SNO+

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SNO+ is a proposed underground physics experiment that aims to make use of the existing infrastructure of SNO and Snolab. The main physics goals are the measurement of pep (see proton-proton chain reaction) solar neutrinos, geo-neutrinos (neutrinos from radioactive decays in the earth's core, mantle, and crust) and neutrinoless double beta decay.

In order to reach these goals liquid scintillator will be used as target material. A neutrino interaction with this liquid produces several times more light than an interaction in a water cherenkov experiment such as Super Kamiokande or SNO. The energy threshold for the detection of neutrinos therefore can be lower and proton-electron-proton (pep) neutrinos can be observed. In addition a liquid scintillator experiment can detect anti-neutrinos like those created in nuclear fission reactors and the decay of Thorium and Uranium in the earth. The option of a measurement of neutrinoless double beta decay in SNO+ (also called SNO++) can be achieved by adding Neodymium to the scintillator. A mass of several 100kg of double beta decaying material could be added to the experiment. This would make SNO++ the largest experiment to study neutrinoless double beta decays.

Collaborators, most of which have previously worked at SNO, have applied for funding in Canada and the US. It is hoped that the experiment can start construction after the SNO heavy water is removed from the acrylic vessel (2008).

The main engineering challenge is that the current SNO vessel is supported by a series of ropes, to prevent the weight of the heavy water inside from sinking it in the surrounding normal water. The proposed liquid scintillator (linear alkylbenzene) is lighter than water, and must be held down instead, but still without blocking the view of its interior.