  The present work shows a quantitative trade-off analysis of the Simbol-X
Mirror Spacecraft (MSC) passive shielding, in the phase space of the various
parameters: mass budget, dimension, geometry, and composition. A simplified
physical (and geometrical) model of the sky screen, implemented by means of a
GEANT4 simulation, has been developed to perform a performance-driven mass
optimization and evaluate the residual background level on Simbol-X focal
plane.
