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found that the reflectivity of a flat target strongly increased below a critical
angle of only about 0.1
°
. In 1927, Compton was awarded the Nobel Prize in
Physics (Figure 1.3a). Ten years later, Debye won the Prize in chemistry for his
investigation of X-ray powder diffractometry. And finally, Kay Siegbahn, son
of Manne Siegbahn, received the Noble Prize for the discovery of X-ray
photoelectron spectroscopy in 1981.
The years of fundamental discoveries were gone now and the time of
industrial applications began. Already in 1924, Siemens & Halske (Germany)
had built the first commercially available X-ray spectrometer with an open
X-ray tube, revolving crystal, and photographic plate. Coolidge developed a
vacuum-sealed cathode-ray tube as shown in Figure 1.4. Samples could easily
be excited now by X-rays instead of electrons. Soller built a collimator
consisting of several parallel metal sheets just right for the collimation of a
broad X-ray beam. In the 1930s, Geiger and Müller developed a gas-filled
photoelectric detector, which allowed for direct pulse-counting instead of a
complicated development of the photographic plate. This detector was
replaced by a gas-filled proportional detector and by a scintillation counter
in the 1940s. Simultaneously, different analyzer crystals were produced with
various spacings and high reflectivity, for example, lithium fluoride and
pentaerythritol.
Figure1.4.
X-ray tube of the Coolidge type used as an X-ray photon source. (a) The vacuum-sealed
glass bulb is an engineering marvel of glass blowing workshops from 1905. Photo of the authors,
reproduced with permission from“Deutsches Röntgenmuseum,”Lennep, Germany. (b) Sketch of
today's X-ray tubes consisting of a metal-glass cylinder. C
=
tungsten-filament used as the cathode;
A
=
metal block with a slant plane used as the anode; W
=
thin exit window. Figure from Ref. [8],
reproduced with permission. Copyright1996, John Wiley and Sons.
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