X-ray efficiencies of blazed gratings in extreme off-plane mountings.

The measured first order diffraction efficiencies in the X-ray wavelength region of a blazed grating ruled with 3600 grooves/mm are reported. The grating is used in an extreme off-plane configuration which means that the incident beam is nearly parallel to the grooves. It appeared that in this configuration the efficiencies are between 40% and 70% of the reflection coefficient of the selected grating material.