Polarization of crystal monochromated X-rays

The polarization ratio in a bent crystal monochromated X-ray beam has been measured by examining the scattering at 90° in two orthogonal planes. The value was found only not to be far removed from the value expected on the basis of an ideally mosaic monochromator, but not even to lie between this value and that expected on the basis of an ideally perfect monochromator. This result has the implication that the polarization factor lies outside the range usually assumed possible. An explanation of this result in terms of large secondary extinction is proposed.