[time-nuts] HP5061B Ion Current

Donald E. Pauly trojancowboy at gmail.com
Thu Mar 23 21:54:10 EDT 2017


The patent that I posted at
http://gonascent.com/papers/hp/US3323008.pdf has many interesting
facts about the cesium beam tube.  It says that the temperature of the
cesium oven is 65° C.  I researched the vapor pressure of cesium at
various temperatures.  With a change of 30° C in the oven temperature,
the cesium pressure goes up or down by 10 to 1.  If the oven
temperature goes up by 5°C, cesium use rate goes up by 1.46 to 1.  If
it goes down by 5°C, cesium consumption decreases by 1.46 to 1.
Cesium oven temperature is quite critical to beam tube life.  The
HP5061A has a switch to reduce cesium oven temperature to increase
beam tube life at a price of slightly worse short term stability.

If the oven is shut off in CS OFF mode, pressure drops to 1.41x10^-6
Torr at 25 at temperatures about 25° C.  This is 2.8 times more that
the 5x10^-7 Torr that is considered a good vacuum for the tube.  good
vaccum is considered 2 μA on the ion pump. This would be 5.6 μA for
the higher pressure.  Therefore, the tube will get somewhat gassy if
the instrument is not used.  If it is stored at temperatures about 25°
C while not in operation, the situation is worse.  I don't know what
is causing higher currents but it must be contaminants beside cesium.


C°  log mm Hg
-18° -8
2° -7
22° -6
47° -5
77 -4
109° -3
155° -2
207° -1
252° -0


More information about the time-nuts mailing list