[time-nuts] COTS cesium standard physics package life

[Bob Camp]

Hi

The real questions are:

1) Over what period of time can you get a replacement under warranty.

2) How long on average is the tube likely to be useful. 

There are numbers for each. It just depends on which one you are after.

Bob

> On Sep 29, 2016, at 8:07 AM, Ruslan Nabioullin <rnabioullin at gmail.com> wrote:
> 
> Hi, I'm unable to fully grasp the lifetime specifications of typical COTS cesium standard physics packages, for both old and new designs. For example, the documentation of an older HP standard specifies a shelf life of two years if the ion pump is operated two or three times per year, yet at the same time the ``beam tube warranty'' period is three years.  Does this mean that if the physics package is fully operating (i.e., LOOP OPEN, OPER, or LTC), then it's guaranteed to last at least three years, but if it's completely shut down, except for vacuum maintenance sessions (using the mode CS OFF) two or three times per year, it will last only two years?  Also, what will the expected lifetime of the package be if the standard is kept as a reserve, specifically, continuously-powered with the mode set to CS OFF (so continuous vacuum maintenance), and activated or deactivated to or from, resp., OPER, as needed, excl. the time spent fully operating (i.e., in this case, the time spent in the OPER mode doesn't count)?
> 
> Thanks in advance,
> Ruslan
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