https://doi.org/10.1140/epjc/s10052-020-8400-1
Regular Article - Experimental Physics
Intense beam of metastable Muonium
1
Institute for Particle Physics and Astrophysics, ETH Zürich, 8093, Zurich, Switzerland
2
Institute of Physics, The University of Tokyo, 153-8902, Tokyo, Japan
3
Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute (PSI), 5232, Villigen, Switzerland
Received:
19
May
2020
Accepted:
24
August
2020
Published online:
1
September
2020
Precision spectroscopy of the Muonium Lamb shift and fine structure requires a robust source of 2S Muonium. To date, the beam-foil technique is the only demonstrated method for creating such a beam in vacuum. Previous experiments using this technique were statistics limited, and new measurements would benefit tremendously from the efficient 2S production at a low energy muon (
keV) facility. Such a source of abundant low energy 
has only become available in recent years, e.g. at the Low-Energy Muon beamline at the Paul Scherrer Institute. Using this source, we report on the successful creation of an intense, directed beam of metastable Muonium. We find that even though the theoretical Muonium fraction is maximal in the low energy range of 2–5 keV, scattering by the foil and transport characteristics of the beamline favor slightly higher energies of 7–10 keV. We estimate that an event detection rate of a few events per second for a future Lamb shift measurement is feasible, enabling an increase in precision by two orders of magnitude over previous determinations.
© The Author(s) 2020
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