Walter Zinn (born 10.02.1906) was an American experimental physicist and a member of the National Academy of Sciences (1956). He was born in Kitchener (Canada). He graduated from Queen's University (1930). From 1930 he lived in the USA. In 1932 — 41 he worked at New York University and in 1942 — 46 at the Metallurgical Laboratory of the University of Chicago. In 1946—56 he was director of the Argonne National Laboratory, in 1956—64 president of the General Nuclear Engineering Corporation and in 1959 —70 vice-president of Combustion Engineering Incorporated.
His work was in the field of nuclear physics, neutron physics and the design and development of nuclear reactors. Independently of others he discovered in 1939 the phenomenon of the emission of secondary neutrons in the fission of uranium nuclei. Together with L. Szilard he was the first to measure the energy spectrum of the neutrons from the fission of uranium and obtained the value closest to the modern one for the mean number of secondary neutrons (the Zinn–Szilard experiment). He took part in the construction and the starting up (1942) of the first nuclear reactor. In 1947 he showed that sources of monoenergetic neutrons can be obtained and in the same year proposed, together with E. Fermi and H. Anderson, a method of measuring the absorption cross-section of thermal neutrons.
In 1951 the first experimental fast-neutron nuclear reactor was built under his direction.
The Atoms for Peace Award (1960), the E. Fermi Medal (1970) and others.