arXiv subjects

A. Vesga-Ramírez

Publications and source records attributed to A. Vesga-Ramírez.

5 recordsLinked to original sources

arXiv2022

Muography in Colombia: simulation framework, instrumentation and data analysis

We present the Colombo-Argentinian Muography Program for studying inland Latin-American volcanoes. It describes the implementation of a simulation framework covering various factors with different spatial and time scales: the geomagnetic effects at a particular geographic point, the development of extensive air showers in the atmosphere, the propagation through the scanned structure and the detector response. Next, we sketch the criteria adopted for designing, building, and commissioning MuTe: a hybrid Muon Telescope based on a composite detection technique. It combines a hodoscope for particle tracking and a water Cherenkov detector to enhance the muon-to-background-signal separation due to extensive air showers' soft and multiple-particle components. MuTe also discriminates inverse-trajectory and low-momentum muons by using a picosecond Time-of-Flight system. We also characterise the instrument's structural (mechanical and thermal) behaviour, discussing preliminary results from the background composition and the telescope-health monitoring variables. Finally, we discuss the implementations of an optimisation algorithm to improve the volcano internal density distribution estimation and machine learning techniques for background rejection.

astro-ph.IM↗

arXiv2021

Study of Spatial Resolution of Muon Hodoscopes for Muography Applications in Geophysics

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 a 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 on optical wavelength shifter fiber. By doing this we measured an increase in the spatial resolution when compared with traditional systems. These results enable the design of new prototypes for the muography of natural and artificial structures of strategic interest. We are currently assembling a prototype detector that will use this methodology.

physics.ins-det↗

arXiv2021

Simulated Annealing for Volcano Muography

Muography or muon radiography is a non-invasive emerging image technology relying on high energy atmospheric muons, which complements other standard geophysical tools to understand the Earth's subsurface. This work discusses a geophysical inversion methodology for volcanic muography, based on the Simulated Annealing algorithm, using a semi-empirical model of the muon flux to reach the volcano topography and a framework for the energy loss of muons in rock. The Metropolis-Simulated-Annealing algorithm starts from an 'observed' muon flux and obtains the best associated inner density distribution function inside a synthetic model of the Cerro Machin Volcano (Tolima-Colombia). The estimated initial density model was obtained with GEOMODELER, adapted to the volcano topography. We improved this model by including rock densities from samples taken from the crater, the dome and the areas associated with fumaroles. In this paper, we determined the minimum muon energy (a 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 Machin. The present inversion correctly reconstructed the density differences inside the Machin, within a 1 percent error concerning our initial simulation model, giving a remarkable density contrast between the volcanic duct, the encasing rock and the fumaroles area.

physics.geo-ph↗

arXiv2019

Muon Tomography sites for Colombian volcanoes

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 geomagnetic 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 Bremstrahlung, nuclear interactions, and pair production. By considering 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 finest 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 criteria --the ``rule of thumb'' criteria-- and found that only Cerro Machin, located at the Cordillera Central (4$^{\circ}$29'N 75$^{\circ}$22'W), can be feasibly studied today through muography. Cerro Negro and Chiles could be good candidates shortly

physics.geo-ph↗

arXiv2017

Astroparticle Techniques: Colombia active volcano candidates for Muon Telescope observation sites

We discuss a methodology to identify observation points for muongraphy of active Colombian Volcanoes and it is found that only Cerro Machin can be studied.

physics.geo-ph↗