High-accuracy X-ray foil optic assembly

Achieving arcsecond angular resolution in a grazing-incidence foil optic X-ray telescope, such as the segmented mirror approach being considered for the Constellation-X Spectroscopy X-Ray Telescope (SXT), requires accurate placement of individual foils. We have developed a method for mounting large numbers of nested, segmented foil optics with sub-μm accuracy using lithographically defined and etched silicon alignment micro-structures. A system of assembly tooling, incorporating the silicon micro-structures, is used to position the foils which are then bonded to a flight structure. The advantage of this procedure is that the flight structure has relaxed tolerance requirements while the high accuracy assembly tooling can be reused. A companion paper by Bergner et al. discusses how our process could be used for the SXT. We have built an assembly truss with a simplified rectilinear geometry designed to experimentally test this alignment and mounting technique. We report results of tests with this system that demonstrate its ability to provide sub-μm alignment of rigid test optics.