Characterization of x-ray transmission gratings

Self-supporting transmission gratings with periods of 1 microm or below are used in combination with grazing-incidence telescopes in celestial x-ray astronomy. They can be produced with sizes up to only a few cm(2); therefore, several hundreds or even thousands of individual elements are needed in order to cover the aperture of a telescope. This large number leads to the problem of characterization of the gratings regarding their x-ray performance. We demonstrate that spectrometry in the resonance domain using H polarization is a suitable method for the determination of the grating wire profile and deviations of the grating surface from a plane. Although developed originally for microwave applications it can be shown that the methods of strict solution of the Helmholtz equation are able to explain even small effects related to imperfections of periodic submicrometer structures.