Joint measurement of the atmospheric muon flux through the Puy de Dôme volcano with plastic scintillators and Resistive Plate Chambers detectors

Abstract

The muographic imaging of volcanoes relies on the measured transmittance of the atmospheric muon flux through the target. An important bias affecting the result comes from background contamination mimicking a higher transmittance. The MU‐RAY and TOMUVOL collaborations measured independently in 2013 the atmospheric muon flux transmitted through the Puy de Dôme volcano using their early prototype detectors, based on plastic scintillators and on Glass Resistive Plate Chambers, respectively. These detectors had three (MU‐RAY) or four (TOMUVOL) detection layers of 1 m2 each, tens (MU‐RAY) or hundreds (TOMUVOL) of nanosecond time resolution, a few millimeter position resolution, an energy threshold of few hundreds MeV, and no particle identification capabilities. The prototypes were deployed about 1.3 km away from the summit, where they measured, behind rock depths larger than 1000 m, remnant fluxes of 1.83±0.50(syst)±0.07(stat) m−2 d−1 deg−2 (MU‐RAY) and 1.95±0.16(syst)±0.05(stat) m−2 d−1 deg−2 (TOMUVOL), that roughly correspond to the expected flux of high‐energy atmospheric muons crossing 600 meters water equivalent (mwe) at 18° elevation. This implies that imaging depths larger than 500 mwe from 1 km away using such prototype detectors suffer from an overwhelming background. These measurements confirm that a new generation of detectors with higher momentum threshold, time‐of‐flight measurement, and/or particle identification is needed. The MU‐RAY and TOMUVOL collaborations expect shortly to operate improved detectors, suitable for a robust muographic imaging of kilometer‐scale volcanoes.

Atmospheric muons as an imaging tool

“…This opportunity has been exploited for the development of the TOMUVOL telescope [38,39,40], composed of planes of glass RPC detectors (see Section 4.3) originally developed in the context of the particle physics CALICE collaboration (R&D for a detector to be operated at future highenergy linear colliders). A joint measurement campaign of the Puy de Dôme in 2013 [41] by the TOMUVOL and MU-RAY collaborations with their detector prototypes, based on two different detector technologies with complementary merits, was crucial to quantify the challenges and prioritize their further developments. They found that, with their detector setups at that time, the backgrounds overwhelmed the signal for opacities larger than 500 mwe from 1 km away; the further characterization of these backgrounds has led to the design of improved detectors with higher momentum threshold and TOF measurement [32], with the goal of a robust muographic imaging of kilometer-scale volcanoes.…”

Plug Formation Imaged Beneath the Active Craters of Sakurajima Volcano With Muography

“…Each tracker consists of at least five MWPCs and five 2‐cm‐thick lead shielding plates. These plates are applied to deflect and absorb the low‐energy (<1 GeV) muons (Oláh et al, ) and electrons (Oláh & Varga, ) that do not penetrate the volcano but appear to come from that direction (Nishiyama et al, ; Ambrosino et al, ). This measurement setting covers the crater region (Figure a) and allows a spatial resolution of less than 10 m at a position of the Minamidake crater rim.…”

A Nuclear Emulsion Detector for the Muon Radiography of a Glacier Structure

“…This radiography technique was first proposed by George [1] and applied for the first time by Alvarez [2]. It recently benefited from several technological improvements and was successfully applied to image magmatic chambers of volcanos [3][4][5], and for archaeological purposes [6].…”

“…Our first results in visualizing the bedrock topography [7] were obtained with a muon detector based on nuclear emulsion films, a technique already used for volcanoes' investigation, together with others, such as plastic scintillators [4] and resistive plate chambers [5]. The detectors had to be installed below the bedrock level, which was possible thanks to the existence of a railway tunnel underneath the target.…”