Demonstration of the muon rf accelerationwith the negative muonium

Muons have been accelerated by using a radio-frequency (RF) accelerator for the first time. Negative muonium ions (Mu−, μ+e−e−) are generated from μ injected to a thin aluminum foil. The generated Mu−’s are extracted with electrostatic field and injected to a radio-frequency quadrupole linac (RFQ). In the RFQ, the Mu−’s are accelerated to 89 keV. Then the accelerated Mu−’s are transported to the micro-channel plate (MCP) detector via a quadrupole magnet pair and a bending magnet. The accelerated Mu−’s are identified with measurements of momentum and time of flight. This work paves the way for a compact muon linac that would enable precision measurements of the muon anomalous magnetic moment and the electric dipole moment. This result also offers new muon-accelerator applications such as transmission muon microscope for use in material and life-sciences research.