Portable muon scattering tomography detectors for security imaging applications

Muon scattering tomography techniques can be used to image the contents of an enclosed volume by measuring the scattering angle of cosmic ray muons as they pass through a volume using particle tracking detectors. The magnitude of the observed muon scatter varies with the density of the objects within a volume, therefore the technique is well suited to distinguishing dense (high-Z) materials from lower density (low-Z) materials. AWE has been investigating muon scattering tomography techniques for use in the identification of special nuclear material (SNM) in transit cargo for a number of years. As part of this work AWE and our partner institutions have plate chamber technology, and a software suite of reconstruction tools and Monte Carlo simulations that we have used to quantify the capability and limitations of muon tomography techniques for SNM identification. Recent work at AWE has focused on the development of portable detector technologies for the imaging of objects and packages at unfixed locations. It is envisaged that portable detectors will be positioned to the sides of the screened objects rather than at the top and bottom with the object in the centre. This work has involved the further development of our Monte Carlo models to provide a more detailed of the horizontal muon flux and the implementation of new tracking algorithms to identify muons coming from either side of the tracking system. Part of this work has also involved investigating the use of portable wire chamber and silicon tracking detectors. Our work has also focused on examining the potential improvements to image quality afforded by the detection of spallation neutrons from muon interactions inside an object. The work presented will provide an overview of these recent developments and draw conclusions on the use of muon scattering tomography techniques for deployable security imaging applications.