Abstract
Abstract The emission of muonium ($\mu^+e^-$) atoms into vacuum from silica aerogel with laser ablation on its surface was studied with various ablation structures at room temperature using the subsurface muon beams at TRIUMF and Japan Proton Accelerator Research Complex (J-PARC). Laser ablation was applied to produce holes or grooves with typical dimensions of a few hundred $\mu$m to a few mm, except for some extreme conditions. The measured emission rate tends to be higher for larger fractions of ablation opening and for shallower depths. More than a few ablation structures reach the emission rates similar to the highest achieved in past measurements. The emission rate is found to be stable at least for a couple of days. Measurements of spin precession amplitudes for the produced muonium atoms and remaining muons in a magnetic field determine a muonium formation fraction of $(65.5 \pm 1.8)$%. The precession of the polarized muonium atoms is also observed clearly in vacuum. A projection of the emission rates measured at TRIUMF to the corresponding rates at J-PARC is demonstrated taking the different beam condition into account reasonably.
Highlights
Applications of intense beams of muons with energies below a few tens of keV (“keV muons”) are growing in a variety of scientific fields
The present issues are to understand better the underlying processes leading to muonium emission with laser ablation, to find the optimal ablation structure, and to confirm the polarization of muonium following emission into vacuum
The muonium emission from the muonium production targets with various laser-ablated structures on their surfaces was studied at room temperature as the development of the thermal muon source for the muon g-2/EDM experiment at Japan Proton Accelerator Research Complex (J-PARC)
Summary
Applications of intense beams of muons with energies below a few tens of keV (“keV muons”) are growing in a variety of scientific fields. Because of the short muon lifetime (2.2 μs), muon cooling is challenging and various innovative methods are under development [6,7,8] One such method is to thermalize the surface muons in the form of muonium atoms in an appropriate material, allow them to diffuse into vacuum where they can be ionized with a laser resonant ionization technique [9, 10]. The present issues are to understand better the underlying processes leading to muonium emission with laser ablation, to find the optimal ablation structure, and to confirm the polarization of muonium following emission into vacuum To address these issues, various ablation structures were examined with the surface muon beams at TRIUMF and J-PARC in 2017. This report describes the results of these measurements and projections on the muonium emission from laser-ablated silica aerogel targets
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
