Cosmic ray generated charged particles for cargo inspection

Abstract

Charged particles continuously rain down on the surface of the Earth. These charged particles primarily consist of muons and electrons. Muons are subatomic particles with the same charge as the electron, but with 200 times the mass. These particles are generated from interactions of primary cosmic-rays, primarily protons, with the upper atmosphere. Decision Sciences International Corporation (DSIC) has created a tracking detector to measure the interactions of these particles with materials through which they pass: multiple Coulomb scattering and ionization energy loss and from these measurements is able to reconstruct a 3-D map of the density and atomic number of the materials in a scan volume. This map can be used to automatically detect bulk contraband (including explosives, narcotics and other materials) in the cargo as well as provide highlighting of anomalous configurations (nested or irregular volumes) for review by authorities. Fusion of the imaging with the sensitive gamma detection capability of the tracking detector enables the detection of nuclear and radiological materials even when concealed in shielding, as well as discrimination of naturally occurring radioactive materials (NORM) from nuclear and radiological threats. Times to clear most non-threat cargo range from 30 to 60 s, with suspicious scenes (heavy shielding, gamma emitting materials or materials with similar signatures to contraband materials) being held longer to confirm the presence of and identify the material. Extended scanning of suspicious scenes typically takes 2–10 min.