Ultra Slow Muon Research Articles

Construction of the experimental set-up for ultra slow muon generation by thermal Mu ionization method at RIKEN-RAL

At KEK-MSL we have been pursuing the Ultra Slow Muon Project, in which thermal muonium atoms (designated as Mu; consisting of a μ + and an e −) are generated from the surface of a hot tungsten foil, placed at the primary 500 MeV proton beam line and ionized by intense lasers synchronized with the emission of Mu. However, because of the high radiation in the primary proton beam line where the present set-up is installed, a slow muon generation started not from a primary proton beam but with much higher intense surface muons is seriously required, in order to understand slow muon generation more deeply and to obtain more intense slow muons. Therefore, we are planning to perform a slow muon generation using intense surface muons, taking the advantage of the intensity of the proton beam at ISIS of 200 μA being about 40 times as large as that of KEK-MSL. In this report, we are presenting a new set-up, a slow beam optics and a laser system operated at 25 Hz prepared for the generation of ultra slow muons at the RIKEN-RAL muon facility.

Production of pulsed ultra slow muons and first μSR experiments on thin metallic and magnetic films

At ISIS, RAL (UK) we have produced a pulsed ultra-slow muon beam (E≲20 eV) and performed the first μSR experiments. Thanks to the pulsed feature, the implantation time is automatically determined and, by adjusting the final muon energy between ∼8 keV and 20 eV, depth slicing experiments are possible down to monolayers distances. We report slicing experiments across a 20 nm copper film on quartz substrate with evidence for a 2 nm copper oxide surface layer. A preliminary experiment on a hexagonal cobalt film suggests the existence of muon precession in the local magnetic field.

Ultra slow muons generated by laser resonant ionization of thermal muonium produced by 500‐MeV protons with hot tungsten

We report recent progress to date on the UT‐MSL/KEK “Ultra Slow Muon” project, in which thermal muonium (Mu) atoms are generated from the surface of a hot tungsten target placed at the primary 500 MeV proton beam line and resonantly ionized by intense u.v. lasers synchronized with the emission of the Mu. The positive muon ionization fragments are collected by electrostatic beam optics to form a beam of slow positive muons.

Intense proton accelerator of Japanese Hadron Project as a basis for μ +μ − colliders

The Japanese Hadron Project which is now under serious considerations as a next generation of high intensity proton accelerator can be considered as a basic for μ + μ − colliders. At the same time, the ideas for providing intense high-quality eV to keV muons proposed in the eighties have been successfully realized recently These ultra-slow muons will have a possible large-scale application to an eventual μ + μ − collider.

Ultra-slow muon facility for advanced μSR studies

A concept, a construction and an account of commissioning experiments up to May 1993 are given for the recently completed ultra-slow positive muon facility at the pulsed muon facility of UT-MSL/KEK. The intense and ultra-slowμ+ beam with an extremely small phase-space volume to be produced in this facility will open new muon sciences includingμSR studies on material surfaces.