Main Page | See live article | Alphabetical index

Los Alamos National Laboratory

Los Alamos National Laboratory (LANL) is a United States Department of Energy (DOE) laboratory, managed by the University of California located in Los Alamos, New Mexico. The Laboratory is one of the largest multidisciplinary institutions in the world. It is the largest institution and the largest employer in northern New Mexico with approximately 6,800 University of California employees plus approximately 2,800 contractor personnel. The annual budget is approximately $1.2 billion.

Approximately one-third of the Laboratory's technical staff members are physicists, one-fourth are engineers, one-sixth are chemists and materials scientists, and the remainder work in mathematics and computational science, biological science, geoscience, and other disciplines. Professional scientists and students also come to Los Alamos as visitors to participate in scientific projects. The staff collaborates with universities and industry in both basic and applied research to develop resources for the future.

The Los Alamos National Laboratory also used to host the e-print archive.

In 2003, dissatisfaction with scandals at the laboratory led the Department of Energy to open its contract with the University of California to bids from other vendors. Names that have been mentioned among those interested in bidding for the laboratory include private contractors such as Lockheed-Martin and other universities such as the University of Texas.


The Laboratory was founded in the midst of World War II as part of what is now called the Manhattan Project to provide nuclear weapons to help end the war.

In September 1942, the difficulties involved with conducting preliminary studies on nuclear weapons at universities scattered throughout the country indicated the need for a laboratory dedicated solely to that purpose. The need for it, however, was overshadowed by the demand for plants to produce uranium-235 and plutonium -- the fissile materials that would provide the nuclear explosives.

The Manhattan District

In the summer of 1942, Col. Leslie Groves was deputy to the chief of construction for the Army Corps of Engineers and had overseen construction of The Pentagon, the world's largest office building. Hoping for an overseas command, Groves objected when he was appointed to take charge of the weapons project. His objections were overruled and Groves resigned himself to leading a project he thought had little chance of succeeding.

The first thing he did was rechristen the project "The Manhattan District." The name evolved from the Corps of Engineers practice of naming districts after its headquarters' city (Marshall's headquarters were in New York City). At the same time, Groves was promoted to brigadier general, which gave him the rank thought necessary to deal with the senior scientists in the project. Within a week of his appointment, Groves had solved the Manhattan Project's most urgent problems. This forceful and effective manner was soon to become all too familiar to the atomic scientists.

Theoretical work on a nuclear weapon was well advanced by September 1942, but a complete understanding of bomb design required the measurement of a number of experimental constants related to the behavior of fast neutrons in various materials. Experiments to make these measurements at private research institutes and academic laboratories were hampered by security and by the difficulty of coordinating work in widely scattered locations. A central weapons laboratory was needed.

Groves and the Manhattan Engineer District had taken charge of the construction of production plants (at Oak Ridge and Hanford), but no provision had been made for a laboratory for bomb design.

Albert Einstein and J. Robert Oppenheimer

Robert Oppenheimer and John Manley took the problem to the Office of Scientific Research and Development (OSRD). The occasion was a meeting of its section charged with the development of nuclear weapons, the S-1 Committee, at Bohemian Grove in northern California. The host was Ernest Lawrence, director of the University of California Radiation Laboratory. As a result of that meeting, Arthur Compton of the University of Chicago Metallurgical Laboratory, who was in charge of plutonium and bomb design work, called another meeting in Chicago. He invited Edwin McMillan, the co-discoverer of the first transuranium elements, neptunium and plutonium.

McMillan, who had been sent by Lawrence to organize work at the Naval Underwater Sound Laboratory at Point Loma, California, had also helped Lawrence organize the Massachusetts Institute of Technology's Radiation Laboratory. Although named after Lawrence's laboratory in California, the MIT lab was to develop radar. Lawrence also had recruited the director, Lee DuBridge, who came from the cyclotron laboratory at the University of Rochester. Apparently, Lawrence intended to recruit the director for the new design laboratory as well.

In Chicago on Sept. 19, McMillan met with Oppenheimer, Manley, Enrico Fermi, Lawrence and Compton to plan the new laboratory. They decided that equipment would be purchased, leased or borrowed to set up a fast-neutron laboratory in a remote location where they would move the theoretical and experimental studies Oppenheimer and Manley had been overseeing.

The selection of a director for the new laboratory was made by Groves. The idea for a new laboratory was presented to him early in October and he took charge of it. Because the scientific nature of the new laboratory would require civilian rather than military leadership, Groves was determined to select someone who had sufficient prestige. Most of all, he wanted a Nobel Prize winner, which he equated to a general in the army of scientists.

Oppenheimer, who had led the weapons theoretical design project for some months, was another possibility. Groves was impressed with the theorist when they met in October 1942. Oppenheimer had built a strong school of theoretical physics at the California Institute of Technology and the University of California, and at that time, it was thought that the new laboratory would be chiefly concerned with theory. Groves, however, found little enthusiasm for Oppenheimer among OSRD scientists. But because most other scientists of comparable stature were tied up in other war projects, no one could suggest a better choice.

The Military Policy Committee that governed the Manhattan District also was unable to suggest an alternative. So, after several weeks, Groves decided on Oppenheimer.

Picking a site

Groves began a search throughout the western United States for a laboratory where theoretical and experimental nuclear weapons research could be coordinated. They initially thought of placing the laboratory at Oak Ridge, Tennessee, because most of the plants to make uranium-235 were planned for a site Groves had just acquired there - or in Chicago, where Compton's Metallurgical Laboratory was located. But Groves believed that the project required a more remote site. It would need a climate that permitted year-round construction, safety from enemy attack, transportation and access to power, water and fuel. It would also have to provide an adequate testing ground and, for reasons of safety and security, should be in a sparsely populated area. Despite this last requirement, Groves also hoped that it would have sufficient buildings to house a small research staff.

After considering a site near Los Angeles, which he rejected on security grounds, and one near Reno, Nev., which he found unsuitable because of winter snows, Groves told Maj. John Dudley of the Manhattan District staff to survey the West for potential sites. Elaborating on his criteria, Groves specified that the site had to be at least 200 miles from any ocean or any international boundary and in a natural bowl ringed by hills that could help secure the site and contain any accidental explosions. Dudley searched parts of California, Nevada, Utah, Arizona and New Mexico. His first choice for the laboratory site was Oak City, Utah. But problems with removing the existing population meant that Dudley recommended his second choice, the town of Jemez Springs, N.M.

Dudley's immediate superior, Marshall, approved the area for a site study, which was conducted by members of the Albuquerque Office of the Corps of Engineers. Oppenheimer and the OSRD scientists, however, needed to approve the site. On Nov. 16, Oppenheimer flew to Albuquerque, where he joined Groves, Edwin McMillan and Dudley. Dudley showed them Jemez Springs, the site he had selected for the new weapons design laboratory. Oppenheimer took one look at the site and told Groves that it would not do.

While Dudley had been told to look for a site enclosed by hills, Oppenheimer wanted an expansive setting. While Dudley wanted good access roads, Oppenheimer only wanted one adequate to haul two heavy howitzers (that would be used to test methods of assembling critical materials) to the site. McMillan thought that there would not be room enough in the narrow valley for the laboratory he and Oppenheimer wanted, and Groves disliked the site as well. Groves asked Oppenheimer if he had a better idea. Oppenheimer proposed Los Alamos. Dudley had visited Los Alamos but thought it was unsuitable because the water supply was inadequate. Although he was unhappy with Oppenheimer's suggestion, Dudley drove the trio to Los Alamos.

Groves liked Los Alamos immediately, he saw that access to the mesa could easily be controlled by shutting off the main entry road, and the road could be widened to accommodate trucks and heavy machinery. Canyons surrounding the site could be used for explosives tests. As Dudley warned, the water supply was marginal, but Groves thought it might do for the 450 scientists and technicians he believed would be needed. Although Los Alamos had been selected as the site of the laboratory that would design nuclear weapons for the Manhattan Engineer District (MED), it was not until December 2, 1942, that Enrico Fermi and his group at the metallurgical laboratory at the University of Chicago achieved an experimental demonstration of a chain reaction.

Construction Begins

The Los Alamos Ranch School closed on Feb. 8, 1943. By that time, digging and trenching on the site had already begun, because Oppenheimer was concerned that a delay in the start of construction, which permitted the final class to finish its curriculum for the year, would postpone completion of the design of the atomic bomb. The Army also acquired other land for the site. Ninety per cent of this land, 54,000 acres of semiarid forest and grazing land, was already controlled by the federal government and easily transferred to the Manhattan Project. The remaining 8,900 acres was purchased in five separate sections. The total cost for all private land was $414,971 or about $4 million in 1993 dollars.

