Optimized structures of multilayer soft X-ray reflectors in the spectral range of 30 to 300 Å

For wavelengths in the spectral range of 30 to 300 Angstrom, the structures of multilayer (ML) soft X-ray reflectors for maximum reflectivity at normal incidence were optimized. A dynamical theory of X-ray scattering was employed in the calculation for ideal ML structures. The calculation indicates that the optimization should be performed for a sufficiently large number of bilayers. The structural parameters optimized for a small number of bilayers do not yield the best performance. It is also observed that for a given number of bilayers, there exists a range of structural parameters for equivalent performance. In the spectral region considered, the maximum reflectivities vary from 40 to 78% with respect to wavelength.