[time-nuts] Lifetime of Cesium tube

Doug Hogarth doug at niceties.com
Thu May 12 21:01:06 EDT 2005

I don't know about 5061 era tubes but my understanding of 5071 era tubes is
similar to what Tom said.
High-perf tubes use about a gram of cesium per year and originally had six
grams, so last about six years.
Standard perf tubes which run at lower oven temperature using less cesium
last around twenty years.
Old prices of those tubes were something like $35K or $25K.

I bought a used 5071A and my estimate from looking at the log was that it
had run around 300 days previously.
I ran it four weeks, then stopped to update firmware, then ran continuous
operation for exactly 365*5 days before it apparently ran out of cesium
couple months ago.  So probably six years total (but I can only be certain
of last 5.1 years).

Couple years ago Agilent started loading high-perf tubes with nine grams of
cesium so expect to last around nine years.
And they lowered the price to around $22K for high-perf and std-perf
(high-perf gets five year warranty and I think std-perf gets longer warranty
but I am not sure).  I choose high-perf, updated firmware again, and have
been running continuous the four weeks since MJD 53474 (and hope to continue
for nine years; my primary use is driving my two geodetic quality GPS
receivers which are part of global monitoring networks IGS/JPL).

Agilent instructions remind you that a good way to "store" 5071A tubes is to
keep them in your 5071A set to Standby.

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