By early December, the M.M. Sundt Construction Co. of Tucson, Ariz., had been engaged to build the buildings surrounding Ashley Pond that would house the Laboratory. Robert Oppenheimer, Edwin McMillan and John Manley had supplied specifications for the new buildings that would supplement the 54 Ranch School buildings. To the existing buildings were added barracks, a mess hall, officers' quarters, an administration building, a theater, an infirmary, as well as apartments, a bachelor dormitory, laboratory technical buildings and utilities for civilian scientists. These were built with great urgency, and the plans were changed constantly both during and after December 1942 as Oppenheimer visited the architect-engineers on a bi-weekly basis to refine the plans.

For the Albuquerque Corps of Engineers, the project became known as the "Buck Rogers Project," because no one had any idea what was going on, having been told that it was to be a "heavy bombardment range," a claim made patently false by the plans.

McMillan and Oppenheimer's fellow theorists at the University of California, and Hugh Bradner and Manley at the University of Chicago, planned the equipment for the new laboratory at Los Alamos. McMillan's office at UC became the center of the planning effort. McMillan ordered the machine tools, the electronic components and other equipment he thought appropriate for a major nuclear physics laboratory, based on his experience at UC's Radiation Laboratory. The largest items were the accelerators. Oppenheimer, McMillan and Manley decided that electrostatic generators (Van de Graaff accelerators), a Cockcroft-Walton machine and a good cyclotron would be required to carry on the experimental measurements that would be transferred to Los Alamos from scattered research sites across the country.

Manley selected the University of Illinois' Cockcroft-Walton accelerator and two Van de Graaff accelerators at the University of Wisconsin: the "long tank," a 22-foot-long machine that could produce energies of up to 2.6 million electron-volts, and the "short tank," a 17-foot-long.

The original technical complex included an administrative building (T Building), which also housed the theoretical physics group and was connected by a walkway to the chemistry and physics laboratories (U and Z buildings). There were separate laboratories for the Van de Graaff and Cockcroft-Walton accelerators at either end of the U and Z buildings and shops (V building), a cryogenic laboratory and the cyclotron (buildings Y and X).

Recruiting the Scientists

In early 1943, J. Robert Oppenheimer had to recruit a scientific staff for a purpose he could not disclose, at a place he could not specify, for a period he could not predict. Adding to these ambiguities was that of the status of the staff - Leslie Groves wanted a military laboratory where scientists served in uniform, a stipulation to which Oppenheimer originally agreed. Most of the scientists who had been recruited to work on defense projects, however, worked for universities under contract to the Office of Scientific Research and Development (OSRD) and they were reluctant to don uniforms.

Another difficulty arose from the fact that many nuclear physicists had already been absorbed by the Radiation Laboratory at the Massachusetts Institute of Technology, which was developing radar from the British ideas; the University of Chicago Metallurgical Laboratory, which was working on ways of producing and purifying the new element plutonium that was expected to be one of the nuclear explosives; and Ernest Lawrence's electromagnetic uranium isotope separation project at the University of California Radiation Laboratory in Berkeley.

In an early recruiting effort, Oppenheimer drafted the team led by Robert R. Wilson at Princeton that had been working on an electromagnetic isotope separation scheme called the isotron. This team was under the direction of Henry Smyth, a physics professor at Princeton. Lawrence, convinced that his calutron electromagnetic separation system would be more successful, had closed down the project freeing the Princeton scientists for Los Alamos.

By January 1943, of the men Oppenheimer had approached, only Robert Bacher, a Cornell physicist on leave to the MIT Radiation Laboratory, had agreed to come. Bacher and I.I. Rabi, originally from Columbia but on loan to the MIT Radiation Laboratory where he was serving as deputy director, met with Oppenheimer, Edwin McMillan, a physics professor at UC working at the Berkeley Radiation Laboratory, and Luis Alvarez, a physics professor at UC on loan to the MIT Radiation Laboratory, in the Biltmore Hotel in New York City on January 30, 1943, to discuss the problem.

Rabi and the others agreed that the Laboratory must demilitarize if the project were to be successful. They argued that military control would lead to friction, loss of morale and "more important, that in any issue in which we were instructed by our military superiors, the whole Laboratory would be forced to follow their instructions, and thus in effect lose its scientific autonomy."

Oppenheimer believed that "the solidarity of the physicists is such, that if these conditions are not met, we will not only fail to have the men from MIT with us, but that many men who have already planned to join the new laboratory will reconsider their commitments."

Groves and Conant were faced with an impasse. Groves would not entirely relinquish Army control, but a compromise was reached: Oppenheimer could tell potential staff that Los Alamos "would be concerned with the development and final manufacture of an instrument of war," including "certain experimental studies in science, engineering and ordnance." However, "at a later date large-scale experiments involving difficult ordnance procedures and the handling of highly dangerous material" would be involved, and this would be a turning point. "During the first period, the laboratory will be on a strictly civilian basis," it was agreed. However, "when the second division of the work is entered upon, which will not be earlier than Jan. 1, 1944, the scientific and engineering staff will be composed of commissioned officers." The ultimate authority over the laboratory would be the Military Policy Committee, composed of Vannevar Bush, head of OSRD; Conant; Groves; Rear Adm. William Purnell of the Pentagon's Joint Committee on New Weapons and Equipment; and Gen. Wilhelm Styer, chief of staff of the Army's services of supply.

Groves would represent the committee at Los Alamos, but Oppenheimer was responsible to Conant as well, and placed in charge of all scientific work as well as "the maintenance of secrecy by the civilian personnel under his control." The compromise mollified the scientists.

Bacher agreed to come and head the Experimental Physics Division of the laboratory until the laboratory was militarized. Rabi refused to leave the Radiation Laboratory but served as a consultant to the Los Alamos laboratory. Bethe came to head the Theoretical Division. Delayed by his work at Chicago, Fermi did not arrive until 1944, when he became head of the new Fermi (F) Division.

Armed with a letter signed by Groves and Conant, Oppenheimer crisscrossed the country adding to his team. To Serber, McMillan and the Berkeley theorists were added Emilio Segre and J.W. Kennedy and their experimental groups from the Berkeley Radiation Laboratory. Felix Bloch and Hans Staub and their group came from Stanford; Marshall Holloway and his group from Purdue University; Victor Weisskopf from the University of Rochester; Donald Kerst from the University of Illinois; and E.A. Long from Columbia University. Conant expedited the transfer of Edward Teller, Robert Christy, Darol Froman and Alvin Graves from the Metallurgical Laboratory at Columbia. Government research laboratories also contributed key personnel: Seth Neddermeyer came from the National Bureau of Standards and D.R. Inglis came from the Ballistic Research Laboratory at Aberdeen, Md. Among those recruited from private laboratories were Edward Condon from Westinghouse Research Laboratories, Cyril Stanley Smith from the National Research Council and Charles Critchfield from the Carnegie Institution of Washington.

Despite these successes, of the 33 physicists Oppenheimer set out to recruit, only 15 came to Los Alamos. John van Vleck, could not be pried loose from Harvard, despite the fact that Conant was its president. Franz Kurie of the UC Radiation Laboratory was not released by Lawrence. Carl Anderson and Wolfgang Panofsky of the California Institute of Technology were among others who could not be recruited.

Some refused to remain at Los Alamos. Felix Bloch resigned to work on radar; E.U. Condon, who came to Los Alamos to serve as Oppenheimer's deputy, resigned in disagreement with Groves's compartmentalization policy. None of these recruits would put on a uniform at Los Alamos, and although soldiers would play a role in its work, the laboratory was never militarized. Groves never raised the issue of converting the Laboratory to a military organization again.

"Here's your damned organization chart"

The early arrivals were accommodated at the Big House. In March 1943, the new Manhattan Engineer District (MED) Laboratory created to design nuclear weapons was under construction near Ashley Pond in Los Alamos. Robert Oppenheimer had assembled the beginnings of a staff for the Laboratory.

Early that same month, Oppenheimer drove to Santa Fe from Berkeley. His principal theoretical assistant, Serber, followed a couple of days later. The housing wasn't ready, so the Army had rented a couple of ranches down in the valley, and most of the people stayed there.

Oppenheimer had to write out passes on ordinary stationery to get his staff past the construction site guards (only one Army lieutenant staffed the security office and the badges that would become ubiquitous were not yet available) and organize his administrative offices.

"Project Y," the code name for Los Alamos military headquarters, had been set up in the Bishop Building on East Palace Avenue in Santa Fe on Jan. 4, and an office had been provided for Oppenheimer in another Santa Fe building soon thereafter. Col. J.M. Harman, the military commander at Los Alamos, arrived on Jan. 16 and, with a staff of six officers, a few civilian experts, and Women's Army Corps secretaries and switchboard operators, planned to provide for the technical personnel. Their work, however, was left up to Oppenheimer.

Oppenheimer had neither the taste nor the inclination for organization. Manley said he had "bugged Oppie for I don't know how many months about an organization chart who was going to be responsible for this and who was going to be responsible for that." Arriving at Oppenheimer's office in LeConte Hall, Manley found that Condon had finally persuaded Oppenheimer that it was necessary. "Here's your damned organization chart!" Oppenheimer exclaimed, throwing a piece of paper at Manley.

