Bond of Bombs The story of atomic bomb

Bond of Bombs: The story of atomic bomb Chung Wen Kao Department of Physics Chung Yuan Christian University, Taiwan Colloquium @ NCTU 18/11/2010 1

Modern Alchemistry In 1919 Rutherford became the first person to transmute one element into another when he converted nitrogen into oxygen through the nuclear reaction 14 N + α → 17 O + p. For centuries, alchemists had searched for something that would turn less valuable metals into gold. They called this the "philosopher's stone. " Finally, Rutherford had discovered how to transmute the elements. 2

The first accelerator During the early 1930 s Ernest Walton and John Cockcroft collaborated to build an apparatus that split the nuclei of lithium atoms by bombarding them with a stream of protons accelerated inside a high-voltage tube (700 kilovolts). The splitting of the lithium nuclei produced helium nuclei. This was experimental verification of theories about atomic structure that had been proposed earlier by Rutherford. The successful apparatus - a type of particle accelerator now called the Cockcroft-Walton generator - helped to usher in an era of particleaccelerator-based experimental nuclear physics. It was this research at Cambridge in the early 1930 s that won Walton and Cockcroft the Nobel Prize in physics in 1951. 3

Discovery of neutron (I) Walther Wilhelm Georg Bothe (B. 1891 – D. 1957 ) was a German nuclear physicist, who shared the Nobel Prize in Physics in 1954 with Max Born. In 1931 Walther Bothe and Herbert Becker in Germany found that if the very energetic alpha particles emitted from polonium fell on certain light elements, specifically beryllium, boron, or lithium, an unusually penetrating radiation was produced. At first this radiation was thought to be gamma radiation, although it was more penetrating than any gamma rays known, and the details of experimental results were very difficult to interpret on this basis 4

Discovery of neutron(II) The next important contribution was reported in 1932 by Irène Joliot-Curie and Frédéric Joliot in Paris. They showed that if this unknown radiation fell on paraffin or any other hydrogen-containing compound it ejected protons of very high energy. This was not in itself inconsistent with the assumed gamma ray nature of the new radiation, but detailed quantitative analysis of the data became increasingly difficult to reconcile with such a hypothesis. Paraffin Wax 5

Another Curie and her husband… Irène Joliot-Curie (B. 1897 – D. 1956) was a French scientist, the daughter of Marie Skłodowska-Curie and Pierre Curie and the wife of Frédéric Joliot-Curie. Jointly with her husband, Joliot-Curie was awarded the Nobel Prize for chemistry in 1935 for their discovery of artificial radioactivity. This made the Curies the family with most Nobel laureates to date. Jean Frédéric Joliot-Curie (B. 1900 – D. 1958) was a French physicist and Nobel laureate. In 1925 he became an assistant to Marie Curie, at the Radium Institute. He fell in love with Irène Curie, and soon after their marriage in 1926 they both changed their surnames to Joliot. Curie. At the time of the Nazi invasion in 1940, Joliot-Curie managed to smuggle his working documents. During the French occupation he took an active part in the French Resistance as a member of the National Front. 6

Discovery of neutron (III) Chadwick reported the Joliot-Curie's experiment to Rutherford, who did not believe that gamma rays could account for the protons from the wax. He and Chadwick were convinced that the beryllium was emitting neutrons. Neutrons have nearly the same mass as protons, so should knock protons from a wax block fairly easily. Chadwick's neutron chamber containing parallel disks of radioactive polonium and beryllium. Radiation is emitted from an aluminium window at the chamber's end "The lions den" of the Cavendish: Rutherford, foreground, with colleagues; Chadwick is at right. 7

Discovery of neutron (IV) Chadwick was able to prove that the neutral particle could not be a photon by bombarding targets other than hydrogen, including nitrogen, oxygen, helium and argon. Not only were these inconsistent with photon emission on energy grounds, the cross-section for the interactions was orders of magnitude greater than that for Compton scattering by photons. 8

Who is Chadwick? Sir James Chadwick (B. 1891 – D. 1974) was an English Nobel laureate in physics awarded for his discovery of the neutron. In 1913 Chadwick went and worked with Hans Geiger at Berlin. He was in Germany at the start of World War I and was interned in Ruhleben P. O. W. Camp just outside Berlin. While he was interned, he had the freedom to set up a laboratory in the stables. He spent most of the war years in Ruhleben until Geiger's laboratory interceded for his release. For this discovery he was awarded the Nobel Prize for Physics in 1935. Ruhleben Gefangenenlager (British Civilian Internment Camp) was established after the outbreak of the First World War at a racetrack in Spandau, a suburb of Berlin, and remained in operation until Armistice Day, 1918. 9

Playing with neutrons 10

Create new elements In 1934, Italian physicists Enrico Fermi and his group at Rome bombarded uranium with neutrons and postulated that transuranic elements might have been produced and which was widely accepted for a few years. He received 1938 Nobel Physics Prize 11

Who is Fermi? Enrico Fermi (B. 1901 – D. 1954) was an Italian physicist, particularly remembered for his work on the development of the first nuclear reactor, and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics. Awarded the Nobel Prize in Physics in 1938 for his work on induced radioactivity, Fermi is widely regarded as one of the leading scientists of the 20 th century, highly accomplished in both theory and experiment. Fermium, a synthetic element created in 1952, the Fermi National Accelerator Lab, the Fermi Gamma-ray Space Telescope, and a type of particles called fermions are named after him. 12

Criticism from chemist Ida Noddack (B. 1896 – D. 1978), was a German chemist and physicist. With her husband Walter Noddack she discovered element 75 rhenium. She was nominated three times for Nobel Prize in Chemistry. Ida Noddack criticized Enrico Fermi's chemical proofs in his 1934 neutron bombardment experiments. Her paper, "On Element 93" suggested a number of possibilities, centering around Fermi's failure to chemically eliminate all lighter than uranium elements in his proofs. She suggested the possibility that "it is conceivable that the nucleus breaks up into several large fragments, which would of course be isotopes of known elements but would not be neighbors of the irradiated element. " However Noddack offered no theoretical basis for this possibility, the paper was generally ignored. 13

Discovery of Nuclear Fission In December 1938, when Otto Hahn and Fritz Strassman looked for transuranium elements in a uranium sample that had been bombarded with neutrons, they found traces of barium. On 22 December 1938, they sent a manuscript to Naturwissenschaften reporting their radiochemical results, which were the irrefutable proof that the uranium had been split into fragments consisting of lighter elements; simultaneously, they communicated these results to Lise Meitner, who had escaped out of Germany earlier that year and was then in Sweden. Meitner, and her nephew, the young physicist Otto Robert Frisch, correctly interpreted these results as being nuclear fission, a term coined by Frisch, which subsequently became internationally known. Frisch confirmed this experimentally on 13 January 1939. 14

