Atomic Bomb Chronology: 1930-1941

1930. 3 U.S.A. Pluto discovered by C.W.Tombaugh. (see plutonium)
1930 Germany Discovery of radiation which penetrates a leadblock by Walter Bethe. (Received 1954 Nobel prize.)
1932. 1.18 France Proton emission from beryllium irradiated by alpha-ray, discovered by Frederick Joliot and Irene Curie.
1932. 2.27 England Neutron discovered by James Chadwick, verifying　Rutherford's Baker Lecture. (Received 1935 Nobel prize.)
1932. 2 U.S.A. Cyclotron developed by Ernest Orlando Lawrence and　M.S.Livingston of California University, 27.5 inch size developing one　million electron volts. (Received 1939 Nobel prize)
1932. 4 England Conversion of element by John Douglas Cockcroftand Ernest Thomas Sinton Walton. Emergence of helium by irradiating highspeed proton to lithium, based on Gamow's tunnel effect. (Received 1951Nobel prize)
1932. 8. 2 U.S.A. Positron discovered by Carl David Anderson, detecting a cosmic-ray shower using a cloud chamber. (Received 1936 Nobel prize)
1932 U.S.A. Deuterium discovered by Harold Clayton Urey. (Received1934 Nobel prize)
1932.12 Albert Einstein seeks refuge in Belgium.
1933. 1.30 Germany Adolf Hitler becomes the Fuehrer of the Third Reich.
1933. 3.30 Leo Szilard escapes from Berlin to Vienna.
1933. 4. 7 Germany Promulgation of anti-Judish law by Nazi government.
1933.5 L. Szilard moves to England.
1933. 9. 9 A. Einstein moves to England.
1933. 9.12 England Idea of chain reaction via neutron by L.Szilard.He took a hint on the Times' report of Rutherford's lecture about atomic　transition. The idea of atomic bomb was patented in 1934. The patent was　transferred in secret to England's navy, 1936.2.
1933.10. 7 Albert Einstein moves to U.S.A.
1933.10 The 7th Solvay meeting. M. Curie, E. Rutherford, N. Bohr,L. Meitner, W. Heisenberg, W. Pauli, E. Fermi, J. Chadwick, G. Gamow, F.and I. Curie, P.M.S. Blackett, R.E. Peierls. In Brussels. On the structure　of proton.
1933.10 G. Gamow escapes from Soviet Union, seeks refuge in U.S.A.　after the Solvay meeting.
1933.12 Italy Weak interaction and beta-decay theory by Enrico　Fermi. (Received 1938 Nobel prize.)
1933 Rudolf Ernst Peierls seeks refuge in England.
1933 Germany Project of rocket development; by v.Brown.
1934. 1.15 France Artificial radioactivity. F. and I. Curie detected　radioactive phosphorus and positron by means of a Geiger counter after irradiating aluminum with alpha-rays from polonium. Blessed by M.Curie who was suffering from leucaemia caused by irradiation. (Recieved 1935Nobel prize)
1934. 5.10 Italy Transuranic elements assumed by E.Fermi based on　experimental results of irradiation of proton from radon and beryllium　to uranium
1934. 9 Germany Possibility of nuclear fission proposed by Ida　Noddack, a feminine scientist, not attracting attention.
1934.10.22 Italy Radioactivity induced by slow neutrons discovered　by E.Fermi.
1934 United Kingdom Hydrogen fusion reaction discovered by Marcus Oliphant and Paul Harteck, Cavendish Laboratory. Bombarding hydrogen2-deutreum, in the form of concentrated heavy water- with deuterium-accelerated nuclei.
1934 U.S.S.R. A small cyclotron was built by Abram I. Alikhanov and Igor Kurchatov. The first cyclotron operating outside U.S.A.
1935. 2 Hans Albrecht Bethe seeks refuge in U.S.A.
1935. 8 Edward Teller seeks refuge in U.S.A.
1935 Eugene Paul Wigner and Johann Ludwig von Neumann seek refuge　in U.S.A.
1935 Japan Meson predicted by Hideki Yukawa. Pi meson is a hadron　involved in alpha-decay and nuclear force. (Received 1949 Nobel prize.)
