Seth Neddermeyer
Encyclopedia
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
physicist who co-discovered the muon, and later championed the implosion design of the plutonium atomic bomb, at the Manhattan Project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...
.
Caltech
Neddermeyer was Carl D. Anderson's Ph.D. student at Caltech. In 1936, he and Anderson discovered the moonMoon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, using cloud chamber
Cloud chamber
The cloud chamber, also known as the Wilson chamber, is a particle detector used for detecting ionizing radiation. In its most basic form, a cloud chamber is a sealed environment containing a supersaturated vapor of water or alcohol. When a charged particle interacts with the mixture, it ionizes it...
measurements of cosmic rays.
Manhattan Project work
While at Los AlamosLos Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
, Neddermeyer was an early advocate for the development of an implosion technique for assembling a critical mass in an atomic bomb. While implosion was previously suggested by Richard Tolman as early as 1942, and discussed in the introductory lectures given to Los Alamos scientists by Robert Serber
Robert Serber
Robert Serber was an American physicist who participated in the Manhattan Project. He was born in Philadelphia, Pennsylvania; he was the eldest son of David Serber and Rose Frankel. He married Charlotte Leof in 1933. Rose Serber died in 1922; David married Charlotte's cousin Frances Leof in...
, Neddermeyer was one of the first to urge its full development. Unable to find much initial enthusiasm for the concept amongst his fellow Los Alamos scientists, Neddermeyer presented the first substantial technical analysis of implosion in late April 1943. Though many remained unimpressed, Robert Oppenheimer
Robert Oppenheimer
Julius Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. Along with Enrico Fermi, he is often called the "father of the atomic bomb" for his role in the Manhattan Project, the World War II project that developed the first...
appointed Neddermeyer the head of a new group to test implosion. Neddermeyer embarked on an intensive series of experiments testing cylindrical implosions.
Nevertheless, seemingly irresolvable problems with shock wave uniformity brought progress on implosion to a crawl. At the urging of James Conant
James Bryant Conant
James Bryant Conant was a chemist, educational administrator, and government official. As thePresident of Harvard University he reformed it as a research institution.-Biography :...
, Oppenheimer, brought in George Kistiakowsky
George Kistiakowsky
George Bogdan Kistiakowsky was a Ukrainian-American chemistry professor at Harvard who participated in the Manhattan Project and later served as President Eisenhower's Science Advisor...
(who had a specialized knowledge in the precision use of explosives) to help jumpstart the flagging program in January 1944.
In April, 1944 tests on the first plutonium-239
Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
produced with neutrons in a nuclear reactor rather than a cyclotron, revealed an unexpected problem: the reactor-bred plutonium contained five times more plutonium-240
Plutonium-240
Plutonium-240 is an isotope of the metal plutonium formed when plutonium-239 captures a neutron. About 62% to 73% of the time when Pu-239 captures a neutron it undergoes fission; the rest of the time it forms Pu-240. The longer a nuclear fuel element remains in a nuclear reactor the greater the...
(a result of reactor neutron bombardment), an unwanted isotope that spontaneously decayed and produced neutrons that promised to cause a pre-detonation, without sufficiently quick critical mass assembly. It now become apparent that only implosion would work for practical plutonium bombs, since neutrons from any amount of plutonium-240
Plutonium-240
Plutonium-240 is an isotope of the metal plutonium formed when plutonium-239 captures a neutron. About 62% to 73% of the time when Pu-239 captures a neutron it undergoes fission; the rest of the time it forms Pu-240. The longer a nuclear fuel element remains in a nuclear reactor the greater the...
which would be produced along with plutonium-239
Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
in a workable reactor production scheme, would cause a predetonation in any gun-type bomb. (See weapons grade plutonium for details). Plutonium-240, once produced in reactor-plutonium, was even more difficult to remove from plutonium-239 than isotopic separation of uranium. These facts made plutonium effectively unusable unless implosion worked. At the same time, it was becoming clear that only plutonium (rather than uranium) could be produced in quantities that would allow regular production (~ one bomb core per month) of atomic bombs. Thus, the implosion technique now suddenly stood as the key to regular production of nuclear weapons.
In mid-June 1944 Kistiakowsky’s report to Oppenheimer about the dysfunctionality within the implosion team led to the ouster of Neddermeyer and his replacement by Kistiakowsky in order to get this essential operation working. Neddermeyer was said to have been much embittered by this event. (Oppenheimer also was unhappy with this choice, but felt that no other possible course would allow timely development of practical weaponized bombs on a war schedule).
Accordingly, it was left to others like Kistiakowsky (who contributed a background in military ordnance and explosives), Robert Christy
Robert Christy
Robert F. Christy is an American theoretical physicist and later astrophysicist who worked on the Manhattan Project. He was also briefly president of Caltech....
(who contributed the insight that a subcritical sphere of plutonium could be imploded to a critical mass), John von Neumann
John von Neumann
John von Neumann was a Hungarian-American mathematician and polymath who made major contributions to a vast number of fields, including set theory, functional analysis, quantum mechanics, ergodic theory, geometry, fluid dynamics, economics and game theory, computer science, numerical analysis,...
(who contributed the breakthrough mathematical model for using shaped charges to create a truly spherical implosion), and Edward Teller
Edward Teller
Edward Teller was a Hungarian-American theoretical physicist, known colloquially as "the father of the hydrogen bomb," even though he did not care for the title. Teller made numerous contributions to nuclear and molecular physics, spectroscopy , and surface physics...
(whose knowledge of the compressibility of metals led to the use of density change to achieve criticality rather than mere, same-density, “assembly”), to complete the work. The implosion method championed by Neddermeyer was used in the first atom bomb exploded (Trinity test
Trinity test
Trinity was the code name of the first test of a nuclear weapon. This test was conducted by the United States Army on July 16, 1945, in the Jornada del Muerto desert about 35 miles southeast of Socorro, New Mexico, at the new White Sands Proving Ground, which incorporated the Alamogordo Bombing...
), the Fat Man
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...
bomb dropped on Nagasaki, and almost all modern weapons.
In 1982, he was awarded with the Enrico Fermi award
Enrico Fermi Award
The Enrico Fermi Award is an award honoring scientists of international stature for their lifetime achievement in the development, use, or production of energy. It is administered by the U.S. government's Department of Energy...
.