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Home , Fritz Haber, Leo Szilard, Tube Alloys

Big

Rob Iliffe Bigger Science

• ‘Big Science’ is term (invented in 1961 by Alvin Weinberg) to describe the of post-WW2 government-funded astronomy and , • Involving the coordination between academia and what in 1960 President Dwight Eisenhower called the ‘Military-Industrial complex’ • The growth of Big Science emerged at same time as the onset of the and was integral to it – notably in development of the (thermonuclear) Bomb. • Now, research ‘teams’ comprising hundreds of individuals are managed by a team leader or director, and scientific articles may have tens or hundreds of authors. The

• The Cyclotron became the quintessential piece of ‘Big Science’ equipment in the middle of the C20th. • Invented by at Berkeley, California, it was a circular , which he called a ‘ merry-go-round’ (carosello) • It accelerated a charged particle beam using high frequency alternating voltage applied between 2 ‘D-shaped’ metal electrodes inside a flat vacuum chamber. • Particle acceleration causes particles to move outwards in a spiral, exiting the D’s through a small gap, so as to hit a target.

Lawrence’s Cyclotron

• Cyclotron was originally a small (5-inch = 13cm) machine made up of glass, sealing wax and bronze, set on a kitchen chair, • It used hydrogen ions and boosted them to an energy of over 80,000 electron volts (MeV) • Lawrence gradually increased power with new machines throughout the 1930s, moving onto an 11-inch 24cm device in 1930, and reaching 1 million MeV in 1932 and then 5 MeV in 1935. • In 1939 his work culminated in a giant 220-ton 60-inch (1.6m) cyclotron, producing energies above 20 MeV.

‘Lawrence’s Laboratory’

• The ‘Radiation laboratory’ at Berkeley was lavishly supported despite the Depression, and became the prototypical ‘Big Science’ laboratory, • It engaged in competition with British scientists and elsewhere to produce transuranic elements. • British had success in 1932, with the discovery of the chargeless by and the splitting of the atom by James Cockcroft and using accelerated proton bombardment. • Meanwhile, and his group in Rome began to use ‘slow’ Neutron-bombardment to test the characteristics of different nuclei. The Berkeley Cyclotron

• Ultimately the Americans produced much bigger scientific instruments than was possible anywhere else, with larger teams • and the Berkeley laboratory involved the collaboration between unprecedented numbers of , and medics. • It became concerned with ‘nuclear science’ more generally from 1936, including the new field of nuclear medicine. • In 1940 Glenn T. Seaborg and others discovered -14, and . • The 184-inch cyclotron with a 4000 ton magnet was opened in 1946, producing energies of over 100 MeV.

Nuclear fission

• The work of Seaborg and his colleagues took place in the context of the momentous series of discoveries in the Twentieth Century. • In 1938 and announced the possible fission (i.e. ‘splitting’) of a atom when it absorbed a neutron. • At the start of 1939 Hahn and the showed that bombarding uranium with produced and krypton, along with a vast amount of energy. • Now in Stockholm with her nephew Otto Frisch, Meitner and Frisch quickly interpreted these results as due to , and calculated the phenomenal amount of energy released. • And within weeks a French group showed that two or three Neutrons were emitted, raising the possibility of a .

Lise Meitner (1878-1968)

• B. Vienna, and privately educated in physics, gaining a PhD in physics at University of Vienna in 1905. • Went to work with and Otto hahn in , becoming the first female professor in physics in Germany (1926), • and later head of physics at the Kaiser Wilhelm Institute for Chemistry. • But had to leave Germany for Sweden because of the Nuremberg Laws, though she had converted to Catholicism in 1908. • While Hahn was given in Chemistry for nuclear fission in 1944, she was not, leading to naming of element 109 as Meitnerium.

Tube Alloys

• Many – including and - realized that nuclear fission could produce a weapon, while correctly surmised that the fissile component was the U-235. • In 1939-40 the British (under the deliberately meaningless heading ‘Tube Alloys’) began to develop techniques for building a Bomb –. • However, at war with Germany, they lacked the resources to increase production of U-235 to beat what they believed to be a vigorous German programme. • Hence, they began to collaborate with the Americans on what became known as the . Enrico Fermi

• B. Rome 1901 – as a boy he was fascinated by electrical and mechanical toys such as gyroscopes; • studied physics intently at High School, and went to the Scuola Normale Superiore in Pisa, • where he impressed teachers with his advanced knowledge of mathematics, quantum physics and General Relativity, but where he also showed an aptitude for experimental work. • In later 1920s he did pioneering work developing Wolfgang Pauli’s Exclusion Principle, and his work led to identification of the ‘neutrino’ (a term Fermi coined) and of a type of force known as ‘Weak interaction’.