Oppenheimer assumed that he would head the theoretical division at Los Alamos as well as directing the Laboratory. Columbia's I.I. Rabi, convinced him that this would not do. Bacher, tapped by Oppenheimer to head the experimental physics division, also argued that Oppenheimer could not perform both jobs. Oppenheimer gave in and appointed Bethe to head the division.

Oppenheimer's estimate that only about 100 scientific staff would be required proved far too conservative. Still, there were only a score of research scientists in the first contingent that arrived in the middle of March.

The adaptation to New Mexico life was hard for both the staff and their families. Because they lived on ranches around Santa Fe, Laboratory families were often without adequate cooking and other facilities while they awaited completion of housing. The transportation to Los Alamos was haphazard. The road was poor and there were too few cars, none of which were in good condition. Eating facilities at the site were not yet in operation and box lunches had to be sent from Santa Fe. It was winter and sandwiches were not viewed with enthusiasm. The car that carried the lunches was inclined to break down. the working day was thus irregular and short, and night work impossible.

The hardships of these early pioneers at Los Alamos were only beginning. Working in a half-built laboratory, they faced the challenge of designing a weapon with nuclear materials yet to be made. The estimates of the amount of uranium-235 that would be required doubled about this time, which meant that the electromagnetic separation facilities planned for Oak Ridge would have to work nearly two months longer than had been planned.

Although the Los Alamos Ranch School in New Mexico provided some housing and office facilities, the new Los Alamos Laboratory required a whole new set of technical buildings as well as barracks, family housing and office space. And although Manhattan Engineer District commander Gen. Leslie Groves found the site ideal from the security point of view and the scientific director, J. Robert Oppenheimer of the University of California, Berkeley, found it idyllic as a retreat for scientists, those who had to build the Laboratory had great difficulty.

Located several thousand feet above the Rio Grande valley, far from sources of labor and construction materials, 40 miles from the nearest railroad, accessible only by inadequate roads, with insufficient water, no natural gas and a limited electrical supply, Los Alamos presented a real challenge to those who had to make the soldiers' and scientists' plans a reality.

The MED's site report, written in November 1942, predicted most of the problems. It was ignored, in the interests of time. Less than a week after it was written, Groves ordered the construction of barracks, a mess hall, officers' quarters, laboratory administration and technical buildings, a theater, an infirmary, apartments, utilities, streets and fencing. Some $26 million was spent on construction in Los Alamos during the war, approximately $200 million in today's dollars. Without a doubt, it would have been cheaper to build in almost any other location.

In January 1943, the estimated population of Los Alamos had risen to 1,500. By January 1944, it reached 3,500, and a year later it reached 5,700. Each new influx of personnel led to a new spate of construction. In the first phase, before the opening of the Laboratory in April 1943, the Sundt Co. of Tucson, Ariz., had built or remodeled 100 buildings. Sundt was selected by Col. Lyle Rosenberg, the Albuquerque district engineer for the Corps of Engineers, because it was well equipped to handle the task and had just completed Camp Luna at Las Vegas, N.M., and was free to take on the job. Because Sundt had its own plumbing, electrical, painting and transportation departments, security was more easily assured.

Construction began on Dec. 6 and was scheduled to be finished on March 15, 1943. Groves wanted 20 percent of the housing ready by Jan. 2, and the technical buildings ready by Feb. 1. Within two months, Sundt completed 54 percent of the construction.

Although they were quickly built, the Sundt houses were neither high quality or inexpensive. Col. John Dudley, who supervised the early construction for Groves, answered the question of "why did we put those horrible houses there?" this way: "An act of Congress had established a civilian housing agency that set up standards for housing in the United States to be built during the war years. It specified what would go on the inside. For instance, it specified showers, no bathtubs.' The manufacturers of bathtubs in the United States had ceased manufacturing bathtubs about 1942. So even if you tried to get them, they were hard to find." Those scientists and officers fortunate enough to be housed in the Ranch School buildings had the only such facilities in town; hence the name, "Bathtub Row."

Building a modern scientific laboratory presented greater problems. By the time the first scientists arrived on March 15, 3,000 construction workers had been at work for three months and had almost completed the administration building, five laboratories, a machine shop, a warehouse and a barracks. The work was far from perfect, and the morale of the workers, who had been building for three months without any idea of what they were working on, was low. They did not welcome the scientists/critics with enthusiasm.

During the first week of April 1943, J. Robert Oppenheimer and the first staff members to arrive at Los Alamos set up experimental equipment, organized their work areas and moved into the newly completed and, in many cases, uncompleted facilities in the technical area. In the midst of these arrangements, Oppenheimer's assistant, Robert Serber, delivered a series of lectures summarizing what was then known about the design of nuclear weapons. This information included not only the early work that had been done at the University of California by theorists assigned to the electromagnetic separation project led by Ernest O. Lawrence in the Radiation Laboratory, but also the results of the work of a June 1942 conference held in Berkeley. At this conference, Oppenheimer, Serber, Hans Bethe from Cornell University's physics department, John Van Vleck from the University of Wisconsin's physics department, Edward Teller who was on leave from Washington University to the University of Chicago's metallurgical laboratory, Felix Bloch from Stanford University's physics department, Richard Tolman, the California Institute of Technology's dean of physical sciences, and Emil Konopinski from the University of Chicago had discussed the work of British and American theorists and the possibility of a "super" bomb conceived by Teller and Enrico Fermi.

During the nine months that elapsed between the summer conference at Berkeley and the opening of the laboratory, both theoretical and experimental work had gone forward at a variety of academic and non-profit laboratories, and it was to summarize the results of this work that Serber conducted his lectures. Serber made his summaries as terse as possible. At the end of each day, he met with Edward Condon, whom Oppenheimer had brought from the Westinghouse Research Laboratories to serve as associate director of the Laboratory, to write up the lectures and supplement them. The ultimate result was LA-1, "The Los Alamos Primer.

"It was not easy to lecture about the fundamentals of nuclear weapons design in a laboratory still under construction, with carpenters and plumbers in the immediate vicinity of the reading room of the Administration Building where the lectures were given. In his first lecture, Serber began, "The object of the project is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast-neutron chain reaction in one or more of the materials known to show nuclear fission." Oppenheimer sent John Manley, the experimental physicist from the University of Illinois who had helped him organize Los Alamos, up to Serber with a note that he should use the word "gadget" instead of "bomb" because the workmen might overhear the lectures. The name stuck. Throughout the project, the device was known as a "gadget."

Serber's lectures made clear the challenges that faced the new laboratory. He concluded, "the immediate experimental program is largely concerned with measuring the neutron properties of various materials and with the ordnance problem. It is also necessary to start new studies on techniques for direct experimental determination of critical size and time scale, working with large but subcritical amounts of active material." This would require the use of particle accelerations that could produce fast neutrons like the Harvard cyclotron, Wisconsin Van de Graff and Illinois Cockcroft-Walton machines that Manley and University of California professor Edwin McMillan had acquired for the Laboratory, but which were, as yet, in pieces waiting reassembly.

The provision of large but subcritical amounts of active material awaited the completion of the uranium isotope separation plants at Oak Ridge, Tennessee, and the production reactors at Hanford, Washington. To prepare this material for the experiments that would determine the critical sizes of a chain-reacting assembly and the times required for chain reaction, the chemistry and metallurgy staff of the Laboratory would also have to be augmented. The small group of theoretical and experimental physicists Oppenheimer and Manley had thought might suffice to design nuclear weapons would give way to a large, multidisciplinary organization.

University of California contract

The contract between the University of California and the Manhattan District of the Corps of Engineers (MED) to operate Project Y, Los Alamos Laboratory, was not signed until April 15, 1943, after the project was already under way. It was the first such contract between them. A rudimentary agreement was first laid out in a letter from Irwin Stewart on Jan. 23, 1943, and called for an Office of Scientific Research and Development (OSRD) contract with the University of California for "certain investigations to be directed by Dr. J. R. Oppenheimer," at a cost of $150,000 covering the period Jan. 1, 1943, to July 31, 1943.

Such contracts had been the standard means of mobilizing university researchers to work in installations such as the radiation laboratory at the University of California, its namesake at the Massachusetts Institute of Technology and the University of Chicago's metallurgical laboratory.

Enter the MED. The decision to transfer work on the atomic bomb from the OSRD to the MED had been made by OSRD head Vannevar Bush and James Bryant Conant, Harvard University president and chairman of the S-1 committee (the committee that oversaw all phases of work on nuclear weapons) of the OSRD early in 1942, and the district was organized in the summer of that year to take charge of the developmental aspects of the project, especially the manufacture of Uranium 235 and plutonium. Gradually, the MED took over those contracts relating to the bomb.

