30 results
1 - Introduction
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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The Discovery of Spontaneous Fission in Plutonium
It was the spring of 1944. In a secluded canyon in New Mexico, 14 miles from the bustling technical area of the wartime Los Alamos Laboratory, three physics graduate students were working inside a Forest Service log cabin filled with electronics. For the past eight months, they had been driving there each day by jeep to search for evidence of “spontaneous fission,” a naturally occurring process in which certain heavy atomic nuclei split of their own accord, emitting neutrons. Anxiously, they puzzled over a startling oscilloscope trace produced by a sample of plutonium. Why were these students studying the phenomenon of spontaneous fission in this canyon? What caused their concern?
The professor in charge of the work, nuclear physicist Emilio Segrè, had fled Italy in 1938 and joined Ernest Lawrence's nuclear physics laboratory in Berkeley, California. In 1943, at the request of theoretical physicist J. Robert Oppenheimer, Segré had moved several of his Berkeley experiments to Los Alamos to be part of Project Y – the secret project to build the first atomic bombs. Jointly directed by Oppenheimer and military engineer Gen. Leslie R. Groves, Project Y was a part of the Manhattan Project (the Manhattan Engineer District). Before World War II, Los Alamos, a small New Mexico town on a high mesa, had been the site of a ranch school for boys.
8 - The Implosion Program Accelerates: September 1943 to July 1944
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 129-162
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By late summer 1944, the implosion program was among the laboratory's highest priorities. It had started out as a small, informally run, back burner effort of a handful of researchers surrounding the reserved Seth Neddermeyer (Chapter 4). Between the fall of 1943 and the summer of 1944, it was transformed into a well-coordinated, multidisciplinary research effort of more than fourteen groups operating within T-Division and the newly created Gadget (G) and Explosives (X) Divisions.
The shift began with a visit in late September 1943 by the great mathematician and physicist John von Neumann. On learning about Neddermeyer's test implosions of small cylindrical metal shells, von Neumann pointed out that their efficiency could be increased using a substantially higher ratio of explosive to metal mass, which would promote more rapid assembly. The suggestion excited leading Los Alamos theorists, including Bethe, Oppenheimer, and Teller, who could now envision an atomic weapon requiring active material having less mass and a lower level of purity than was needed in the gun device – advantages of particular interest to General Groves.
Theorists, particularly Bethe and Teller, spent more and more time on implosion questions, while von Neumann continued to work on theoretical aspects of the implosion in Washington, D.C. The new implosion theory group was set up in March 1944 under Teller to develop the mathematical description of implosion. Additional experimentalists joined the program. Neddermeyer's E-Division group expanded from five to roughly fifty.
20 - The Legacy of Los Alamos
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 403-417
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The United States would not have been able to complete the atomic bomb project without its vigorous economy and substantial industrial facilities. However, the scientific resources of the nation were just as important, given the existing gaps in scientific knowledge at the time Los Alamos opened its doors. President Roosevelt's decision to support atomic bomb research preceded the first demonstration of a divergent chain reaction, the development of an industrial-scale method for separating 235U, and determination of plutonium's chemical and physical properties. In organizing the American atomic bomb project, Vannevar Bush drew on a sizable community of well-trained scientists having a wide repertoire of techniques and approaches. In bringing these tools to bear on the wartime problem of building the atomic bomb, the Los Alamos scientists developed a new approach to research.
What were the elements of this approach? First, the research was bound even more tightly than was conventional science to the behavior of artifacts and apparatus. The bombs had to explode, the detonators to fire, and the shape of the gadgets was constrained by that of the B-29 bomb bays. The technology had, in principle, to be totally reliable. Malfunctioning meant failure – it could no longer be construed as but another step in the process of understanding the physical world. In a context in which the lack of funding was not a constraint on research, one result was that solutions were often approached in several ways at once.
Epilogue
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 398-402
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The Japanese began surrender negotiations one day after the Nagasaki bombing. Communities everywhere experienced the war's end with heartfelt relief. Los Alamos scientists were particularly proud of the unique role they had played in bringing the war to a close. The relief – and pride – were short-lived, for most of those who had worked on the bomb suffered loss of focus, while confronting an array of difficult choices, for example, whether to feel guilty for adding atomic bombs to the world's arsenal, and whether to continue working at Los Alamos. For a short time, the technical work of the laboratory slowed down, almost to a halt.
