Abstract
A PAPER on gamma-radiography was read by Mr. C. Croxson at a meeting of the Industrial Radiology Group of the Institute of Physics, held at Loughborough College, Loughborough, on February 27. Mr. Croxson explained that gamma-radiography is complementary to radiography by X-rays, the chief advantages of radiography by a gamma-ray source being due to the high penetration Of gamma-rays and to the fact that a source of gamma-rays is relatively small and can therefore be used in locations quite inaccessible to an X-ray equipment. In the past, sources of up to about 250 mgm. of. radium element have been used, but recent work has shown that radon (radium emanation) sources are superior for some work since, for the same source size, radon has an initial intensity sixty or seventy times greater than that of radium : with the smaller source sizes thus obtainable, source-film distances of as low as three inches become practical without serious loss in definition. The main disadvantage lies in the short half-life period of radon of about 3-85 days compared with 1,590 years for radium, but since the decay-rate is known, exposures can be readily calculated from exposure curves worked out for radium sources of known intensity. As a war-time measure, the radium is transported in a steel container, three inches thick. For use, the gamma-ray source is transferred to an exposure bomb which has an aperture for the emerging beam, the container being carefully designed to avoid scattered radiation marring any radiograph made.
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GAMMA-RADIOGRAPHY. Nature 151, 424–425 (1943). https://doi.org/10.1038/151424a0
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DOI: https://doi.org/10.1038/151424a0