On Feb. 13, 1943, Oppenheimer and Groves met with Underhill to negotiate a long-term contract to operate Los Alamos Laboratory. The fact that this occurred after the site, equipment and men for the project had been selected suggests that the contract was an afterthought.

Bringing in the University of California in 1943 made recruiting for the work of the Laboratory easier. Underhill, however, insisted on more UC involvement.

A letter of intent was drafted by the Army and signed by Underhill March 3, 1943. The detailed contract required five days to negotiate, from April 15 to April 20, 1943. Underhill succeeded in obtaining the conditions traditional in OSRD contracts. Because the work at Los Alamos had already started, Underhill and the Army gave up the attempt to include an agreement for negotiation with the Army in the contract, and although the main part of the contact was signed on April 20, the negotiation agreement was not added until a year later.

For reasons of security, UC had no representative at Los Alamos with authority comparable to Oppenheimer or the military commander. Only Oppenheimer, Lawrence, McMillan and other members of the University of California faculty recruited for "Project Y" understood the true implications of the work. Neither Underhill nor the regents were told the true purpose of the project. It was not until November of 1943 that Ernest Lawrence, the director of the University of California Radiation Laboratory who had helped to organize Los Alamos, came into Underhill's office, shut the door and asked: "You know what they're doing down in Los Alamos?" When Underhill confessed he did not, Lawrence told him that an atomic bomb was being designed there. Underhill was forbidden, however, to tell the regents.

To ensure UC control and protect the secrecy of Los Alamos, material for the Laboratory was routed through UC's purchasing office in Los Angeles, which shipped it on to Los Alamos, where Mitchell ran the procurement office. The purchasing office was organized March 16, 1943, and branch offices were set up in April 1943 in New York and Chicago to handle emergency requests. Eventually, some 300 UC employees staffed these offices, including 32 buyers and 22 expediters. They purchased approximately $400,000 worth of items (about 6,000) per month during the war.

The arrangement created difficulties and delays that did not diminish as the Laboratory expanded. Orders sent to the Los Angeles office had to be carefully written, because the employees of the purchasing office had no direct contact with the user groups at the Laboratory, no knowledge of its work and therefore could not understand its significance or urgency. Oppenheimer and his staff occasionally complained about inefficient and inexperienced buyers, but as these offices were seriously understaffed and deliberately kept ignorant of the purpose of their work, the inefficiency was probably inherent in the circumstances.

The University of California connection also helped stock the shelves of the Laboratory's library, which was organized and catalogued by Charlotte Serber, the wife of Robert Serber, the theorist who gave the first set of lectures at Los Alamos in April 1943. UC lent 1,200 books and 50 journals to start the library. New books were purchased through Los Angeles, which placed the orders through the library at the University of California. During the course of the war, the number of books rose to 3,000, journals to 160 and 1,500 microfilm reproductions were made.

Although the University of California was kept largely in ignorance about the nature of the project at Los Alamos until after the war, at which time it tried to terminate the contract, Lawrence, Sproul and Underhill finally agreed to continue to operate the Laboratory for the MED's successor, the Atomic Energy Commission, in 1947. The contract, although born in secrecy, was adequate to operate the Laboratory and to complete its wartime mission.

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 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. 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.

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.

The research side of the Laboratory was organized in divisions that reflected traditional academic disciplines: theoretical physics under Hans Bethe of Cornell University; experimental physics under Robert Bacher, also of Cornell; and chemistry and metallurgy under Joseph Kennedy of UC Berkeley; and Cyril Stanley Smith of the American Brass Co.

The Theoretical Physics Division had been organized in March. Edward Teller, who had worked at George Washington University, Columbia University and as a physicist for the Manhattan Engineer District at the Metallurgical Laboratory of the University of Chicago before joining Oppenheimer's summer study of bomb design at the UC Berkeley in 1942, headed one group; Robert Serber, Oppenheimer's assistant at Berkeley in 1942 and 1943 after leaving the University of Illinois, another; Victor Weisskopf of the University of Rochester in New York, a third; and Richard Feynman of Princeton, a fourth. Donald A. Flanders of New York University came later in the summer of 1943 to form a computing group.

The Experimental Physics Division organized shortly thereafter included Robert R. Wilson of Princeton as head of the Cyclotron Group; John H. Williams of the University of Minnesota as head of the Electrostatic Generator Group; Manley as head of the D-D Source Group; Darol Froman, a professor at the University of Denver who had worked as a group leader at the Navy's Radio and Sound Laboratory in San Diego and as a research associate at the Metallurgical Laboratory, as head of the Electronic Group; and Emilio Segre' of the UC Radiation Laboratory as head of the Radioactivity Group. The first three groups had to await the completion of their accelerator laboratories. Segre' and his associates made preliminary measurements of spontaneous fission in uranium and plutonium at the Radiation Laboratory in Berkeley in April and May before transferring the work to Los Alamos. Froman\'s group was busy helping to equip the laboratories.

The Chemistry and Metallurgy Division, which was enlarged to purify the plutonium that would be produced in production reactors at the Hanford Engineering Works for use in the bomb, would require its own large dust-free laboratory. While that was being built, plutonium research at the Metallurgical Laboratory of the University of Chicago; the UC Berkeley's chemistry department; and Iowa State College would have to be coordinated. Charles A. Thomas of the Monsanto Chemical Co. visited the Laboratory in late May 1943 to discuss the position. He did not accept it until July. Brazier designed the new building with his advice.

The new Ordnance Division would be headed by Navy Capt. William S. Parsons, who did not arrive at Los Alamos until June, although he made a preliminary visit in May. The division, like all others at the Laboratory, was divided into groups, and the initial group leaders were all physicists from universities or civilian research bureaus: Edwin M. McMillan from UC's Radiation Laboratory; Kenneth T. Bainbridge of Harvard University's cyclotron laboratory, Robert B. Brode of UC Berkeley's physics department; and Charles L. Critchfield and S.H. Neddermeyer from the National Bureau of Standards. The whole organization was knit together with a governing board, including Hawkins; the division leaders; and other administrative staff heads. Oppenheimer intended it to be an advisory board, but it gradually became a policy-making body to assist in coordinating the scientific and engineering effort.

Oppenheimer also made use of a coordinating council, composed of division and group leaders, to communicate with staff members and exchange information and opinions. Oppenheimer rejected compartmentalization when he instituted the Laboratory colloquium in May 1943. Hans Bethe suggested the establishment of a weekly technical colloquium, and the governing board placed Teller in charge of the weekly meetings of the staff members. Groves objected that this was a major security hazard but Oppenheimer defended it as a tool that could enhance security by giving staff members a better understanding of the need for secrecy. Groves permitted it to maintain morale and unity among the staff, but forbade discussion of work at other laboratories and of production schedules.

The Plutonium Gun

Military guns are simple in design and a known quantity by virtue of their long use by the armies and navies of the world. The decision to use a gun to assemble active material in a fission bomb came about because gun technology is so well known.

During the July 1942 conference hosted by J. Robert Oppenheimer at Berkeley, Calif., it was taken for granted that a large caliber gun would be used to shoot two pieces of uranium into a supercritical assembly. After the discovery of plutonium, the use of guns became more problematic. Light element impurities could cause predetonation if sufficient assembly velocity was not achieved. Despite this concern, the elegant simplicity of gun technology gave Oppenheimer cause for optimism as Los Alamos came into existence. And despite the simplicity of gun assembly, a great deal of uncertainty remained about the nuclear materials and what the final product would look like.

Because of such uncertainty, Oppenheimer took personal control of gun development. As he noted, "At the present time our estimates are so ill founded that I think it better for me to take responsibility for putting them [design specifications] forward." With two types of fissile material to use, Oppenheimer faced a crucial first decision. Should the Laboratory develop a gun capable of using plutonium, the more difficult material to use, and adjust the gun to use uranium? Or, should two different guns be developed simultaneously?

Oppenheimer chose to develop the plutonium gun, code named "Thin Man" and then make the necessary changes to accommodate uranium. He believed that uranium presented few metallurgical problems and any changes in the gun would be minor.

With the help of Richard Tolman of the National Defense Research Committee, Oppenheimer proceeded with an experimental program. Their most significant impact on this program was choosing two key persons: Edwin Rose and Charles Critchfield. Rose, an engineer and gun designer, observed that a gun weapon could be delivered by aircraft if much of the steel used in the normal construction of guns was eliminated.

Since a fission gun would be fired only once, much of the steel used to ensure safety after repeated firings was unnecessary.

Critchfield, a mathematical physicist, brought a wealth of ordnance experience to the Laboratory. Critchfield realized that the Naval Gun Factory needed as much as six months to build the full-scale guns needed by the Laboratory. He suggested that time could be saved by testing at reduced scale using 20mm anti-aircraft guns and 3-inch naval cannon. These could be procured immediately. When the full-scale guns arrived, only the most promising nuclear designs would need to be tested.

