SNO+ is a liquid scintillator detector for studying neutrinos. The experiment is located 2km underground in Vale's Creighton mine near Sudbury, Ontario, Canada. The heart of the SNO+ detector is a 12m diameter acrylic sphere filled with 800 tonnes of liquid scintillator which floats in a water bath. This volume is monitored by nearly 10,000 photomultiplier tubes (PMTs), which are very sensitive light detectors. The acrylic sphere, PMTs and PMT support structure are re-used from the original Sudbury Neutrino Observatory (SNO) experiment. As a result, SNO+ strongly resembles its predecessor SNO but has a new rope-net added to hold the acrylic vessel down as it is becomes buoyant with scintillator.
Liquid scintillator is an organic liquid that gives off light when charged particles pass through it. SNO+ will detect neutrinos when they interact with electrons and nuclei in the detector to produce charged particles which, in turn, create light as they pass through the scintillator. The flash of light is then detected by the PMT array. This process is very similar to the way in which SNO detected neutrinos except that, in the SNO experiment, the light was produced through the Cherenkov process rather than by scintillation. Scintillation light will produce signals 50 times brighter in SNO+ expanding the capabilities of the new experiment, thereby allowing SNO+ to explore new neutrino physics measurements and studies.
The scintillator in the SNO+ experiment will be primarily composed of linear alkylbenzene (LAB), which is a new scintillator for this type of experiment. LAB was developed by SNO+ for use in neutrino detectors because it has good light output, is very transparent, is a "mild" chemical to work with (it has properties much like those of mineral oil), and is compatible with the SNO+ acrylic vessel. LAB is used commercially to manufacture dish soap, among other things, which means that it is readily available. The CEPSA Química plant in Bécancour, Québec produces excellent quality LAB for SNO+ and is a "local" Canadian supplier.