[time-nuts] HP5061B Cesium Oven Properties

Donald E. Pauly trojancowboy at gmail.com
Wed Mar 29 23:02:13 EDT 2017


The cesium oven acts as an evaporator for liquid cesium which melts at
28.5° C.  One of our beam tubes has 83°C for its operating
temperature.  It also calls for a A11R11 and A11R12 of 3.83 K and
42.2K which is 3.51K.  Oven power is specified at 2.2V and 0.9A or
1.98 W.  Being in a vacuum allows less heater power.  Oven temperature
is very critical to provide enough cesium in the beam but at the same
time not wasting it.  A switching power supply runs the oven as well
as providing 1.2V at 3.4A to the hot wire ionizer which is 4.08 Watts.

It took 10 minutes from a cold start for the cesium oven current to
drop from being pegged to its final value.  After stabilizing, we
connected a 470 Ω across the thermistor from the beam tube to shut off
the heater.  Here is the beam current versus time in minutes as the
oven cooled off.  Note that it took 17 minutes for the beam current to
drop to half value.  Continuous lock was maintained.

time beam
0     20
3     18
5     17
8     16
9     15
11    14
14    12
17    11

We then reapplied oven power and watched the beam current increase and
oven current decrease.

time beam oven
0      16     over 50
3       20    missed
5       22    missed
6       21    15
8       20     15
10     20     14

Finally we applied oven power from a 35 minute cooldown and waited for
lock.  If the oscillator oven is stable, the cesium oven will achieve
lock in only two minutes.  There is no need to waste cesium if you do
not need the instrument to be locked.

time beam status
0      8       unlock
2      10     lock
3       12    lock
4       18    lock


More information about the time-nuts mailing list