Atomic Bomb Chronology: 1942-1944

1942.1.24 U.S.A. Concentration of the atomic power research (Pile Plan) to the Chicago's Metallurgical Laboratory. [A. Compton, E. Lawrence,L. Szilard and others]
1942. 9 U.S.S.R. Soviet Atomic Bomb Project started. Led by Igor Vasilievich Kurchatovi40 years oldj.
1942.3 U.S.A. Naming of new elements by G.Seaborg: Neptunium for93 and Plutonium for 94. (Named for planets Uranus, Neptune and Pluto)
1942.3 Soviet Union Beria, the director of secret police, reports western situation of the nuclear development to Stalin, based on spy's information.
1942.4.18 U.S.A. The first bombing of Tokyo by several B-25 bombers taking off an aircraft carrier "Hornet" in the Pacific Ocean.
1942.4.23 U.S.A. Chemistry Conference at Chicago Metallurgical Laboratory[G.Seaborg,E.Wigner,J.Wheeler and others] on plutonium-separation technology including precipitation method.
1942.4 U.S.A. An experimental facility for ultra-micro chemical analysis established at Chicago Metallurgical Laboratory.
1942.4 Soviet Union A letter from G. Flerov to Stalin estimating western development of nuclear fission technology from the fact that papers relating to nuclear fission were gone from scientific journals.
1942.5.14 U.S.A. J. Conant's report of the atomic bomb development research presented to V. Bush, director of the Carnegie Institution of Washington.
1942.5.15 U.S.A. Delayed neutrons are below 1% of prompt neutrons. K (criticality factor) of prompt neutron is 1 or less and K including delay neutron is 1 or more.
1942.5.18 U.S.A. G. Bright resigned the person in charge of nuclear fission study using fast neutron claiming insufficient secrecy. He required a new research institute.
1942.5.26 U.S.A. Magnets for cyclotron of 184 inches that develops Calutron completed. Gross weight was 4000 t.
1942.5 U.S.A. The designing of Chicago Pile number 1 (CP-1) starts.[E.Fermi, H.Anderson]
1942.6.5 Japanese corps defeated at Midway naval battle.
1942.6.11 U.S.A. R. Oppenheimer named as successor of G.Bright: Arrived at Chicago to research nuclear fission caused by fast neutrons.
1942.6.13 U.S.A. 'Nuclear fission bomb' report to the president submitted by V. Bush and J. Conant. Scientists are convinced of feasibility of plutonium plan.
1942.6.17 U.S.A. The production of plutonium started. 45-inch cyclotrons of St. Louis University and Washington University were used. 136 kg uranium nitro-oxide(VI) was irradiated continuously for one month.
1942.6.17 U.S.A. President Franklin Roosevelt authorized the atomic bomb development plan.
1942.6.25 U.S.A. The 1st S-1 committee meets. Participants: Conant,Briggs, Compton, Lawrence, Urey, Murphrey, Major General Wilhelm D. Styer,Colonel George C.Marshall, Colonel Kenneth D. Nichols. Centrifuge separation method and gas dispersion method were unfinished. Electric power required was estimated as 108,000 KW.
1942.6.27 U.S.A. Conference at Chicago's Metallurgical Laboratory.[Compton, Allison, Fermi, Seaborg, Szilard, Teller, Wigner, Walter Zinn].Start of feasible nuclear warfare study encouraged by A.Compton.
1942.7.9 U.S.A. S-1 committee approves construction of heavy water factory at Canada Trail. Order given to Consolidated Co.
