From: Dominic-Luc Webb 
To: Michael Burr 
cc: ATM list 
Reply-To: Dominic-Luc Webb 


On Thu, 27 Mar 2003, Michael Burr wrote:

> Does anyone know of empirical information regarding the thickness of
> aluminum coatings, and how variances in thickness from the center to the
> edge of a mirror might affect the mirror's figure?

OTOH the thickness is about 50 nm. I do not see how this translates to 1/2
wave. I assumed it was more like 1/10th wave for most people, since we test
somewhere close to 500 nm. Peter Brooks long ago mentioned some books about
this chambers that discusses these issues. I also recall an interesting
test he proposed using electrical resistance and measuring the distance
between the electrodes. I suspect his thinking derives from his working
knowledge base in the electronics industry.

Dominic

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