Imaging a nuclear reactor using cosmic ray muons

The passage of muons through matter is dominated by the Coulomb interaction with electrons and nuclei. The muon interaction with electrons leads to continuous energy loss and stopping of the muons. The muon interaction with nuclei leads to angular diffusion. We present experimental images of a nuclear reactor, the AGN-201M reactor at the University of New Mexico, using data measured with a particle tracker built from a set of sealed drift tubes. The data are compared with a geant4 model. In both the data and simulation, we identify specific regions corresponding to elements of the reactor structure, including its core, moderator, and shield.