Search

A multi-wire proportional chamber-based muo- graphy observatory is under development for the monitoring of the internal structure of Mt Sakurajima in Kyushu, Japan. We investigated the limits of large-scale and high-definition muography. We adjusted the parameters of a modified Gaisser model and found that the spectral index of γ  =  - 2.64 and normalization factor of C  = 0.66 reproduce more accurately the measured fluxes than the original parameters at large thickness. A thickness and zenith angle-dependent correction is suggested to the measured muon flux due to the energy cut which is introduced to suppress the background particles. The multiple scattering of muons was simulated across the standard rock and sea-level atmosphere up to the distance of 5 km. We found that multiple scattering decreases from 10 mrad to 4 mrad across the rock due to the decrease in the steepness of muon spectra. The multiple scattering falls down to about 2 mrad after the object in the atmosphere due to the increase in observed arrival zenith angles. The 2 m 2 sized multi-wire proportional chamber-based Muographic Observation System (MMOS) was operating between February and June 2018. Three tracking systems operated reliably with tracking efficiencies of above 95%. The muon flux has been measured correctly down to 10 -3  m -2  sr -1  s -1 The average density map of Mt Sakurajima has been measured with angular resolution of 12 mrad × 12 mrad (spatial resolution of 34 m × 34 m from the distance of 2.8 km). The average density values were found between 1.4 and 2 g cm -3 , except at the crater regions where lower densities were observed.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'., (© 2018 The Author(s) Published by the Royal Society. All rights reserved.)

By observing the growth of a research community, particularly the factors of size and strength of involvement, it is possible to evaluate the vitality of a new field. The emerging technology of muography, a new visualization technique to look through gigantic objects with an elementary particle called the muon, is the focus of this study. Recently, the initial applications of muography to the study of structures such as pyramids and volcanoes have been expanding to include more commercial interests such as inspecting social infrastructures and energy and mineral resources. Evolutions of the research networks of muography will be discussed with particular attention to the chronological and lateral structures that could be an indicator of the development of this new technology.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'., (© 2018 The Author(s).)

High-energy muons that are generated via the reaction between primary cosmic rays and the Earth's atmosphere can be used to map out the density distribution in shallow parts of a volcano's interior. This new subterranean imaging technique called muography has been applied to three different kinds of volcano dynamics in Japan: lava dome formation, vulcanian explosions and magma convection. Taking all of the observational data together, it appears that muography can serve as a new and alternative volcano observation technique, providing a fresh approach to understanding eruption mechanism. This review describes observational studies in which muography has been used to explore the volcano's interior.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'., (© 2018 The Author(s).)