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How do radioactive isotopes measure the thickness of metal or plastic sheets?

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radioactivity Figure 1: Radioactive decay of beryllium-7 to lithium-7 by electron capture (EC; see text).

Radioactive isotopes are used in industry to measure the thickness of materials like metal or plastic sheets through a process involving radiation absorption.1

This is typically accomplished using a device known as a beta gauge. In this process, a radioactive source emits radiation—often beta particles—that passes through the material being measured. As the radiation travels through the sheet, the material absorbs a portion of it. A detector placed on the opposite side of the sheet measures the intensity of the radiation that successfully passes through. Because the amount of absorption is directly related to the thickness and density of the material, the detector can determine the thickness of the sheet based on the remaining radiation intensity.21

This method allows for precise, non-contact monitoring and control of production processes in manufacturing.1