[time-nuts] Confused about Rubidium oscillators

[Bob Camp]

Hi

In a Cs beam tube, you start with a bucket of metal at one end of the tube.
You shoot it towards the other end of the tube. When you have shot it all,
the tube stops working. That's a "well defined wear-out" or "use-up"
mechanism. 

The comparison they are making is to a Cs beam tube.

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bob Smither
Sent: Wednesday, November 14, 2012 11:56 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Confused about Rubidium oscillators

Do Rb oscillators wear out?  I have found:

"There are no "wear-out" or "use-up" mechanisms in a Datum
Efratom Rubidium oscillator."
  -- Datum - Note About Rubidium Oscillators

and

"Atomic Vapor Oscillators have no wear out mechanism."
  -- FEI - Precison Oscillator Overview, 2007, p19.

But also:

"Unlike a quartz crystal oscillator which has no clearly-defined "wear out"
period and, if well-designed, can actually improve as time goes on, a
Rubidium
reference has a definite lifetime associated with its lamp:  As the unit
operates, the Rubidium within the lamp is gradually consumed and eventually,
too
little vapor is available for the atomic resonance to be detected and the
unit
fails."
  -- http://www.ka7oei.com/10meg_rubidium1.html

and

The page at:
 
http://www.oscilent.com/esupport/TechSupport/ReviewPapers/IntroQuartz/vigcom
p.htm
also mentions a wear out mechanism.

and

"These OCXOs maintain performance characteristics comparable to Rubidium
oscillators without their high cost and inherent wear out,"
  --
http://www.microwavejournal.com/articles/2301-an-ocxo-with-rubidium-oscillat
or-performance

Finally I found:

"Problems with rubidium cell wear-out have been solved and manufacturers now
offer essentially unlimited warranties against cell failure."
  --http://www.endruntechnologies.com/frequency-standard-oscillators.htm

so maybe both points of view are correct?

I recall seeing something about rejuvenating Rb oscillators on this list, so
I
suspect Clint is correct.

Whose right?  As a time-nut, do you leave your Rb oscillators on 24/7?

Thanks,
-- 
Bob Smither, PhD                                   Circuit Concepts, Inc.
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