1936. 1.27 Denmark Liquid-drop model of atomic nucleus proposed by　Niels Bohr.
1936 England Energy production by conversion of hydrogen to　helium proposed in a lecture by Francis William Aston.
Ｅ＝ｍｃ2. A glass of water is enough for a full speed cruise of the Queen Mary in Atlantic Ocean.
1937. 4.26 Germany,Spain Guernica. Indiscriminate bombing by German　air force assisting Franco army. Protested by P. Picasso in famous painting.
1937 U.S.A. Cyclotron with 60 inches diameter and 220 tons magnet; Planed by E.Lawrence as a medical appliance, depending on private contribution.
1938. 3.13 Germany Austria annexed.
1938. 7.14 Italy Jews banned from public office.
1938. 7.17 L.Meitner with a help by N.Bohr escapes carrying an expired　passport from Germany to Stockholm via Copenhagen.
1938. 8 Emilio Gino Segre seeks refuge in U.S.A.
1938. 9 France Radioactivity with a half life of 3.5 hr produced　by neutron irradiation of uranium is from lanthanum, reported by Curie and Savitch.
1938 U.S.A. Uranium 235 and uranium238(ratio　of 1:139 in natural uranium), analyzed by Alfred Nier by means of Dempster's　mass spectrometer.
1938 Germany Isotope-separating device developed by Klaus Cladius　and G.Dicker employing a gas thermal diffusion method.
1938.12.19 Germany Uranium nuclear fission: Barium is detected　by Otto Hahn and Fritz Strassmann after irradiation by neutron of uranium　at Kaiser Wilhelm Institute. They asked L.Meitner's comments by a letter.　Beginning of the Barium Fantasy. (Received 1944 Nobel prize.)
1939. 1. 2 E.Fermi travels to U.S.A. Awarded Nobel prize and seeks refuge　in U.S.A with a help of N. Bohr. Fermi's wife is a Jew.
1939. 1. 6 Denmark A theoretical explanation of nuclear fission of　uranium written by L.Meitner and Otto Frisch employing a liquid drop model and theory of relativity. Next day N.Bohr brought a copy of the paper to　U.S.A. Conversion of one fifth of the mass of a proton to energy is plausible.
1939. 1.13 Denmark Detection of uranium nuclear fission by a cloud　chamber by Otto Frisch. Later nuclear fission of thorium was verified.　Thorium nuclear fission is triggered with fast neutron.
1939. 1.14 Denmark Nuclear Fission named by Otto Frisch, an analogy　of bacterial cell division called binary fission, suggested by William Arnold, an American Biologist.
1939. 1.16 U.S.A. N.Bohr travels to New York.
Bohr did not wish to make the nuclear fission story public, but John Feurer　announced the news at a meeting at Princeton University.
1939. 1.17 Denmark Otto Frisch submits a　paper of the theory and experiments　on nuclear fission of uranium.
1939. 1.25 U.S.A. Verification of the uranium nuclear fission by means　of an oscilloscope by Herbert Anderson, a student of Fermi. Emission of neutron by irradiating hydrogen with deuteron accelerated by means of cyclotron　at Columbia University. Failure in previous experiment by Fermi in Rome　was due to an obstruction by aluminum foils.
1939. 1.26 France Verification of uranium nuclear fission by J. and　I. Curie. They failed to detect neutron emission.
1939. 1.26 U.S.A. The fifth Washington meeting sponsored by American　Physics Society. N. Bohr, E. Fermi, Otto Stern, H.C. Urey, Gregory Bright,　Issidor Isaac Rabi, G. Gamow, E. Teller, Merle Tuve. Lectures by N.Bohrand E.Fermi on the uranium nuclear fission called "splitters."
1939. 1.28 U.S.A. Verification of uranium nuclear fission by Richard　Roberts and Robert Meyer. Emission of neutron on irradiating lithium with　deutron accelerated by a van de Graaff accelerator, was employed for irradiation　of uranium. Demonstration to members in the Washington Conference. Delayed　neutron was detected in later experiments, a discovery suggesting a possibility　of reactor control.
