[Paper Review] Muon Tomography sites for Colombian volcanoes

A. Vesga-Ramírez, D. Sierra-Porta+7 more|arXiv (Cornell University)|May 28, 2017

Astrophysics and Cosmic Phenomena4 citations

TL;DR

This study uses detailed Monte Carlo simulations of cosmic ray muons to identify optimal observation sites for muon tomography at 13 active Colombian volcanoes. By modeling muon energy loss, geomagnetic effects, and atmospheric shower development, the authors determine that only Cerro Machín is currently feasible for muography, requiring 100–125 days of data acquisition for 100 muons per pixel with a hybrid telescope at 114–150 m depth.

ABSTRACT

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

Motivation & Objective

• To identify the most suitable observation sites for muon tomography at active Colombian volcanoes.
• To estimate the muon flux emerging from volcanic edifices using detailed simulations of cosmic ray interactions.
• To determine the required data acquisition time for achieving statistically significant muon flux measurements with a hybrid muon telescope.
• To evaluate the feasibility of muography for shallow volcanic structures in the Andean region, considering topography and background flux.

Proposed method

• Simulated cosmic ray muon flux using CORSIKA and MAGNETOCOSMICS to model atmospheric shower development and geomagnetic effects.
• Tracked muon propagation through volcanic rock using energy loss equations, including ionization, radiative, and nuclear contributions.
• Integrated muon energy loss along trajectories through geological structures to compute emerging flux at potential observation points.
• Applied a hybrid muon telescope model with variable acceptance to estimate exposure times for 100 detected muons per pixel.
• Used topographic data to assess shielding effects and identify unobstructed observation points with minimal muon flux attenuation.
• Applied a 'rule of thumb' methodology combining technical and logistical criteria to rank feasibility across multiple sites.

Experimental results

Research questions

• RQ1 Which Colombian volcanoes are technically feasible for muon tomography based on muon flux and observation site accessibility?
• RQ2 What is the minimum data acquisition time required to achieve a statistically significant muon flux measurement at potential observation points?
• RQ3 How do geomagnetic effects and atmospheric shower development influence the muon flux at high-altitude volcanic sites?
• RQ4 To what extent does topography shield muons, and how does this affect the detectability of density variations in volcanic edifices?
• RQ5 Can muography resolve shallow density structures in volcanic conduits with sufficient spatial resolution and sensitivity?

Key findings

• Only Cerro Machín, located at 4°29′N, 75°22′W in the Cordillera Central, is currently feasible for muon tomography due to favorable topography and muon flux conditions.
• The estimated minimum data acquisition time for 100 muons per pixel ranges from 100 to 125 days, depending on the observation point and telescope acceptance.
• High-energy muons (10 TeV) at zenith angles of 82°–84° have a flux of approximately 10 muons per square meter per day at the site.
• Muon energy loss is dominated by ionization, with significant contributions from radiative losses and nuclear interactions along the path through rock.
• The simulation results were validated using updated underground muon propagation codes, confirming the exposure time estimates.
• Cerro Negro and Chiles may become viable candidates in the near future with improved instrumentation and site access.