| 摘要 |
A method of non-destructively, on-line determining the density profile in a plate-shaped material with a density which varies discretely or continuously over the plate thickness, while the density at a specific depth of the plate is assumed to be constant, such as for instance plates based on wood, by means of X-rays or gamma rays from a source placed on one side of the plate. Two detectors are placed on the other side of the plate, one detector measuring in the emitting direction of the source and the other detector measuring in the other direction and being movable relative to the plate. The counting number of the second detector is adjusted by means of the counting number of the first detector. By a suitable choice of emitting direction and detecting direction it is possible to provide a measurement of the density in a specific measuring volume merely by dividing the counting number of the second detector by the counting number of the first detector. As a result, the attenuation in the material is left out. The angle of incidence must be substantially identical with the angle of reflection.
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