File: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."