Cavity Location by Muon Tomography

Muon tomography (or muography) is one of the most effective methods for locating unknown underground voids. If the geometric conditions are favorable for the measurements, no other geophysical method can compete with it, neither when resolution nor when simplicity is considered. In the last years, thanks to the continuous R&D of our low-cost, portable muon detectors, as well as the improved data processing methods, we have completed several successful natural and artificial cavity exploration projects, demonstrating that location is possible even if the characteristic size of cavity is 5% of the rock thickness between the detector and surface. Here we present case studies carried out in Hungarian underground sites, where we could find unknown cavities and verify the method by locating known artificial shafts and adits with high precision. Reaching these unknown caves is in progress either by conventional caving exploration techniques or by drilling. Further measurements are ongoing by the new upgraded detectors. By decreasing gas consumption and supporting electric power by solar cells, we are able to measure even at remote locations without the need of any direct access, for durations of several months