Bond of Bombs: The story of atomic bomb

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

2. 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 14N + α → 17O + 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.

3. The first accelerator During the early 1930s 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 particle-accelerator-based experimental nuclear physics. It was this research at Cambridge in the early 1930s that won Walton and Cockcroft the Nobel Prize in physics in 1951.

4. Discovery of neutron (I) In 1931 WaltherBothe 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 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.

5. 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

6. 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.

7. 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 chambercontaining 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.

8. 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.

9. 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.

10. Playing with neutrons

11. 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

12. 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 20th 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.

13. Criticism from chemist 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. 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.

14. 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.

15. 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

16. Hahn after WWII 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. Safe House, Farm Hall.

17. 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 = mc2, 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.

18. Lise Meitner as a refugee 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. Dirk Coster (B.1889– D.1950), was a Dutch physicist known as the co-discoverer of Hafnium. Adriaan Daniël Fokker (B1887 – D.1972), was a Dutch physicist and musician. In his 1913 thesis, he derived the Fokker-Planck equation along with Max Planck

19. 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.

20. 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.

21. Nuclear chain reaction A nuclear chain reactionoccurs 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. 235U) or the fusion of light isotopes (e.g. 2H and 3H). 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.

22. Who is Szilard? LeóSzilárd(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

23. 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.

24. 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

25. Szilárd and Fermi 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." An image from the Fermi–Szilárd "neutronic reactor" patent

26. 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 Reichskanzlerand 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.

27. Einstein–Szilárd letter TheEinstein–Szilárd letterwas a letter sent to United States President Franklin D. Roosevelt on August 2, 1939, that was signed by Albert Einstein but largely written by LeóSzilárd. 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 in1939, reenacting the signing of their letter to President Roosevelt warning him that Germany may be building an atomic bomb.

28. 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 radium-like 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……….

29. 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 Freiherrvon 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.

30. Carl Friedrich Freiherr von Weizsäcker 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.

31. 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

32. Weizsäcker, Bohr and Heisenberg 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. Ivan Supek (B. 1915 – D. 2007) was a Croatian physicist Niels Bohr and Margrethe Bohr

33. World War II began 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.

34. Reply from Roosevelt THE WHITE HOUSEWASHINGTON 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.

35. 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.

36. Frisch–Peierls memorandum The Frisch–Peierls memorandumwas 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. 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. Otto Robert Frisch (B. 1904, Vienna  – D.1979), The opening paragraph of the Frisch–Peierls memorandum Sir Rudolf Ernst Peierls, (B.1907, Berlin – D. 1995, Oxford),

37. Who isPeierls ? Sir Rudolf Ernst Peierls, (B.1907 – D. 1995), was a German-born 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 the theory of positive carriers to explain the 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.

38. MAUD committee 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. Sir Henry Thomas Tizard (B. 1885 - D.1959 ) was an English chemist and inventor.

39. 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.

40. 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.

41. 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.

42. 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.

43. Who is Bretscher? Egon Bretscher (B.1901-D.1973) Born near Zurich, Switzerland in 1901 and educated at the ETH there, Bretscher gained a PhD 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. Egon Brestcher (right)

44. What Feather remembered… 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. Norman Feather (B.1904 – D.1978), was an English physicist. Interview with Norman FeatherBy Charles Weiner In Edinburgh, Scotland(James Clerk Maxwell Physics Building)February 25, 1971

45. 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.

46. Creation of OSRD 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. Sir Marcus 'Mark' Laurence Elwin Oliphant (B. 1901 – D. 2000) Vannevar Bush (B. 1890 – D.1974)

47. Pearl Harbor, Dec 7th 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

48. U.S. effort quickly caught up 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. 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.

49. 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.

50. 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.