One of the approximately 10,000 Hammamatsu R1408 photomultiplier tubes used to detect radiation produced by neutrino-deuterium interactions at the Sudbury Neutrino Observatory (SNO). The nominal 8-inch (20.6 cm) diameter photomultiplier tubes were specially manufactured for the experiment using very low-background borosilicate glass and surrounded a large acrylic vessel located 2 km underground at the Creighton mine in Sudbury, ON. The vessel contained 1,000 tonnes of heavy water on loan from AECL. The large SNO collaborative team showed that neutrinos change “flavour” on their trip to the earth from the Sun, thereby solving a long-standing “missing-neutrino” puzzle. The leader of the experiment, Art McDonald, a Chalk River alumnus, was awarded the Nobel Prize in Physics for his part in the project.