1939. 1.30 U.S.A. Verification of uranium nuclear fission by Phillip　Abelson. Luis Walter Alvarez transferred the news of nuclear fission of　uranium to Abelson. They found tellurium-52 and zirconium-40 as the fission　products. J.R.Oppenheimer, as noted by Alvarez, predicted neutron emission　and possibility of developing atomic bomb.
1939. 2.7 U.S.A. Nuclear fission of 235uranium is caused　by slow neutron, a theory proposed by N.Bohr and John Archibald Wheeler.
1939. 3.17 U.S.A. The first meeting on nuclear energy for military　purposes. The first proposal by scientists (G.P. Pegram and E.Fermi) of　the development of atomic bomb to Navy. E. Fermi talked on the controlled　reaction by slow neutron, explosion by fast neutron and reaction in the　supernova.
1939. 3 France More than one neutron emitted with nuclear fission　of uranium observed by J. Curie, Hans Halban and Lew Kowarski.
1939. 3 U.S.A. About two neutrons emitted with nuclear fission　of uranium verified independently by L.Szilard and Walter Zinn.
1939. 4.22 France Number of neutrons emitted with nuclear fission　of 235uranium is 3.5 /fission. Later corrected to 2.6/fission.By F.J.Curie, H.Halban and L.Kowarski.
1939. 4.29 Germany A secret conference about a research program on the nuclear bomb in Berlin. A trade embargo on uranium and radium. Letter of Paul Harteck.
1939. 4 U.S.A. John Dunning's request to Alfred Nier to separate235uranium.
1939. 5 N. Bohr returns to Copenhagen in order to support refugee　scientists.
1939. 7.3 U.S.A. Idea of nuclear reactor (pile) by E.Fermi and L.Szilard.Natural uranium as fuel and graphite as moderator of neutron energy.
1939. 8. 2 U.S.A. A letter of A.Einstein to President Roosevelt.L. Szilard, E. Teller and E. Wigner persuaded Einstein to warn President　Roosevelt of German menace. The letter suggested the possibility of uranium　bomb.
1939 Otto Frisch seeks refuge in England.
1939. 9. 1 World War II begins with the German invasion　of Poland. Blitzkrieg by tanks.
1939. 9. 3 England and France go to war against Germany.
1939. 9.16 Germany A secret conference in Berlin on Bohr's paper about　nuclear fission.
1939. 9.26 Germany The second Berlin meeting. Start of German nuclear　bomb project: Kurt Diepner, Erich Bagge , W. Heisenberg and Paul Harteck.
1939.10.11 U.S.A. Einstein's letter to President Roosevelt, presented　by Alexander Sachs.
1939.10.21 U.S.A. The 1st uranium advisory committee. Financial aid　to development of nuclear reactor rather than to yet uncertain atomic bomb.[A. Lyman, J. Briggs, A. Sachs, L. Szilard, E. Teller and E. Wigner]
1939.10 England An idea by J. Chadwick for an atomic bomb utilizing　natural uranium based on a paper by R.Peierls, mass needed for critical　state: 30-40 tons.
1939.12.6 Germany Report by W.Heisenberg of the possibility of a uranium　bomb to Germany Department of War.
1939.12 U.S.A. A discovery by Edwin Mattison McMillan of the existence　of the radioactive substance that stays in uranium on nuclear fission experiment.
1939 U.S.A. A theory of energy production in stars by Hans Albrecht　Bethe, the carbon cycle. (Received 1967 Nobel Prize.)
1940.2.1 England An idea by O.Frisch and E.Peierls of highly　enriched uranium bomb presented in a 3 page memo describing the critical　mass as 600 g. Presented via Mark Oliphant of Birmingham University to　Henry T. Tizard.
1940.2.29 U.S.A. Separation of uranium235 by A.Nier. 1/1,000,000,000gon a nickel film was sent to John R.Dunning in a letter. Uranium chloride(IV)or uranium fluoride(IV) was used. Minnesota University.