Oppenheimer continued his direct supervision of the gun program until June 1943 when Navy Capt. William Parsons became the first Ordnance Division Leader at the Laboratory.

Work on Thin Man continued until July 1944 when Emilo Segre's experiments on the spontaneous fissioning of plutonium proved that a gun could not be used to assemble this material. Oppenheimer made the decision to abandon Thin Man and redirect much of the Laboratory's resources to develop the implosion method.

After the reorganization, gun work focused on uranium assembly, code named "Little Boy." Oppenheimer's earlier decision in 1943 to concentrate on Thin Man on the belief that a uranium gun did not present major technical problems proved prophetic. Little Boy was developed with few major complications.

Weapon Materials

As the staff at Los Alamos began research in the spring of 1943, the most formidable problems it confronted were related to the new materials that would be used in atomic bombs. These materials, uranium-235 and plutonium, were largely unknown. Uranium-235 formed only a tiny fraction of natural uranium (less than 1 percent) and plutonium had been discovered only two years earlier at the University of California, Berkeley, Radiation Laboratory by chemistry professor Glenn Seaborg and his associates. One of Seaborg's associates was Emilio Segre', who had been a member of Enrico Fermi's team at the University of Rome. Fermi and his colleagues originally thought that their bombardment of uranium by slow neutrons in the mid-1930s had produced elements heavier than uranium, or transuranic elements.

Further investigations by Otto Hahn and Fritz Strassman, German chemists at the Kaiser Wilhelm Institute for Chemistry in Berlin, however, had revealed that the uranium fissioned instead. The discovery of fission led in turn to the discovery of the chain reaction that, if sustained, would provide the energy for atomic weapons. Segre', who had fled the anti-Semitic laws imposed by the Fascist regime of Benito Mussolini in Italy, had found a job as a research associate in UC's Radiation Laboratory. There, he investigated the products of the bombardment of uranium by the cyclotron, then the most powerful "atom-smasher" in the world.

After plutonium was discovered by Seaborg at the beginning of 1941, Segre' established that the new element fissioned when struck by fast neutrons, opening the way to its use in an atomic bomb. As Los Alamos was being set up in the spring of 1943, he and his associates at Berkeley turned their attention to spontaneous fission in uranium and plutonium. This process, if proved, might cause an atomic weapon to predetonate, blowing the fissile material apart before it had a chance to undergo an efficient chain reaction.

The possibility of spontaneous fission was real. After Fermi suggested it and UC Berkeley chemist Willard F. Libby sought in vain for it in 1939, the Russian physicists G.N. Flerov and K.A. Petrzhak discovered it in natural uranium in 1940. Segre' had, consequently, to ensure that plutonium and uranium-235 would not have a spontaneous fission rate large enough to cause predetonation in the gun-assembled fission weapon planned.

Working with his graduate students Segre' and two UC chemists, Arthur Wahl and Joseph Kennedy, measured rates of spontaneous fission in natural uranium and plutonium in 1942 and 1943. The plutonium was made by the 60-inch Crocker medical cyclotron at the UC Radiation Laboratory by the bombardment of uranium-238 by deuterons, the ions of heavy water (deuterium). By June 24, 1943, they found that such plutonium had a rate no greater than five spontaneous fissions per kilogram each second, or 18 spontaneous fission per gram of plutonium per hour, an acceptable rate.

These measurements at Berkeley were very difficult; the detectors used were so sensitive that cellos playing in the next room were suspected of causing more counts during the daytime than night-time. The lights left on in the daytime were found to produce photoelectrons that caused the disparity. Leaving a flashlight on at night made up the difference. The coincidence of pulses from several alpha- particles arising from the radioactive decay of plutonium could also mimic spontaneous fission, and extraordinary measures were taken to prepare materials of the right thickness and to calibrate the ionization chambers used to detect fission fragments to exclude these and other signals.

Although the results with plutonium produced in the Crocker medical cyclotron were encouraging, several researchers suggested that plutonium produced in nuclear reactors by the bombardment of uranium-238 by neutrons might have an isotope, plutonium-240, that would be likely to fission spontaneously. If this were only 1 percent of the reactor-produced plutonium and it had a high-spontaneous fission rate, predetonation would be much more likely.

At Los Alamos, chemists already planned to make plutonium that very highly purified by removing lighter elements that might react with alpha particles from decay to produce neutrons that could predetonate the bomb. Plutonium-240, however, could not be chemically separated from plutonium-239 without building huge isotope separation plants similar to those under construction at Oak Ridge, Tenn., used to separate uranium-235 from uranium-238. To investigate the possibility of spontaneous fission in plutonium, Los Alamos Director J. Robert Oppenheimer invited Segre' and his group to move to Los Alamos to continue their experiments there.

Because of the delicacy of their detectors, the group could not remain in the technical area around Ashley Pond, where most of the scientific activity of the Laboratory was concentrated. They sought a place far from disturbances that might upset their instruments and ended up in Pajarito Canyon, 14 miles away. Shielded from radiation by the distance and housed in an old cabin, they found the solitude they required.

On June 17, 1943, word came to Los Alamos of a study of spontaneous fission in polonium by Frederic Joliot and Pierre Auger in occupied Paris. The rate they reported one spontaneous fission in every 1017 atoms of polonium would be sufficient to rule out polonium as an element in the neutron initiator then planned for atomic bombs, because the neutrons produced in the process would pre-ignite the chain reaction. If a similar rate was found in plutonium, it might rule out the use of that element as the nuclear explosive.

Although Los Alamos scientists believed the rate reported was too high, and probably due to impurities in polonium that were difficult to remove, Oppenheimer and the other members of the Laboratory's governing board agreed to give Segre' all the necessary facilities to pursue their research in Pajarito Canyon.

As June 1943 ended, the future of Los Alamos' program for a plutonium bomb seemed in doubt. Only time would tell if plutonium could be used in nuclear weapons and, if so, how. The resolution of those questions was to have a pervasive effect on the new Laboratory and the world.

Although Los Alamos was conceived in September of 1942 and occupied in April 1943, it was not until after the first plutonium arrived in Los Alamos July 10, 1943, that the first physics experiment was conducted at Los Alamos. On July 15, John H. Williams' Electrostatic Generator Group (P-2) observed neutrons from the fission of plutonium-239. Much of the intervening time was spent getting the necessary equipment up and running. The pressure tanks that enclosed the two Van de Graaff accelerators arrived during the course of the lectures and reviews defining the Los Alamos research program. On May 15, the University of Wisconsin "long tank" Van de Graaff produced its first beam. On June 7, the University of Illinois Cockcroft-Walton accelerator followed suit and three days later the "short tank" Van de Graaff, also from the University of Wisconsin, accelerated its first protons.

The "long tank" Van de Graaff had first priority because it would produce 1 MeV (megaelectronvolt) neutrons to cause fission in plutonium. An electron-volt is a unit of energy equal to the energy gained by an electron in passing through a potential difference of one volt. It could measure the number of neutrons produced per fission and the time between "fast" fissions of the type to be expected in a nuclear weapon. Up to that point, these quantities had been measured only in "slow fission" with thermal neutrons, and the fission of plutonium had been studied only through observation of the fission fragments (atomic nuclei) produced.

The Van de Graaff accelerators used at Los Alamos for these experiments were invented in 1929 by Robert J. Van de Graaff, a Princeton University physics professor.

Joseph McKibben, a postdoctoral physicist, and David Frisch, a graduate student at the University of Wisconsin, used deuterons (ions of heavy hydrogen) from the short tank to bombard carbon and other deuterons to produce fast neutrons and directed them at various materials to see which would reflect them best. By September 1942, they had narrowed their search to dense elements like lead, bismuth, tantalum, tungsten, platinum, gold and uranium, but the scattered neutrons from these elements were still very hard to detect. Before the short tank was moved to Los Alamos, McKibben and Frisch ran the accelerator around the clock to get the data they needed.

Four University of Wisconsin graduate students, Alfred O. Hanson, Morris Blair, David L. Benedict and James Hush used the long tank to measure fission cross sections (the probability that the neutron would cause fission) for uranium-235. Bombarding lithium targets to produce neutrons of up to 1.8 MeV to make these measurements, they found the fission cross-section to be about 1.66 barns. Although a uranium atom was not as big as a real barn, this was the name used by physicists for the unit of measurement for nuclear cross sections.

The group succeeded in getting the long tank into operation first and demonstrated that the number of neutrons produced in fast fission of plutonium was adequate to sustain a fission chain reaction. The neutron number was measured using an almost invisible speck of plutonium, about 142 micrograms, which had been produced in the cyclotron at Washington University in St. Louis. "Before we had to turn it over to the chemists," Richards recalled, "we were to measure as many of its physical cross sections as possible. In particular we needed to verify that it produced neutrons upon fission and to measure roughly the number of neutrons per fission. Many of us worked 18- to 20-hour days during this period, but we got the crucial measurements done. We arranged to take a few days vacation afterward. Some of us camped up in the beautiful Pecos Valley."