Responses to the war's end at Los Alamos varied a great deal. Laura Fermi recalls children parading through the streets, banging on pots and pans and joyfully making mini-explosions, while their parents grappled with the sobering implications of their achievement. Depression typically followed a short period of relief. Richard Feynman recalls that while he sat on a jeep and pounded on drums during one of the many end-of-the-war parties held at Los Alamos, he noticed that Robert Wilson was not jubilant. Feynman also became depressed soon afterward. Only a few of the scientists saw hope in the fact that the bomb was so destructive – believing that nuclear weapons might actually end all wars because the second use of so terrible a weapon was unlikely.
11 - Uranium and Plutonium: Early 1943 to August 1944
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 205-227
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The story of the production of fissionable materials at Los Alamos is about the challenges of working with little-known, scarce substances under difficult experimental conditions, as well as the excitement of discoveries and unexpected turns in the course of all-out efforts to achieve practical results quickly. The interplay between the plutonium and uranium efforts within CM-Division reflects the wartime strategy of pairing complicated and straightforward tasks. In this way, personnel, equipment, and time could be focused on the most demanding problems. Thus, the relatively simple effort to produce uranium gun parts at Los Alamos complemented the more difficult effort to produce plutonium spheres, just as the relatively simpler gun program as a whole later complemented the more complex implosion program. Those implementing the less intricate effort were under pressure to proceed rapidly and produce absolutely reliable results meeting all contingencies so that more of the group's resources could be diverted to the thornier problem. Consequently, the uranium program was remarkably fast-paced and rigorous. The need to make the most of resources and save time weighed especially on Joseph Kennedy, Arthur Wahl, and Cyril Stanley Smith in CM-Division, because they had to adjust to the changing requirements of the other divisions, for whom they provided support services, while at the same time working to achieve their own goals.
5 - Research in the First Months of Project Y: April to September 1943
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 67-90
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As soon as the Los Alamos Laboratory opened its doors, committees were formed to plan the research program and cope with practicalities. Robert Serber offered an indoctrination course early in April 1943 to acquaint scientists with the current state of research on the atomic bomb. Conferences that month laid out specific research objectives. Even though many fission constants were poorly determined and the accuracy of approximations was generally low, Los Alamos physicists were confident that a reasonably efficient gun bomb could be built. Acceptance of the gun as a workable assembly lent optimism to the entire project. As a fallback, Oppenheimer established a small research effort under Seth Neddermeyer to explore implosion assembly.
The Planning Board
Committees helped Oppenheimer make major decisions, with Groves's approval. The first informal committee – Robert Wilson, Edwin McMillan, Oppenheimer, Edward Condon (the associate director), John Manley, and Serber – met on 6 March 1943 and considered practicalities, such as when people and equipment would arrive and who would handle services rendered by the machine and electronics shops.
This initial planning group gave way several weeks later to a larger committee called the Planning Board, which coordinated the technical program over the next month. Oppenheimer, Condon, Dana Mitchell, and Julian Mack provided administrative guidance, while Wilson, Serber, John Williams, McMillan, and Donald Mastick planned the scientific program.
Preface
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp ix-xvi
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The story of the Los Alamos project to build the first atomic bombs has been told often. Why then another history of Project Y, as it was known during World War II? Three features distinguish this account: it is a history of the technical developments; it is based on the full complement of documents, both classified and unclassified, of wartime Los Alamos; and it explores for the first time the methodology by which researchers at Los Alamos succeeded in their wartime mission.
Unlike earlier histories of Los Alamos, this book treats in detail the research and development that led to the implosion and gun weapons; the research in nuclear physics, chemistry, and metallurgy that enabled scientists to design these weapons; and the conception of the thermonuclear bomb, the “Super.” Although fascinating in its own right, this story has particular interest because of its impact on subsequent developments. Although many books examine the implications of Los Alamos for the development of a nuclear weapons culture, this is the first to study its role in the rise of the methodology of “big science” as carried out in large national laboratories.
Our primary aim is to recount this technical history, but we have not ignored the social context entirely. Although we largely leave for other historians the problem of analyzing the social community at Los Alamos in wartime – for example, the role of women, of foreign scientists, and of military personnel – we do provide an abbreviated account of the establishment and early years of the unique community that grew around the Los Alamos Laboratory.
