Principles and Perspectives of Radiographic Imaging with Muons.

Luigi Cimmino

doi:10.3390/jimaging7120253

Abstract

Radiographic imaging with muons, also called Muography, is based on the measurement of the absorption of muons, generated by the interaction of cosmic rays with the earth’s atmosphere, in matter. Muons are elementary particles with high penetrating power, a characteristic that makes them capable of crossing bodies of dimensions of the order of hundreds of meters. The interior of bodies the size of a pyramid or a volcano can be seen directly with the use of this technique, which can rely on highly segmented muon trackers. Since the muon flux is distributed in energy over a wide spectrum that depends on the direction of incidence, the main difference with radiography made with X-rays is in the source. The source of muons is not tunable, neither in energy nor in direction; to improve the signal-to-noise ratio, muography requires large instrumentation, long time data acquisition and high background rejection capacity. Here, we present the principles of the Muography, illustrating how radiographic images can be obtained, starting from the measurement of the attenuation of the muon flux through an object. It will then be discussed how recent technologies regarding artificial intelligence can give an impulse to this methodology in order to improve its results.

Highlights

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Deviation Muography is usually used for the detection of high density materials in small size objects and is based on the multiple Coulomb scattering experienced by muons when passing through matter [7,8,9,10]
In absorption Muography, the attenuation of the muon flux is used to measure the absorption of muons into matter

Summary

A Brief Overview

The muographic methodology is used for imaging the interior of a body, exploiting the high penetration capacity of cosmic muons [1,2,3,4,5,6]. The secondary cosmic radiation is not isotropic, we assume that the muons, since they were produced, have traveled in a straight line through the atmosphere and that the variation of the muon flux with the zenith angle is negligible, if detectors with small angular aperture are used This hypothesis is not entirely true in general, but is a common practice in the field of Muography. Being n = 1.85 the mean value of n when we consider angles up to 70◦ and muons with energy greater than 1 GeV, which allows us to take n = 2 over a large energy range; i⊥ = iθ=0(0) is the vertical muons flux and at sea level it is ∼70 m−2 s−1 sr−1 [37,38].

The Technique of Radiographic Imaging with Muons

The 3D Reconstruction Technique and Expected Performance

Future Development

Findings

Conclusions