No, the CSAC is a Rubidium standard. It measures the ~6.8 GHz ground-state hyperfine splitting in 87Rb using coherent population trapping with a modulated 780 nm diode laser. This signal is used to lock the local oscillator to the atomic transition frequency. And all that in a tiny package with 120 mW power consumption. Pretty cool stuff!
Edit: At second glance, it seems liks they are actually using Cesium now (some other demonstrators use Rubidium). The principle is the same, but the hyperfine splitting is 9.192631770 GHz (by definition) and the laser wavelength is 894 nm.
Rubidium fountains actually launch ions up against gravity so that they are in free fall (in a vacuum, with magnetic fields nulled out) during their sample period. That's not something I can see being miniaturized, or put in use on a moving platform.
Atomic fountains use neutral atoms. It is almost impossible to see the effect of gravity on ions since a single stray electron anywhere in your system creates a way larger Coulomb force.
Fountains need to have a minimum size in order to achieve a sufficient flight time when throwing the atoms up on a ballistic trajectory. Obviously, they also have to be very carefully aligned with respect to gravity.
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They put a tiny Cs vapor cell in there? That's pretty neat.
No, the CSAC is a Rubidium standard. It measures the ~6.8 GHz ground-state hyperfine splitting in 87Rb using coherent population trapping with a modulated 780 nm diode laser. This signal is used to lock the local oscillator to the atomic transition frequency. And all that in a tiny package with 120 mW power consumption. Pretty cool stuff!
Edit: At second glance, it seems liks they are actually using Cesium now (some other demonstrators use Rubidium). The principle is the same, but the hyperfine splitting is 9.192631770 GHz (by definition) and the laser wavelength is 894 nm.
This is borderline retro encabulator talk.
great thanks
Is it Caesium?
I thought Rubidium fountains were easier to minaturise. I can't see where I can find out how the device is made - there's not much detail.
Ah - you're right, it's Caesium. https://ww1.microchip.com/downloads/en/DeviceDoc/A3405FE2-C1...
I used to run an NTP server, in the pool. But it was stratum 2; it would stroke my ego to run a stratum 1 server. But 3.5 kilodollars: I'll wait.
Rubidium fountains actually launch ions up against gravity so that they are in free fall (in a vacuum, with magnetic fields nulled out) during their sample period. That's not something I can see being miniaturized, or put in use on a moving platform.
Atomic fountains use neutral atoms. It is almost impossible to see the effect of gravity on ions since a single stray electron anywhere in your system creates a way larger Coulomb force.
Fountains need to have a minimum size in order to achieve a sufficient flight time when throwing the atoms up on a ballistic trajectory. Obviously, they also have to be very carefully aligned with respect to gravity.
Yeah, though apparently they have a tendency to slowly leak and cause the parts to fail - very limited lifespan.