Multilayer option for conical foil x-ray mirrors

Multilayers used at grazing incidence offer likely the only real opportunity for extending imaging techniques in x-ray astronomy to tens of keV, or well beyond the usual upper bound when using single material reflecting surfaces. There are several reasons why conical foils are particularly suited for multilayer applications. For one thing, many of the arguments made in the past in favor of foil reflectors still hold, since multilayers do not eliminate the need of extreme oblique incidence. We show, additionally, that foil reflectors offer other important advantages which are likely to be essential toward the realization of wide band x-ray mirrors. Successful multilayer depositions on segments of our epoxy replicated foil reflectors have already been reported. In this paper we review our own efforts at multilayer deposition on replicated surface foils, addressing in detail such relevant issues as consistency, quality and uniformity of the deposits, boundary roughness and potential, stress-induced foil shape distortions. Finally, we present detailed mirror design and modeling aimed at future wide-band astronomical research.