Who is Hahn? Otto Hahn (B. 1879 – D. 1968) was a German chemist and Nobel laureate who pioneered the fields of radioactivity and radiochemistry. He is regarded as "the father of nuclear chemistry" and the "founder of the atomic age". From 1948 to 1960 Otto Hahn was the founding President of the newly formed Max Planck Society for the Advancement of Science, which through his tireless activity and his worldwide respected personality succeeded in regaining the renown once enjoyed by the Kaiser Wilhelm Society. Nuclear fission experimental setup, reconstructed at the Deutsches Museum, Munich Otto Hahn's notebook 15

Hahn after WWII Safe House, Farm Hall. At the end of World War II in 1945 Hahn was suspected of working on the German nuclear energy project to develop an atomic reactor or an atomic bomb. But his only connection was the discovery of fission, he did not work on the program. Hahn and nine German physicists (including Max von Laue, Werner Heisenberg and Carl Friedrich von Weizsäcker) were interned at Farm Hall, Godmanchester, near Cambridge, England from 3 July 1945 to 3 January 1946. While they were there, the German scientists learned of the dropping of the American atom bombs on Hiroshima and Nagasaki. Hahn was on the brink of despair, as he felt that because he had discovered nuclear fission he shared responsibility for the death and suffering of hundreds of thousands of Japanese people. Early in January 1946, the group was allowed to return to Germany. 16

Who is Lise Meitner? Lise Meitner (B. 1878 – D. 1968) was an Austrian-born, later Swedish physicist who worked on radioactivity and nuclear physics. Meitner was part of the team that discovered nuclear fission, an achievement for which her colleague Otto Hahn was awarded the Nobel Prize. Meitner is often mentioned as one of the most glaring examples of women's scientific achievement overlooked by the Nobel committee. Meitner also first realized that Einstein's famous equation E = mc 2, explained the source of the tremendous releases of energy in atomic decay, by the conversion of the mass into energy. She and Frisch had discovered the reason that no stable elements beyond uranium (in atomic number) existed naturally; the electrical repulsion of so many protons overcame the "strong" nuclear force. The element 109 was named meitnerium in her honour. 17

Lise Meitner as a refugee Dirk Coster (B. 1889– D. 1950), was a Dutch physicist known as the co-discoverer of Hafnium. Adriaan Daniël Fokker (B 1887 – D. 1972), was a Dutch physicist and musician. In his 1913 thesis, he derived the Fokker-Planck equation along with Max Planck When Adolf Hitler came to power in 1933, Meitner was acting director of the Institute for Chemistry. In July 1938, Meitner, with help from the Dutch physicists Dirk Coster and Adriaan Fokker, escaped to Holland. She was forced to travel under cover to the Dutch border, where Coster persuaded German immigration officers that she had permission to travel to the Netherlands. She reached safety, though without her possessions. Meitner later said that she left Germany forever with 10 marks in her purse. Before she left, Otto Hahn had given her a diamond ring he had inherited from his mother: this was to be used to bribe the frontier guards if required. It was not required, and Meitner's nephew's wife later wore it. 18

Who is Strassmann? Friedrich Wilhelm "Fritz" Straßmann (B. 1902 – D. 1980) was a German chemist who, with Otto Hahn in 1938, identified barium in the residue after bombarding uranium with neutrons, which led to the interpretation of their results as being from nuclear fission. In 1933 he resigned from the Society of German Chemists when it became part of a Nazi-controlled public corporation. He was blacklisted. Hahn and Meitner found an assistantship for him at half pay. Strassmann considered himself fortunate, for "despite my affinity for chemistry, I value my personal freedom so highly that to preserve it I would break stones for a living. " During the war he and his wife Maria Heckter Strassmann concealed a Jewish friend in their apartment for months, putting themselves and their three year old son at risk. Strassmann was recognized by Yad Vashem Holocaust Memorial as Righteous Among the Nations. 19

Who is Frisch? Otto Robert Frisch (B. 1904, Vienna – D. 1979), Austrian-British physicist. Frisch was Jewish, born in Vienna, Austria in 1904, the son of a painter and a concert pianist. He himself was talented at both but also had inherited his aunt Lise Meitner's love of physics. The accession of Adolf Hitler to the chancellorship of Germany in 1933 made Otto Robert Frisch make the decision to move to London, England where he worked with the physicist Blackett on cloud chamber technology and artificial radioactivity. He followed this with a five year stint in Copenhagen with Niels Bohr where he increasingly specialized in nuclear physics, particularly in neutron physics. Later he played a very important role in the design of the atomic bomb. 20

Nuclear chain reaction A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. The specific nuclear reaction may be the fission of heavy isotopes (e. g. 235 U) or the fusion of light isotopes (e. g. 2 H and 3 H). The nuclear chain reaction is unique since it releases several million times more energy per reaction than any chemical reaction. The concept of a nuclear chain reaction was first realized by Hungarian scientist Leó Szilárd in 1933. He filed a patent for his idea of a simple nuclear reactor the following year. 21

Who is Szilard? Leó Szilárd (B. 1898 – D. 1964) was a Hungarian physicist who conceived the nuclear chain reaction and worked on the Manhattan Project. Szilárd was born into a Jewish family of Budapest at the time of the Austro-Hungarian monarchy before World War I as the son of a civil engineer. During his time in Berlin he was working on numerous technical inventions. 1928 German patent application on the linear accelerator, 1929 German patent application on the cyclotron, since 1926 work with Einstein on the construction of a refrigerator without moving parts (US patent 1, 781, 541 on November 11, 1930). In 1873 Buda and Pest were officially merged into Budapest. Due to the prosperity and the large Jewish community of the city, Budapest was often called as the "Jewish Mecca 22

Very poor and inefficient way During 1933 Szilárd fled to London to escape Nazi persecution, where he read an article in The Times summarizing a speech given by Ernest Rutherford which rejected the possibility of using atomic energy for practical purposes: We might in these processes obtain very much more energy than the proton supplied, but on the average we could not expect to obtain energy in this way. It was a very poor and inefficient way of producing energy, and anyone who looked for a source of power in the transformation of the atoms was talking moonshine. But the subject was scientifically interesting because it gave insight into the atoms. 23

Concept of chain reaction Although nuclear fission had not yet been discovered, Szilárd was reportedly so annoyed at this dismissal that he conceived of the idea of the nuclear chain reaction while walking to work at St Bartholomew's Hospital waiting for traffic lights to change on Southampton Row in Bloomsbury, though his friend Jacob Bronowski notes that he never knew Szilárd to wait for traffic lights. The following year he filed for a patent on the concept. St Bartholomew's Hospital The King Henry VIII Gate at Barts, which was constructed in 1702. Note Henry VIII above the 24

