Abstract
Two recent letters in the correspondence columns of Nature (Tasker and Towers, 156, 695; 1945, and Roberts,157, 695; 1946) have brought to notice the work of Prof. J. J. Trillat and his colleagues at the Centre National de la Recherche Scientifique, on secondary electron photography. This work, carried put during the war years, is described in a series of notes in the Comptes Rendus and the Revue Scientifique, Paris, between 1941 and 1945; the fact that it was not referred to earlier is an example of the difficulty of consulting? war-time foreign journals. Most of the experiments are concerned with the surface appearances of metal specimens. A low-speed photographic film is placed in contact with the metal surface and irradiated with X-rays of 150–200 kV. The direct effect of the X-rays on the film is small, but the secondary electrons emitted by the metal produce an image of the surface. Differential blackening is produced by metals of different atomic numbers, and with careful control the method is capable of qualitative analysis. Both macroscopic and microscopic photography are possible. For example, a reflexion electron photograph of a magnesium-aluminium alloy containing some manganese, under the microscope shows the distribution of the heavy element around the magnesium-aluminium crystals. This opens up an interesting field in surface metallurgy, with relatively simple apparatus. Alternatively, the secondary electrons from a thin sheet of lead may be used to ‘radiograph’ very thin objects such as paper or tissue sections. The results are similar to those obtained with very soft X-rays.
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Secondary Electron Photography. Nature 158, 869 (1946). https://doi.org/10.1038/158869a0
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DOI: https://doi.org/10.1038/158869a0