Bragg Xray Spectrometer:
Bragg's spectrometer is similar to an ordinary prism spectrometer. Two lead slits S1 and S2 define a narrow beam of X-rays coming from the target T.
This narrow beam of X-rays is then incident on the crystal C, mounted on the table of the spectrometer. The reflected beam after passing through the slit S2 enters the ionization chamber D filled with methyl bromide. The ionization current is detected by the electrometer E. Instead of an ionization chamber, photography plate or scintillation counter can be used. The ionization current is recorded as the glancing angle θ is varied by rotating the crystal table. The chamber is rotated through double the angle through which the crystal is rotated so that the angle of incidence is equal to the angle of reflection.
A graph is plotted between the intensity of ionization and the glancing angle. In the case of sodium chloride crystal, the curve is as shown in fig. A1 and B1 correspond to two characteristic radiations in the incident beam. The maxima A2, B2and A3, B3 are produced by second and third order reflections. The maxima A1, A2 and A3 occur when θ is equal to 5.9°,11.75° and 18° respectively. The peak intensities occur whenever the Bragg equation nλ = 2d sin θ is satisfied.