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

Abstract

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.