A proposed study on trapping of positive muon in defects in the vicinity of metal surfaces

We aim to reveal the dynamics of positive muon (μ+) trapping in the vicinity of metal surfaces through the precise measurement of trapping rates during muon thermal diffusion in metals. This trapping strongly dominates the time evolution of the muonium atom (Mu: μ+e−) emitted to vacuum from the surface, since it is the positive muon reaching the surface within its lifetime (∼ 2.2 μs) that contributes to Mu emission in vacuum. In order to pursue the trapping rate on the order of ≈ 10−1 μs−1, statistics of ≈ 10−7 Mu atoms in vacuum would be needed, and use of the UT-MSL/KEK (Meson Science Laboratory, University of Tokyo, located at National Laboratory for High Energy Physics, Japan) and/or RIKEN-RAL (RIKEN-Rutherford Appleton Laboratory muon facility, UK) would facilitate obtaining these statistics within a reasonable time.