Frisch–Peierls memorandum

It was written by expatriate German-Jewish physicists Otto Frisch and Rudolf Peierls in March 1940 while they were both working for Mark Oliphant at the University of Birmingham in Britain during World War II.

[6] In 1932, he was awarded a Rockefeller Fellowship, which he used to study in Rome under Enrico Fermi,[7] and then at the Cavendish Laboratory at the University of Cambridge under Ralph H. Fowler.

[10] In 1937, Mark Oliphant, an Australian and newly appointed professor of physics at the University of Birmingham, recruited him for a new chair there in applied mathematics.

He worked at the Physikalisch-Technische Reichsanstalt in Berlin until 1930,[12] when he obtained a position at the University of Hamburg under the Nobel Prize-winning scientist Otto Stern.

Stern found Frisch a position in Britain with Patrick Blackett at Birkbeck College at the University of London, and a grant from the Academic Assistance Council.

When the outbreak of the Second World War in September 1939 prevented his return to Copenhagen, Oliphant found him a position at the University of Birmingham.

During the Christmas holiday in 1938, Frisch visited his aunt Lise Meitner in Kungälv in Sweden, where she had relocated after Germany's annexation of Austria.

While there she received the news that her former colleagues Otto Hahn and Fritz Strassmann in Berlin had discovered that the collision of a neutron with a uranium nucleus produced barium as one of its byproducts.

[25] On 16 April, Bohr, Placzek, Wheeler, Eugene Wigner and Leon Rosenfeld discussed whether it would be possible to use a nuclear chain reaction to make an atomic bomb, and concluded that it was not.

At the University of Liverpool, Chadwick and the Polish refugee scientist Joseph Rotblat tackled the problem, but their calculations were inconclusive.

[26] At Cambridge, Nobel Prize in Physics laureates George Paget Thomson and William Lawrence Bragg wanted the government to take urgent action to acquire uranium ore to keep it out of German hands.

The Secretary of the Committee for Imperial Defence, Major General Hastings Ismay asked Sir Henry Tizard for an opinion.

It was not considered worthwhile to immediately acquire the uranium, but Tizard's Committee on the Scientific Survey of Air Defence was directed to conduct research into the feasibility of atomic bombs.

[27] Thomson, at Imperial College London, and Oliphant, at the University of Birmingham, were tasked with carrying out a series of experiments on uranium.

By February 1940, Thomson's team had failed to create a chain reaction in natural uranium, and he had decided that it was not worth pursuing.

Peierls knew that questions of this nature related to the work on microwave radar, and Oliphant was doubtless aware of this too, but the façade of secrecy was maintained.

In addition, some part of the energy set free by the bomb goes to produce radioactive substances, and these will emit very powerful and dangerous radiations.

[41]Peierls' starting point was a paper by Francis Perrin, in which he had derived critical mass calculations in terms of nuclear constants.

For this, Frisch turned to a 1939 Nature article by L. A. Goldstein, A. Rogozinski and R. J. Walen at the Radium Institute in Paris, who gave a value of (11.2±1.5)×10−24 cm2.

[44] From this, Frisch could calculate the volume of the sphere from the well-known equation: The mass then comes out to be: Frisch and Peierls then considered the speed of a uranium fission chain reaction, exponential in nature, where "τ is the time required for the neutron density to multiply by a factor e." The available data was very approximate, but their central point – that a bomb was possible using fast (~2 MeV) neutrons – remains.

"[39] Using modern values he found that to be "equal to about a microsecond, which makes the point about the rapidity of fission with fact [sic] neutrons".

[47] The memorandum was given to Oliphant, who passed it on to Tizard in his capacity as the chairman of the Committee for the Scientific Survey of Air Warfare (CSSAW).

The MAUD Committee and report helped bring about the British nuclear program, the Tube Alloys project.

Oliphant convinced the Americans to move forward with nuclear weapons, and his lobbying resulted in Vannevar Bush taking the report directly to the president.

[54] Leo Szilard later wrote: "if Congress knew the true history of the atomic energy project, I have no doubt but that it would create a special medal to be given to meddling foreigners for distinguished services, and that Dr Oliphant would be the first to receive one.