Not only was the number adequate to sustain an explosive chain reaction, but it was greater than the number of neutrons produced in the fission of uranium-235, to which the Los Alamos experimenters compared it. The experiment also showed that the delay in neutron emission in fast fission of plutonium was so small as not to threaten the possibility of an efficient chain reaction.

In the late summer of 1943, experimental work at Los Alamos was focused on the designs for two gun-type atomic weapons. One would fire a uranium "bullet" into a uranium "target," while the other would use plutonium bullets and targets and, to overcome problems that might be caused by impurities in plutonium, would fire the bullet at a higher velocity.

Implosion Method

It had also occurred to Richard Tolman, a professor of physics at the California Institute of Technology and vice-chairman of the National Defense Research Committee, that fissionable material might be assembled by detonating a high explosive around a hollow sphere and crushing it into a critical mass. Because of the difficulty of implementing this idea, however, few paid much attention to it. Robert Serber, a University of California physics professor, mentioned it in his indoctrination lectures at Los Alamos in April 1943 as one of "various other shooting arrangements" that had been suggested "but as yet not carefully analyzed."

Upon hearing Serber's lectures, Seth Neddermeyer, another professor of physics from Cal Tech, seized upon the idea enthusiastically. He recognized that blowing a sphere of uranium-235 or plutonium together in this matter would assemble these materials more rapidly than a gun could and proposed that it be explored. Oppenheimer agreed to a small program, which was set up on South Mesa.

The Ordnance Engineering Group (E-5) under Neddermeyer's direction, pursued experiments there and in Pennsylvania, at the Bruceton Explosives Research Laboratory of the NDRC. At Bruceton, "implosion charges" were fabricated for them by George Kistiakowsky of Harvard University, who was head of the project. Neddermeyer and Edwin M. McMillan, a University of California physicist who traveled there with him, were impressed that when a shell of explosives surrounding an iron pipe was set off, it closed the pipe. They returned to Los Alamos to repeat the experiment, varying the explosives, the pipe size and the arrangements, and studying the remains. A small plant was built at Anchor Ranch to cast the high explosives used in these experiments.

In September 1943, Oppenheimer asked John von Neumann, a Princeton mathematician who had been working on shaped charges, fluid dynamics and the computation of ballistic trajectories as a consultant to the Army's Aberdeen Proving Ground in Maryland, to look into the theoretical problems faced at Los Alamos.

Von Neumann agreed to spend some time as a consultant, working primarily in his office at the National Academy of Sciences in Washington, D.C., but with an occasional visit to Los Alamos. His first, in September, acquainted him with the implosion program. He suggested that shaped charges would produce an appropriate spherical detonation wave and pointed out that the method was not only likely to be faster than the gun, but that it would produce higher pressures and reduce the amount of active material required, making the bomb more efficient.

The Laboratory was galvanized by von Neumann's insight. Theorist Edward Teller scolded Charles Critchfield, who had been working on the project, for overlooking the greater efficiency to be expected from implosion, and Manhattan Engineer District Commander Leslie Groves chided Navy Capt. William Parsons for focusing on the "safer" gun method.

Kistiakowsky was persuaded to come to Los Alamos to head a new program to develop the high explosives. A diagnostic program, involving X-ray and photographic techniques as well as the "terminal observations" Neddermeyer had employed, was begun.

New ideas for diagnosing an imploding system, including the use of a betatron electron accelerator, magnetic fields, electric pins and natural sources of radioactivity to produce signals that would indicate the rate of collapse inside the sphere, were subsequently introduced.

Calculations showed that an inward-moving spherical shock wave would be disrupted by the interference of detonation waves from the high-explosive segments and by instabilities arising as the tamper material was pushed into the heavier nuclear core by the implosion. This led to a fuller understanding of the behavior of a symmetric implosion and greater doubt that it could be achieved. What was needed was an explosive lens to convert the detonation wave to a spherically convergent form.

Under Kistiakowsky's direction, a new site, Sawmill, off S-Site, was constructed between December 1943 and May 1944. James Tuck, a member of the British Mission at Los Alamos, had worked in England on the use of combinations of different explosives to "focus" detonation waves and headed a group to develop an explosive lens for the implosion gadget. After von Neumann suggested a workable design for the lens, Lt. Cmdr. Norris Bradbury, a Stanford physics professor assigned to the Dahlgren Proving Ground of the U.S. Navy Ordnance Bureau, was recruited in June 1944 to solve the problem of casting the high explosives for the design.

Even if the appropriate explosive lenses could be produced, they would have to be set off simultaneously to create a symmetrical implosion. After experiments with a variety of Primacord and electric detonators, Luis Alvarez, a University of California Radiation Laboratory physicist who had come to the Laboratory from radar work at the Massachusetts Institute of Technology, and his student, Lawrence Johnson, devised such a system in May 1944.

Although progress had been made, Kistiakowsky was skeptical about the success of the program in the spring of 1944. He predicted that by October they might be able to "recommend a design of the gadget that will have a finite chance of properly functioning," but added that in "November or December the test of the gadget failed. Project staff resumes frantic work, Kistiakowsky goes nuts and is locked up." The consequences of such a failure, however, would be devastating to the program.

In the summer of 1944, Emilio Segre's group at Pajarito Site found that plutonium from nuclear reactors had an isotopic impurity, plutonium-240, that prohibited its use in a gun-type assembly. Since all of the plutonium that would be used in the atomic bomb would be produced in reactors, this meant that the vast investment in the Hanford production reactors built by DuPont would go down the drain unless implosion could be perfected.

The Laboratory was reorganized to accomplish this. New division, G for gadget and X for explosives, were set up to develop the nuclear and high-explosive components of the implosion device. The Laboratory's Governing Board was divided into administrative and technical boards to manage the growing effort. Even then, the Technical Board's tasks were increasingly assumed by lower-level interdivisional committees and conferences that coordinated the effort required.

The reorganization of the Laboratory was accompanied by a vast expansion in personnel, as no stone was left unturned in the search for a suitable design and the development of suitable components for the gadget. From roughly 1,100 personnel, Laboratory employment grew within a year to more than 2,500. Implosion meant an explosion of the Laboratory population.

It was not clear, however, that the much more complicated implosion device would work. Before it could be used in combat, a test would be required.

Computers were people using desk calculators when Los Alamos began. By the end of the war, Los Alamos scientists were using the first electronic computer. John von Neumann was the primary agent of this change, which led to the Laboratory's strong program in computer science and technology, as well as making it possible to calculate the behavior of nuclear explosives.

Early calculations relating to the diffusion of neutrons in a critical assembly of uranium were made by Eldred Nelson and Stanley Frankel, who were members of Robert Serber's group in the Radiation Laboratory at the University of California, Berkeley, in 1942. When they came to Los Alamos in the spring of 1943, they ordered the same sorts of machines that they had used in California: Marchant and Friden desk calculators to make the calculations required in the design of nuclear weapons.

To perform some of these repetitive calculations, a group of scientists' wives were recruited to form a central computing pool. These "computers" included Stanley Frankel's wife, Mary; Josephine Elliott; Beatrice Langer; Mici Teller; Jean Bacher; and Betty Inglis. This became group T-5 under New York University mathematician Donald (Moll) Flanders when he arrived in the late summer of 1943.

The mechanical calculators tended to break down under heavy use by physicists and had to be shipped back to the manufacturer until physicists Richard Feynman of Princeton University and Nicholas Metropolis of the University of Chicago learned to repair them. Although Theoretical (T) Division Leader Hans Bethe at first objected that this was a waste of time, he relented when the number of working calculators diminished.

Dana Mitchell, whom Laboratory Director J. Robert Oppenheimer had recruited from Columbia University to oversee procurement for Los Alamos, recognized that the calculators were not adequate for the heavy computational chores and suggested the use of IBM punched-card machines. He had seen them used successfully by Wallace Eckert at Columbia to calculate the orbits of planets and persuaded Frankel and Nelson to order a complement of them.

In September 1943, von Neumann made the first of many visits to Los Alamos. A mathematician at the Institute for Advanced Study at Princeton, he had been asked by Oppenheimer to serve as a consultant in hydrodynamics, and during his visits he became aware of the work on implosion being conducted by Seth Neddermeyer and his group.

Von Neumann, who also was a consultant on explosives for the Army, pointed out that shaped charges could be used to produce a more uniform shock wave for this purpose. He subsequently developed Neddermeyer's one-dimensional theory of implosion with Edward Teller, the theoretical physicist from the Metallurgical Laboratory of the University of Chicago. When von Neumann had difficulty with the pure high-density incompressible phase of implosion, he suggested a test implosion to determine physical quantities that could not be calculated analytically. He subsequently formulated another model for computation, and Teller set up a group in T Division devoted to the theory of implosion.

