Imaging individual barium atoms in solid xenon for barium tagging in nEXO.
Abstract
Double-β-decay involves the simultaneous conversion of two neutrons into two protons,
and the emission of two electrons and two neutrinos; the neutrinoless process, although
not yet observed, is thought to involve the emission of the two electrons but no neutrinos.
The search for neutrinoless-double-β-decay probes fundamental properties of neutrinos,
including whether or not the neutrino and antineutrino are distinct particles. Double-β-decay
detectors are large and expensive, so it is essential to achieve the highest possible
sensitivity with each study, and removing spurious contributions ('background') from
detected signals is crucial. In the nEXO neutrinoless-double-β-decay experiment, the
identification, or 'tagging', of the 136Ba daughter atom resulting from the double-β
decay of 136Xe provides a technique for discriminating background. The tagging scheme
studied here uses a cryogenic probe to trap the barium atom in a solid xenon matrix,
where the barium atom is tagged through fluorescence imaging. Here we demonstrate
the imaging and counting of individual barium atoms in solid xenon by scanning a focused
laser across a solid xenon matrix deposited on a sapphire window. When the laser irradiates
an individual atom, the fluorescence persists for about 30 seconds before dropping
abruptly to the background level-a clear confirmation of one-atom imaging. Following
evaporation of a barium deposit, the residual barium fluorescence is 0.16 per cent
or less. Our technique achieves the imaging of single atoms in a solid noble element,
establishing the basic principle of barium tagging for nEXO.
Type
Journal articleSubject
nEXO CollaborationPermalink
https://hdl.handle.net/10161/19576Published Version (Please cite this version)
10.1038/s41586-019-1169-4Publication Info
nEXO Collaboration (2019). Imaging individual barium atoms in solid xenon for barium tagging in nEXO. Nature, 569(7755). pp. 203-207. 10.1038/s41586-019-1169-4. Retrieved from https://hdl.handle.net/10161/19576.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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