Cesium beam atomic clocks are actually just a very selective band pass filter / detector. There is a DC output in microamperes which is proportional to how well centered the input frequency is in relationship to the resonance of the Cesium atoms in the ambient conditions as they drift across the tube. To use this filter as a clock, it is slaved to a quartz oscillator which is them multiplied and phase locked, with a small bit of FM at 137 hz prior to being fed into the tube. If the frequency is too low, the output will be in phase with the FM, if the frequency is too high, the phase will be opposite, and if it is centered, there will be a 274 hz "2x" output, which is used to indicate lock.
Thus, the cesium isn't actually sampled at ~9.192 Ghz, but rather a much slower rate. The actual loop maintaining phase is as slow as possible to keep phase noise down, which is part of why they take a while to lock on startup.
Further complicating things is the need for a small persistent magnetic field in the tube, as getting zero in all 3 dimensions is a much harder problem. This bias keeps things stable, but also changes the frequency slightly, but is offset out in the divider chain.
Thus, the cesium isn't actually sampled at ~9.192 Ghz, but rather a much slower rate. The actual loop maintaining phase is as slow as possible to keep phase noise down, which is part of why they take a while to lock on startup.
Further complicating things is the need for a small persistent magnetic field in the tube, as getting zero in all 3 dimensions is a much harder problem. This bias keeps things stable, but also changes the frequency slightly, but is offset out in the divider chain.