1942.7.27 U.S.A. Plutonium arrives at Chicago from St. Louis.
1942.7 U.S.A. The Berkley summer study. A. Compton had asked theoretical physicist J. Robert Oppenheimer of the University of California-Berkleyto study the feasibility of a nuclear weapon. Oppenheimer convened a summer study at UC-Berkley. [Oppenheimer, H.Bethe, E.Teller, John Van Vleck, FelixBloch, Richard Tolman, Emil Konopinski, Robert Serber, L.Alvarez, J.Lawson,Robert Thornton, Robert Becker] Feasibility concluded. The chief uncertainties lay in the experimental values for neutron cross-sections, numbers of neutrons that would be produced in fission and cause other atoms to fission in a rapid chain reaction. The scientists suggested that such a reaction could be initiated by assembling a critical mass--an amount of nuclear explosive adequate to sustain it--either by firing two subcritical masses of plutonium or uranium 235 together or by imploding (crushing) a hollow sphere made of these materials with a blanket of high explosives (Tolman). Teller saw another possibility: by surrounding a fission bomb with deuterium and tritium, a much more powerful "superbomb" might be constructed. This concept was based on studies made by Bethe before the war of energy production in stars. When the detonation wave from the fission bomb moved through the mixture of deuterium and tritium nuclei, they would fuse together to produce much more energy than fission, just as elements fused in the sun produce light and heat. The summer conferences, the results of which were later summarized by Serber in "The Los Alamos Primer" (LA-1),provided the theoretical basis for the design of the atomic bomb, which was to become the principal task at Los Alamos during the war, and the idea of the H-bomb, which was to haunt the Laboratory in the postwar era. Seldom has a physics summer school been as portentous for the future of mankind. By Robert Seidel.
1942.8.11 U.S.A. Manhattan Engineering District (MED) created by Colonel James C. Marshall.
1942.8.20 U.S.A. Plutonium separated as a solid by Burris Cunningham and Louis B.Werner.
1942.9.14 U.S.A. Purchase of the uranium ore advised by S-1 committee.
1942.9.17 U.S.A. Colonel Leslie R. Groves (46 years old) is appointed to the commander of MED and the director Manhattan Project.
1942.9.18 U.S.A. Uranium ore purchased: 1250 tons stored in open-air on Staten Island since 1940.
1942.9.19 U.S.A. The highest priority of supply given to Manhattan Project by War Production Board.
1942.9.21 U.S.A. L. Groves and J. Marshall visit the Navy Research Institute.
1942.9.23 U.S.A. L. Groves promoted to Brigadier General.
1942.9 U.S.A. Trouble at Chicago: Repellence by L.Szilard, E.Fermi, J.Wheeler and others to Stone & Webster Co.
1942.9 U.S.A. Clinton, Tennessee (Site X): 5200 acres site purchased for factory of separation of Uranium235. Oak Ridge is the name of residence area. For full-scale production of enriched uranium and for the pilot-scale production of plutonium.
1942.9 Anglo-French atomic power accord.
1942.10.5 U.S.A. L. Groves visits Chicago's Metallurgical Laboratory.
1942.10.18 U.S.A. L. Groves, V. Bush and J.R. Oppenheimer talk at Berkeley:
1942.11.5 U.S.A. Construction of production plant with the electromagnetic separation method ordered by L. Groves to Stone and Webster Co. [Electric supply by General Electric; magnets by Allice Chalners; container by Westinghouse.]
1942.11.10 U.S.A. L. Groves generally entrusts the "PlutoniumProject" to DuPont Corp. (Carpenter, president of DuPont, proposed another plutonium production factory site than Clinton.)
1942.11.12 U.S.A. Construction of uranium-235 production plant decided by Military Policy Committee. Without construction of small scale testing pilot plants.
1942.11.14 U.S.A. Pilot plant omission approved by MED Review Committee. Plutonium plan is entrusted to DuPont, not to Stone & Webster.
1942.11.16 U.S.A. Looking for a suitable site for a new laboratory to design nuclear weapons: [Groves, Oppenheimer, McMillan and Major John Dudley.] Los Alamos was recommended by Oppenheimer rather than Jemes Springs the place Dudley, an officer entrusted with search, had selected.
1942.11.16 U.S.A. The construction of Chicago Pile number 1 (CP-1):[E.Fermi,W.Zinn,Herbert.Anderson]
1942.12.2 U.S.A. Self-sustaining chain reaction in Chicago Pile number 1 ( Critical State) [Fermi, Zinn, Anderson] Output 50W, 4.5minutes operation. 350 t pure graphite, 35 t metallic uranium. Eugene Wignerhanded Fermi a bottle of Bertolli Chianti and passed around paper cupsto the crew. Arthur Compton called the head of the NDRC, James Conant, and told him cryptically, " the Italian navigator has just landed in the New World," the secret phrase agreed to, signaling success. On12.12 output rose to 200W.
