The Los Alamos Primer is a printed version of the first five lectures on the principles of nuclear weapons given to new arrivals at the top-secret Los Alamos laboratory during the Manhattan Project. The five lectures were given by physicist Robert Serber in April 1943. The notes from the lectures which became the Primer were written by Edward Condon.
The Los Alamos Primer was composed from five lectures given by the physicist Robert Serber to the newcomers at the Los Alamos Laboratory in April 1943, at the start of the Manhattan Project. The aim of the project was to build the first nuclear bomb, and these lectures were a very concise introduction into the principles of nuclear weapon design. Serber was a postdoctoral student of J. Robert Oppenheimer, the leader of the Los Alamos Laboratory, and worked with him on the project from the very start. The five lectures were conducted at April 5, 7, 9, 12, and 14, 1943; according to Serber, between 30 and 50 people attended them. Notes were taken by Edward Condon; the Primer is just 24-pages-long. Only 36 copies were printed at the time. [1]
Serber later described the lectures: [1]
Previously the people working at the separate universities had no idea of the whole story. They only knew what part they were working on. So somebody had to give them the picture of what it was all about and what the bomb was like, what was known about the theory, and some idea why they needed the various experimental numbers.
In July 1942, Oppenheimer held a "conference" at his office at Berkeley. No records were preserved, but the Primer arose from all the aspects of bomb design discussed there. [1]
The Primer, though only 24-pages-long, consists of 22 sections, divided into chapters: [1]
The first paragraph states the intention of the Los Alamos Laboratory during World War II: [1]
The Primer contained the basic physical principles of nuclear fission, as they were known at the time, and their implications for nuclear weapon design. It suggested a number of possible ways to assemble a critical mass of uranium-235 or plutonium, the most simple being the shooting of a "cylindrical plug" into a sphere of "active material" with a "tamper"—dense material which would reflect neutrons inward and keep the reacting mass together to increase its efficiency (this model, the Primer said, "avoids fancy shapes"). They also explored designs involving spheroids, a primitive form of "implosion" (suggested by Richard C. Tolman), and explored the speculative possibility of "autocatalytic methods" which would increase the efficiency of the bomb as it exploded.
According to Rhodes,
Serber discussed fission cross sections, the energy spectrum of secondary neutrons, the average number of secondary neutrons per fission (measured by then to be about 2.2), the neutron capture process in U238 that led to plutonium and why ordinary uranium is safe (it would have to be enriched to at least 7 percent U235, the young theoretician pointed out, 'to make an explosive reaction possible'). The calculations Serber reported indicated a critical mass of metallic U235 tamped with a thick shell of ordinary uranium of 15 kilograms: 33 pounds. For plutonium similarly tamped the critical mass might be 5 kilograms: 11 pounds. Tamper always increased efficiency: it reflected neutrons back into the core and its inertia...slowed the core's expansion and helped keep the core surface from blowing away. So there might be a third basic component to their atomic bomb besides nuclear core and confining tamper: an initiator - a Ra + Be source or, better, a Po + Be source, with the radium or polonium attached perhaps to one piece of the core and the beryllium to the other, to smash together and spray neutrons when the parts mated to start the chain reaction. The immediate work of experiment, Serber concluded, would be measuring the neutron properties of various materials and mastering the ordnance problem - the problem, that is, of assembling a critical mass and firing the bomb. [2]
The Primer became designated as the first official Los Alamos technical report (LA-1), and though its information about the physics of fission and weapon design was soon rendered obsolete, it is still considered a fundamental historical document in the history of nuclear weapons. Its contents would be of little use today to someone attempting to build a nuclear weapon, a fact acknowledged by its complete declassification in 1965. [3]
In 1992, an edited version of the Primer with many annotations and explanations by Serber was published with an introduction by Richard Rhodes, who previously published The Making of the Atomic Bomb . The 1992 edition also contains the Frisch–Peierls memorandum, written in 1940 in England. [3] [4]
The physicist Freeman Dyson, who knew Serber, Oppenheimer, and other participants of the Manhattan Project, called the Primer a "legendary document in the literature of nuclear weapons". He praised "Serber's clear thinking", but harshly criticized the Primer's publication, writing "I still wish that it had been allowed to languish in obscurity for another century or two." Acknowledging that it was unclassified in 1965, and that it can't be useful to any bomb designer from 1950, Dyson still thinks that such publication can be dangerous: [3]
There is nothing here that would have been technically useful to a Russian bomb designer in 1950 or to an Iraqi bomb designer in 1990. But the primer contains much more than technical information. It conveys a powerful message that bomb designing is fun. The primer succeeds all too well in recreating the Los Alamos mystique, the picture of this brilliant group of city slickers suddenly dumped into the remotest corner of the Wild West and having the best time of their lives building bombs. It helps to perpetuate the myth. ... This is what I mean by seduction-the myth, unfortunately containing an element of truth, that building bombs is a wild, consciousness-raising adventure.
