Re: ATM Has anyone worked with membrane mirrors?

[astillma@nit.AirTouch.COM (Anthony Stillman)]

Medium or substrait solidifacation under rotation

I can only draw on work I've seen or done my self in this area.  I know that
with exopy mirrors it is vital that it set up very slowly, that is over days
to weeks and oviously that the rotation rate be held constant.  

I worked with a varity of hot waxes over water to build a substrait for 
the epoxy to set up on.  I didn't have much sucess, I believe this was due
to embalance in the turn table and rotation rate variations.  I have much more
skill in this area now, so my next try, should I get to it should bare out my
beliefs or disprove them.

Figure under pressure differentials with gravity and orientation

I believe this is an ideal application for eletrostatic figure adjustment.
The electrodes need not be simple rings.  A multi-pole electode configuration
below the membrane could be used to differentially adjust for mass distortion.

Clearly, some sort of feedback mechanism would be helpful.  It might be optical
or it might use capacitance between the membrane and the electordes.  Other
ideas anyone?  Elaborate on these?  


Edge fabracation

I too though of optical means to create a rim.  I think this will work but 
scalability is problematic.  It isn't just that the edge needs to be smooth, 
it needs to be uniform.  An o-ring can do smooth but its compression is
irregular.  A metal edge or glass edge is regullar but it is rearly truly
smooth at the very edge.

Here again I thing electrostatic fields could be helpfull.  Specifically a 
ring/s of tiny electordes near the edge and close to the membrane.  Each 
electrode would be positively biased with respect to the membrane to push it 
away.  Adjustments in the bias could be used to adjust the tension of the 
membrane in localized areas.  I say rings for additional area to make
adjustments and to compensate for high order effects and field interaction.

Clearly an automated adjustment system with feedback would be useful here too.

Anthony