Detection of cavities in a salt mine with cosmic muons: expected results and first data.

Renewable energy dependence on variable weather creates mismatches with energy demand. One possible solution is to produce and store green hydrogen by energy surpluses for later use. While surface storage options are limited, subsurface storage in salt caverns (200 m to 2 km deep) is more suitable due to their favorable properties. However, imaging these caverns is difficult because traditional geophysical methods often lack the resolution or depth penetration needed, making it challenging to study such formations effectively. Many of the limitations of conventional geophysical prospecting methods can be addressed by Muon Radiography (MR), an advanced technique that uses cosmic muons to detect underground density variations. Because muons penetrate deeply, their attenuation reveals information about the density and structure of the material, allowing for the identification of cavities with high spatial resolution over several hundred meters. This article presents a MR project aimed at imaging and characterizing underground salt caverns in southern Sicily. A muon detector was first installed at the surface to collect a calibration sample of free-sky muons, then moved to an underground gallery at [Formula: see text] m ASL to test the method near a known tunnel. The paper includes expected results from synthetic data and first data analysis from the calibration and underground samples.