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Q: Fachverband Quantenoptik und Photonik

Q 53: Precision Spectroscopy of Atoms and Ions IV (joint session A/Q)

Q 53.2: Talk

Thursday, March 5, 2026, 11:30–11:45, N 3

Precision Angular Profiling of a Thermal Hydrogen Dissociation Source via Recombination Calorimetry — •Maximilian Balthasar Hüneborn, Sebastian Böser, and Martin Fertl for the Project 8 collaboration — Johannes Gutenberg-Universität Mainz, Mainz, Germany

Project 8 aims for a 40-meV neutrino mass sensitivity using cyclotron radiation emission spectroscopy (CRES) with atomic tritium to avoid molecular energy uncertainties. At JGU Mainz, the test setup characterizes beam dynamics using a thermal hydrogen dissociation source. Molecular hydrogen flows at up to 20 SCCM through a 1 mm inner diameter tungsten capillary heated to approximately 2200 K, with differential pumping suppressing recombination backgrounds. Precise angular beam profiling is essential to study the beam formation process. We measure the beam profile via a calorimetric wire detector that quantifies recombination heat on a movable tungsten wire, enabling minimally disruptive measurements of beams. A newly built tilt mechanism overcomes the limited angular coverage (-15° to +30°) of the standard translation stage, allowing comprehensive characterization of the beam's full divergence profile. This enables direct comparison between calorimetric and mass spectrometry data, confirming theoretical models of capillary beam output and validating the source geometry's role in atomic beam formation for future tritium operation.

Keywords: atomic hydrogen; dissociation; calorimetry; neutrino mass; beam characteristics