Muon Imaging 2: Two Dimensional Density Mapping using Naturally Occurring Cosmic Ray Muons

S.J. Stanley1, D. Rhodes2, P.M. Jenneson3, W.B. Gilboy3 and S.J.R. Simons4

1 Nexia Solutions, Hinton House, Risley, Warrington, UK, Email: sjs20@nexiasolutions.com

2 Nexia Solutions, B170 Technology Centre, Sellafield, Seascale, Cumbria, UK.

3Dept. of Physics, University of Surrey, Guildford, Surrey,UK

4Dept. of Chemical Engineering, University College London, Torrington Place. London, UK.

ABSTRACT

Cosmic ray muon based imaging systems have great potential particularly in the Nuclear sector, where the high energy nature (up to 1012 GeV) of these naturally occurring particles provides a means to ‘peer through’ objects which otherwise would be inaccessible. These may include lead lined silos, vessels, intermediate material transport modules, etc. Because muons only show detectable interactions with high atomic number material they also offer a means to detect the quantity and location of heavy metal elements and their associated compounds. Previous work has not only shown that cosmic ray muons can be detected, but also that their approximate location at the time of detection can also be obtained. This opens up possibilities for the collation of muon trajectory data which in turn can be used to track muon events both entering and leaving the object of interest allowing attenuation based image processing. The random nature of muon events at sea level, in terms of direction and energy, can be overcome by allowing a suitably large data collection period which serves to average out short term statistical uncertainties. In this work the first attempts at two dimensional muon attenuation mapping are described. More specifically multiple plane prototype muon detection system has been used to image the resultant attenuation maps for a number of lead phantoms. It is believed that future work in this area will serve to significantly improve both the coverage area and the spatial resolution of the system though improved detector technology providing a powerful tool for the rendering of either large or dense objects.

Keywords Imaging, muons, storage vessel, nuclear, cosmic ray, tomography, legacy waste.