Feasibility of three-dimensional density tomography using dozens of muon radiographies and Filtered BackProjection for volcano
Abstract. This study is the first trial to apply the method of filtered backprojection (FBP) method to reconstruct three-dimensional (3D) bulk density images via cosmic-ray muons, We also simulated three-dimensional reconstruction image with dozens of muon radiographies using FBP method for a volcano and evaluated its practicality. FBP method is widely used in X-ray and CT image reconstruction but has not been used in the field of muon radiography. One of the merits to use FBP method instead of ordinary inversion method is that it doesn't require an initial model, while ordinary inversion analysis need an initial model. We also added new approximation factors by using data on mountain topography into existing formulas to successfully reduce systematic reconstruction errors. From a volcanic perspective, airborne radar is commonly used to measure and analyze mountain topography. We tested the performance and applicability to the model of Omuroyama, a monogenetic scoria cone located in Shizuoka, Japan. As a result, it was revealed that the density difference between the original and reconstructed images depended on the number of observation points and the accidental error caused by muon statistics depended on the multiplication of total effective area and exposure period. Combining above all things, we established how to evaluate an observation plan for volcano using dozens of muon radiographies.