gamma backscatter device
Customs hand-held gamma backscatter device detects differences in density behind a solid surface. The instrument is placed against a surface and emits a narrow beam of gamma energy.
Items of low density allow the beam to pass through and disperse. Higher densities reflect the beam. The degree of reflection is displayed as a numeric value. Significant changes of density trigger an audible alarm. It is very effective in the examination of vehicles, ship cabins and container walls.