Polarization by gratings used at grazing incidence

The polarization introduced by gold-coated and aluminum-coated concave reflection gratings used in a grazing incidence monochromator has been measured over the spectral range from 20 nm to 130 nm. In every case the polarization ratio (P = R(p)/R(s)) is greater than 0.8 for wavelengths less than 40 nm and appears to be approaching unity below 20 nm. For both new and aged or contaminated gratings, the observed polarizations are consistent with those calculated assuming reflection occurs at a plane thin multilayer region with the optical constants chosen to simulate the grating surface.