Estimation of X-ray scattering impact in imaging degradation for the   SIMBOL-X telescope
  The imaging performance of X-ray optics (expressed in terms of HEW, Half-Energy-Width) can be severely affected by X-ray scattering caused by the surface roughness of the mirrors. The impact of X-ray scattering has an increasing relevance for increasing photon energy, and can be the dominant problem in a hard X-ray telescope like SIMBOL-X. In this work we show how, by means of a novel formalism, we can derive a surface roughness tolerance - in terms of its power spectrum - from a specific HEW requirement for the SIMBOL-X optical module. 
D. Spiga, G. Pareschi, R. Canestrari, V. Cotroneo