Mumbai University > First Year Engineering > Sem 1 > Applied Physics 1

Marks: 5M

Year: Dec 2015

1. The essential parts of a Bragg spectrometer are shown in figure.

1. It is similar in construction to an optical spectrometer.
2. It consists of three parts
   • A source of X-rays.
   • A crystal held on a circular table which is graduated and provided with venire.
   • A detector (ionization chamber).
3. X-rays from an X-ray tube, limited by two narrow lead slits S_1 andS_2, are allowed to fall upon the crystal C.
4. The crystal is mounted on the circular table T, which can rotate about a vertical axis and its position can be determined by the venire V.
5. The table is provided with a radial arm (R) which carries an ionization chamber (I). This arm also can be rotated about the same vertical axis as the crystal.
6. The position of this arm can be determined by a second venire.
7. The ionization chamber is connected to an electrometer (h) to measure the ionization current.
8. Hence we can measure the intensity of the diffracted beam of X-rays, diffracted in the direction of the ionization chamber.
9. $S_3$ is a lead slit, to limit the width of the diffracted beam.
10. In practice, the crystal table is geared to the ionisation chamber so that the chamber turns through 20 when the crystal is turned through Ө.