Dyson compared bomb-building with LSD synthesis: "Nuclear weapons and LSD are both highly addictive. Both have been manufactured extensively by bright young people seduced by a myth and searching for adventure. Both have destroyed many lives and are likely to destroy many more if the myths are not dispelled. ... Books that present either LSD or nuclear bombs as a romantic adventure can be a danger to public health and safety." [3]
His article, titled "Dragon's Teeth", reflects another analogy he uses in his criticisms: [3]
We are here confronting an ethical dilemma that is at least 350 years old, the same dilemma that John Milton confronted in his historic battle for the freedom of the press in 17th-century England. Milton in his famous appeal with the title "Areopagitica", addressed to the English parliament in 1644, conceded to his enemies the point that books "are as lively and as vigorously productive as those fabulous dragon's teeth, and being sown up and down, may chance to spring up armed men." He conceded that the risks of letting books go free into the world could be lethal as well as irreversible. He argued that the risks must still be accepted, because the censorship of books was the greater evil. He lost the argument, and in his day the censors prevailed. In our day, the censors have lost their grip, but the ethical dilemma remains. Books have not lost their power to spring up armed men, to seduce and to destroy. The fact that this primer was declassified 26 years ago does not mean that we can spread it over the world without some responsibility for the consequences.
Dyson concludes his review writing: "With luck, this charming little book will be read only by elderly l physicists and historians, people who can appreciate its elegance without being seduced by its ma" [3]
Other reviews, however, were more favorable. John F. Ahearne writes that the book "remains mathematical", and that it can be useful to young scientists: "the insight to be gained from reading Serber's lucid descriptions of how to analyze complex events by using first approximations. Serber was speaking in many cases to a group of experimentalists who, as one of the experimental group leaders is noted as saying, found "a qualitative argument was more convincing than any amount of fancy theory." A good physicist should be able to get an approximate answer to any complex question using what he or she carries around in the head, the well known "back of the envelope" calculation." [5]
Paul W. Henriksen praised the book, writing that "one will be even more impressed with the magnitude of the effort to build an atomic bomb to try to end World War II". He notes that the "annotated version is fascinating in several respects. It is a rare instance in which one of the contributors to a historical event has gone back and explained his work, its importance, and the mistakes that were made at the same time." He also notes that the book is "one of the few books to deal at all with the technical side of the bomb project." [6]
Matthew Hersch writes that the book has "power to amaze", and that "The Los Alamos Primer is a work bound to be read differently by different generations ... [it] is a rich text that peers into a moment of innovation that had global consequences." [7]
Frank A. Settle also finds the primer to be unique in style and context, and sees it as "a significant contribution to the technical and scientific history of this important period." [4]
"Fat Man" was the codename for the type of nuclear weapon the United States detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the first being Little Boy, and its detonation marked the third nuclear explosion in history. It was built by scientists and engineers at Los Alamos Laboratory using plutonium from the Hanford Site, and was dropped from the Boeing B-29 Superfortress Bockscar piloted by Major Charles Sweeney.
Little Boy was the name of the type of atomic bomb used in the bombing of the Japanese city of Hiroshima on 6 August 1945 during World War II, making it the first nuclear weapon used in warfare. The bomb was dropped by the Boeing B-29 Superfortress Enola Gay piloted by Colonel Paul W. Tibbets Jr., commander of the 509th Composite Group, and Captain Robert A. Lewis. It exploded with an energy of approximately 15 kilotons of TNT (63 TJ) and caused widespread death and destruction throughout the city. The Hiroshima bombing was the second nuclear explosion in history, after the Trinity nuclear test.
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Theodore Brewster "Ted" Taylor was an American theoretical physicist, specifically concerning nuclear energy. His higher education included a PhD from Cornell University in theoretical physics. His most noteworthy contributions to the field of nuclear weaponry were his small bomb developments at the Los Alamos Laboratory in New Mexico. Although Taylor is not widely known to the general public, he is credited with numerous landmarks in fission nuclear weaponry development, including having developed the smallest, most powerful, and most efficient fission weapons ever tested by the US. Though Taylor was not considered a brilliant physicist from a calculative viewpoint, his vision and creativity allowed him to thrive in the field. The later part of Taylor's career was focused on nuclear energy instead of weaponry, and included his work on Project Orion, nuclear reactor developments, and anti-nuclear proliferation.
Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types:
In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties, density, shape, enrichment, purity, temperature, and surroundings. The concept is important in nuclear weapon design.
Operation Sandstone was a series of nuclear weapon tests in 1948. It was the third series of American tests, following Trinity in 1945 and Crossroads in 1946, and preceding Ranger. Like the Crossroads tests, the Sandstone tests were carried out at the Pacific Proving Grounds, although at Enewetak Atoll rather than Bikini Atoll. They differed from Crossroads in that they were conducted by the Atomic Energy Commission, with the armed forces having only a supporting role. The purpose of the Sandstone tests was also different: they were primarily tests of new bomb designs rather than of the effects of nuclear weapons. Three tests were carried out in April and May 1948 by Joint Task Force 7, with a work force of 10,366 personnel, of whom 9,890 were military.
Haroutune Krikor Daghlian Jr. was an American physicist with the Manhattan Project, which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico and died 25 days later from the resultant radiation poisoning.
Seth Henry Neddermeyer was an American physicist who co-discovered the muon, and later championed the implosion-type nuclear weapon while working on the Manhattan Project at the Los Alamos Laboratory during World War II.
Robert Serber was an American physicist who participated in the Manhattan Project. Serber's lectures explaining the basic principles and goals of the project were printed and supplied to all incoming scientific staff, and became known as The Los Alamos Primer. The New York Times called him “the intellectual midwife at the birth of the atomic bomb.”
A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lower mass, or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 or plutonium-239. The first full-scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons.
The Manhattan Project was a research and development project that produced the first atomic bombs during World War II. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army Corps of Engineers. The Army component of the project was designated the Manhattan District; "Manhattan" gradually became the codename for the entire project. Along the way, the project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion. Over 90% of the cost was for building factories and producing the fissionable materials, with less than 10% for development and production of the weapons.
"Thin Man" was the code name for a proposed plutonium gun-type nuclear bomb that the United States was developing during the Manhattan Project. Its development was abandoned when it was discovered that the spontaneous fission rate of nuclear reactor-bred plutonium was too high for use in a gun-type design due to the high concentration of the isotope plutonium-240 in the plutonium produced at the Clinton Engineer Works.
Plutonium-240 is an isotope of plutonium formed when plutonium-239 captures a neutron. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project.
Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.
The demon core was a sphere of plutonium that was involved in two fatal radiation accidents when scientists tested it as a fissile core of an early atomic bomb. It was manufactured by the Manhattan Project, the U.S. nuclear weapon development effort during World War II. It was a subcritical mass that weighed 6.2 kilograms (14 lb) and was 8.9 centimeters (3.5 in) in diameter.
A modulated neutron initiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons, as its role is to "kick-start" the chain reaction at the optimal moment when the configuration is prompt critical. It is also known as an internal neutron initiator. The initiator is typically placed in the center of the plutonium pit, and is activated by impact of the converging shock wave.
The uranium hydride bomb was a variant design of the atomic bomb first suggested by Robert Oppenheimer in 1939 and advocated and tested by Edward Teller. It used deuterium, an isotope of hydrogen, as a neutron moderator in a uranium-deuterium ceramic compact. Unlike all other fission-based weapon types, the concept relies on a chain reaction of slow nuclear fission. Bomb efficiency was adversely affected by the cooling of neutrons since the latter delays the reaction, as delineated by Rob Serber in his 1992 extension of the original Los Alamos Primer.
The Los Alamos Laboratory, also known as Project Y, was a secret laboratory established by the Manhattan Project and operated by the University of California during World War II. Its mission was to design and build the first atomic bombs. Robert Oppenheimer was its first director, serving from 1943 to December 1945, when he was succeeded by Norris Bradbury. In order to enable scientists to freely discuss their work while preserving security, the laboratory was located on the Pajarito Plateau in Northern New Mexico. The wartime laboratory occupied buildings that had once been part of the Los Alamos Ranch School.
A tamper is an optional layer of dense material surrounding the fissile material. It is used in nuclear weapon design to reduce the critical mass of a nuclear weapon and to delay the expansion of the reacting material through its inertia. Due to its inertia it delays the thermal expansion of the fissioning fuel mass, keeping it supercritical longer. Often the same layer serves both as tamper and as neutron reflector. The weapon disintegrates as the reaction proceeds and this stops the reaction, so the use of a tamper makes for a longer-lasting, more energetic and more efficient explosion. The yield can be further enhanced using a fissionable tamper.
