12-20 July 2017
BEXCO
Asia/Seoul timezone
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Contribution

BEXCO - Room F(201/202/203/204)

[CRD147] Development of cosmic-ray muon spectroscopy to investigate chemical and physical states of steels in large-scale architecture

Speakers

  • Takuro FUJIMAKI

Primary authors

Co-authors

Description

In Circum-Pan-Pacific Earthquake Belt, large-scale architectures are exposed to a danger of big earthquakes. In Japan, about 9,600 bridges on highways have been exposed to severe natural environment and hard wares over 50 years after construction. Aging effects in these architectures are worried to cause serious deterioration and accidents by earthquakes. It is urgently required to develop a nondestructive inspection method to explore inner-status of architectures mostly made of iron reinforced concrete (RC) or pre-stressed concrete (PC). In order to study chemical as well as physical states of steels inside architectures made of RC or PC, we are developing a cosmic-ray muon spectroscopy [1]. Cosmic-ray muons shining on the surface of the earth are known to have the following properties; high energy, mixed charge state of positive and negative muons, and partial spin-polarization (-0.33 for positive muon). In our recent experiments in iron or concrete blocks using cosmic-ray muons, time evolution of decay positrons and electrons were successfully observed with reference to the time of stopping of the incoming muons. Signals of decay electrons from negative muons stopped in heavy elements are separated from those of decay positrons, by nature of different lifetimes of negative muons in heavy elements. After subtraction of decay electrons, we have successfully extracted muon spin rotation with 47.2±0.7MHz in frequency and 8.7±4.6 μs-1 in relaxation rate in iron blocks, corresponding to 50 MHz and 0.80μs-1 observed in highly purified iron sample. This method is quite promising to investigate steels at near-surface (20 cm thick from the surface). Experimental studies on reference data associated with original state of commercially available steels for RC and/or PC with tension, and their chemical products by accelerated corrosion are in progress by using intensive muons provided by an accelerator. We will discuss the potential or limit of cosmic-ray muon spectroscopy with respect to application for nondestructive diagnostics of large-scale architectures.