Szilárd and Fermi An image from the Fermi–Szilárd "neutronic reactor" patent During 1938 Szilárd accepted an offer to conduct research at Columbia University in Manhattan, and moved to New York, and was soon joined by Fermi. After learning about the successful nuclear fission experiment conducted during 1939 in Germany by Otto Hahn, Fritz Strassmann, Lise Meitner, and Otto Robert Frisch, Szilárd and Fermi concluded that uranium would be the element capable of sustaining a chain reaction. Szilárd and Fermi conducted a simple experiment at Columbia and discovered significant neutron multiplication in uranium, proving that the chain reaction was possible and enabling nuclear weapons. Szilárd later described the event: "We turned the switch and saw the flashes. We watched them for a little while and then we switched everything off and went home. " 25

Nazi Germany and coming war On 30 January 1933, Adolf Hitler was appointed Chancellor of Germany by Hindenburg. At Hindenburg's death on 2 August 1934, the Nazi-controlled Reichstag merged the offices of Reichspräsident and Reichskanzler and reinstalled Hitler with the new title Führer. By the time the Nuremberg Laws were passed in 1935, Jews were stripped of their German citizenship and denied government employment. With growing threat from Nazi Germany World war II becomes inevitable in 1939. 26

Einstein–Szilárd letter The Einstein–Szilárd letter was a letter sent to United States President Franklin D. Roosevelt on August 2, 1939, that was signed by Albert Einstein but largely written by Leó Szilárd. The letter advised Roosevelt that Nazi Germany might be researching the use of nuclear fission to create atomic bombs and suggested that the U. S. should begin studying the possibility itself. He later regretted signing the letter. Albert Einstein and Leo Szilard in 1939, reenacting the signing of their letter to President Roosevelt warning him that Germany may be building an atomic bomb. 27

Content of the letter ……In the course of the last four months it has been made probable — through the work of Joliot in France as well as Fermi and Szilard in America — that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radiumlike elements would be generated. Now it appears almost certain that this could be achieved in the immediate future. This new phenomenon would also lead to the construction of bombs, and it is conceivable — though much less certain — that extremely powerful bombs of a new type may thus be constructed. A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air………. 28

Content of the letter The United States has only very poor ores of uranium in moderate quantities. There is some good ore in Canada and the former Czechoslovakia. while the most important source of uranium is Belgian Congo……. I understand that Germany has actually stopped the sale of uranium from the Czechoslovakian mines which she has taken over. That she should have taken such early action might perhaps be understood on the ground that the son of the German Under-Secretary of State, von Weizsäcker, is attached to the Kaiser-Wilhelm-Institut in Berlin where some of the American work on uranium is now being repeated. Ernst Freiherr von Weizsäcker (B. 1882 – D. 1951) was a German diplomat and politician. He served as Secretary of State at the Foreign Office from 1938 to 1943, and as German Ambassador to the Holy See from 1943 to 1945. He was a member of the prominent Weizsäcker family, and the father of German President Richard von Weizsäcker and physicist and philosopher Carl Friedrich von Weizsäcker. 29

Carl Friedrich Freiherr von Weizsäcker (B. 1912 – D. 2007) was a German physicist and philosopher. He was the longest-living member of the research team which performed nuclear research in Germany during the Second World War, under Werner Heisenberg's leadership. During the Second World War, Weizsäcker joined the German nuclear energy project, participating in efforts to construct an atomic bomb. He was present at a crucial meeting at the Army Ordnance headquarters in Berlin on 17 September 1939, at which the German atomic weapons program was launched. In July 1940 he was co-author of a report to the Army on the possibility of "energy production" from refined uranium, and which also predicted the possibility of using plutonium for the same purpose including the production of a new type of explosives. 30

Debate about Weizsäcker There is ongoing debate as to whether he, and the other members of the team, actually willingly pursued the development of a nuclear bomb for Germany during this time. Historians have been divided as to whether Heisenberg and his team were sincerely trying to construct a nuclear weapon, or whether their failure reflected a desire not to succeed because they did not want the Nazi regime to have such a weapon. In a recent report based on additional documents from Russian archives, historian Mark Walker concludes that "in comparison with Diebner [and] Gerlach. . . Heisenberg and finally Weizsäcker did obviously not use all power they commanded to provide the National Socialists with nuclear weapons 31

Weizsäcker, Bohr and Heisenberg Ivan Supek (B. 1915 – D. 2007) was a Croatian physicist According to Ivan Supek (one of Heisenberg's students and friends), he was informed in confidence by Bohr's wife Margrethe about the meeting. In his interview claimed that Weizsäcker was the main figure of the famous and controversial in Copenhagen in September 1941. Allegedly, he tried to persuade Bohr to mediate for peace between Germany and Great Britain. According to Weizsäcker's own account, he had persuaded Heisenberg to meet Bohr in order to broker an accord of the international nuclear physicist "community" not to build the bomb. Niels Bohr and Margrethe Bohr 32

World War II began with the German invasion of Poland on September 1, 1939, the Einstein– Szilárd letter was signed by Einstein on August 2, and it was hand-delivered to Roosevelt by the economist Alexander Sachs on October 11, 1939. The letter advised Roosevelt of the existence of the German nuclear energy project and warned that it was likely the Germans were working on an atomic bomb using uranium, and that the U. S. should be concerned about locating sources of uranium and researching nuclear weapon technology. At this time the U. S. policy was neutral in the war. 33

Reply from Roosevelt THE WHITE HOUSE WASHINGTON October 19, 1939 My dear Professor: I want to thank you for your recent letter and the most interesting and important enclosure. I found this data of such import that I have convened a Board consisting of the head of the Bureau of Standards and a chosen representative of the Army and Navy to thoroughly investigate the possibilities of your suggestion regarding the element of uranium. I am glad to say that Dr. Sachs will cooperate and work with this Committee and I feel this is the most practical and effective method of dealing with the subject. Please accept my sincere thanks. 34

Uranium Committee (1939– 1941) As a result of the letter Roosevelt asked Lyman James Briggs, director of the National Bureau of Standards, secretly to organize the Briggs Advisory Committee on Uranium. The committee's first meeting was on October 21, 1939, in Washington, D. C. ; $6, 000 was budgeted for conducting neutron experiments conducted by Fermi and Szilárd at Columbia. Four aspects of uranium seem to be critical from the start: Finding reliable sources of uranium ore in places where the supply cannot be interfered by other countries. Developing mass production methods of extracting uranium-235 from ore and/or creating plutonium. Making uranium (fission) chain-reaction bombs. Using controlled fission to power machines and synthesize isotopes. 35

Frisch–Peierls memorandum The Frisch–Peierls memorandum was written by Otto Frisch and Rudolf Peierls while they were both working at the University of Birmingham, England. The memorandum contained new calculations about the size of the critical mass needed for an atomic bomb. The memorandum contradicted the common thinking of the time that many tons of uranium-235 would be needed to make a bomb, requiring delivery by ship. Otto Robert Frisch (B. 1904, Vienna – D. 1979), The calculation in the memorandum showed that a bomb might be possible using as little as one pound of uranium-235, and could be quite practical for aircraft to carry. The memorandum is dated March 1940. Sir Rudolf Ernst Peierls, (B. 1907, Berlin – D. 1995, Oxford), The opening paragraph of the Frisch–Peierls memorandum 36

