THE TAKAGI EQUATIONS IN EVALUATING THE CONTRIBUTIONS OF SOME SYSTEMATIC-ERRORS IN SCANNING LLL X-RAY INTERFEROMETERS

We have determined the modulation parameters of the x-ray fringes emit ted by a scanning symmetric LLL x-ray interferometer in order to estim ate the contributions - in the budget of systematic errors related to the value of the Si d(220) lattice parameter - made by aberrations occ urring during a non-ideal trajectory of the movable component. We have followed the Takagi approach to the dynamic theory of x-ray diffracti on and used a computational tool which solves the relevant equations f or any wavefront, for any absorption of the incident radiation and for the most common geometric configurations.