1942.12.4 U.S.A. L.Szilard opposed by L.Groves for a security clearance because he is a foreign citizen. Finally Szilard, because of his earlier brilliant works, was treated like E. Fermi and E. Wigner.
1942.12.23 U.S.A. Feasibility of plutonium plan reported by A.Comptonto L.Groves. The first atomic bomb was scheduled to be completed by 1945.Later, it would be possible to produce one per month.
1942.12.28 U.S.A. DuPont Corp. takes charge of the plutonium plan. he reward other than the necessary expense was 1 dollar.
1942.12 U.S.A. Construction of a plant with gas dispersion method(K25) entrusted to Kellex Co. by L.Groves. An independent power supply was also constructed not relying on TVA.
1943.1.4 U.S.A. Uranium enrichment by liquid thermal dispersion method is reported by R.Gunn and P.Abelson. Navy was not told of the critical state of Chicago Pile.
1943.1.15 U.S.A. Pile design at Clinton commenced. Water cooling was suggested by E.P. Wigner.
1943.1 U.S.A. L.Groves entrusts the operation of the production plant with the gas dispersion method to Union Carbide Co.
1943.1 Soviet Union Development of nuclear weapons is decided.
1943.2.1 U.S.A. Plutonium plant site at Hanford(Site W) outside of Richland ,Wash. Cost: $5,100,000.
1943.2.2 Soviet Union German army corps surrenders in Stalingrad, USSR.
1943.2.18 U.S.A. Construction of uranium235 separation factory (Queen Mary) at Clinton starts.
1943.2.27 England Explosion of German heavy water factory in Norway by Norwegian resistance. German nuclear research was greatly hindered.
1943.3.6 Japan Navy gives up atomic bomb development. Priority shifted to the radar research.
1943.3.15 U.S.A. J.Robert Oppenheimer (38 years old) arrives at LosAlamos as the director.
1943.3.17 U.S.A. Design specification of Calutron decided
1943. 3.22 U.S.S.R. Kurchatov made attention to Plutonium. Study of back numbers of Physical Review. Asking to set Soviet intelligence to find out British and the American progress.
1943. 3 U.S.A. A American officer named George Racey Jordan in charge of expediting deliveries through the Gore Field, Air Port for Lend-Lease to Soviet Union, suspected Soviet's transport of US confidential contained in many black suitcases. His report to Washington was ignored. Transport of nuclear materials was later revealed.
1943.3 U.S.A. XA magnet for Calutron completed: The radius of gyration: 3-4 feet. Magnetic field: 3410 oersted.
1943.4.1 U.S.A. N-A barrier for the gas dispersion method entrusted by L.Groves to Widell Hershey Co.
1943.4 U.S.A. Los Alamos starts: [J.R. Oppenheimer, John Manley,H. Bethe, E. Teller, E. Kopinowsky, Felix Bloch, Stanley Frankel, Eldred Nelson, Robert Serber, Robert Wilson, Richard Feynmann, John Williams and many others]. Average age, 26 years old. Finally 3000 people. Edward Condon left soon after opening hating militaristic regulation.
1943.4 U.S.A. Implosion Method for firing A-bomb proposed by Seth Neddermeyer. Blowing a sphere of uranium-235 or plutonium would assemble these materials so rapidly that they explode.
1943.5.25 U.S.A.- England talks at the White House on Churchill's request for information of atomic bomb.
1943.6 U.S.A. William Parsons, Commander (43 years old) arrived at Los Alamos. A technology officer dealing with radar, he later engaged in dropping of Little Boy.
1943.7.2 Japan Yoshio Nishina reports the feasibility of A-bomb to army. Employing thermal diffusion method.
1943.7 U.S.A. Number of secondary neutrons from fission of plutonium assessed as 2.9 by Robert Wilson with material obtained by 184-nch cyclotron at Los Alamos.
1943.7.17 U.S.A. Starting of test shot of gun-type ignition. [W.Parsons]
1943.7.22 England - U.S.A. talk of about A-bomb at Downing Street 10.[Churchill, Sir John Anderson, Lord Cherwell, Henry H.Stimson, V. Bush, Harvey H. Bandy]. Bush promised Churchill to convey his concern for Soviet Union's threat.
