Acceleration of positive muons by a radio-frequency cavity

TL;DR

This paper demonstrates the successful acceleration of positive muons from thermal energies to 100 keV using a radio-frequency quadrupole, achieving phase space reduction and paving the way for muon accelerator development.

Contribution

It presents the first demonstration of accelerating thermal muons to 100 keV with phase space reduction using RF quadrupole technology.

Findings

Achieved muon acceleration from thermal energy to 100 keV.

Demonstrated phase space reduction by factors of 200 and 410 in horizontal and vertical planes.

Measured emittance values indicate good acceleration efficiency.

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 $0.85 \pm 0.25 ~\rm{(stat.)}~^{+0.22}_{-0.13} ~\rm{(syst.)}~\pi~$mm$\cdot$mrad and $0.32\pm 0.03~\rm{(stat.)} ^{+0.05}_{-0.02} ~\rm{(syst.)}~\pi~$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.