Abstract: Technology for estimating the density of a material is disclosed. A radiation sensor includes at least two radiation detectors each configured to produce electronic signals having a characteristic time parameter, a pulse-shape discriminator to distinguish amongst the detector signals using the characteristic time parameters, and radiation shielding that is configured to provide different radiation paths to the detectors wherein the different radiation paths include at least some different material. A method includes providing at least two detectors and two radiation paths through a radiation shield, measuring the intensity of radiation at each of the detectors, and combining the measures of intensity to estimate a density of a material found in greater amounts in one radiation path than in the other radiation path.

Abstract: A radiation sensor includes a radiation source, at least two scintillators having distinguishable scintillation-light-emission-decay characteristics, and shielding configured to provide radiation-paths of different shielding between the source and the at least two scintillators. The shielding is configured such that the scintillators are primarily sensitive to radiation passing through different paths. The signals produced from scintillation events can be sorted by the scintillator that is the source of the event. A source-scintillator-based comparison of the signals may be used to provide information about the material in one or more of the radiation paths. The sensor may be disposed within a borehole to measure the density of the fluid in the borehole.