Development of cosmic-ray muon spin rotation radiography to investigate chemical and physical states of steels in large-scale architecture

Abstract

We propose a cosmic-ray muon spin rotation radiography to investigate physical and chemical status of steels in large-scale architectures based on the experimental results obtained for Fe and concrete by using cosmic-ray and accelerator muons. Spin polarized positive muons contained in the cosmic-rays were stopped in the Fe plates provide a characteristic spin rotation signal of decay positrons. Signals of decay electrons from negative muons stopped in Fe are separated from those of decay positrons, by nature of their different lifetimes in the samples. After subtraction of decay electrons, we have successfully extracted muon spin rotation with 47.2 ± 0.7 MHz in frequency and 8.7 ± 4.6 μs -1 in relaxation rate. These values are consistent with those obtained from reference experiment using intensive muons provided by an accelerator, verifying validity of analysis. This method is quite promising to investigate steels at near-surface (20 cm thick from the surface).

Observing the polarization of cosmic-ray muons in student physics laboratory

“…The polarized muons, originated mainly from two sources including the decay of meson beam produced by modern accelerator and by the high-energy cosmic-ray primaries, find many exciting applications in various scientific fields, ranging from the μ spin spectroscopy [7], μ spin rotation radiography [8,9] to the proton radius measurement via μ-atom [10] as well as particle physics. Particularly, the charged cosmic-ray detected in terrestrial laboratory at sea level are dominated by the muons from the decay of mesons (approximately 90% of π) produced by the interactions of high-energy cosmic-ray primaries with atmospheric nuclei at high altitudes.…”