First muon acceleration using a radio-frequency accelerator

S Bae,T Iijima,K Futatsukawa,T Morishita,K Hasegawa,M Otani,N Kawamura,E Won,Y Sue,R Kitamura,S Li,H Iinuma,K Ishida,S Choi,T Yamazaki,N Saito,Y Fukao,K Shimomura,B Kim,T Mibe,Yasuhiro Nakazawa ,Hayon Michelle Choi ,H S Ko ,G.p Razuvaev ,Yasuhiro Miyake ,Yasuhiro Kondo

doi:10.1103/physrevaccelbeams.21.050101

Abstract

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.

Highlights

Since its invention, the radio-frequency accelerator has accelerated a wide variety of particles from electrons to rare isotopes, and greatly contributed to the progress of various branches of science
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
A new muon g − 2=electric dipole moment (EDM) experiment is proposed at Japan Proton Accelerator Research Complex (J-PARC)

Summary

INTRODUCTION

The radio-frequency (rf) accelerator has accelerated a wide variety of particles from electrons to rare isotopes, and greatly contributed to the progress of various branches of science. This enables three-dimensional imaging of living cells, which is impossible with the use of transmission electron microscopes Another application of USM acceleration is precise measurement of the muon anomalous magnetic moment aμ 1⁄4 ðg − 2Þμ=2 and electric dipole moment (EDM). The precision is 0.54 ppm, and the measured value is approximately 3 standard deviations from the Standard Model prediction [5,6,7] To improve this precision, a new muon g − 2=EDM experiment is proposed at Japan Proton Accelerator Research Complex (J-PARC). The Mu−’s have a sharp peak near zero energy, and the accelerated Mu−’s are separated from the penetrating μþ’s because they have opposite charge Using this slow Mu− source and a prototype RFQ of the J-PARC linac [20], we conducted the muon acceleration experiment in a multipurpose experimental area (D2 area) of MUSE

EXPERIMENTAL APPARATUS

RESULT

Findings

CONCLUSION