Apparatus and methods are disclosed for milling selected regions on the
surface of a multilayer-film reflective surface of an X-ray mirror to correct the
reflected wavefront produced by the mirror, thereby producing a more uniform or
otherwise more desirable phase distribution of the reflected wavefront. The milled
multilayer films include multiple lamina sets each including respective layers
of at least two respective substances. The layers usually are "stacked" alternatingly
at a fixed period length on a mirror substrate. By selectively removing one or
more surficial layers in selected locations, local corrections of the phase shift
of the reflective wavefront are achieved. At each milling location, the depth profile
can be stepwise or smoothly gradated. Milling methods can include lapping, ion-beam
bombardment, plasma-enhanced chemical vapor machining (CVM), reactive-ion etching,
photochemical reactions, or laser ablation.
