First muon acceleration using a radio frequency accelerator

Muons have been accelerated by using a radio frequency accelerator for the first time. Negative muonium atoms (Mu$^-$), which are bound states of positive muons ($mu^+$) and two electrons, are generated from $mu^+$s through the electron capture process in an aluminum degrader. The generated Mu$^-$s are initially electrostatically accelerated and injected into a radio frequency quadrupole linac (RFQ). In the RFQ, the Mu$^-$s are accelerated to 89 keV. The accelerated Mu$^-$s are identified by momentum measurement and time of flight. This compact muon linac opens the door to various muon accelerator applications including particle physics measurements and the construction of a transmission muon microscope.