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Industry : Gauging
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Radioisotopes are used during manufacturing processes in a number of different ways. One application is in gauging (measuring precisely). Gauging works because radiation loses energy as it passes through substances. This principle can be used to measure the presence or the absence of material between the source and the detector.
The radiation that passes through a material is measured and compared with the radiation that would pass through a required thickness of the material. If more radiation is measured, the material is too thin; if less radiation is measured, the material is too thick. During manufacturing, instruments that are sensitive to the measurements will activate controls to maintain the proper thickness. The advantage in using this form of gauging or measurement is that there is no contact with the material being gauged. For example:
- Some machines, that manufacture plastic film use radioisotope gauging to measure the thickness of the plastic film. The film runs at high speed between a radioactive source and a detector. The detector signal strength is used to control the plastic film thickness as it is continuously made.
- The height of the coal in a hopper can be determined by placing high-energy radioactive sources at various heights along one side with focusing collimators directing beams across the load. Detectors placed opposite the sources register the breaking of the beam and, hence, the level of coal in the hopper. A light beam could not do the same job in a very dusty atmosphere.
- When the intensity of radiation from a radioisotope is reduced by matter in the beam, some radiation is scattered back towards the radiation source. The amount of 'backscattered' radiation is related to the amount of material in the beam, and this too can be used to measure characteristics of the material. This principle is used to measure different thicknesses of coatings.
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