1943.7.24 Indiscriminate bombing of Hamburg: the first carpet bombings with 7.28 bombs per second. A huge fire storm developed.
1943.7.25 Italy Mussolini is arrested and executed.
1943.8.19 Quebec Conference. [Winston Churchill, Franklin Roosevelt].Without mentioning about an international agreement regarding to atomic bomb development or Anglo-French atomic power accord.
1943.8.29 Germany Disarmament of Denmark corps.
1943.9 U.S.A. John von Neumann arrives at Los Alamos to support S.Neddermeyer's implosion group with a mathematics division.
943.9.29 Niels Bohr escapes to Sweden by a motor boat. Protection of Denmark- residing Jews was appealed to Swedish government.
1943.10.6 England N. Bohr seeks refuge in England on the flight of a Mosquito bomber. Due to altitude anoxia he fainted. His son Aage Bohr arrived at London after one week . R. Tolmann, as a visitor to England, transmits an invitation by L. Groves to the Manhattan Project.
1943.10 U.S.A. Calutron constructed. Due to shortage of copper for coil of electromagnet, silver owned by Department of Treasury was used. To the request of 5 - 10 tons, Department of Treasury replied that they weigh silver by troy ounce. 395,000,000 Troy ounce, worth $300,000,000dollars. A race-truck on the 2nd floor; vacuum pump room on the 1st floor; operation personnel 4800 people.
1943.10 U.S.A. Start of construction of Hanford pile (100-B) for production of plutonium.
1943.10 U.S.A. Critical state produced by the implosion method.[J.V. Neumann, E. Teller] Critical state produced by compression of explosive substance less than critical mass because of less escape of neutrons.
1943.11.4 U.S.A. The critical state of Clinton Pile (Oak Ridge, X-10):800 KW; air cooling with blower; A graphite atomic pile; 7.5KW: 1944 Feb.,1800KW 1944. June, 3800jv: Owed greatly to G.Seaborg.
1943.11.16 England Bombing of German heavy water factory in Norway by B-17 bombers. Heavy water factory exploded previously was repaired April. Germany decided to move the factory to Germany.
1943.11.20 U.S.A. Start of separating plutonium at Clinton, processing with a remote control plant of 5 tons of uranium bombarded by neutrons.
1943.11.29 U.S.A. Start of remodeling B-29 bomber for A-bomb. [Norman Ramsey. External size of bomb decided. Thin Man (for Roosevelt) and Fat Man (for Churchill)]. (N.F.Ramsey received Nobel Prize in 1989.)
1943.12. 3 British Mission: English scientists join Manhattan Project(Quebec accord) [Wallace Ackers, Otto Frisch, R. Peierls, William J. Penny,George Placzek, P.B. Moon, James L. Tuck, Egon Bretcher, Klaus Fuchs, James@Chadwick, Geoffrey Taylor, Niels and Aage Bohr]
1943.12.14 U.S.A. U. S. Army Special Corps (ALSOS) landed in Italy: [Commander Boris T. Pash] Confirmation of improbable German development of A-bomb. This was not passed on to the Manhattan Project scientists.
1943.12.22 U.S.A. Impossibility of production of N-A barrier for gaseous diffusion method found in study by F. Simon and R. Peierls.
1943.12 British Mission: English scientists join Manhattan Project(Quebec accord) [Wallace Ackers, Otto Frisch, R. Peierls, William J. Penny,George Placzek, P.B. Moon, James L. Tuck, Egon Bretcher, Klaus Fuchs, James Chadwick, Geoffrey Taylor, Niels and Aage Bohr.]
1943.12 U.S.A. Nuclear fission of uranium235caused by neutrons in cosmic rays discovered by E.Segre. Possibility of slowing down of core reaction speed implied. Change to Little Boy from Thin Man. The full length from 17 feet to 6 feet.
1943.12.31 U.S.A. N. Bohr showed R. Oppenheimer a paper handed by Heisenberg. The paper was a design of pile. Explosive power of pile and possibitily to use as a weapon was investigated, Negative conclusion was conveyed to Groves.
