Wu_experiment_at_Bureau_of_Standards.jpg
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Summary
Description Wu experiment at Bureau of Standards.jpg |
English:
Photo taken during the
Wu experiment
, an elementary particle experiment performed by American physicist
Chien-Shiung Wu
at the US
National Bureau of Standards
(now
NIST
in 1956 that established the nonconservation of
parity
in elementary particle reactions involving the
weak force
.
Tsung-Dao Lee
and
Chen-Ning Yang
, the theoretical physicists who originated the idea of parity nonconservation and proposed the experiment, were awarded the 1957 Nobel Prize in physics for this result. In the experiment, the intensity of
gamma rays
emitted by the radioactive isotope
en:cobalt 60
cooled to near absolute zero and placed in a
magnetic field
was measured. The picture shows the column containing the cobalt-60, detectors and magnetizing coil being slid into a glass Dewar flask, before being inserted in the large magnet in background, which will cool the sample to cryogenic temperatures.
Caption:" Low temperature experiments at the Bureau demonstrated that the quantum mechanical law of conservation of parity does not hold in the beta decay of cobalt-60 nuclei. Apparatus used in the parity studies. An outer dewar flask is being place on a glass vacuum chamber containing a sample of radioactive cobalt-60. The large magnet in the background cools the sample almost to absolute zero by adiabatic demagnetization. The magnetic field of a solenoid is then used to polarize the cobalt nuclei. " |
Date | |
Source | Retrieved January 29, 2014 from Annual Report of the National Bureau of Standards for 1957 , miscellaneous publication 227, US Government Printing Office, Washington D.C., p. 22 reprinted in Research Highlights of the National Bureau of Standards on Google Books |
Author | A. V. Astin, Director, Bureau of Standards |
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public domain
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of the
US Code
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