A novel technique to detect special nuclear material using cosmic rays

We present a novel method to detect special nuclear material using cosmic rays. Muon Scattering Tomography (MST) is a method in homeland security for scanning cargo containers and vehicles for special nuclear material with cosmic muons. These are abundant, highly penetrating, not harmful against organic tissue, cannot be screened against, and can easily be detected. Muons undergo multiple Coulomb scattering when passing through material, and the amount of scattering is proportional to the ℤ² of the material. By reconstructing incoming and outgoing tracks, we can obtain variables to determine the ℤ of the target material. In a real life application, this has to happen on a timescale of 1 min and thus with small numbers of muons. We have built a detector system using resistive plate chambers (RPCs). 12 layers of RPCs allow for the readout of 6 × and 6 y positions, by which we can reconstruct incoming and outgoing tracks. In this work we detail the performance of two algorithms by which we separate high-ℤ targets from low-ℤ background.