THE EXPERIMENT

The experiment was carried out at Hanford in the preliminary stages, however, it was moved to the Savannah Plant near Augusta in Georgia. The plant had was chosen as it had shielding against cosmic radiation. The shielded location was 11m from the reactor and 12m underground.

A nuclear reactor with with a neutrino flux of 12-13 per second per centimeters squared was used to send neutrinos into a tank of water. The tank held 200 litres of water, and also had 40 kg of dissolved cadmium chloride in it. There were three lines of scintillators with 110 5 inch or 27 cm photomultiplier tubes on it. These tubes were used to collect gamma rays released from an annihilation reaction.

The theory is that the neutrino's will react with protons in the water, which causes it to decay to a neutron and a positron. This positron will react with an electron causing an annihilation which release a pair of gamma rays, each going in a opposite directions. These gamma rays cause the scintillator to visibly flash.
Cowan and Reines thought that this was not conclusive enough and decided that the neutrons should be measured as well. This was done with the cadmium. The neutrons cause the cadmium to become unstable and give off gamma rays of there own. The experiment was set out in a way that the gamma rays were released from the annihilation were detected first, then 5 microseconds later the gamma rays from the cadmium are seen on the scintillator. This created a distinctive signature for the detection of the neutrino reaction, the gamma pair hits, then 5 microseconds later the neutron gamma ray hits.