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The MURAVES project aims to study the inner structure of the upper part of the Mt. Vesuvius volcano by muon radiography (muography) technique. Very high energy muons, produced by cosmic rays in the atmosphere, can penetrate large thickness of rocks. By measuring the attenuation of the muons flux trough the volcano cone is possible to obtain a 2D im...
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We discuss the geophysical inversion methodology for volcanic muography based on the Simulated Annealing algorithm, using a semi-empirical model of the muon flux reaching the volcano, its surrounding topography and a framework for the energy loss of muons in rock. We determined the minimum muon energy -- as function of the arrival direction -- need...
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... Scintillator-based particle detectors are well-established tools for muography (Tanaka et al. 2003 ;Marteau et al. 2012 ;Saracino et al. 2016 ;Lo Presti et al. 2020 ;Pe ˜ na-Rodr íguez et al. 2020 ). With their robust, modular and relati vel y simplified design compared to highenergy physics detectors, they are appropriate to deal with the main challenge of rough field operations (Lesparre et al. 2012a ). ...
Muography is increasingly used to image the density distribution of volcanic edifices, complementing traditional geophysical tomographies. Here we present a new muon data processing algorithm, and apply it to a new generation of scintillator-based muon detectors, to image the relative density distribution in La Soufriére de Guadeloupe volcano (Lesser Antilles, France). Our processing method iteratively searches for the best fit of each muon trajectory, accounting for all the hits registered by the detector related to the particular muon event. We test the performance of our algorithm numerically, simulating the interaction of muons with our detector and accounting for its exact assemblage including the scintillator bars and lead shielding. We find that our new data processing mitigates the impact of spurious signals coming from secondary particles, and improves the amount of successfully reconstructed events. The resulting two-dimensional muon images at La Soufriére have higher angular resolution than previous ones and capture the heterogeneous structure of the dome. They show density anomalies located on the summit southern region, which includes a boiling acid lake and degassing fractures, where the rock is the most porous and fumarolic activity is ongoing. This work shows the importance of combining numerical simulations of muon propagation with precise raw data processing to obtain high-quality results. It is also a first step towards fully assessing the noise contamination sources when performing muon tomography, and their correction, prior to geophysical interpretations.
... This indicates that muography detectors perceive higher flux than expectation. This sort of flux excess has been observed in many research groups (Carbone et al., 2014;Ambrosino et al., 2015) and it originates from the following three possible causes: combinatorial background (Saracino et al., 2017); low-energy muon, electromagnetic and hadronic components of cosmic rays (Nishiyama et al., 2016;Gómez et al., 2017); upward-going particles entering from the rear side of the detector (Jourde et al., 2013). Muography detectors must be designed so that they have the rejection capability of these noise signals before the data is combined with gravity data. ...
Muography is surely one way to shed light on the density structure of the underground, but it is not the only one. Classical gravity surveys also provide information on the mass distribution of the entire Earth. Although these two methods differ in sensitivity, combining the two (joint inversion) would combat the weaknesses of each method and improve the resolution of three‐dimensional imaging. This chapter introduces one formulation of the joint inversion following an early work done by the author's group, and tries to review further technical developments and applications by other researchers. Future technical prospects are discussed at the end.
... These elementary particles can penetrate through geological structures with the thicknesses of beyond a kilometer with only a few milliradians of deflections along their paths. The applicability of muography has already been demonstrated for volcano imaging thanks to the recent progress in the development of observation instruments [21][22][23][24][25][26][27][28][29][30] and imaging techniques [31][32][33][34] . Various volcanic phenomena, such as magma ascent and descent 35 , the degassing process 36 , plug formation 37 , magma intrusion into lava domes 38 , tectonic evolution 39 , hydrothermal processes 40,41 or long-term tephra deposition 42 , have already been measured with muographic imaging. ...
Post-eruptive destabilization of volcanic edifices by gravity driven debris flows or erosion can catastrophically impact the landscapes, economies and human societies surrounding active volcanoes. In this work, we propose cosmic-ray muon imaging (muography) as a tool for the remote monitoring of hydrogeomorphic responses to volcano landscape disturbances. We conducted the muographic monitoring of Sakurajima volcano, Kyushu, Japan and measured continuous post-eruptive activity with over 30 lahars per year. The sensitive surface area of the Multi-Wire-Proportional-Chamber-based Muography Observation System was upgraded to 7.67 m2; this made it possible for the density of tephra within the crater region to be measured in 40 days. We observed the muon flux decrease from 10 to 40% through the different regions of the crater from September 2019 to October 2020 due to the continuous deposition of tephra fallouts. In spite of the long-term mass increase, significant mass decreases were also observed after the onsets of rain-triggered lahars that induced the erosion of sedimented tephra. The first muographic observation of these post-eruptive phenomena demonstrate that this passive imaging technique has the potential to contribute to the assessment of indirect volcanic hazards.
