STUDY OF THE REFLECTIVITY IN THE XUV DOMAIN OF NORMAL-INCIDENCE MULTILAYER MIRRORS

The development of multilayer optics has profound implications for sof t-X-ray/UV astronomy, since it allows to extend the use of normal-inci dence telescopes to cover the XUV region where lines are formed at gre atly different temperatures (10(5)-10(7) K). A multilayer mirror consi sts of alternating thin layers of suitable materials deposited on a su bstrate and its performance depends not only on the optical properties of the materials but also on the design of the multilayer. In this st udy we have computed the reflectivity of multilayer mirrors to select both the materials and the multilayer design to achieve the best perfo rmance in the wavelength range from 30 to 350 Angstrom; Our calculatio ns show that high theoretical reflectivities, from 0.2 to 0.8 and rela tively narrow bandpasses, from similar to 1 Angstrom to similar to 30 Angstrom, can be obtained, in the wavelength range from 30 to 350 Angs trom by a suitable choice of the materials and of the multilayer desig n.