COMMENTS ON THE USE OF ASYMMETRIC MONOCHROMATORS FOR X-RAY-DIFFRACTION ON A SYNCHROTRON SOURCE

Crystals of germanium or silicon provide monochromatic radiation on synchrotron radiation beamlines. By using asymmetrically cut crystals, it is possible to alter the properties of the beam in position, angle, wavelength space. The results obtained from using two types of asymmetrically cut monochromators are compared with theory. For single crystal focusing monochromators, the asymmetry results in a dispersion term and a resultant broadening of the focal spot. The expression for the broadening given here differs from that given previously for these type of monochromators and has implications for the design of beamlines where the x-ray source has a small size. Asymmetric channel cut monochromators are not commonly used for x-ray diffraction on a synchrotron. However, we show here that, compared with a symmetric monochromator, intensity gains of three or more can be obtained with a simple compact design. © 1995 American Institute of Physics.