‘
THE BRAGG X-RAY SPECTROMETER
205
parallel grooves, as for optical gratings, the reected-components
of
x-ray beam combine or interfere With each“other to_produce
maxima and minima of intensity. This grating method was uSed
by Compton and Doan 9 to obtain the rst direct measurements
of the wave-length of X—rays (see the-rst chapter in this book—).
The rst reliable dimcz‘ion experiments With X-rays were
carried out With ne slits as early as 1909 by Walter and Pohl and
interpreted by Sommerfeld
1911.
The next two sections Will
'
_' give a discussion of the diffraction of 'X—rays by. meansof crystals.
9—10.
The Bragg X—ray Spectrometer.—In gure“ 9—10, an
x-ray beam, collimated by narrow slits 1 and B, strikës the surface
of a crystal C, is diffracted and passes through a slit D into an
ionization chamber] and is recorded by the electroreter E.
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