Project Title:

Oblique-Angle, Ion-Beam Sputtering for Mirror Finishing and Polishing

92-1-08.15-6000D                                                  NAS08-39820
Oblique-Angle, Ion-Beam Sputtering for Mirror
     Finishing and Polishing
Spire Corporation
One Patriots Park
Bedford, MA  01730-2396
Charles C. Blatchley                                 (617-275-6000)

Abstract:

     The firm will ion mill lightweight metals at cryogenic
temperatures to demonstrate that amorphous surfaces and isotropic
sputtering can be created in this way. If successful, this process
will overcome the principal limitation of ion milling for many
otherwise ideal mirror metals that tend to recrystallize and form
texture due to differential sputtering. For each of several
metals, the project will determine the angle of maximum sputtering
at liquid nitrogen temperature. Since ions reaching the sides of a
crack will necessarily sputter more slowly, typically by a factor
of several times, this relatively oblique angle will rapidly
remove micro-cracks. Asperities can similarly be removed by near-
normal incidence, provided no new features are created in the
process. The combination of select angles and low temperature
should make it possible to ion polish virtually any mirror metal
through an easily automated, highly deterministic process.

Potential Commercial Application:

Potential Commercial Applications:  The expected result is
computer-controlled, one-load figuring and polishing of optical
components to replace iterative mechanical finishing and
measurement. Space and terrestrial telescopes, guidance, tracking,
and remote imaging systems would benefit from both reductions in
cost and improvements in mirror quality.

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