Non-specular scattering from multilayer mirrors at normal incidence

The first measurements are reported of non-specular scattering of EUV radiation normally incident on a multilayer mirror. The scattering from a Mo/Si multilayer mirror has been measured as a function of angle and wavelength. A peak in the angular distribution of scattered light is observed which is due to the correlation of the roughness of different interfaces. The scattering from correlated roughness can be described by a simple kinematic theory of scattering. In the region of the Bragg reflectivity peak dynamical effects lead to a reduction in the scattering from the simple kinematic theory. The total integrated scatter (TIS) has been measured and is found to peak on the short wavelength side of the Bragg peak. The TIS is less than 1% of the incident intensity.