Montage d'un détecteur circulaire pour étudier la désintégration du x négatif. Mesuré par Georges Claude

The photographs were taken in the West Workshop and shows the completed assembly of an unusual wheel built up of seventeen scintillation counters. The wheel was part of the detection equipment in an experiment to examine the decay products of the negative ξ particle. Of particular interest, was the rare decay giving an electron, which occurred about five times in ten thousand decays (the usual decay giving a pion). The wheel had to be very large (about 3 metres across) so that it would still catch the decay particles even though it was not right close to the target where the ξ was produced but was preceeded by a gas Cherenkov counter, which distinguished between an electron and a pion.