[time-nuts] Pendulums & Atomic Clocks & Gravity

Jack Hudler jack at hudler.org
Sun May 27 16:35:06 EDT 2007

DARPA may not have funded an instability study but, they sure bought a lot
of it.
I have two 1 meter by 10cm blanks of Zerodur. 
Unfortunately I don't have the lot pedigree or know the grade. 
They were lumped in with a lot I bought at DMRO auction in New Mexico about
10 years ago.

Just another life project waiting for the right amount Time, Materials, and
Invar to complete.

I'd love to have a couple of ~1500x200x100mm bars for an amateur LODTM
(Large optical diamond turning machine).
Talk about a bunch of Invar!!! Try holding +-50 nm for up to 120 hours!


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Dr Bruce Griffiths
Sent: Saturday, May 26, 2007 10:48 PM
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Pendulums & Atomic Clocks & Gravity

Tom Van Baak wrote:
I guess that DARPA didn't want to fund a study of dimensional 
instability that might span several decades.
Zerodur is available in rod form (<4m length) from Schott:
You can even order it online. However it is relatively expensive as is 
most optical quality glass in these days of Lead, Arsenic, and Thorium 
free varieties.
However It comes in several varieties some of which are more stable than 
It is best at constant temperature or at least stay below 130C for the 
standard variety.
It makes nice ring laser gyros - widely used, at least before the advent 
of fibre ring laser gyros.

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