The new IBM punched-card machines were devoted to calculations to simulate implosion, and Metropolis and Feynman organized a race between them and the hand-computing group. "We set up a room with girls in it. Each one had a Marchant. But one was the multiplier, and another was the adder, and this one cubed, and all she did was cube this number and send it to the next one," said Feynman. For one day, the hand computers kept up: "The only difference was that the IBM machines didn't get tired and could work three shifts. But the girls got tired after a while."

Feynman worked out a technique to run several calculations in parallel on the punched-card machines that reduced the time required. "The problems consisted of a bunch of cards that had to go through a cycle. First add, then multiply, and so it went through the cycle of machines in this room - slowly - as it went around and around. So we figured a way to put a different colored set of cards through a cycle too, but out of phase. We'd do two or three problems at a time," explained Feynman. Three months were required for the first calculation, and Feynman's technique reduced it to two or three weeks.

The first implosion calculation showed that the fissile material would be strongly compressed and that a high yield would result from assembling a relatively small amount of fissile material if a spherically symmetrical implosion was produced. Although much work on explosives lenses, detonators and other components of the device was required to accomplish this, the Trinity test July 16, 1945, showed that the calculation was correct. About a dozen other calculations of implosion were done to refine it before the end of the war.

In the meantime, von Neumann brought news of computer developments elsewhere, such as Bell Laboratory's relay computer and Howard Aiken's Mark I electromechanical calculator at Harvard where Aiken was director of the Harvard Computation Laboratory. The Mark I was even used to run an unclassified version of one of the Los Alamos problems. Although it took several times as long as the Los Alamos machines, it computed to far greater precision.

Von Neumann saw that problems like those encountered at Los Alamos could be solved by electronic computers similar to the electronic numerical integrator and calculator (ENIAC) being developed at the University of Pennsylvania. In 1944 and 1945, he formulated ways to translate mathematical procedures into a language of instructions for such a machine. And he recommended to Teller, who had conceived of a thermonuclear or "super" bomb, that one of the computational problems associated with its design be used to test the ENIAC, because it would be much more demanding than the ballistic trajectories the Army had designed it to calculate. Metropolis and Frankel traveled to the University of Pennsylvania early in 1945 to discuss the problem with the developers of ENIAC, John Mauchly and J. Presper Eckert.

The calculations were run in December 1945 and January 1946. A half-million punched cards of data were transferred from Los Alamos to Philadelphia to run it, and mathematician Stan Ulam, who von Neumann had recruited to come to Los Alamos from Princeton, recalled "the spirit of exploration and of belief in the possibility of getting trustworthy answers in the future. This partly because of the existence of computing machines that could perform much more detailed analysis and modeling of physical problems."

In the postwar era, von Neumann continued to arrange for access to the ENIAC for Los Alamos scientists and also built an improved version of the electronic computer at the Institute for Advanced Study at Princeton, where Oppenheimer became director. Inspired by his example, Los Alamos had Metropolis build the mathematical analyzer, numerical integrator and computer, or MANIAC, which was completed in 1952 and was responsible for the calculations of Mike, the first hydrogen bomb. It was followed by MANIAC II, the IBM-built STRETCH supercomputer and a series of commercial super computers that have made the Laboratory the world's largest scientific computing center.

Von Neumann also helped Ulam and Metropolis develop new means of computing on such machines, including the Monte Carlo method, which has found widespread application. His influence on the development of electronic computers was far-reaching, and he continued to foster their development at Los Alamos up to the time of his death in 1957 while serving on the Atomic Energy Commission.

The wartime work of the Laboratory created a need for computing that stimulated von Neumann, Metropolis, Ulam and others to reduce previously insoluble physical problems to a form in which they could be calculated automatically. The use of these techniques not only made possible the design of nuclear and thermonuclear weapons, but also the solution of many other scientific problems, ranging from aerodynamics to molecular biology. What began with a brief visit to the Laboratory by von Neumann in September 1943, has become a revolution in science and technology.

In October 1943, the 9812th Special Engineer Detachment (SED) of the Manhattan Engineer District (MED) began to supply technical personnel to the Laboratory. Scientists who had not been recruited in the early days of the Laboratory, but who had been drafted into the Army, were now routed to New Mexico to make a different contribution to the war than any they could have anticipated.

So, even though Robert Bacher, who headed the Experimental Physics Division, and other Los Alamos scientists had refused to don a uniform, the military had scientists in uniform at Los Alamos. In fact, 42 percent of the Laboratory wore uniforms. "Although the Army had failed to get the senior scientists in uniform as it wanted to, it did succeed in getting some very young men who were students in engineering and physics - some of them with Ph.D.s."

Bernice Brode, the wife of Robert Brode who was in charge of the group that designed fusing and firing of the bomb, recalled in her "Tales of Los Alamos," "The SED boys were quite different from the regular post soldiers. They looked, in spite of the uniforms, like budding professors instead of combat troops. Shortly after they came up to the Hill, some high brass from Washington came for a formal military review in the baseball field in front of the Big House (at Fuller Lodge).

"All of us came with our children to see the show. The MPs, the post soldiers, the Women's Army Corps (WAC) and even the doctors made a fine upright showing as they marched across the field, but the newly arrived SED boys were terrible. They couldn't keep in step. Their lines were crooked. They didn't stand properly. They waved at friends and grinned. The situation was not helped by the fact that they received the loudest applause from the bleachers. The visiting brass let it be known that they were displeased, and one general even called them a disgrace to the army."

Despite their performance as GIs, these young men "worked long hours in the tech area," according to Brode, and "although they often worked late into the night to meet a deadline, they were expected to arise at dawn for inspection and drill by tough sergeants from the regulars.

"Once, when a sergeant became irritated by his yawning, half-hearted crew and shouted, If you guys think I like this job, you got another think coming,' one of the SED boys offered to lead the drill in his place. He shouted orders in imitation of the sergeant's voice: Thumbs up, thumbs down. Thumbs wiggle-waggle.' Even the sergeant broke down and dismissed them. My husband and others who used the SED boys finally got their discipline relaxed, the drill stopped, and the inspection let go so they could sleep in the morning."

By the end of 1943, nearly 475 SEDs had arrived. By 1945, the unit included 1,823 men. Most were mechanical, electrical and chemical engineers. About 29 percent of them had college degrees. Because of their special skills, exemption from drill was not the only privilege accorded them. They were all permitted to be non-commissioned officers, and two-thirds of them ranked sergeant or higher.

Since many had no basic training, the members of other military units, such as the military police, who were also assigned to Los Alamos, resented their "apparent infringement on the military prerogative." According to Lt. Edith C. Truslow, a WAC then at Los Alamos, "Even before the nature of the project was published, many enlisted men tried to obtain transfers to the SED."

The SED was the result of the shortage of scientific and technical personnel at the time the Laboratory was founded.

In May 1943, the MED had established the detachment with an initial allotment of 675 men, divided into a headquarters detachment and four separate companies. Soldiers were recruited through the Army specialized training program, at universities and colleges throughout the country, and the Roster of Scientific and Specialized Personnel. The National Defense Research Committee, founded to mobilize academic and industrial science in 1940, had compiled the roster.

The establishment of the 9812th SED at Los Alamos allowed the MED to route civilian scientists and technicians whose deferments they could not or would not arrange to the Laboratory. The MED was often reluctant to intervene with local draft boards to secure deferments because it could not reveal the nature of its work. In late 1943, however, when fathers and those with occupational deferments began to be drafted, Laboratory Director J. Robert Oppenheimer predicted disaster for the project. The MED's Selective Service Section took drastic steps to secure their deferments, and by the end of the war, more than 60,000 deferment actions, involving scientists at Los Alamos; Oak Ridge, Tenn.; Chicago; and Berkeley, Calif., among other MED installations, were processed.

Nevertheless, when in February 1944 the War Department forbade the deferment of men under 22 in the employment of the Army or its contractors, a number of the younger civilian scientists found themselves drafted and reassigned to the Laboratory as members of the SED. They thus joined those who had already been inducted and wound up far from the front.

For those who were drafted and wound up in the SED, conditions were, if superior to their uniformed companions, inferior to those of civilian scientists who had won deferments at Los Alamos. Unlike them, SED technicians and scientists could not bring their families to Los Alamos or to surrounding communities.

Their commander, Maj. Peer de Silva, who was also the Post Military Intelligence Officer, refused to allow their wives to be hired at Los Alamos so that they could be quartered on-site. This, the official Army history tells us, "severely strained the morale of many junior scientists and technicians."

As they arrived at Los Alamos, the members of the SED found themselves assigned to test sites being completed at Anchor Ranch and S-Site. As they became familiar with the work, they won support from their civilian supervisors in matters of military discipline and promotion. George Kistiakowsky, who headed the division in charge of explosives development at S-Site, took their complaints to Oppenheimer and MED Commander, Gen. Leslie Groves.