Who is Peierls ? Sir Rudolf Ernst Peierls, (B. 1907 – D. 1995), was a Germanborn British physicist. Rudolf Peierls had a major role in Britain's nuclear program, but he also had a role in many modern sciences. His impact on physics can probably be best described by his obituary in Physics Today: "Rudolph Peierls. . . a major player in the drama of the irruption of nuclear physics into world affairs. . . ". In 1929, he studied solid-state physics in Zurich under the tutelage of Werner Heisenberg and Wolfgang Pauli. His early work on quantum physics led to theory of positive carriers to explain thermal and electrical conductivity behaviors of semiconductors. He was a pioneer of the concept of "holes" in semiconductors. The ironic truth is that both Peierls and Frisch were excluded from working on radar (then known as RDF) as it was considered too secret for scientists with foreign backgrounds. 37

MAUD committee Sir Henry Thomas Tizard (B. 1885 - D. 1959 ) was an English chemist and inventor. Marcus Oliphant passed the document on to Henry Tizard, chairman of the Committee on the Scientific Survey of Air Defence who, as a result, requested the setting-up of what was to become the secret MAUD Committee. The Maud Committee (Military Application of Uranium Detonation) was the beginning of the British atomic bomb project. Maud Committee first met on 10 April 1940 to consider Britain's actions regarding the "uranium problem“. On the other hand, situation deteriorated very fast. Sir Marcus 'Mark' Laurence Elwin Oliphant, (B. 1901 – D. 2000) was an Australian physicist and humanitarian who played a fundamental role in the first experimental demonstration of nuclear fusion and also the development of the atomic bomb. 38

Nazi was marching! (1940) Germany invaded France, invaded Belgium, invaded the Netherlands, and invaded Luxembourg on 10 May 1940, the same day Neville Chamberlain resigned as British Prime Minister. The Netherlands and Belgium were overrun using blitzkrieg tactics in a few days and weeks, respectively. British troops were forced to evacuate the continent at Dunkirk, abandoning their heavy equipment by the end of the month. On 10 June, Italy invaded France, declaring war on both France and the United Kingdom; twelve days later France surrendered and was soon divided into German and Italian occupation zones, and an unoccupied rump state under the Vichy Regime. 39

London was burning! (1940) The Blitz was the sustained bombing of Britain by Nazi Germany between 6 September 1940 and 10 May 1941, during the Second World War. The Blitz hit many towns and cities across the country, but it began with the bombing of London for 76 consecutive nights. By the end of May 1941, over 43, 000 civilians, half of them in London, had been killed by bombing and more than a million houses were destroyed or damaged in London alone. 40

MAUD committee The biggest problem faced by the MAUD Committee was to find a way to separate the 0. 7% of uranium-235 from the 99. 3% of uranium-238. This is difficult because the two types of uranium are chemically identical. However, Franz Simon had been commissioned by MAUD to investigate methods. Simon reported in December 1940 that gaseous diffusion was feasible, calculating the size and cost of the industrial plant needed. The MAUD Committee realized that an atomic bomb was "not just feasible; it was inevitable". Dr Philip Baxter at ICI made the first small batch of gaseous uranium hexafluoride for Professor James Chadwick in 1940. ICI received a formal contract later in 1940 to make 3 kg of this vital material for the future work. Sir Francis Simon, (B. 1893 – D. 1956), was a German and later British physical chemist and physicist who devised the method, and confirmed its feasibility, of separating the isotope Uranium-235 and thus made a major contribution to the creation of the atomic bomb. 41

MAUD Committee The breakthrough with plutonium was at the Cavendish Laboratory by Egon Bretscher and Norman Feather. They realized that a slow neutron reactor fuelled with uranium would theoretically produce substantial amounts of plutonium-239 as a by-product. This is because U-238 absorbs slow neutrons and forms a new isotope U-239. The new isotope's nucleus rapidly emits an electron through beta decay producing a new element with a mass of 239 and an atomic number of 93. This element's nucleus then also emits an electron and becomes a new element of mass 239 but with an atomic number 94 and a much greater half-life. Bretscher and Feather showed theoretically feasible grounds that element 94 would be readily 'fissionable' by both slow and fast neutrons, and had the added advantage of being chemically different from uranium, and could easily be separated from it. This new development was also confirmed in independent work at Berkeley Radiation Laboratory also in 1940 by Seaborg. 42

Who is Bretscher? Egon Brestcher (right) Egon Bretscher (B. 1901 -D. 1973) Born near Zurich, Switzerland in 1901 and educated at the ETH there, Bretscher gained a Ph. D degree in organic chemistry at Edinburgh in 1926. He returned to Zurich as privatdocent to Peter Debye, later moving in 1936 to work in Rutherford’s laboratory at the Cavendish in Cambridge as a Rockefeller Scholar. Here he switched to research in nuclear physics, proposing with Norman Feather in 1940 that the 239 isotope of element 94 could be produced from the common isotope of uranium-238 by neutron capture and that, like U-235, this should be able to sustain a nuclear chain reaction. In addition, he devised theoretical chemical procedures for purifying this unknown element away from the parent uranium; this element was named Plutonium by Nicholas Kemmer. In 1944 he became a part of the British Mission to the Manhattan Project in Los Alamos, New Mexico led by James Chadwick, where he made the first measurements on the energy released in fusion processes. 43

What Feather remembered… Norman Feather (B. 1904 – D. 1978), was an English physicist. Feather: Oh, it was before that. Because it was in December, 1940, that Bretscher and I put in a minority report, or shall we say were allowed to put in an appendix, to a feasibility document for the Directorate. We said that we believed that if uranium 235 had the characteristics which were suitable for this job of a bomb, if 235 uranium had it, then we believed 239 plutonium would have it. Although no one had any at that time. And that probably technically the chemical process of separating plutonium 239 from a reactor might be less difficult than separating isotope-wise 235 uranium, in the isotope separation plant. That was in December ‘ 40. Interview with Norman Feather By Charles Weiner In Edinburgh, Scotland (James Clerk Maxwell Physics Building) February 25, 1971 44

MAUD committee On 15 July 1941 the Maud Committee approved its two final reports and disbanded. Their report concluded that a bomb was feasible, describing it in technical detail, providing specific proposals for developing a bomb and including cost estimates and so it recommended that the work should be continued with high priority in cooperation with the Americans. 45

