neutron—neutron sonde

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neutron—neutron sonde A radioactive instrumental package for lowering down a borehole. It comprises a neutron source and detector. The number of neutrons backscattered to the detector is proportional to the number of hydrogen atoms within the rocks surrounding the borehole. It can be used to determine the porosity of the surrounding rocks. See also NEUTRON—GAMMA SONDE; and NEUTRON LOG.