μSR research at the phasotron of the Laboratory of Nuclear Problems of the JINR

The most important results from the last thirty years of the study of matter using muons at the 680-MeV proton accelerator (phasotron) at the JINR Laboratory of Nuclear Problems are reviewed. The muon technique, which has become known as the μSR method, was first widely used by a group of investigators from the Laboratory of Nuclear Problems, the Kurchatov Institute, and the Institute of Theoretical and Experimental Physics. The principles of the μSR method are described, along with the experimental conditions under which these studies are performed at the phasotron. The results of the experimental measurement of the asymmetry coefficient in μ + →e + decay are discussed, along with results of the experiments which led to the discovery of two-frequency muonium spin precession, the sub-barrier incoherent diffusion of a positively charged muon in metals, and muonium in solids. The most important results on the study of semiconductors,dielectrics, ferro- and antiferromagnets,high-temperature superconductors, the diffusion of positively charged muons in metals, and chemical reactions involving muonium are presented, and the use of negatively charged muons to study matter is discussed.