. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . D Fig. 4. Impurities in beryllium foil, x-ray collection. A, all radiation recorded; B. C, D, characteristic emission from dif- ferent impurities separately selected—manganese, nickel and calcium respectively. or AgL characteristic radiation to form the picture. The distribution of the copper can thus be shown in one picture and the distribution of the silver in the other. Another way of displaying this same result is to regard the two pictures as components of a colour picture and photograph them through differe
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . D Fig. 4. Impurities in beryllium foil, x-ray collection. A, all radiation recorded; B. C, D, characteristic emission from dif- ferent impurities separately selected—manganese, nickel and calcium respectively. or AgL characteristic radiation to form the picture. The distribution of the copper can thus be shown in one picture and the distribution of the silver in the other. Another way of displaying this same result is to regard the two pictures as components of a colour picture and photograph them through different filters in register on the same piece of colour film. In this way the copper was made to appear red and the silver green. In principle one can attach a given colour to a given x-ray wavelength, which may be a useful technique for presenting in one picture the relative positions of several elements. As an example of the identification of inclusions in a surface, fig. 4 shows some impurities in a piece of beryllium foil (3). In A all the emitted x-rays were used to form the picture and the impurities show up as emitting more strongly than the beryl- lium. In 5, C, and D the pulse analyser was set to pass the characteristic radiation from three different types of impurity in turn, which were identified as manganese, nickel and calcium respectively. The in- formation may again be presented on one picture in colour. The energy resolution of the proportional counter is not good enough for the separation of character- istic radiation from elements which differ by less than about four in atomic number. However, it seems that there would be sufficient intensity reflected from a curved crystal in the spectrometer to form the picture, in which case adjacent elements would easily be separable. The instrument, therefore, can show up either the topography of a surface by electron scattering with a resolution of well below I //, or the distribution of an element over a surface by x-ray e
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