Re: ATM "exotic" mirror materials

[goffaxe@azstarnet.com (Valerie & Bob Goff)]

>Here are the coefficients of thermal expansion for various materials.
>All are given in units of inverse degrees C.
>
>Ordinary glass:        9e-6
>Pyrex:         3.2e-6
>Fused quartz:  5.5e-7
>Zerodur:       1e-7
>
>
>Mark Marr-Lyon
>o9938156@unicorn.it.wsu.edu


And fused silica is  4.7 x 10e-7
and ULE is 0.6 x 10e-7
BK-7 is .................
and F-2 is.......................
and the glass-ceramics all have problems. Dr Steve Jacobs of the University
of ArizonaFound, many years ago, during thermal cycles used to determine the
TEC of these materials, that they never would come back to the same length
for the same temperature, a property not found in true glasses. Then there
is the problem of scattering from the surface of these glass-ceramics.
I'll use ULE every time it is suggested. Fused quartz, fused silica, and ULE
polish like glass, logically, not in fits and starts like glass-ceramics. 
FQ ans FS and ULE all work faster if you put a few drops of lemon juice in
the polishing slurry; filter it well first.
Then, for exotic materials there is a project in my lab to polish
Graphite-Epoxy-essentially 0 TEC Stiff and light after all ................

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OPTICS IS LIGHT WORK

Bob