Conventional radiography of sediment cores in rectangular coring tubes

The coring tubes are made of transparent acrylic glass which has a small coefficient of absorption of X-rays at low and moderate levels of radiation energy. This permits observation and radiography of the cores to be undertaken before they are extruded from the coring tubes.

Schematic diagram of experimental setup for radiography of a sediment sample. From Axelsson and Händel 1972 (Geogr. Ann. 54 A).

As shown above the X-rays are diverging from the focus of the X-ray tube. The X-ray radiograph is thus a central projection of the X-rayed sediment core. Thin, horizontal layers in thick sediment cores may therefore be projected as thick and diffuse on the radiographs if their distance to the centre of projection is great. Therefore, it is important to use a large film-to-focus distance during X-raying, to use rather thin coring tubes, and to restrict the vertical movement of the coring tube between the exposures, so that the image interpretation may be restricted to areas close to the centre of X-ray projection. Stereoradiographs facilitate the image interpretation and may be used to calculate the real thickness of sediment layers also in rather thick sediment cores, projected at a relatively great distance from the centre of projection on the X-ray radiographs.

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