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The nEXO experiment

nEXO is a collaboration of 28 universities and institutes in 7 countries over 3 continents which intends to search for the neutrinoless double beta decay of 136Xe. A link to the homepage can be found here.

Artist’s view of nEXO at the SNOlab underground laboratory.

Compared to the predecessor EXO-200, where 200 kg of liquid Xenon were used, nEXO is a large scale experiment with a total xenon mass of about 5 tons enriched to ≈ 90% of 136Xe. The detector will be a cylinder 1.3 m in diameter and the lateral surface will be covered with Silicon photomultipliers (SiPM). These SiPMs detect the scintillation light of the xenon atoms that were excited by the electrons emitted in a possible 0νββ-decay event. At the bottom of the cylinder, a panel of anodes will collect the secondary electrons which are also produced in such events and are drifted to the anode by strong electrical fields in the cylinder. Both signal channels allow an accurate measurement of the event energy, with an energy resolution of about 1% (σ) or less at the total decay energy (Q-value). The whole setup works as a time-projection-chamber, where the charge (x-y position) and the light information (z position) is used to determine the three dimensional position of each event. Since the decay rate is very low, one needs exceptionally radiopure materials, ultra-pure xenon, very efficient scintillation light detection, low electronic noise, good energy resolution, operation deep underground and possibly the tagging of the daughter nucleus (136Ba). Further information on the neutrinoless double beta decay and the nEXO experiment can be found under the following links: