MESSRS. W. EDWARDS AND Co., Allendale Works, Vaughan Road, London, S.E.5, have recently published details of their Finch electron diffraction camera intended for industrial research. This camera is of the type developed by Prof. G. Ingle Finch, who has done so much to improve the technique of electron diffraction. The camera uses a cold cathod discharge tube as a source of electrons. The fine beam, which is necessary for a sharp diffraction pattern, is obtained by using a series of diaphragms and by focusing the beam upon the screen with a magnetic coil. A useful feature is that both the diaphragm and specimen holders are standardized so that they will fit any of the six ports in the instrument. Moreover, all the necessary adjustments of the diaphragm and specimen can be made in vacua from the outside. The joints are ground and polished flats held in contact by the atmospheric pressure, a point of importance in routine work where quickness in changing specimens is essential. In this instrument the specimen can be exchanged and the system evacuated in a matter of minutes. Only one criticism—a minor one—can be made. The shape and size of the window are such that the eyes must be held quite close if the whole pattern is to be seen, and the screen is then rather near for comfortable vision. Suitable pumps are supplied, a variety of systems being available to suit individual needs, or a standard unit is made up ready for use. This instrument is noteworthy as it marks the entry of the diffraction camera into the industrial research laboratory, where it should yield valuable information upon metallic surface structure, to mention only one of the many possible industrial fields of investigation.
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An Electron Diffraction Camera. Nature 143, 327–328 (1939). https://doi.org/10.1038/143327d0