... Besides, comparing the inversions of synthetic data with one and three muographic view points, Barnoud et al. (2019) show that the resolution of the resulting density model is improved when using multiple points of view. Another difficulty in such a joint inversion is that the density estimated by muography is often lower than the density estimated by gravimetry due to the detection of 1) non-ballistic low-energy muons scattered by the volcanic edifice (Nishiyama et al., 2014a(Nishiyama et al., , 2016Gómez et al., 2017;Rosas-Carbajal et al., 2017), 2) muons coming from the backward direction (Jourde et al., 2013) and 3) other charged particles (Oláh and Varga, 2017;Saracino et al., 2017). Tests on synthetic data show that this offset leads to artifacts in the inversion results so that it should be corrected. ...
Imaging the internal structure of volcanoes helps highlighting magma pathways and monitoring potential structural weaknesses. We jointly invert gravimetric and muographic data to determine the most precise image of the 3D density structure of the Puy de Dôme volcano (Chaîne des Puys, France) ever obtained. With rock thickness of up to 1,600 m along the muon lines of sight, it is, to our knowledge, the largest volcano ever imaged by combining muography and gravimetry. The inversion of gravimetric data is an ill-posed problem with a non-unique solution and a sensitivity rapidly decreasing with depth. Muography has the potential to constrain the absolute density of the studied structures but the use of the method is limited by the possible number of acquisition view points, by the long acquisition duration and by the noise contained in the data. To take advantage of both types of data in a joint inversion scheme, we develop a robust method adapted to the specificities of both the gravimetric and muographic data. Our method is based on a Bayesian formalism. It includes a smoothing relying on two regularization parameters (an a priori density standard deviation and an isotropic correlation length) which are automatically determined using a leave one out criterion. This smoothing overcomes artifacts linked to the data acquisition geometry of each dataset. A possible constant density offset between both datasets is also determined by least-squares. The potential of the method is shown using the Puy de Dôme volcano as case study as high quality gravimetric and muographic data are both available. Our results show that the dome is dry and permeable. Thanks to the muographic data, we better delineate a trachytic dense core surrounded by a less dense talus.
... A more recent and highly relevant application is in volcanology, to reveal internal structure [3] and dynamics of the upper part of the magma conduit [4]. Various volcanos have been studied all over the world, and prove that muography is useful and can be meaningfully combined with other methods [5][6][7][8]. For the same basic applications, the tracking detector system, called the Sakurajima Muography Observatory (SMO) installed at the Sakurajima volcano (see figure 1, Kyushu, Japan) is currently the world's largest muographic telescope. ...
... In 2012, our collaboration, which involves physicists, geologists and volcanologists from Istituto Nazionale di Geofisica e Vulcanologia (INGV), Istituto Nazionale di Fisica Nucleare (INFN), the University of Florence and the University of Naples, submitted to the Italian Ministry of Research a proposal for a muographic and gravimetric measurements campaign on Vesuvius with the purpose of better defining the volcanic plug at the bottom of the crater. The proposal was approved and the project was named the MUon RAdiography of VESuvius (MURAVES) [9][10][11]. ...
... This solution, first [72]) that, with the same number of readout channels, increases the resolution by a factor two at the cost of a thicker (and more expensive) detection layer and of a more complex coordinate reconstruction. (Bottom) Triangular-section bars (as in MURAVES [73]) allow the use of a Centre of Gravity algorithm to improve spatial resolution (that depends on scintillator light yield and FE electronics noise) with the same number of readout channels. ...
... adopted at the Fermi National Accelerator Laboratory (USA), has been used for the MU-RAY [74], MURAVES [73] and MIMA [72] muography detectors. In this case, incident particles always cross two adjacent bars and the reconstruction of the particle impact coordinate takes advantage of the different amplitudes of signals produced in the two bars, roughly proportional to the track length in each scintillator. ...
... This is easily reduced by a modest redundancy in the number of layers and an upper limit on the χ 2 of the track fit. The cosmic flux at sea level is sufficiently low with respect to typical data acquisition times that random coincidences of aligned hits from distinct particles can usually be neglected; exceptionally, however, combinatorial background may be induced by several temporally correlated particles, for example those produced from the same cosmic shower [73]. Soft muons are actual muons with relatively low momenta (as opposed to "ballistic" muons, defined as those whose speed can be approximated with the speed of light). ...
