Millikelvin Atomic Tritium for Project 8

The most powerful technique for directly studying the absolute neutrino mass is spectroscopy of beta-decay electrons around their maximum energy. Project 8 has pioneered a new frequency-based measurement method, cyclotron radiation emission spectroscopy (CRES). To reach a sensitivity of 40 meV/c², we will combine this with magnetically cooling, slowing, and trapping atomic tritium (T), rather than the molecular T₂ used by KATRIN and Phase II of Project 8.

Our atomic system will begin with producing a high current of atoms (~ 10¹⁹/s), likely in a ~2200 K tungsten tube, which has been studied in the lab, or possibly in a discharge-based source. Surface collisions will cool these to ~ 20 K. Atoms will then enter a magnetic evaporative cooling beamline (MECB) to both cool and slow the beam. Finally, the slowed few-millikelvin atoms will pass through a small opening into a > 10 m³ magneto-gravitational trap, giving a steady-state density of ~ 10¹⁷ m⁻³.

This contribution will highlight the present status of Project 8’s calculation, simulation, and prototyping work on the atomic system and show how these efforts support our design sensitivity to the absolute neutrino mass.