| 摘要 |
<p>Disclosed is an instrument for detecting neutron backscatter from an object including a source of neutrons (12), a neutron detector (14) capable of detecting thermal neutrons and a housing (10) which is impervious to water and having at least one external operating surface (20) for placing adjacent the object, the source and detector being located within the housing in such a way that the distance between the detector and the operating surface(s) is less than 25 mm and the distance between the detector and any other external surface of the housing is at least 50 mm.</p> |