Creation of OSRD Sir Marcus 'Mark' Laurence Elwin Oliphant (B. 1901 – D. 2000) Vannevar Bush (B. 1890 – D. 1974) Their reports were sent to Briggs, but were ignored. One of the members of the MAUD Committee, Mark Oliphant, flew to the United States in late August 1941 to find out why the U. S. was ignoring the MAUD Committee's findings. He reported that "this inarticulate and unimpressive man (Briggs) had put the reports in his safe and had not shown them to members of his committee. " Oliphant then met with the whole Uranium Committee and other physicists to galvanize the USA into action. As a result, in December 1941 Vannevar Bush created the larger and more powerful Office of Scientific Research and Development—which was empowered to engage in large engineering projects in addition to research—and became its director. 46

Pearl Harbor, Dec 7 th 1941 December 6: Vannevar Bush holds a meeting to organize an accelerated research project, still managed by Arthur Compton. Harold Urey is assigned to develop research into gaseous diffusion as a uranium enrichment method, while Ernest O. Lawrence is assigned to investigate electromagnetic separation methods. December 7: The Japanese attack Pearl Harbor. The United States issues a formal declaration of war against Japan the next day. Four days later, Nazi Germany declares war on the United States. December 18: First meeting of the OSRD sponsored S-1 project, dedicated to developing fission weapons 47

U. S. effort quickly caught up James Bryant Conant (B. 1893 – D. 1978) was a chemist, educational administrator, and government official. As the President of Harvard University he reformed it as a research institution. As a result of the MAUD Report, the British had started a uranium bomb program referred to by the codename Tube Alloys. Perceived slowness on the part of the United States had become a contentious issue between American and British scientists. Upon entry into the war, the U. S. placed increasing importance on working cooperatively with the British program. British realized that their pioneering effort would have no value if it were not quickly capitalized. On June 17, 1942, Roosevelt approved a proposal by Bush to dissolve the original S-1 Section and created the S-1 Executive Committee, chaired by James B. Conant, with the membership of Briggs, Compton, Urey, Lawrence, and Edgar Murphee. The program entered into increased cooperation between the OSRD and the U. S. Army. 48

S-1 Executive Committee (1942) The Advisory Committee on Uranium, now called the S-1 section, meets to establish the first timetables for bomb production. The first large scale contracts for research into isotope separation are also let. From Left: Harold Urey, Ernest Lawrence, James B. Conant, Lyman Briggs, Eger Murphree, Arthur Compton. 49

Who is Urey? Harold Clayton Urey (B. 1893 – D. 1981) was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934. He played a significant role in the development of the atom bomb. Urey became interested in nuclear systematics. This led to his discovery of deuterium. During this time, Urey isolated deuterium by repeatedly distilling a sample of liquid hydrogen. In 1931, he and his associates went on to demonstrate the existence of heavy water. Urey was awarded the Nobel Prize in Chemistry in 1934 for this work. During World War II, Urey's team at Columbia worked on a number of research programs that contributed towards the Manhattan Project to develop an atomic bomb for the United States. Most importantly, they developed the gaseous diffusion method to separate uranium 235 from uranium-238. In autumn 1941, Urey, with G. B. Pegram, led a diplomatic mission to England to establish co-operation on development of the atomic bomb. 50

Who is Lawrence? Ernest Orlando Lawrence (B. 1901 – D. 1958) was an American physicist. In 1939, Lawrence was awarded the Nobel Prize in Physics for his work in inventing the cyclotron and developing its applications. During World War II, Lawrence eagerly helped to ramp up the American investigation of the possibility of a weapon utilizing nuclear fission. His Radiation Laboratory, became one of the major centers for wartime nuclear research, and it was Lawrence who first introduced J. Robert Oppenheimer into what would soon become the Manhattan Project. An early champion of the electromagnetic separation method to enrich uranium and increase its percentage of fissile U-235. After the war, Lawrence campaigned extensively for government sponsorship of large scientific programs. Lawrence was a forceful advocate of "Big Science" with its requirements for big machines and big money. 51

Uranium enrichment During the first half of 1942, at Columbia University, Harold Urey worked on the gaseous diffusion and centrifuge systems for isotope separation. At Berkeley, Ernest Lawrence continued his investigations on electromagnetic separation using the "calutron" he had converted from his thirtyseven-inch cyclotron. Phillip Abelson at the National Bureau of Standards to the Naval Research Laboratory, continued his work on liquid thermal diffusion but with few positive results, and he had lost all contact with the S-1 Section of the Office of Scientific Research and Development. 52

Uranium enrichment Meanwhile Eger Murphree’s group hurriedly studied ways to move from laboratory experiments to production facilities. Despite the difficulties encountered with the centrifuge and gaseous diffusion methods, and even with Lawrence's successes at Berkeley, no clear-cut victor had yet emerged. The question of which method of uranium enrichment would prove most effective remained wide open. Eger Vaughan Murphree (B. 1898 – D. 1962) was an American chemist, best known for his co-invention of the process of fluid catalytic cracking. He worked at Exxon, and served from 1947 to 1962 as its VP of research and engineering. He was also briefly involved in the Manhattan Project. 53

Manhattan Project The Manhattan Project was the codename for a project conducted during World War II to develop the first atomic bomb. The project was led by the United States, and included participation from the United Kingdom and Canada. Formally designated as the Manhattan Engineer District (MED), it refers specifically to the period of the project from 1942– 1946 under the control of the U. S. Army Corps of Engineers, under the administration of General Leslie R. Groves. The scientific research was directed by American physicist J. Robert Oppenheimer. Leslie Richard Groves (August 17, 1896 – July 13, 1970) 54

Who is Oppenheimer? J. Robert Oppenheimer (B 1904 –D 1967) was an American theoretical physicist and professor of physics at the University of California, Berkeley. He is best known for his role as the scientific director of the Manhattan Project, the World War II effort to develop the first nuclear weapons at the secret Los Alamos National Laboratory in New Mexico. For this reason he is remembered as "The Father of the Atomic Bomb". In reference to the Trinity test in New Mexico, where his Los Alamos team first tested the bomb, Oppenheimer famously recalled the Bhagavad Gita: "If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one. " and "Now I am become Death, the destroyer of worlds. " 55

Manhattan project in 1942 September 17: Col. Leslie Groves is assigned command of the Manhattan Engineering District. Six days later he is appointed to Brigadier General. September 24: After a visit to Tennessee, Groves purchases 52, 000 acres (210 km²) of land in Tennessee for "Site X", which will become the Oak Ridge, Tennessee laboratory and production site. September 26: The Manhattan Project is given permission to use the highest wartime priority rating by the War Production Board. October 15: Groves appoints Robert Oppenheimer to coordinate the scientific research of the project at the "Site Y" laboratory. November 16: Groves and Oppenheimer visit Los Alamos, New Mexico and designate it as the location for "Site Y". 56

