Density Imaging of Volcanoes with Atmospheric Muons using GRPCs

Their capability to penetrate large depths of material renders high-energy atmospheric muons a unique probe for geophysical explorations. Provided the topography of the target is known, the measurement of the attenuation of the muon flux permits the cartography of matter density distributions revealing spatial and possibly also temporal variations in extended geological structures. A collaboration between volcanologists, astroparticleand particle physicists, TOMUVOL, was formed in 2009 to study tomographic muon imaging of volcanoes with high-resolution tracking detectors. By exploiting Glass Resistive Plate Chambers (GRPCs) with a semidigital readout developped for ILC hadronic calorimetry within the CALICE collaboration, TOMUVOL aims to improve the understanding of volcanic processes and may finally contribute to reducing volcanic hazards. In 2011, TOMUVOL operated a muon telescope with three parallel detection planes at the flank of the Puy de Dôme, an inactive volcanic dome situated in the Massif Central (southcentral France). This contribution presents preparatory work towards muon tomography as well as flux measurements obtained after the first months of data taking.