10 - The Nuclear Properties of a Fission Weapon: September 1943 to July 1944
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 178-204
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Between the summers of 1943 and 1944, the Theoretical Division, under Hans Bethe, and the Physics Division, under Robert Bacher, collaborated in studying the nuclear physics of the atomic bomb. T-Division's responsibilities included calculating critical mass and efficiency. The lack of hard nuclear-constant data was particularly troubling. While P-Division worked to improve the experimental data using available detectors, accelerators, and other devices, T-Division developed flexible models based on the changing set of available data. To cross-check their results, researchers often used different methods to solve the same problem. For example, the Water Boiler, a nuclear pile using enriched uranium in a water solution, provided a means of checking critical mass calculations. As a backup, Richard Feynman made calculations on uranium hydride, then being considered as a potential active material. Teller's investigation of the hydrogen bomb (the Super) was an alternative approach to a nuclear weapon. The opportunity to conduct physics research on a larger scale than had ever before been attempted gave the Los Alamos physicists the experience of working in well-funded multi-disciplinary groups, which included both experimentalists and theorists, as well as electronics experts, chemists, and metallurgists.
Nuclear Theory: Critical Mass and Efficiency
In September 1943, T-Division was refining its critical mass and efficiency predictions and calculating the damage the bomb could cause. Up to this point, the division had remained somewhat informal in its organization to accommodate changing priorities, but by October it had begun to subdivide into groups: Bethe took on the problem of implosion, Victor Weisskopf led the calculations of efficiency, Robert Serber spearheaded diffusion theory, Edward Teller assumed responsibility for both the Super and implosion, Feynman led the uranium hydride calculations, and Donald Flanders headed the computational effort.
18 - The Test at Trinity: January 1944 to July 1945
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 350-377
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Just before dawn on 16 July 1945, the area selected for the Trinity test – the desolate Jornada del Muerto region of New Mexico – no longer swarmed with activity, as it had in the past several weeks. The thunder-storms that had worried Groves and Oppenheimer through the night had stopped. The scientists, who had worked almost nonstop in preparing for the first atomic bomb test, waited tensely for the test to begin.
Arranging their apparatuses around the gadget – ionization chambers, seismographs, motion picture cameras, and other devices – they prepared to record physical aspects of the explosion: light, heat, neutrons, gamma rays, and other features. The data would indicate what to expect of combat atomic bombs and how to achieve the most destruction. But even the most careful preparations could not guarantee a successful test, because the weather had to be just right to prevent heavy fallout from reaching populated areas. Completing the test on schedule became of paramount importance when President Harry S. Truman announced that he would meet with Churchill and Stalin at Potsdam on 16 July 1945.
The Experimental Program
Because only a limited number of measurements could be taken at Trinity, the ones to be selected became a critical topic of discussion. A panel consisting of Fussell, Moon, Bernard Waldman, and Victor Weisskopf was assembled to evaluate proposals. Data were needed on both the performance and the effects of the weapon.
12 - The Discovery of Spontaneous Fission in Plutonium and the Reorganization of Los Alamos
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 228-248
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During the spring of 1944, Emilio Segrè's group in P-Division made the startling observation that the first samples of pile-produced 239Pu had an unusually high spontaneous fission rate, with a neutron emission approximately five times that of cyclotron-produced 239Pu. This finding confirmed the gnawing suspicions of Fermi, Segrè, Seaborg, and others that the neutron bath in the production piles at Clinton and Hanford might cause the formation of a significant quantity of 240Pu, an as-yet-unobserved spontaneously fissioning isotope of plutonium. However, the alarmingly high rate of the spontaneous fission was unexpected. This rate increased the neutron background enough to make it highly probable for a gun-assembled gadget to predetonate and thus undermined the plutonium gun program.
Determined not to lose the heavy investment made in plutonium production, Groves forced the laboratory to change course. The primary technical objective shifted from developing a gun weapon to developing a plutonium implosion assembly. Within days after Oppenheimer officially announced the spontaneous fission discovery, the laboratory reorganized its work force to focus on implosion. Two new divisions were established – X (Explosives) under Kistiakowsky, and G (Gadget) under Bacher. Most of the groups in these new divisions were moved out of the earlier Research and Ordnance Engineering divisions. Unfortunately, at this point experiments in the implosion diagnostic program were indicating that an implosion weapon would be extremely difficult, if not impossible, to achieve.
4 - Setting Up Project Y: June 1942 to March 1943
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 40-66
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By the time a fast-neutron fission laboratory was conceived early in 1942, theorists and experimentalists had made initial calculations for the bomb, including new estimates of critical mass and efficiency. Some progress had been made on designing methods for assembling the weapon and on a program for measuring nuclear constants central to bomb calculations. On the whole, however, research languished because of poor information exchange among the various groups involved, which were scattered throughout the United States. Oppenheimer, who replaced Gregory Breit as coordinator of the fast-fission project, recommended to Groves that the effort be centralized. Groves, who recognized the security benefits of centralization, readily complied, thereby setting in motion plans for establishing the Los Alamos Laboratory.
