Atom-Source Development for Project 8*

The Project 8 experiment aims to make a direct measurement sensitive to much of the unexplored range of neutrino masses. Past experiments used molecular tritium, which has a large energy smearing from its final states. Project 8 will use atomic tritium to reach m_β ≤ 40 meV. This requires ∽10²⁰ T atoms held at tens of mK in a several-cubic-meter magnetic trap. The efficiencies of cooling the atoms and their trapped lifetime require ≥ 10¹⁹ atoms/s at the source. Phase III of Project 8 will include an Atomic Tritium Demonstrator to confirm we can produce, cool, and trap sufficient atomic T for the final Phase IV experiment.

I will discuss work at the University of Mainz to develop a high-flux tritium-compatible atom source and designt he downstream elements of a full atomic-tritium experiment. Our tests extend to a hydrogen flow of 20 sccm, 20 times the previously-published values for this type of source. Recent progress includes boosting the atomic signal/background ratio 100-fold and separation of the atom signal from background via low-energy ionization. Upgrades are underway to definitively determine if the present atom source provides sufficient atomic flux for Project 8's neutrino mass sensitivity. Designs for a higher-output atom source, if needed, and the subsequent cooling and trapping stages are in progress will be tested in due course.