Decision on enrichment Walter S. Carpenter Jr. (1888 -1976) served Du. Pont for eight decades. Du. Pont supplied explosives and a host of other products to the war effort. He also guided Du. Pont’s heavy involvement in perhaps the most ambitious research and development undertaking in history, the Manhattan Project The Military Policy Committee met on November 12, 1942, and its decisions were ratified by the S-1 Executive Committee two days later. The Military Policy Committee, acting on Groves's and James Conant's recommendations, cancelled the centrifuge project. Gaseous diffusion, the pile, and the electromagnetic method were to proceed directly to full-scale, eliminating the pilot plant stage. The S-1 Executive Committee approved these recommendations and agreed that the gaseous diffusion facility was of lower priority than either the pile or the electromagnetic plant but ahead of a second pile. The scientific committee also asked Du. Pont to look into methods for increasing American supplies of heavy water in case it was needed to serve as a moderator for one of the new piles. Now that the various committees had finally chosen which horses to back, the only things left to do were to get final presidential approval and to run the race. 57

Italian navigator has landed The first controlled nuclear reaction occurred at CP-1 (Chicago Pile 1), on an old squash court under the University of Chicago's Stagg Field. The 1942 feat marked the start of the Atomic Age. The first major scientific hurdle of the project was solved on December 2, 1942, beneath the bleachers of Stagg Field at the University of Chicago, where a team led by Enrico Fermi, initiated the first artificial self sustaining nuclear chain reaction in an experimental nuclear reactor named Chicago Pile-1. A coded phone call from Compton saying, "The Italian navigator [referring to Fermi] has landed in the new world, the natives are friendly" to Conant in Washington, D. C. , brought news of the experiment's success. 58

Mass production of plutonium Glenn Theodore Seaborg (B. 1912 – D. 1999) was an American scientist who won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements. Using lanthanum fluoride as a carrier, Seaborg isolated a weighable sample of plutonium in August 1942. Seaborg's discovery and subsequent isolation of plutonium were major events in the history of chemistry, but it remained to be seen whether they could be translated into a production process useful to the bomb effort. The laboratory process created by Seaborg would have to be scaled-up a billion-fold to be implemented in an industrial separation plant. By the end of January 1945, the highly purified plutonium underwent further concentration in the completed chemical isolation building, where remaining impurities were removed successfully. Los Alamos received its first plutonium from Hanford on February 2. While it was still by no means clear that enough plutonium could be produced for use in bombs by the war's end, Hanford was by early 1945 in operation. 59

Little Boy The Hiroshima bomb, Little Boy, was made from uranium 235, a rare isotope of uranium that has to be physically separated from the more plentiful uranium-238 isotope, which is not suitable for use in an explosive device. Since U-235 makes up only 0. 7% of raw uranium and is chemically identical to the 99. 3% of U-238, various physical methods were considered for separation. During the Manhattan Project enriched uranium was given the codename oralloy, a shortened version of Oak Ridge alloy, after the location of the plants where the uranium was enriched. The term oralloy is still occasionally used to refer to enriched uranium. There about 2, 000 tonnes (t, Mg) of highly enriched uranium in the world, produced mostly for nuclear weapons, naval propulsion, and smaller quantities for research reactors. 60

Little Boy The uranium bomb was a gun-type fission weapon. One mass of U-235, the "bullet, " is fired down a more or less conventional gun barrel into another mass of U-235, rapidly creating the critical mass of U-235, resulting in an explosion. The method was so certain to work that no test was carried out before the bomb was dropped over Hiroshima, Also, the bomb that was dropped used all the existing extremely highly purified U-235 (and even most of the less highly purified material) so there was no U-235 available for such a test anyway. 61

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Thin Man "Thin Man" plutonium gun test casings. Emilio Gino Segrè (B. 1905 – D. 1989) was an Italian physicist and Nobel laureate in physics. In 1943– 1944, development efforts were directed to a gun-type fission weapon with plutonium, called "Thin Man". The chain reaction of U-235 was slow enough that gun-type assembly would work. But In April 1944, experiments by Emilio G. Segrè on the newly reactorproduced plutonium from Hanford showed that it contained impurities in the form of the element plutonium-240. "early" neutrons from spontaneously fissioning Pu-240 would start the chain reaction more quickly during detonation. This would release enough energy to disperse the critical mass with only a minimal amount of plutonium reacted, reducing the resulting yield of the weapon. In July 1944, based on the measurements of spontaneous fission for Hanford plutonium, the decision was made to cease work on a gun-type assembly for plutonium. There would be no "Thin Man. " 63

Implosion Ideas for alternative detonation schemes had existed for some time at Los Alamos. One of the more innovative was the idea of "implosion". Using chemical explosives, a sub-critical sphere of fissile material could be squeezed into a smaller and denser form. When the fissile atoms were packed closer together, the rate of neutron capture would increase, and the mass would become a critical mass. The metal needed to travel only very short distances, so the critical mass would be assembled in much less time than it would take to assemble a mass by a bullet impacting a target. 64

Nuclear Test “Trinity” Because of the complexity of an implosion-style weapon, it was decided that, despite the waste of fissile material, an initial test would be required. The first nuclear test took place on July 16, 1945, near Alamogordo, New Mexico, under the supervision of Groves's deputy Brig. Gen. Thomas Farrell. Oppenheimer gave the test the code name "Trinity". It was conducted by the United States on July 16, 1945, at a location 35 miles (56 km) southeast of Socorro, New Mexico on the White Sands Proving Ground, headquartered near Alamogordo. 65

Now I am become Death Oppenheimer later recalled that, while witnessing the explosion, he thought of a verse from the Hindu holy book, the Bhagavad Gita: If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one. . . Years later he would explain that another verse had also entered his head at that time: namely, the famous verse; "Kalo Asmi Loka-ksaya-krit Pravardho, Lokan Samartum iha Pravattah" and was quoted by Oppenheimer after the successful detonation of the first nuclear weapon. He translated it as "Now I am become Death, the destroyer of worlds. " 66

What is Gita ? The Bhagavad Gītā also more simply known as Gita, is a sacred Hindu scripture, considered among the most important texts in the history of literature and philosophy. The Bhagavad Gita comprises roughly 700 verses, and is a part of the Mahabharata. The teacher of the Bhagavad Gita is Lord Krishna, who is revered by Hindus as a manifestation of God (Parabrahman) himself, and is referred to within as Bhagavan, the Divine One. The content of the Gita is the conversation between Lord Krishna and Arjuna taking place on the battlefield before the start of the Kurukshetra war. Responding to Arjuna's confusion and moral dilemma about fighting his own cousins, Lord Krishna explains to Arjuna his duties as a warrior and prince and elaborates on different Yogic and Vedantic philosophies, with examples and analogies. This has led to the Gita often being described as a concise guide to Hindu theology and also as a practical, self-contained guide to life. During the discourse, Lord Krishna reveals His identity as the Supreme Being Himself, blessing Arjuna with an awe-inspiring vision of His divine universal form. 67

