  A feasibility demonstration of three-dimensional (3D) muon tomography was
performed for infrastructure equivalent targets using the proposed portable
muography detector. For the target, we used two sets of lead blocks placed at
different heights. The detector consists of two muon position-sensitive
detectors, made of plastic scintillating fibers (PSFs) and multi-pixel photon
counters (MPPCs) with an angular resolution of 8 msr. The maximum
likelihood-expectation maximization (ML-EM) method was used for the 3D imaging
reconstruction of the muography simulation and measurement. For both simulation
and experiment, the reconstructed positions of the blocks produce consistent
results with prior knowledge of the blocks' arrangement. This result
demonstrates the potential of the 3D tomographic imaging of infrastructure by
using eleven detection positions for portable muography detectors to image
infrastructure scale targets.
