For radiation incident at grazing angles, total external reflection arises where nearly 100% of the incident radiation is reflected for incident angles (angles between incident ray and reflecting surface by convention) smaller than approximately 1 degree. For years, astronomers have exploited the properties of total external reflection to build grazing-incidence x-ray telescopes. Achieving arcsecond angular resolution in a grazing-incidence foil optic X-ray telescope requires accurate placement of individual foils.
A method has been developed for mounting large numbers
of nested, segmented foil optics with sub-um accuracy using lithographically
defined and etched silicon alignment micro-structures. The first
generation design using this method attempted to use a diamond machined
reference flat to align the edges of the curved plates. Feasibility
was demonstrated, but structural deformations from bolts, etc., reduced
accuracy. Precise, accurate, repeatable positioning of the micro-structures
was also demonstrated, but design problems were identified. This
project will create the "final" production-ready "Assembly Truss" to
position
the optic foils in the Flight Modules to be used in the next generation
X-Ray telescope.
Figure. Single flight module in operation. An additional
module would focus
the cross-axis X-rays. The flight modules will be
assembled
into a close-packed
final telescope configuration. Each module will focus
to itsown detector so
precision alignment of the modules with each other is
not critical.
