Density-Contrast Detectability of a Massive Sulphide Orebody by Underground Muon Imaging

This paper computes the muon attenuation, exposure and resolution budget for imaging a massive sulphide orebody with cosmic-ray muons. Sight lines through 180 metres of host rock at a density of 2.75 grams per cubic centimetre present an opacity of 4.95e+04 grams per square centimetre (495 metres of water equivalent), which sets a minimum muon energy of 108.1 GeV and a transmitted vertical intensity of 0.03747 per square metre per second per steradian. For a detector of 1 square metres with the stated acceptance and efficiency, divided among 150 image elements, the stated feature produces a flux contrast of 0.3027 and reaches five standard deviations in 33.05 days of counting, while the target precision of 0.05 per image element requires 48.46 days. A deployment of 200 days delivers a per-element precision of 0.02461, corresponding to a thickness sensitivity of 4.43 metres. The combined angular resolution is 7.309 milliradians, of which tracking contributes 2.121 milliradians and multiple scattering at the threshold momentum 6.994 milliradians. The budget is compared with published muography of the same class of target, for which underground muon imaging trials in operating mines have reported density anomalies consistent with known orebodies and voids, with detectors deployed in drifts beneath the target volume. Every number is computed by the accompanying script from the stated inputs. Computed, not measured.