Groves and Oppenheimer took the first step toward creating the laboratory in early 1943 by recruiting many of the world's best scientists. The temporary nature of the project and the urgency of its mission aided the recruitment effort, but the task was complicated by the delicate issue of whether Los Alamos would be a military or a civilian establishment – an issue never formally resolved. The standard caricature of Oppenheimer as an other-worldly intellectual and Groves as a burly martinet highlights the misalignment between the military and scientific communities that joined in Project Y. Surprisingly, Oppenheimer and Groves developed a collaboration that was both congenial and fruitful.
15 - Finding the Implosion Design: August 1944 to February 1945
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 293-314
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The accelerated implosion effort, which began in August 1944, made rapid progress. By October 1944, James Conant was giving a lensed implosion device a 50–50 chance of working on schedule, if all went smoothly, for a test at Trinity on 1 May 1945 and a “3:1” chance for a test on 1 July. But he added, “In my opinion, the probabilities of success by the gun method (Mark 1) within the next year are very much greater than by the implosion method. Indeed the gun method seems as nearly certain as any untried new procedure can be.”
Overcoming asymmetries remained the outstanding technical problem of the implosion program. By mid-fall 1944, two experimental strands of the implosion program were converging on this problem: research on the explosive lens and on the electric detonator. In addition, in T-Division, Robert Christy put forth a conservative proposal for overcoming the asymmetry: try to implode a solid sphere rather than a spherical shell of active material. However, calculations indicated that the “Christy gadget” was intrinsically far less efficient than the hollow weapon, and that such a device would require a modulated initiator to activate the explosion at the most favorable moment. The call for the development of the implosion initiator added another thorny problem to the program.
As the time approached when sizable quantities of plutonium would become available, gross design features had to be frozen in order to begin final bomb production.
Critical Assembly
- A Technical History of Los Alamos during the Oppenheimer Years, 1943–1945
- Lillian Hoddeson, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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This 1993 volume is a lucid and accurate history of the technical research that led to the first atomic bombs. The authors explore how the 'critical assembly' of scientists, engineers and military personnel at Los Alamos, responding to wartime deadlines, collaborated to create a new approach to large-scale research. The book opens with an introduction laying out major themes. After a synopsis of the prehistory of the bomb project, from the discovery of nuclear fission to the start of the Manhattan Engineer District, and an overview of the early materials programme, the book examines the establishment of the Los Alamos Laboratory, the implosion and gun assembly programmes, nuclear physics research, chemistry and metallurgy, explosives, uranium and plutonium development, confirmation of spontaneous fission in pile-produced plutonium, the thermonuclear bomb, critical assemblies, the Trinity test, and delivery of the combat weapons. Readers interested in history of science will find this volume a crucial resource for understanding the underpinnings of contemporary science and technology.
Name Index
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 493-500
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16 - Building the Implosion Gadget: March 1945 to July 1945
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 315-334
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After the implosion design was frozen at the end of February 1945, the program shifted its emphasis from research to constructing actual bomb components, including explosive lenses, detonators, initiators, and the plutonium hemispheres. Kistiakowsky reported on X-Division's work in April: “One can now state with a reasonable degree of assurance that all major research and design gambles involved in the freeze of the program of the X-Division have been won. Progress is more and more determined by the rate of supply of manufactured items.” By May, he concluded, “The activities in X-Division have lost all semblance to research and have become so largely production and inspection and testing that their brief summary here seems impractical” (at which point his division progress reports stopped abruptly). However, most of the crucial components of the implosion gadget remained problematic, almost to the time of the Trinity test, and most underwent last-minute change.
The Cowpuncher Committee
Oppenheimer launched the final phase of Project Y's implosion effort with his appointment on 1 March 1945 of the powerful Cowpuncher Committee to “ride herd” on the program. Besides Oppenheimer, the members included Bethe, Kistiakowsky, Parsons, Bacher, Samuel Allison, Cyril Smith, and Kenneth Bainbridge. The committee oversaw eight major programs: (1) fabrication and inspection of explosive lenses; (2) design and construction of electric detonators and detonator circuits; (3) diagnostic tests to determine timing, compression, and symmetry; (4) research in chemistry and metallurgy; (5) study of the critical mass and time constant of the plutonium nuclear explosion; (6) design of the inner metal parts of the implosion assembly; (7) coordination of the Trinity program; and (8) assignment of shop priorities.