1944.1 U.S.A. A new type barrier for gaseous diffusion method(J barrier) employed.
1944.1 U.S.A. George B. Kistiakowsky arrives at Los Alamos for the chemical explosive division supporting Neddermeyer's implosion device.
1944.1 U.S.A. Start of navy liquid thermal diffusion plant construction:300 columns. [P.Abelson]
1944.2.1 U.S.A. Separation of plutonium at Clinton plant finished. A pilot test. 190 mg.
1944.2.20 England Sink of German heavy water, blasting of boat transporting from Norway to Germany. End of German development of nuclear weapons.
1944. 2 U.S.A. Klaus Fuchs met with Harry Gold, a Soviet intelligence agent.
1944.2 Japan A report by Yoshio Nishina indicating difficulty of production of uranium fluoride. The method considered was that had been given up by P. Abelson.
1944.3.1 U.S.A. The first plutonium 239 from Clinton arrives at Los Alamos.
1944.3.3 U.S.A. Start of test dropping of atomic bombs by B-29.Dropping of mock bomb of Thin Man bomb failed due to hitting against bomb-bay door.
1944.3.27 Belgium government sells the pre-emption of all the uranium resource in Congo to U.S.A. and England. [Sir John Anderson, Ambassador John G. Winant] for $375,000,000 dollars.
1944. 3 U.S.A. Fuchs leaked data (including draft of his own paper) of gaseous diffusion to Soviet agent.
1944.3 U.S.A. The first transportation of enriched uranium 235from Clinton to Los Alamos. 10% enrichment.
1944.3 U.S.A. Kenneth T. Bainbridge is assigned to the responsible person of the first A-bomb test, Trinity. Trinity named by J. Oppenheimer.
1944.3 U.S.A. Peppermint operation: Portable Geiger counters, X-ray films and so on for inspecting radioactivity were prepared for Normandy invasion by Allied forces.
1944.3 U.S.A. Prediction of fireball associating with A-bomb explosion by H.Bethe and Robert Christy. Emergence of a fireball and impulse wave of air heated by soft X-rays given out in chain raction.
1944.4.28 U.S.A. Liquid thermal diffusion method for enriching uranium235 is recommended by J.Oppenheimer to L.Groves.
1944.4 U.S.A. Explosive Lens for ignition of A-bomb: An idea developed by James L. Tuck. Production of spherical impulse wave by combinatorial ignition of explosives with various burning velocity.
1944.4 U.S.A. IBM computer arrival at Los Alamos. [J. Neumann, Stanislaw Ulam] For the hydrodynamics of implosion, and interference of impulse waves.
1944.5.16 Churchill - N.Bohr talk: Bohr's suggestion on international cooperation of A-bomb development, treatment of Soviet Union. His apocalyptic viewpoint was not understood.
1944.5 U.S.A. R. Peierls moved to theory division by J.Oppenheimer.
1944.5 U.S.A. Calutron completion: A new plant for uranium235high enrichment: radius, 2 feet.
1944.5 U.S.A. Alamogordo Bombing Range chosen for Trinity by J.Oppenheimer and K.Bainbridge.
1944.6.6 D-day: Normandy invasion by allied forces. D.Eisenhower commanding.1500 tanks, 12,000 airplanes, 156,000 soldiers, 1200 battleships.
1944.6.12 U.S.A. A liquid thermal diffusion plant at Clinton approved.
1944.6.13 Germany V-1 rocket bombs London: 8070 rockets were launched by 1944.9.4. 29% of them flew to London.
1944.6 U.S.A. G. Kistiakowsky as director of explosive section. S.Neddermeyer withdrew as an adviser.
1944.6 U.S.A. Highly enriched uranium 235 from Clinton arrived at Los Alamos.
1944.7.11 U.S.A. Absence of feasibility of Plutonium bomb, concluded.[Midsummer Crisis] Too much plutonium240 was detected in Clinton sample by E.Segre. J.Oppenheimer was persuaded not to resign by RobertF. Backer.