Germany Surrender (May, 1945) By late 1944, the Red Army had driven the Germans back into Central Europe and the Western Allies were advancing into Germany. Hitler realized that Germany had lost the war, but allowed no retreats. In April 1945, Soviet forces attacked the outskirts of Berlin. Hitler's followers urged him to flee to the mountains of Bavaria to make a last stand in the National Redoubt. But Hitler was determined to either live or die in the capital. On 29 April, Hitler dictated his will and political statement On 30 April 1945, , when Soviet troops were within a block or two of the Reich Chancellery, Hitler committed suicide, shooting himself in the temple while simultaneously biting into a cyanide capsule. On 2 May, Berlin surrendered. 68

War was not over… The Battle of Iwo Jima (February 19 – March 26, 1945), or Operation Detachment, was a battle in which the United States fought for and captured Iwo Jima from Japan. The U. S. invasion was charged with the mission of capturing the three airfields on Iwo Jima. The battle produced some of the bloodiest and fiercest fighting in the Pacific Campaign of World War II. Of the more than 18, 000 Japanese soldiers present at the beginning of the battle, only 34 were taken prisoner. The rest were killed or were missing and assumed dead. The lessons learned on Iwo Jima served as guidelines for the following Battle of Okinawa and the planned invasion of the Japanese homeland. 69

And become bitter and bitter… The Battle of Okinawa, codenamed Operation Iceberg, [was fought on the Ryukyu Islands of Okinawa and was the largest amphibious assault in the Pacific War. The 82 -day-long battle lasted from early April until mid. June, 1945. The battle resulted in one of the highest number of casualties of any World War II engagement. Japan lost over 100, 000 troops, and the Allies suffered more than 50, 000 casualties. Simultaneously, more than 100, 000 civilians (12, 000 in action) were killed, wounded, or committed suicide. Approximately one-quarter of the civilian population died due to the invasion. Some military historians believe that Okinawa led directly to the atomic bombings of Hiroshima and Nagasaki, as a means of avoiding the planned ground invasion of the Japanese mainland. 70

Frank Report The Franck Report of June 1945 was a document signed by several prominent nuclear physicists recommending that the United States not use the atomic bomb as a weapon to prompt the surrender of Japan in World War II. The report was named for James Franck, the head of the committee that produced it. The committee was appointed by Arthur Compton and met in secret, in all-night sessions in a highly secure. The report recommended that the nuclear bomb not be used, and proposed that either a demonstration of the "new weapon" be made before the eyes of representatives of all of the United Nations, on a barren island or desert, or to try to keep the existence of the nuclear bomb secret for as long as possible. The Franck Report was signed by James Franck (Chairman), Donald J. Hughes, J. J. Nickson, Eugene Rabinowitch, Glenn T. Seaborg, and Leo Szilard. Franck took the report to Washington June 12, and a separate committee, appointed by the President, met on June 21 to reexamine the use of the atomic bomb. However this committee reaffirmed that there was no alternative to the use of the bomb. 71

Who is James Franck? James Franck (B. 1882 – D. 1964) was a German physicist and Nobel laureate. In 1920, Franck became ordinarius professor of experimental physics and Director of the Second Institute for Experimental Physics at the University of Göttingen. While there he worked on quantum physics with Max Born, who was Director of the Institute of Theoretical Physics. In 1925, Franck received the Nobel Prize in Physics, mostly for his work in 19121914, which included the Franck-Hertz experiment, an important confirmation of the Bohr model of the atom. 72

A man of courage Mention should be made of Professor Franck's courage in following what was morally right. He was one of the first who openly demonstrated against the issue of racial laws in Germany, and he resigned from the University of Göttingen in 1933 as a personal protest against the Nazi regime under Adolf Hitler. Later, in his second homeland, his moral courage was again evident when in 1945 (two months before Hiroshima) he joined with a group of atomic scientists in preparing the so-called "Franck Report" to the War Department, urging an open demonstration of the atomic bomb in some uninhabited locality as an alternative to the military decision to use the weapon without warning in the war against Japan. This report, although failing to attain its main objective, still stands as a monument to the rejection by scientists of the use of science in works of destruction. 73

Frank’s Medal George Charles de Hevesy, (B 1885 – D 1966) was a Hungarian radiochemist and Nobel laureate, recognized in 1943 for his key role in the development of radioactive tracers to study chemical processes such as in the metabolism of animals. When Nazi Germany invaded Denmark in World War II, the Hungarian chemist George de Hevesy dissolved the gold Nobel Prizes of Max von Laue and James Franck in aqua regia to prevent the Nazis from stealing them. He placed the resulting solution on a shelf in his laboratory at the Niels Bohr Institute. After the war, he returned to find the solution undisturbed and precipitated the gold out of the acid. The Nobel Society then recast the Nobel Prizes using the original gold. 74

Szilárd petition The Szilárd petition, drafted by scientist Leó Szilárd, was signed by 155 scientists working on the Manhattan Project in Oak Ridge, Tennessee, and the Metallurgical Lab in Chicago, Illinois. It was circulated in July 1945 and asked President Harry S. Truman to consider an observed demonstration of the power of the atomic bomb first, before using it against people. However, the petition never made it through the chain of command to President Truman. It also was not declassified and made public until 1961. 75

Hiroshima, 1945. 8. 6 By executive order of President Harry S. Truman the U. S. dropped the nuclear weapon "Little Boy" on the city of Hiroshima on Monday, August 6, 1945 Before Bomb After Bomb 76

After the bomb According to most estimates, the immediate effects of the blast killed approximately 70, 000 people in Hiroshima. Estimates of total deaths by the end of 1945 from burns, radiation and related disease, the effects of which were aggravated by lack of medical resources, range from 90, 000 to 140, 000. Emperor Hirohito, the government, presented a letter of protest to the Government of the United States through the Government of Switzerland on August 10, 1945 and the war council were considering four conditions for surrender: the preservation of the kokutai (Imperial institution and national polity), assumption by the Imperial Headquarters of responsibility for disarmament and demobilization, no occupation of the Japanese Home Islands, Korea, or Formosa, and delegation of the punishment of war criminals to the Japanese government. 77

Nagasaki, 1945. 8. 9 On the morning of August 9, 1945, the U. S. B-29 Superfortress Bockscar, carried the nuclear bomb code-named "Fat Man", with Kokura as the primary target and Nagasaki the secondary target. By the time they reached Kokura a half hour later, a 70% cloud cover had obscured the city, prohibiting the visual attack required by orders. At 11: 01, the "Fat Man" weapon, containing a core of ~6. 4 kg (14. 1 lbs. ) of plutonium-239, was dropped over the city's industrial valley. 78

