TRIUMF Develops Accelerator-Driven Ion Source to Test Barium-Tagging Techniques for Neutrinoless Double Beta Decay Detection
Researchers at TRIUMF are commissioning an accelerator-driven barium ion source designed to benchmark 'Ba-tagging' techniques for the proposed nEXO experiment, which aims to detect neutrinoless double beta decay in liquid xenon. The nEXO experiment targets a half-life sensitivity exceeding 10²⁸ years over a decade of operation, and Ba-tagging would help distinguish true decay signals from background noise by identifying the barium daughter nucleus produced in the decay. If successful, this infrastructure could significantly improve the sensitivity of one of the most ambitious searches for physics beyond the Standard Model.
The nEXO collaboration is developing a tonne-scale liquid xenon time projection chamber to search for neutrinoless double beta decay (0νββ) in xenon-136, a rare process that, if observed, would demonstrate that neutrinos are their own antiparticles and provide evidence for physics beyond the Standard Model. A key background-suppression strategy under investigation is 'Ba-tagging,' which involves extracting and identifying the barium-136 daughter nucleus produced in the decay to confirm genuine signal events. To test and optimize the various Ba-tagging methods being pursued by different research groups, a dedicated barium ion source is required. TRIUMF is developing an accelerator-driven ion source for this purpose, in which radioactive barium ions are injected into and stopped within a liquid xenon volume, then collected electrostatically and detected via gamma spectroscopy. The paper provides a status update on the commissioning of this ion source. The work represents an enabling infrastructure effort rather than a physics result, supporting the broader nEXO program ahead of its potential construction.
What's missing
The paper is a brief conference-style status update (3 pages) and does not report ion beam intensities or purities demonstrated, or a timeline for when the source will be ready to benchmark Ba-tagging techniques. The current sensitivity of the detection setup and any preliminary gamma spectroscopy results are not disclosed. Open questions include whether electrostatic collection efficiency in liquid xenon is sufficient for realistic Ba-tagging benchmarking, and how the accelerator-driven source compares in performance to alternative ion sources being used by other groups.
What different sources said
- arXiv physicsCenter
Experimental updates on development of accelerator-driven ion source at TRIUMF to benchmark Ba-tagging techniques for future neutrinoless double beta decay searches
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