Riding back to Albuquerque with the general after one of Groves' trips to Los Alamos, Kistiakowsky insisted that the SED receive better treatment. "Of course Groves immediately told me that as a civilian I had no business to tell him anything about Army matters," Kistiakowsky recalled, "and I said that the SEDs were part of my technical staff, they had to report to me, they had to work for me and therefore I had the authority. Well, I got absolutely nowhere. I then used my ultimate weapon: I said I would resign."

Before he could resign, Maj. T.O. Palmer was appointed to replace de Silva as commander of the SED in August 1944. He developed a system under which the groups and divisions made promotion recommendations. This maintained morale, even though conflicting military and laboratory duties continued to be a problem.

In addition to the ordnance test sites, SEDs were assigned to the group of computers working under Richard Feynman using IBM punched-card calculators. Feynman objected to the Army's refusal to tell the SEDs what they were working on. "They came to work, and what they had to do was work on IBM machines-punching holes, numbers that they didn't understand. Nobody told them what it was."

Feynman convinced Oppenheimer to get special permission "so I could give a nice lecture about what we were doing, and they were all excited: We're fighting a war; we see what it is!' They knew what the numbers meant." This led to a "complete transformation" according to Feynman. "They began to invent ways of doing it better. They improved the scheme. They worked at night, they invented several of the programs that we used, and so my boys came through, and all that had to be done was to tell them what it was."

Val Fitch, who later won a Nobel Prize in Physics recalls, "A number of young men, like myself, very early in their lives and careers, were exposed to superb physicists who were remarkable in many respects, and it had a profound influence upon us." After another summer at Los Alamos in 1948, Fitch received his Ph. D. from Columbia University in 1954 and went on to win the 1980 Nobel Prize in Physics for his work in particle physics.

Many other members of the SED went on to scientific careers. Los Alamos provided all of them an opportunity to associate with some of the leading physicists, chemists and metallurgists of their time. Some, like Bill Hudgins, returned to Los Alamos to work on the MANIAC and STRETCH computers. Gerold Tenney, a long-time group leader in WX Division and others also became part of the postwar staff. Among those who had to don a uniform in World War II, the SEDs were surely among the most fortunate. Before they could muster out, however, the SEDs had to complete the biggest test of all - Trinity.

The Los Alamos Laboratory was organized in 1943 to design a nuclear weapon that the Army hoped would win World War II. In the course of the next two years, the Laboratory designed a weapon using uranium-235 assembled by firing one part of a critical mass into another, but this technique was found to be inadequate for plutonium, because isotopic impurities of plutonium-240 would cause it to predetonate.

In the second year of its existence, therefore, the Laboratory was reorganized to solve the much more difficult problems of implosion - the uniform compression of plutonium to a super-critical mass that had been proposed by Seth Neddermeyer of the California Institute of Technology, John von Neumann of the Institute for Advanced Study at Princeton and others.

Trinity test site

Because of the uncertainties attending almost every phase of the implosion weapon, it was decided almost at the beginning of the effort that the implosion bomb would have to be tested. After various test sites were considered, a location in the Jornado del Muerto desert in central New Mexico was selected. Harvard physicist Kenneth Bainbridge planned and University of Minnesota physicist John Williams supervised the construction of the facilities to support a test there.

Los Alamos Director J. Robert Oppenheimer named the site "Trinity" after a poem by John Donne that he had been reading. To capture the plutonium that might be lost if the bomb fizzled, Manhattan Engineer District Commander Leslie Groves ordered a container, called "Jumbo," to be built at a cost of more than $12 million. Jumbo was the largest item that had ever been shipped by rail, and several trestles on the railroads from the factory that built it in Ohio to the Trinity site had to be rebuilt.

By the time Jumbo arrived, the production of plutonium at the Hanford Engineer Works had increased so that Groves was less chary of it, and Oppenheimer and his colleagues believed that there was less chance of a fizzle. Consequently, the container was relegated to the sidelines and hung not far from Ground Zero to serve as an indicator of the power of the bomb. It emerged unscathed although the tower was destroyed.

The TRINITY High Explosive Test Stack

The construction of the Trinity site was rapidly accomplished in the winter and spring of 1945, and by June, Bainbridge was ready to calibrate the instruments that would be used to measure the blast, heat and radiation of the "gadget" using a 100-ton stack of high explosives tagged with fission products from the Hanford pile. The 100-ton test was the largest man-made explosion up to that time and made it possible for the Los Alamos scientists to refine their instruments before the much larger blast anticipated from the gadget.

The design of the gadget had been fixed in February 1945 when Groves ordered a design freeze so that the device could be ready by July. A conservative solid-core design by Robert Christy, a member of the Theoretical Physics (T) Division, the gadget required the development of detonators, fuses and high-explosive lenses that were not yet perfected. Given a clear goal, however, Los Alamos scientists and technicians succeeded in producing all of the components of the device successfully by July 13.

On that day, assembly of the gadget began at Trinity. A crew led by Norris Bradbury, a professor of physics at Stanford University who had come to Los Alamos by way of the Naval Reserve and Dahlgren Proving Grounds, assembled the high-explosive lenses that had been brought from V-site at Los Alamos the day before escorted by Harvard professor George Kistiakowsky, who had led the high-explosives effort at the Laboratory since November 1943. Bradbury, Kistiakowsky and five G (gadget) engineers' began their work at 1 p.m. After the tamper and the active material were inserted into the spherical case, the final high-explosives were inserted, "as slowly as the G-engineers wished," said Kistiakowsky.

Saturday, July 14, 1945, the assembled gadget was hoisted to the top of the 100-foot tower on which it would be detonated. The firing unit was wired by late afternoon. Bradbury's schedule for Sunday, July 15, called for the staff to "look for rabbit's feet and four-leaved clovers." The detonation was scheduled for 4 a.m., Monday, July 16.

Meantime, Los Alamos scientists had conducted a test of the implosion assembly at Los Alamos that seemed to indicate that it would not work.

Kistiakowsky was roundly criticized by Groves and Oppenheimer. His peacetime boss, James Bryant Conant of Harvard University, who was the scientific head of the atomic bomb effort, subjected him to a two-hour interrogation as to the causes of the failure of that effort. Kistiakowsky, however, was sure that the assembly would work, and Theoretical Division Leader Hans Bethe got him off the hook when he reported that calculations showed that the detectors used for the Los Alamos test could not have distinguished between success and failure.

As the test approached, the weather worsened, as the meteorologist assigned to predict it had warned. A thunderstorm broke over the site late on July 15, and the test was postponed from 4 a.m. to 5:30 a.m. to avoid the possibility of a rain-out of fission products from the bomb cloud. In nearby settlements, members of the health physics team were ready to evacuate the population should the test greatly exceed expected yields. Although most scientists believed that the yields would be low, Edward Teller, group leader of the Super and General Theory Group (F-1) in F (Fermi) Division, bet that it might exceed 40 kilotons, and Enrico Fermi, head of F Division, was heard taking side-bets that the bomb would incinerate New Mexico. Groves called the governor of New Mexico to alert him that an evacuation of the state might be required.

Oppenheimer was in a state of high tension during the early morning hours, but, as predicted, the weather cleared and the countdown for the test was begun at 5:10 a.m. "As we approached the final minute," Groves recalled, "the quiet grew more intense. I was on the ground (at Base Camp) between [ Vannevar] Bush [chairman of the Office of Scientific Research and Development] and Conant. As I lay there in the final seconds, I thought only what I would do if the countdown got to zero and nothing happened." At the control point, Joe McKibben, who had been with Project Y since the beginning, threw the switch that started the precise automatic timer at minus 45 seconds. Only Donald Hornig, a physical chemist from Harvard University, on the arming party, could stop the explosion.

The 1945 TRINITY nuclear explosion

At 5:29:45 a.m., the gadget exploded with a force of 21,000 tons of TNT, evaporating the tower on which it stood. Groves' deputy, Gen. Thomas Farrell, wrote that the "whole country was lighted by a searing light with the intensity many times that of the midday sun. It was golden, purple, violet, gray and blue. It lighted every peak, crevasse and ridge of the nearby mountain range with a clarity and beauty that cannot be described but must be seen to be imagined. Seconds after the explosion came first the air blast pressing hard against the people, to be followed almost immediately by the strong, sustained awesome roar that warned of doomsday and made us feel we puny things were blasphemous to dare tamper with the forces heretofore reserved for the Almighty." Oppenheimer was reminded of the quotation from his favorite Sanskrit text, the Bhagavad-Gita, "I am become Death, the Destroyer of Worlds." To his brother, Frank, who had helped construct the site, he said only, "It worked."

Los Alamos had succeeded in producing a nuclear weapon only two years, three months and 16 days after it was formally opened. The implosion bomb was, however, a vast departure from the nuclear weapon first envisaged. That device, the gun-type uranium weapon, did not need to be tested. Farrell commented to Groves immediately after the Trinity test, "The war is over." "Yes," Groves replied, "just as soon as we drop one or two of these things on Japan."

External link