Witness of Nagasaki bomb 彭明敏目睹了 8月 9日美軍對長崎投擲原子彈的歷史事件。原子彈爆炸的後果，實在難以描寫。有些水泥建築物仍屹立著，但是，裡面所有木料和其他易燃物都在頃刻間化為烏有。據說在學校教室內，從整齊排列的白灰燼所在可以看出在死亡瞬間正坐在書桌旁的每一個學生。熱度竟有那樣強烈。大部分的醫科學生都罹難，其中包括四位曾經慷慨輸血給我的台灣留學生。他們有用的生命被消滅，我卻仍活著，這真是悲劇的命運。 79

Japan surrender (August, 1945) Hirohito recorded on August 14 his capitulation announcement which was broadcast to the Japanese nation the next day despite a short rebellion by militarists opposed to the surrender. In his declaration, Hirohito referred to the atomic bombings: Moreover, the enemy now possesses a new and terrible weapon with the power to destroy many innocent lives and do incalculable damage. Should we continue to fight, not only would it result in an ultimate collapse and obliteration of the Japanese nation, but also it would lead to the total extinction of human civilization. Such being the case, how are We to save the millions of Our subjects, or to atone Ourselves before the hallowed spirits of Our Imperial Ancestors? This is the reason why We have ordered the acceptance of the provisions of the Joint Declaration of the Powers. 80

Regret of Einstein The atomic bombings of Japan occurred three months after the surrender of Germany, whose potential for creating a Nazi a-bomb had led Einstein to push for the development of an a-bomb for the Allies. Einstein withheld public comment on the atomic bombing of Japan until a year afterward. A short article on the front page of the New York Times contained his view: "Prof. Albert Einstein. . . said that he was sure that President Roosevelt would have forbidden the atomic bombing of Hiroshima had he been alive and that it was probably carried out to end the Pacific war before Russia could participate. " Einstein later wrote, "I have always condemned the use of the atomic bomb against Japan. " In November 1954, five months before his death, Einstein summarized his feelings about his role in the creation of the atomic bomb: "I made one great mistake in my life. . . when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification - the danger that the Germans would make them. " 81

Hydrogen Bomb The idea of a thermonuclear fusion bomb ignited by a smaller fission bomb was first proposed by Enrico Fermi to his colleague Edward Teller in 1941 at the start of what would become the Manhattan Project. Stanislaw Ulam, a coworker of Teller's, made the first key conceptual leaps towards a workable fusion design. Ulam's two innovations were that compression of thermonuclear fuel before extreme heating was a practical path towards the conditions needed for fusion, and the idea of staging or placing a separate thermonuclear component outside a fission primary component, and somehow using the primary to compress the secondary. Teller then realized that the gamma and X-ray radiation produced in the primary could transfer enough energy into the secondary to create a successful implosion and fusion burn. 82

Ivy Mike The 10. 4 Mt "Ivy Mike" shot of 1952 appeared to vindicate Teller's long-time advocacy for the hydrogen bomb. Following the Soviet Union's first test detonation of an atomic bomb in 1949, President Truman announced a crash development program for a hydrogen bomb. On November 1, 1952, the Teller–Ulam configuration was tested at full scale in the "Ivy Mike" shot at an island in the Enewetak Atoll, with a yield of 10. 4 megatons (over 450 times more powerful than the bomb dropped on Nagasaki during World War II). The device, dubbed the Sausage, used an extra-large fission bomb as a "trigger" and liquid deuterium—kept in its liquid state by 20 short tons (18 metric tons) of cryogenic equipment—as its fusion fuel, and weighed around 80 short tons (70 metric tons) altogether. 83

Who is Edward Teller (B. 1908 – D. 2003) was a Hungarianborn American theoretical physicist, known colloquially as "the father of the hydrogen bomb, " In his later years he became especially known for his advocacy of controversial technological solutions to both military and civilian problems, including a plan to excavate an artificial harbor in Alaska using thermonuclear explosives. He was a vigorous advocate of Ronald Reagan's Strategic Defense Initiative, perhaps overselling the feasibility of the program. Over the course of his life, Teller was known both for his scientific ability and his difficult interpersonal relations and volatile personality, and is considered one of the inspirations for the character Dr. Strangelove in the 1964 movie of the same name. 84

Oppenheimer Controversy December 1953, partly as the result of evidence provided by the U. S. Army's Signals Intelligence Service, Oppenheimer was accused of being a security risk, and President Dwight D. Eisenhower asked him to resign. Oppenheimer refused and requested a hearing to assess his loyalty. The public hearing that followed in April-May 1954 focused on Oppenheimer's past Communist ties and his association during the Manhattan Project with suspected disloyal or Communist scientists. 85

Oppenheimer Controversy Teller detailed ways in which he felt that Oppenheimer had hindered his efforts towards an active thermonuclear development program, and at length criticized Oppenheimer's decisions not to invest more work onto the question at different points in his career, saying: If it is a question of wisdom and judgment, as demonstrated by actions since 1945, then I would say one would be wiser not to grant clearanc After a public hearing, the authorities agreed with Teller. Oppenheimer's security clearance was eventually stripped. After the Oppenheimer controversy, Teller became ostracized by much of the scientific community, Nobel Prize winning physicist Isidor I. Rabi once suggested that "It would have been a better world without Teller”. 86

War in the shadow of bombs A photograph of Operation Castle thermonuclear test, Castle Romeo shot The liquid deuterium fuel of Ivy Mike was impractical for a deployable weapon, and the next advance was to use a solid lithium deuteride fusion fuel instead. In 1954 this was tested in the "Castle Bravo" shot (the device was code-named the Shrimp), which had a yield of 15 megatons (2. 5 times higher than expected) and is the largest U. S. bomb ever tested. In the Soviet Union, the design was known as Andrei Sakharov's "Third Idea, " first tested in 1955. Similar devices were developed by the United Kingdom, China, and France, though no specific code names are known for their designs. 87

Hahn as Peace Maker Immediately after the Second World War, Hahn reacted to the dropping of the atomic bombs on Hiroshima and Nagasaki by coming out strongly against the use of nuclear energy for military purposes. He saw the application of his scientific discoveries to such ends as a misuse, or even a crime. Consequently, he initiated the Mainau Declaration of 1955, in which a large number of Nobel Prize-winners called attention to the dangers of atomic weapons and warned the nations of the world urgently against the use of "force as a final resort". He was also instrumental and one of the authors of the Göttingen Manifesto of 1957, in which, together with 17 leading German atomic scientists, he protested against a proposed nuclear arming of the new West German armed forces. In January 1958, Otto Hahn signed the Pauling Appeal to the United Nations for the "immediate conclusion of an international agreement to stop the testing of nuclear weapons". Right up to his death, he never tired of warning urgently of the dangers of the nuclear arms race between the great powers and of the radioactive contamination of the planet. From 1957, Hahn was repeatedly nominated for the Nobel Peace Prize by a number of organizations. 88