| 摘要 |
<p>A system includes a tool for measuring properties of a formation. The tool includes a tool body, a neutron source to emit neutrons disposed within the tool body, a neutron detector disposed within the tool body spaced apart from the neutron source, and a neutron shield arranged in operational relationship to the neutron detector, the neutron shield defines an exterior surface and an interior volume, the neutron shield to prevent neutrons having an energy below a first predetermined threshold from traveling from the exterior surface to the interior volume. The neutron shield is movably coupled to the tool body, wherein the neutron shield defines a non-occluded position relative to the neutron detector such that the neutron detector is at least partially outside the interior volume, and the neutron shield defines an occluded position relative to the neutron detector such that the neutron detector is disposed within the interior volume.</p> |