Roman Science

• Fermi was already the outstanding Italian , and was made Professor of Physics at the Sapienza University of Rome in 1926; • he was an excellent team leader (‘the pope of physics’) and gathered a group of talented students, making Rome an international centre of physics. • From 1934 Fermi and his team did numerous experiments firing neutrons into different elements and developing techniques for using ‘slow’ neutrons • He induced radioactivity in 22 elements, wrongly believing that he had discovered two new elements; he was awarded the Nobel Prize in 1938 for this and his discovery of slow neutron-induced nuclear reactions. • At this point he decided to leave Italy because his wife was Jewish and felt threatened by new racial laws.

Chain Reaction

• Fermi arrived in New York on 2 Jan. 1939, moving to ; he was quickly told of Meitner and Frisch’s findings and within days began work confirming all the recent results. • He and Leo Szilard designed a ’pile’ with uranium oxide and rods that would slow down the emitted neutrons. • After getting government support for purchase of graphite and uranium, Fermi moved his work to the soon after the Japanese bombed Pearl Harbor in December 1941. • Fermi moved to build the pile under the university squash court, and after meticulous planning, Pile-1 went critical on 2 December 1942. Soon after the pile went ‘critical’, the chairman of the National Defense Research Committee, James B. Conant, was told:

‘the Italian navigator has just landed in the new world’.

Fermi later became known as ‘the architect of the atomic bomb’

The Manhattan Project

• Managed by the US Army from June 1942, the programme was led by General Leslie C. Groves • while weapons research programme was directed at Los Alamos, New Mexico by Robert Oppenheimer. • The production of a working Atomic Bomb was not certain until the Chain Reaction at Chicago, after which two weapons were envisaged: • U-235 was used to produce a gun-type fission weapon (nicknamed ‘’) though this required a vast facility for uranium enrichment, which took place near Oak Ridge Tennessee. • Reactors for producing plutonium (an implosion device nicknamed ‘Fat- man’) were built at Oak Ridge and Hanford Washington.

The Gadget (Il Aggeggio)

• Oppenheimer proposed a test of Plutonium (implosion by ‘high- lens’) device in early 1944 - • Los Alamos Lab. now focussed on design of explosive arrangement. • ‘’ test site was chosen at Alamogordo, New Mexico • After many problems with and the heat of the Plutonium core, the weapon was fully assembled by the evening of 15 July 1945. • Bets were taken on the yield; Fermi also offered to have a bet with members of the military about whether the atmosphere would ignite. • The Gadget detonated at 5.29 AM local time, with a yield of c. 22kt.

Trinity test site, Alamogordo, New Mexico. The Decision to drop Bombs on japan

• War ended in Europe on 8 May 1945, and Allies called for unconditional surrender of Japanese forces on 26 July. • New US President Harry Truman had to consider massive recent number of casualties sustained in Japanese conflict, • Along with likely future losses of US soldiers from an invasion of Japan • Also significant was imminent Soviet invasion from the North. • Plans for possible drop of a began in December 1944, but this was not a viable option until the Trinity test in July 1945. • Two different committees discussed the area to be hit by any bombs, as well as the effects of a ‘non-combat’ demonstration. Hiroshima and Nagasaki

• For different reasons, including the limited number of bombs, the idea of a demonstration detonation was rejected before Trinity test. • With no Japanese surrender, Truman authorized the use of the ‘special bomb’ after getting agreement from the British. • Hiroshima was target of first U-235 ‘Little Boy’ fission weapon on 6 August, detonating at 8.15 a.m. local time and killing 70-80,000. • Afterwards, Truman warned the Japanese that they should expect an unprecedented ‘rain of ruin’ if they did not surrender – • When this did not happen, the US dropped a second Bomb (‘’) on the industrial city of Nagasaki, killing 50-60,000 people.

Science and ethics

• Scientists such as were deeply compromised by their work during the First World War, • even earlier, the pioneers of eugenics may have some responsibility for the mistreatment of various groups in the 1930s and 40s. • Work on the Bomb during and after WW2 put scientists in difficult positions, with political and national decisions governing their work on fission and then fusion (Thermonuclear) weapons. • Oppenheimer was opposed to development of practical Thermonuclear weapons (the ‘Super’), • while Fermi was involved in their design, though opposed to their practical construction. Oppenheimer and , with Princeton IAS computer used to produce calculations for meteorology and also Monte Carlo simulations for Hydrogen Bomb Fermi, 1953:

• [The] history of science and technology has consistently taught us that scientific advances in basic understanding have sooner or later led to technical and industrial applications that have revolutionized our way of life. It seems to me improbable that this effort to get at the structure of matter should be an exception to this rule. What is less certain, and what we all fervently hope, is that man will soon grow sufficiently adult to make good use of the powers that he acquires over nature.

• Fermi (orig. 1953) "The Future of Nuclear Physics,” in Cronin, J.W (ed.). Fermi Remembered. (Chicago, 2004).