By using a very detailed simulation scheme, we have calculated the cosmic ray background flux at 13 active Colombian volcanoes and developed a methodology to identify the most convenient places for a muon telescope to study their inner structure. Our simulation scheme considers three critical factors with different spatial and time scales: the geo-magnetic effects, the development of extensive air showers in the atmosphere, and the detector response at ground level. The muon energy dissipation along the path crossing the geological structure is modeled considering the losses due to ionization, and also contributions from radiative Bremßtrahlung, nuclear interactions, and pair production. By examining each particular volcano topography and assuming reasonable statistics for different instrument acceptances, we obtained the muon flux crossing each structure and estimated the exposure time for our hybrid muon telescope at several points around each geological edifice. After a detailed study from the topography, we have identified the best volcano to be studied, spotted the best points to place a muon telescope and estimated its time exposures for a significant statistics of muon flux. We have devised a mix of technical and logistic rules –the “rule of thumb” criteria– and found that only Cerro Machín, located at the Cordillera Central (4°29'N 75°22'W), can be feasibly studied today through muography. Cerro Negro and Chiles could be good candidates shortly.
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-needed to cross the volcanic building, the emerging integrated flux of muons and the density profile inside a model of Cerro Machín volcano (Tolima, Colombia) within a maximum error of 1% concerning the theoretical model.
Muon radiography, also known as muography, is a non-destructive geophysical technique for the study of the internal structure of large objects such as volcanoes. This is possible by constructing an image based on the differential absorption of the directional flux of high-energy atmospheric muons produced during the interaction of cosmic rays with the atmosphere. So this no other source of radiation is required for this technique. Many muon telescopes are being built with crossed scintillator bars and so, the resolution of each panel is essentially given by the total surface of the bar crossings. Enhancing the resolution may require covering the same area with smaller scintillator bars, which adds costs and build complexity as more scintillators and fibers are required. More channels also require more acquisition electronics which have to be synchronized, increasing the complexity of the system, with associated operating issues, and the final cost. In this work, we propose a novel analysis approach to obtain reliable sub-pixel resolution, by measuring and comparing the average signals measured at each end of the scintillation bar. This analysis approach achieves sub-pixel resolutions, augmenting the spatial resolutions of existing designs. To study the feasibility of this technique we designed a laboratory setup, to emulate muon light pulses with a pulsed laser light located at different points
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