Atom-Source Development for Project 8*

The Project 8 experiment will make a direct measurement with sensitivity to much of the unexplored range of neutrino masses. Past experiments used molecular tritium, which has an unavoidable energy smearing from its final states. A population of atomic tritium containing ~10²⁰ atoms at tens of mK held in a several-cubic-meter magnetic trap will be required to reach m_β ≤ 40 meV. The efficiency of cooling the atoms and their lifetime in the trap require, coincidentally, ≥ 10²⁰ atoms/s from the source. Phase III of Project 8 includes building an Atomic Tritium Demonstrator to confirm we are ready to produce, cool, and trap atomic tritium with methods suitable for the final Phase IV experiment.

This talk will discuss experiments to develop a cold, high-flux atom source. Our tests extend to a hydrogen flow of 20 sccm, some 40 times the previously-published values for this type of source. Recent progress includes a redesign that boosted the atomic signal 100-fold and installation of a new mass spectrometer to suppress previous systematic uncertainties. Further upgrades to the test stand and its instrumentation are underway to definitively determine whether the present atom source provides sufficient atomic flux. Designs for a higher-output source, should it be required, and the subsequent cooling and trapping stages are in progress; each will be installed on the hydrogen test stand in due course. Following measurement of each stage with hydrogen, a copy will be added to a parallel tritium beamline for final verification.