1944.7.17 U.S.A. The highest priority is given to "IMPLOSION"by J.Oppenheimer. The abandonment of THIN MAN. Implosion at 10 km/sec is required in Plutonium bomb. Feasibility was considered of an implosive type uranium bomb in order to obtain multiple bombs.
1944.8.1 U.S.A. Tinian Is. occupation: 6 runways for B-29 bombers were made for attacking Japan.
1944. 8. 5 U.S.A. David Greenglass, a communist, joined Los Alamos for supporting development of implosion lens.
1944.8.7 U.S.A. Time table of A-bomb production presented by L.Groves. Several bombs may be made until March-June ,1945 if implosion method is effective. Otherwise, one bomb is produced by August, 1945.
1844. 8.14 U.S.A. Klaus Fuchs joined Los Alamos. Chadwick informed Fuchs that his service was requested.
1944.8.25 U.S.A. Advance into Paris by U. S. Army. Special unit(ALSOS) advanced into Paris next to tanks. [B.Pash, Samuel A. Goudsmit].They questioned F.J. Curie at the Radium Research Institute and confirmed the absence of German A-bomb development.
1944.8.26 Roosevelt - N.Bohr talk. Suggestion by Bohr on international cooperation of A-bomb development , treatment of Soviet Union. His apocalyptic viewpoint was not understood.
1944.8 U.S.A. Colonel Paul W. Tibbets (29 years old) made commander of the 509th Composite Group. He was a test pilot of B-29 bomber.
1944.8 U.S.A. General Curtis LeMay made commander of the 20thbomber corp. A strategy of taking off Chinese base for bombing Japan considered.
1944.9.8 Germany V-2 rocket bombing of London: 4320 rockets were launched till March 27, 1945. 1050 of them dropped on England.
1944.9.13 U.S.A. Start of charging of metal uranium at Hanford Pile: 250 t uranium, 100,000 rods of graphite,11m* ~8.5mH)
1944.9.18 Hyde Park Accord reached. [F. D. Roosevelt and W. Churchill]A secret accord deciding atomic bombing of Japan.
1944.9.19 U.S.A. A note of post-war strategy: Sent by V.Bush andJ.B.Connant to Henry L.Stimson, the secretary of war. Danger of making A-bomb secret. Participation of Soviet Union to any accord is essential.
1944.9.19 U.S.A. Seizure by ALSOS of German uranium ore (68 tons). [B.Pash] 30 tons were found in Toulouse, October ,1944.
1944.9.26 U.S.A. The critical state achieved in Hanford Pile. Operation with 9MW. Rising of cooling water temperature from 10 to 60 deg C. It was due to absorption by xenon135, a fission product, of neutrons. Cross section of xenon135 of neutron-absorption is 150 times of cadmium. Critical state in the 2nd Pile in December 1944. Critical state in the 3rd Pile in 1945.
1944. 9 U.S.A. Robert Christy proposed a bombing core not a shell of plutonium but a nearly solid subcritical ball (in the form of two fitted hemispheres). The imploding detonation wave would simply squeeze the solid mass to criticality.
1944.9 U.S.A. Start of Calutron operation: 100 g daily production of 10% enriched uranium.
1944.10.25 Japan Kamikaze commando at Layte naval battle.
1944.10.30 U.S.A. Start of operation of Navy liquid thermal diffusion plant at Philadelphia navy arsenal.
1944.10 U.S.S.R. Production of plutonium(several micrograms) by Boris Kurchatov [a brother of Igor Kurchatov]
1944.11.24 U.S.A. Bombing Japan by B-29 bombers from Northern Mariana base with a large formation of 100 bombers. The high altitude bombing failed due to a high speed air current. The discovery of jet stream.
1944.11.28 U.S.A. Taking out of irradiated slugs from Hanford Pile:8.3 tons.
1944.11 U.S.S.R. Metallic uranium refined.
1944.11 U.S.A. Start of operation of Calutron: 90 g daily production of 80% enriched uranium.
1944.11 U.S.A. Start of implosion experiment with shaped explosives. Implosive process was examined by X-ray camera taking hi-speed successive pictures.
1944.12.26 U.S.A. Separation of irradiated slugs from Hanford Pile.
1944 U.S.A. A balloon bomb from Japan cuts the power supply to Hanford Pile.

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