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Proposal for a cryogenic source of atomic tritium for neutrino-mass measurements and precision spectroscopy

A. Semakin, J. Ahokas, T. Kiilerich, and S. Vasiliev

F. Nez and P. Yzombard

V. V. Nesvizhevsky

E. Widmann

P. Crivelli

C. Rodenbeck, M. Röllig, and M. Schlösser

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Phys. Rev. Research 8, 033096 – Published 23 July, 2026

DOI: https://doi.org/10.1103/clnf-gq66

Abstract

We propose a concept for a cryogenic source of atomic tritium at sub-Kelvin temperatures and energies suitable for magnetic trapping. The source is based on the dissociation of solid molecular T2 films below 1 K by electrons from a pulsed rf discharge, a technique recently demonstrated for atomic hydrogen, combined with buffer-gas cooling and magnetic confinement. We analyze the key processes limiting the source performance, adsorption, spin exchange, and recombination, and show that atomic tritium fluxes exceeding 1015 s−1 at temperature of ∼200 mK can be achieved. Such a source would enable Doppler-free two-photon 1S–2S spectroscopy in atomic tritium for high-precision measurements of the triton charge radius, providing a crucial benchmark for bound-state QED and improving the comparison between electronic, muonic, and scattering determinations of nuclear sizes in light systems. Beyond spectroscopy, using atomic tritium source avoids molecular final-state broadening in β decay and is therefore necessary for next-generation neutrino-mass measurements; combined with detector technologies such as sub-eV resolution quantum sensors or cyclotron radiation emission spectroscopy, it enables an order-of-magnitude improvement compared to the current best experimental limit. Additionally, the source can be used to generate a beam of low-field-seeking deuterium atoms for loading magnetic traps, an important benchmark before trapping tritium atoms, which is useful for precision spectroscopy.

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Phys. Rev. Research 8, 033096– Published 23 July, 2026
  • Received 2 March 2026
  • Accepted 1 July 2026
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