Contents
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp v-vi
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List of Illustrations
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp vii-viii
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2 - Early Research on Fission: 1933–1943
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 12-23
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Following the discovery of nuclear fission in 1938, scientists in Germany, France, Great Britain, the Soviet Union, Japan, and the United States began to investigate the possibility of exploiting this energy source for military purposes. The United States alone was able to draw its governmental, industrial, and scientific capabilities into an efficient bombbuilding collaboration. It had not only the manpower, materials, and industrial support needed for the expensive project – eventually to cost $2.2 billion – but also a sizable and competent physics community well versed in technology, strengthened by talented emigrés, with ties to government and industry, and close international contacts. Some American scientists, like Ernest Lawrence, were experienced in managing large research efforts. This community also included older scientific statesmen, like Vannevar Bush, with political experience and proven abilities in coordinating government-sponsored applied research projects. On 9 October 1941 Bush persuaded President Franklin Roosevelt to authorize American research on the feasibility of a fission bomb.
The Discovery of Nuclear Fission
The events leading to Los Alamos began in 1933, when Frédéric Joliot and Irène Curie produced artificial radioactivity by bombarding aluminum with alpha particles. The next year Enrico Fermi and his co-workers in Rome bombarded a variety of elements with neutrons, the neutral fundamental particles that James Chadwick had discovered in 1932. Upon bombarding uranium, Fermi's group found an unexplained radioactive substance and speculated that they had created a new transuranic element.
9 - New Hopes for the Implosion Weapon: September 1943 to July 1944
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 163-177
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Two developments in the spring of 1944 offered hope for overcoming the asymmetry problems of the implosion weapon. The asymmetry arose in part because the detonation waves diverging from the various initiation points met and interacted to produce small regions of markedly increased pressure. Furthermore, the multiple detonations of the surrounding explosive were not adequately simultaneous. The first problem would be dealt with by the three-dimensional explosive lens, suggested by James Tuck in May and given its basic design by John von Neumann. The second problem could be solved, as Luis Alvarez had suggested in May, by replacing the original inherently variable Primacord detonation distribution systems with electric detonators of highly superior reproducibility, thus providing a means of achieving adequately simultaneous detonation at several points. Developing and producing practical explosive lens and electric detonator systems would require a concerted research and development effort right up to the Trinity test in July 1945.
In view of these difficulties, it seemed wise to try testing the device. The decision to do so was made early in 1944. By the fall of that year, the site selection committee had fixed on the Jornada del Muerto region of south central New Mexico.
Explosives
The research and development of high explosives – materials that detonate at supersonic speeds by a process involving chemical reaction and a shock wave – was (arguably) the most pivotal and problematic component of the implosion program.
3 - The Early Materials Program: 1933–1943
- Lillian Hoddeson, University of Illinois, Urbana-Champaign, Paul W. Henriksen, Roger A. Meade, Catherine L. Westfall, Michigan State University
- With contributions by Gordon Baym , Richard Hewlett , Alison Kerr , Robert Penneman , Leslie Redman and Robert Seidel
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- 28 May 1993, pp 24-39
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A comprehensive American program of research on plutonium and 235U isotope separation evolved between mid-1941 and mid-1942. Plans were formulated for the construction of plutonium production reactors, uranium separation plants, and centralized bomb research facilities. The program for producing 235U by gaseous diffusion was slowed both by the technical problem of finding a suitable isotope separation filter, or “barrier,” and by the difficulty of coordinating Kellogg Company employees and Columbia University researchers. Despite such obstacles, plans for providing fissionable materials were well on the way to being implemented by 1943.
Expansion of the American Atomic Bomb Program
In June 1941, Vannevar Bush persuaded President Roosevelt to form the Office of Scientific Research and Development (OSRD), under the aegis of the Office of Emergency Management. With Bush as director, the OSRD assumed responsibility for mobilizing scientific resources and applying research to national defense. James Conant replaced Bush as chairman of the National Defense Research Committee, which now operated as a unit of the OSRD. Recommendations for research contracts were channeled through Conant and placed by Bush. The Advisory Committee on Uranium, essentially a research organization, became the S-1 Section of OSRD and remained in place throughout the war. Bush and Conant established three subsections of S-1: one on theoretical research under Fermi; one on power production under George Pegram, physicist and dean of the graduate faculties at Columbia University; and a third on heavy water and isotope separation under Columbia chemist Harold Urey.