1940.2 U.S.A. Uranium research budget of $6000 authorized: the　purchase cost of graphite for E.Fermi and L.Szilard.
1940.3.2 U.S.A. Verification of uranium235 fission　with slow neutron by J.Dunning (irradiation by a cyclotron of a sample　separated by A.Nier. (Colombia University)
1940.4.9 Germany Invasion and occupation of Denmark.
1940.4.10 England George Paget Thomson committee. Small scale separation　experiments utilizing uranium fluoride(VI) agreed.
1940.4.24 England The 2nd George Paget Thomson committee.
1940.4.28 U.S.A. The 2nd uranium advisory committee. Necessity of basic research admitted. George B. Pegram and E. Fermi sit in.
1940.5.10 U.S.A. President Roosevelt's appeal for cooperation of　The American Scientists Federation. E. Teller decides to participate in　nuclear weapon research.
1940.5.27 U.S.A. A new 93rd element is discovered through irradiation　of uranium oxide using deutrons accelerated by a cyclotron. Called Neptuniumby E.McMillan. (Received 1951 Nobel Prize)
1940.5.27 U.S.A. The possibility of nuclear fission of transuranic　elements proposed by Louis A. Turner.
1940.6 France H. Halban and L. Kowarski escape to England carrying180 L heavy water with all the data of J.Curie. An test of a chain reaction　utilizing the heavy water carried out at the Cavendish Laboratory failed.
1940.6.14 France Paris falls to the German army.
1940.6 U.S.A. National Defense Research Committee(NDRC) swallows　up uranium advisory committee. Project for enriching 235uranium and elimination of refugee scientists discussed.
1940.6 England A gas dispersion method experiment by Franz Simon,　utilizing a copper partition for separating vapor and carbon dioxide.
1940.6 England Renaming of George Paget Thomson committee to MAUD　committee.
1940.6 Soviet Union Uranium Committee established in Academy of　Science by Igor Kurchatov. Interrupted due to German invasion in June,1941.
1940.10 Japan Army commander Suzuki's report of the possibility　of developing an atomic bomb based on a survey of uranium deposit in Chinese　and Burma.
1940.11 U.S.A. E. McMillan moves to radar research at MIT.
1940.11 U.S.A. Start of experiment on gas dispersion method for　enriching uranium-235 by H.Urey and J.Dunning. Uranium fluoride(VI) vaporizes　at 56 deg C.
1940.12.15 U.S.A. Nuclear fission of the new element 94239foreseen by E.Fermi and E. Segre. The possibility of a new element produced　in a nuclear reactor.
1940.12.16 U.S.A. A new element 94239. A plan for production　utilizing the 60-inchs cyclotron proposed by E. Lawrence, E. Segre, E.Fermi and G. Pegram.
1940.12.28 England A new idea of heavy water nuclear reactor by H.Halban.　A method for separation of element 93, discovered by Pletcher was conveyed　to U.S.A.
1940.12 England A plan for a factory for separation of uranium235by F.Simon. (MAUD committee, gas dispersion method.)
1940.12 England A possibility of nuclear fission of new element94 reported to MAUD committee.
1940.12 Japan A measurement of cross-section started by Yoshio　Nishina. Blueprint of 60-inch cyclotron was a gift of E. Lawrence.
1940 Soviet Union Spontaneous fission of uranium discovered　by George Flerov.
1941 U.S.A. P.Abelson moves to Navy Research Institute in order　to develop a small size nuclear reactor for submarine.
1941.1.28 U.S.A. A new element 94238discovered by E.Segreand Glenn T. Seaborg. Uranium oxide was irradiated by deutrons accelerated　with a cyclotron. (Received 1951 Nobel prize.)
1941.2.23 U.S.A. New element 94 chemically separated as a solution　by E. Segre, G. Seaborg and Arthur Wall.
1941.3.6 U.S.A. New element 94239 by irradiation of 1.2kg uranium oxide with neutrons emitted from beryllium irradiated by deutron.1 microgram of element was obtained. E. Segre and G. Seaborg.
1941.3.17 U.S.A. E. Lawrence proposes promotion of "uranium plan" based on conviction of the enriching method of uranium-235 utilizing　cyclotron.
