[time-nuts] Fundamental limits on performance

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Thu Sep 17 16:01:58 UTC 2009

From: time-nuts-bounces at febo.com [time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths [bruce.griffiths at xtra.co.nz]
Sent: Wednesday, September 16, 2009 21:06
To: chris at chriscaudle.org; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Fundamental limits on performance

Chris Caudle wrote:
> I found it interesting that one of the limits of stability seems to be the
> ability to process the crystals at high temperatures to drive off
> impurities.  The JHU crystals are apparently in some type of glass
> enclosure which can take the high temperatures, and the paper seemed to
> indicate that the standard metal capped packages can't take the higher
> temperatures.
Bliley BFG61 package:
> Just seemed interesting, I would assume that the JHU guys know about those
> types of advances in packaging, but the paper didn't mention it.

I think it's safe to assume that the APL guys know a "lot" about this kind of packaging..<grin>

Look at the JHU site there is a little on the oscillator.
The BFG61 package uses an intermediate internal ceramic plate that more
closely matches the thermal expansion of the quartz crystal.

--  Similar to a fairly conventional "graded seal", I would imagine

There is a huge amount of "art" in building this sort of package (actually, there's a lot of art in building high performance oscillators in general).. I would imagine that there are a very limited number of people who actually are skilled at making the package, sealing it, etc.  It's not like it's a skill set or market that would justify training thousands of operators.

Same kind of thing as any limited production item (like high performance electron gun cathodes, etc.)

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