[time-nuts] Lifetime of Cesium tube

Chuck Harris cfharris at erols.com
Thu May 12 19:18:08 EDT 2005

Richard (Rick) Karlquist (N6RK) wrote:
>>The end of life can be due to several things, but most notable is 
>>a shortage
>>of cesium ions to send hurling down the length of the tube, and an excess
> 1.  Cesium atoms, not ions, are launched down the tube.  They
> then get ionized by the hot wire ionizer.

I stand corrected.
> 2.  My understanding talking to the CBT people is that
> there is plenty of cesium in the tube to last its expected 
> life.  In most cases, the tube will fail for other reasons
> long before the cesium is exhausted.  

Only if the tube is made in a suboptimal way.  To quote your
collegue Dave Carlson:

  "CBTs manufactured after December 2002 now have more Caesium
   to extend their expected operating life."

I think that would tend to indicate that the tubes are expected
to run out of cesium at end of life.
>>of other molecules for the cesium ions to run into.  Either 
>>condition results
>>in a shortage of cesium molecules for the detector to detect.
> Atoms not molecules

Molecule: A unit of matter, the smallest portion of an *element* or
compound that retains chemical identity with the substance in mass.

A single Cesium atom is the smallest portion of the Cesium element that
retains chemical identity with Cesium in mass.  It is both an
atom, and a molecule.  So is gold, iron, copper, nickel, ..., but not
oxygen, nitrogen, fluorine, chlorine, ...
>>A c-beam is essentially a notch filter.  The beam is modulated 
> No, it's a bandpass filter.

A notch filter is simply a very narrow filter.  It can be bandpass,
or band reject, depending on which engineer wrote the definition.
The C-beam is a notch filter that happens to be a bandpass filter.


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