Feasibility Study of a New Cherenkov Detector for Improving Volcano Muography

Abstract

Muography is an expanding technique for internal structure investigation of large volume object, such as pyramids, volcanoes and also underground cavities. It is based on the attenuation of muon flux through the target in a way similar to the attenuation of X-ray flux through the human body for standard radiography. Muon imaging have to face with high background level, especially compared with the tiny near horizontal muon flux. In this paper the authors propose an innovative technique based on the measurement of Cherenkov radiation by Silicon photo-multipliers arrays to be integrated in a standard telescope for muography applications. Its feasibility study was accomplished by means of Geant4 simulations for the measurement of the directionality of cosmic-ray muons. This technique could be particularly useful for the suppression of background noise due to back-scattered particles whose incoming direction is likely to be wrongly reconstructed. The results obtained during the validation study of the technique principle confirm the ability to distinguish the arrival direction of muons with an efficiency higher than 98% above 1 GeV. In addition, a preliminary study on the tracking performance of the presented technique was introduced.

Measurement of single and multiple cosmic muons at high altitudes with the MEV telescope

“…A search for multiple track events was also performed in the same dataset, resulting in a small sample of events which were identified as two-track events, either coming from the Etna side or from the opposite (open sky) side. Upgrade activities are in progress to complement the MEV telescope with additional detectors and electronics contributing to better improve the selection of the incoming direction for tracks very close to the horizontal, namely a measurement of the time-of-flight between the two outermost detectors (although on a limited baseline) and the addition of a Cerenkov detector to provide directionality information [4].…”

Proof-of-Principle of a Cherenkov-Tag Detector Prototype

“…Starting from the assumption that atmospheric muon flux is downward oriented only, the incoming direction of muons inside the field of view of a telescope can be distinguished from the slope of reconstructed trajectories. In a previous paper [22], we proposed a new kind of Cherenkov detector, as a part of the R&D activities of the project for Muography of Etna Volcano (MEV) [23,24]. The feasibility study, developed by means of Monte Carlo simulations with Geant4, explored the usage of such detector to reduce the background noise due to "upward-scattered" muons, i.e., secondary cosmic-ray particles scattered near the detector that traverse it perfectly miming the tracks of downward going particles in opposite directions [14].…”

“…The goal is to ensure that when a charged particle traverses both tiles, the Cherenkov radiation produced will be detected only by the SiPMs of the exit tile, while the photons emitted in the first radiator are blocked by the light absorbing coating. In order to make this clearer, in Figure 1 we report an example from [ 22 ], in which a muon (red track), with kinetic energy equal to , traverses the detector from up to down and produces Cherenkov photons (green lines). In the first tile traversed, the photons stop in light absorbing foil between the two radiators; in the second tile traversed, instead, the photons are directed toward the instrumented face and can be detected by the SiPMs.…”