Imaging methods based on the absorption or scattering of atmospheric muons, collectively named under the neologism “muography”, exploit the abundant natural flux of muons produced from cosmic-ray interactions in the atmosphere. Recent years have seen a steep rise in the development of muography methods in a variety of innovative multidisciplinary approaches to study the interior of natural or human-made structures, establishing synergies between usually disconnected academic disciplines such as particle physics, geology, and archaeology. Muography also bears promise of immediate societal impact through geotechnical investigations, nuclear waste surveys, homeland security, and natural hazard monitoring. Our aim is to provide an introduction to this vibrant research area, starting from the physical principles at the basis of the methods and describing the main detector technologies and imaging tools, including their combination with conventional techniques from other disciplines, where appropriate. Then, we discuss critically some outstanding issues that affect a broad variety of applications, and the current state of the art in addressing them. Finally, we review several recent developments in the application of muography methods to specific use cases, without any pretence of exhaustiveness.
... In 1970, the Nobelist Louis Alvarez and his collaborators performed a radiographic measurement of the Chephren Pyramid in Egypt and they were able to exclude the existence of a hidden burial chamber [3]. Following these pioneering measurements, more recently muon absorption radiography was taken again into consideration, at first by Japanese groups [4] and later by Italian, French, Canadian, American, and other groups ( [5][6][7][8][9][10][11][12][13], to name a few) for application in the fields of volcanology, archaeology, and mining. The MURAVES project (MUon RAdiography of VESuvius) [14], born of the collaboration between INGV (National Institute of Geophysics and Volcanology) and INFN (National Institute of Nuclear Physics), aims to study the interior of Mount Vesuvius near Naples using muon radiography. ...
Muon absorption radiography is an imaging technique based on the measurement of the absorption of cosmic ray muons. This technique has recently been used successfully to investigate the presence of unknown cavities in the Bourbon Gallery in Naples and in the Chephren Pyramid at Cairo. The MIMA detector (Muon Imaging for Mining and Archaeology) is a prototype muon tracker for muon radiography for application in the fields of archaelogy and mining. It is made of three pairs of X-Y planes each consisting of 21 scintillator bars with a silicon photomultiplier readout. The detector is compact, robust, easily transportable, and has a low power consumption: all of which makes the detector ideal for measurements in confined and isolated environments. With this detector, a measurement from inside the Temperino mine in the San Silvestro archaeo-mining park in Tuscany was performed. The park includes about 25 km of mining tunnels arranged on several levels that have been exploited from the Etruscan time. The measured muon absorption was compared to the simulated one, obtained from the information provided by 3D laser scanner measurements and cartographic maps of the mountain above the mine, in order to obtain information about the average density of the rock. This allowed one to confirm the presence of a partially accessible exploitation opening and provided some hints regarding the presence of a high-density body within the rock.
... Details concerning the muon detector are available in [14][15][16]29,30]. We briefly report here some of the most relevant features. ...
Muon radiography, also known as muography, is an imaging technique that provides information on the mass density distribution inside large objects. Muons are naturally produced in the interactions of cosmic rays in the Earth's atmosphere. The physical process exploited by muography is the attenuation of the muon flux, that depends on the thickness and density of matter that muons cross in the course of their trajectory. A particle detector with tracking capability allows the measurement of the muons flux as a function of the muon direction. The comparison of the measured muon flux with the expected one gives information on the distribution of the density of matter, in particular, on the presence of cavities. In this article, the measurement performed at Mt. Echia in Naples (Saracino 2017 Sci. Rep. 7 , 1181. ( doi:10.1038/s41598-017-01277-3 )), will be discussed as a practical example of the possible application of muography in archaeology and civil engineering.
This article is part of the Theo Murphy meeting issue ‘Cosmic-ray muography’.
... The seed for the MURAVES [1] project was the development, with funding received from INFN, of an innovative plastic scintillator detector (MU-RAY [2,3]) with a 1 m 2 surface that has been used as a prototype for technology assessment and also as a muography instrument in short data taking campaigns (i.e. Vesuvius and Mt. ...
Cosmic-ray muon radiography (muography), an imaging technique that can provide measurements of rock densities within the top few 100 m of a volcanic cone, has now achieved a spatial resolution of the order of 10 m in optimal detection conditions. Muography provides images of the top region of a volcano edifice with a resolution that is considerably better than that typically achieved with other conventional methods (i.e. gravimetric). We expect such precise measurements, to provide us with information on anomalies in the rock density distribution, which can be affected by dense lava conduits, low-density magma supply paths or the compression with the depth of the overlying soil. The MUon RAdiography of VESuvius (MURAVES) project is now in its final phase of construction and deployment. Up to four muon hodoscopes, each with a surface of roughly 1 m ² , will be installed on the slope of Vesuvius and take data for at least 12 months. We will use the muographic profiles, combined with data from gravimetric and seismic measurement campaigns, to determine the stratigraphy of the lava plug at the bottom of the Vesuvius crater, in order to infer potential eruption pathways. While the MURAVES project unfolds, others are using emulsion detectors on Stromboli to study the lava conduits at the top of the volcano. These measurements are ongoing: they have completed two measurement campaigns and are now performing the first data analysis.
This article is part of the Theo Murphy meeting issue ‘Cosmic-ray muography’.
