Acceleration of positive muons by a radio-frequency cavity

Abstract

Acceleration of positive muons from thermal energy to $100$keV has been demonstrated. Thermal muons were generated by resonant multi-photon ionization of muonium atoms emitted from a sheet of laser-ablated aerogel. The thermal muons were first electrostatically accelerated to $5.7$keV, followed by further acceleration to 100 keV using a radio-frequency quadrupole. The transverse normalized emittance of the accelerated muons in the horizontal and vertical planes were $0.85\pm 0.25(stat.){}_{-0.13}^{+0.22}(syst.)\ddot{\mathrm{I}}€$mm$\cdot$mrad and $0.32\pm 0.03{(stat.)}_{-0.02}^{+0.05}(syst.)\ddot{\mathrm{I}}€$mm$\cdot$mrad, respectively. The measured emittance values demonstrated phase space reduction by a factor of $2.0\times 10^2$ (horizontal) and $4.1\times 10^2$ (vertical) allowing good acceleration efficiency. These results pave the way to realize the first-ever muon accelerator for a variety of applications in particle physics, material science, and other fields.

version accepted for publication in PRL