Cosmic radiation has been known since the first decades of the 20th century: it has been considered for many years, the best source of projectiles to investigate the core of matter, from nuclei to elementary particles. Nowadays, cosmic ray muons are very important in particle and nuclear physics, because they are used for detector testing and calibration, and for detector alignment in complex measurement apparatuses, thanks to their high penetration capability [1]. However, cosmic ray radiation has been already applied in fields beyond pure physics. The first use of these particles to inspect large volumes dates back to 1955, when the depth of rock above an underground tunnel was measured by E. P. George [2]. A more spectacular experiment took place in 1970, when Nobel Prize L. W. Alvarez [3] inspected the Chefren pyramid searching for hollow vaults (finding none!). In both cases muon absorption was used to estimate the thickness of the material crossed by cosmic-ray particles. Other applications such as inspection of volcanoes followed [4,5]. More recently, a novel muon tomography technique has been proposed [6], exploiting the multiple scattering through an object to generate its image. A prototype able to inspect volume of about 10-1 m3 provided the proof of principle that such technique can be used to scan large objects. The underlying physics of muon tomography is the multiple Coulomb scattering (MCS) [7,8] of the muons crossing a given material. The first large-volume muon tomography prototype was constructed and operated at the INFN National Laboratory in Legnaro [9]. Now various research groups worldwide are developing this technique to address various needs and to propose civil applications, such as, among others, the detection of special nuclear materials in ports and borders ([10]), the detection of shielded radioactive sources hidden in scrap metal containers entering steel mills ([11], [12]) and the inspection of the inner part of a blust furnace ([13]).
Furthermore, due to their property of crossing very thick materials, cosmic rays appear also to be a suitable tool for the realization of measurement systems, specially as a helpful alternative to traditional optical systems, when detectors are not mutually visible. After a preliminary study [14], a new case has been investigated, namely a stability monitoring system for historical buildings by means of cosmic ray tracking [15, 16].
An overview of the applications of the cosmic ray muons for civil usages, with special focus on the last development of the various techniques will be reported and presented.
References
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[10] http://www.decisionsciencescorp.com/
[11] G. Bonomi et al., International Journal of Modern Physics: Conference Series, 27 (2014) 1460157 [European Commission Mu-Steel project (RFCS - CT-2010-000033)]
[12] S. Raggi et al., Journal of Physics: Conference Series, 409 (2013) 012046
[13] European Commission Mu-Blast project (RFCS-630643) [2014-2016].
[14] I. Bodini et al., G. Bonomi, D. Cambiaghi, A. Magalini and A. Zenoni, Meas. Sci. Technol. 18 (2007) 3537–3546
[15] A. Donzella, Il nuovo cimento, Vol. 37 C (2014) 223
[16] G. Bonomi et al., Proceedings of the “28th European Conference on Modelling and Simulation”, ISBN: 978-0-9564944-8-1