Bruce Griffiths wrote:
Probably the temperature fluctuations of the absorption cell is more
significant than that of the lamp itself.
The lamp itself shifts intensity sligthly, but the three most sensitive
points to temperature and temperature shifts is the resonator cavity
(pulls the frequency as it detunes), buffert gas shift change with
temperature and this balance the wall-shift so shift in temperature
change the buffer-gas/wall shift balance and shift in temperature will
cause the OCXO to shift and that needs to be canceled in the loop.
The main effect of the lamp temperature is to shift S/N.
All according to my limited knowledge in the field.
The effects to consider are:
1) The effect of temperature fluctuations of the electronics.
Probably dominated by the short term temperature fluctuations of the
internal crystal oscillator.
The magnetic field applied could also vary. To the best of my knowledge,
I do not know of a way to servo the magnetic field in the fashion it is
done for cesium beams. This servo is part of the modernisation that made
cesiums much more stable.
2) The effect of temperature fluctuations of the Rubidium lamp and
associated optical filters.
Mainly shift in intensity and also the temperature widening of the
relevant wavelength. Likewise with the rubidium filter cell absorbing
the unwanted wavelength.
3) The effect of temperature fluctuations on the Rubidium absorption
cell hyperfine transition frequency.
Buffert-gas mix vs. wall-shift balance depend on temperature. At some
temperature the buffert-gas completely cancels the wall-shift. We can
expect the gas-mixture to shift over time and thus the
shift-compensation for a certain temperature, so there is a wear
mechanism in play.
4) The effect of temperature fluctionations on the Rubidium frequency
resonator.
Resonator cavity frequency shifts with temperature as material expand
(on rising temperature). The Q of the resonator plays a role in the
amount of frequency pulling.
These effects is well covered in the literature.
Cheers,
Magnus
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