Ice-Thickness Precision Budgets for Muon Imaging of Alpine Glacier Bedrock

This paper computes the muon attenuation, exposure and resolution budget for imaging an Alpine valley glacier with cosmic-ray muons. Sight lines through 120 metres of glacier ice over rock at a density of 0.92 grams per cubic centimetre present an opacity of 1.104e+04 grams per square centimetre (110.4 metres of water equivalent), which sets a minimum muon energy of 22.51 GeV and a transmitted vertical intensity of 0.4988 per square metre per second per steradian. For a detector of 0.5 square metres with the stated acceptance and efficiency, divided among 200 image elements, the stated feature produces a flux contrast of 0.2396 and reaches five standard deviations in 9.512 days of counting, while the target precision of 0.03 per image element requires 24.27 days. A deployment of 120 days delivers a per-element precision of 0.01349, corresponding to a thickness sensitivity of 1.619 metres. The combined angular resolution is 15.26 milliradians, of which tracking contributes 1.768 milliradians and multiple scattering at the threshold momentum 15.16 milliradians. The budget is compared with published muography of the same class of target, for which muography of the Aletsch and Eiger glaciers in Switzerland has reported bedrock topography beneath more than one hundred metres of ice, in agreement with radar soundings. Every number is computed by the accompanying script from the stated inputs. Computed, not measured.