https://www.febo.com/pipermail/time-nuts/2017-April/thread.html
We performed an experiment with our working HP5061B which had been cold overnight. This was to better determine lock time from cold ovens. We found that the crystal oscillator oven heats up about twice as fast as does the cesium oven. Therefore the lock time is not much different whether the crystal oscillator was cold or hot. Our crystal oven has been running 34 when hot. The cesium oven has been running about 14 when hot. Here is our data as a function of measurement time in minutes versus meter readings. "+" denotes a pegged meter. The instrument was powered on at 0 minutes except for the cesium heater. The cesium heater was turned on at 13 minutes. The crystal oven had nearly stabilized by that time. Oscillator heater current was stable 15 minutes after power up and undershoots a bit at about 23 minutes. Note that first signs of beam current occur 7 minutes after cesium oven was powered up. First signs of 2nd harmonic occurred 9 minutes after cesium oven was on. We conclude that lock is feasible 23 minutes after a cold start. If the crystal oven is left on, lock can likely be achieved 20 minutes after the cesium oven is powered up. The ion pump preserves beam tube vacuum if the crystal oven is left on. If it is left off for long periods, high ion pump current may delay the application of power to the cesium oven until the vacuum is pumped down. For those who only occasionally need the stability of a cesium clock, you can have full performance 23 minutes after a cold start, or 20 minutes if the crystal and the ion pump are hot. If you use cesium for an hour a day, tube lifetime will be extended by 24 to 1 over continuous operation. If a beam tube lasted five years in continuous operation, it will last 120 years if used an hour per day. A similar benefit will occur if you use it continually for 2 weeks once a year. It does no good to waste cesium unless you are using the instrument. Time Ces Osc Beam 2nd 0 + 0 0 0 7 + 0 0 0 11 55 0 0 0 13 40 + 0 0 15 42 34 0 0 20 42 34 2 0 22 42 32 6 2 23 25 32 10 5 no lock 24 19 32 12 9 lock (free run back to OPR) 28 19 34 20 34 normal beam current _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.