[time-nuts] Need some wisdom from the cesium beam tube gurus out there

[Skip Withrow]

Hello Time-Nuts,

I have been checking out some cesium beam tubes lately and have run into an
interesting one.  The tube is a standard HP 05061-6077 unit.  There are two
labels on these tubes, one at the end that has a serial number, and the
other large label on the side that has the operating information (and the
serial number).  Problem with this tube is the large label is completely
BLANK.  It appears that there was never any information on this label.  The
source that it came from was pretty closely connected to HP, so it could be
a tube that escaped before testing/characterization.

The nice thing is that it works!  Using some random nominal resistors for
the oven temperature I get good beam current.  Changing the electron
multiplier voltage also dramatically changes the beam current.  I see the 3
peaks around the on-frequency point quite nicely.

So, the question is - how do I determine the operating point of the tube
with no data?  I could fire up a known tube and set the beam current for
the same value, but how would the oven temperature vs. electron multiplier
voltage be resolved.  I would think that a lower oven temp and higher EM
voltage would give the same beam current as a higher oven temp and lower EM
voltage.

I'm sure the HP did not do any characterization of the tube until it was
all buttoned up.  So how did they determine the temperature of the oven?
Just from the value of the internal thermistor?

I suspect the answer is what kind of S/N ratio do I want?  If that is the
case then I would be tempted to run at the lowest oven temp and highest EM
voltage that gave me a usable signal - for the sake of tube life.

Any thoughts?

Thanks,
Skip Withrow