[time-nuts] What does determine the short term stability of an Rb vapor cell standard?

cdelect at juno.com cdelect at juno.com
Mon Mar 26 23:08:13 UTC 2018


Here is an clip from one of the space qualified ones Bob mentioned.

"The RAFS employs classical rubidium gas cell atomic frequency standard
principles. It utilizes a physics package with a discrete isotopic filter
cell for best stability. The relatively large, cool absorption cell
provides exceptionally high signal-to-noise ratio and excellent short
term stability. The addition of a thin film spectral filter increased the
signal-to-noise ratio even higher."

Highlights are:
-"classic" architecture, meaning a separate discrete  filter cell.
-"large cool absorption cell", the 5065A cell is large and runs at around
65 degrees C.
-"thin film spectral filter", this is what the "super" mod adds to the
5065A

Telecomm comparisons are: (not universal)
-small size combined filter and absorption cell, This requires a "hot"
cell, well above 65 degrees.
-only a few have spectral filters.

Conclusions:
- A bigger cell is more stable than a smaller
- a cooler cell is more stable than a hotter
- a separate discrete filter sell allows higher stability than a combined
arraignment.
- These requirements run counter to the telecomm requirements of low
power, small size, fast warmup, and LOW cost.

Cheers,

Corby


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