1941.3.28 U.S.A. Verification of nuclear fission of new element 94239by E.Segre,G.Seaborg and Joseph Kennedy. Irradiation of new element 94by paraffin-decelerated neutron emitted from beryllium irradiated by deutron.　About 1.5 times of that by uranium irradiation.
1941.3 U.S.A. Improved measurement of cross section of uranium235by M.Tuve (the result was transmitted to England).
1941.3 England Critical mass of uranium235 calculated by R.Peierls.
1941. 3 U.S.A. Lend-Lease Act. President Roosevelt proposed to help Britain and other countries defend themselves against Germany.
1941.4 Japan Army approves atomic bomb research.
1941. 5 United Kingdom Klaus Fuchs, a German emigre theoretical physicist, a student of R. Peierls, started research of atomic bomb. A stalwart communist and Soviet espionage agent.
1941. 6.22 Germany Invasion by Hitler into Soviet Union.
1941. 7. 3 U.S.S.R. Formation of State Defence Committee (GKO)
[Stalin,Molotov,Voroshilov,Malenkov and Beria]
1941.5.18 U.S.A. Cross section of new element 94239 assessed　by E.Segre and G.Seaborg. Nuclear fission caused by slow neutron is 1.7times of that in uranium235.
1941.5 Japan A lecture by Tokutaro Hagiwara of explosive uranium235.
1941.6.23 England George Paget Thomson and MAUD committee reports　convincing evidence of developing uranium235bomb.
1941.7.7 England The conclusion of MAUD committee transmitted to　U.S.A.
1941.7.11 U.S.A. A memorandum regarding a nuclear fission of the94th element by E.Lawrence. (Possibility of plutonium bomb)
1941.7.24 U.S.A. The cross section of new element 94239:The nuclear fission caused by slow neutron is 3.4 times of that of uranium238.
1941.8 England Encouragement by M.Oliphant to nuclear power project　in U.S.A.
1941.9 U.S.A. Triggering by atomic bomb of hydrogen bomb studied　by E. Fermi and E. Teller.
1941.9 U.S.A. Construction of a graphite pile started by E. Fermiand L. Szilard.
1941.10.9 U.S.A. MAUD report brought to President Roosevelt by Vannevar　Bush. Atomic bomb development project started with transferring the focus　from nuclear reactor to atomic bomb.
1941.10 Discussion by N. Bohr and W. Heisenberg of a heavy water　type pile in Copenhagen.
1941.11.6 U.S.A. The 3rd NSA report of Compton committee. (Uranium　bomb possible within 3-4 years. Fifty to one hundred million dollars for　uranium enriching plant.)
1941.11.27 U.S.A. Submission of the 3rd NAS report to President Roosevelt.
1941.11 U.S.A. Separation of uranium235 by J.Dunning　and U.Booth. (A gas dispersion method using uranium fluoride(VI).)
1941.12.1 U.S.A. Data of nuclear fission of new element 94239given to A.Compton by E.Lawrence.
1941.12.2 U.S.A. Separation of 100 micrograms uranium235by E.Lawrence.
1941.12.6 U.S.A. Submission of plutonium bomb project by A.Compton.
1941.12.6 A counterattack to Germany corps by Soviet Union in Moscow.
1941.12.8 Japan A surprise attack on Pearl Harbor. (In U.S.A. date　was 12.7)
1941.12.9 U.S.A. A plutonium bomb project started by A. Compton and　V. Bush without report to President Roosevelt.
1941.12.16 U.S.A. V. Bush required participation of Engineering Brigade　in atomic bomb project.
1941.12.18 U.S.A. OSRD creates the S-1 committee, a special committee　created by V.Bush. [Connant, Briggs, Pegram, Compton, Lawrence, Urey, Samuel　Allison, G.Bright, Edward Condon and Henry DeWolf Smyth]
1941.12.20 U.S.A. Budget for developing atomic bomb of $651,000 (half　year portion) authorized.
1941.12 U.S.A. Calutron built by E.O. Lawrence: A 184-inch cyclotron　to separate U235. By the summer of 1942 most of the design problems　had been solved. The new machine was named Calutron after the University　of California.

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