| 摘要 |
A device for taking air gap backscatter radiation measurements at a pair of predetermined distances from the surface of a material is disclosed. The ratio of the first and second measurements are a function of the density of the material when one of the distances is sufficiently large that the measurement is dependent on the chemical content of the material but is independent of surface irregularities and density and when the second distance is greater than the average surface irregularity but sufficiently proximate to the material so that the measurement is independent of surface irregularities but is dependent on the density and the chemical content of the material. The device includes a housing slidably supported between a pair of end plates, a carrying handle for the device and a source within the housing. When the handle is in a first position, the source is disposed in a storage or "safe" position. Rotation of the handle to a second position moves the source to a first "use" position, and rotation of the handle to a third predetermined position also places the source in the use position and raises the housing with respect to the end plates. Differential backscatter radiation measurements are taken while the device is in its two use positions.
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