-235 in water as a neutron source. They designed the instruments they would need for these jobs, which also would require time to make. The research program planned in May 1943 as a result of the Serber lectures and the Lewis Committee review was one of the most ambitious ever planned for a single laboratory. The addition of chemistry, metallurgy, and ordnance would only make it more challenging. It became clear that Los Alamos would have to be a special kind of place to accomplish its goal.
- Robert W. Seidel
Next: Organization of Research at Los Alamos