); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi,
First take a look at the leapsecond.com website. Click on various lab reports and then rb-cells. You will see pictures of rubidium cells from various instruments. Take a look at the 5065A cell. You will see a long narrow neck coming out of the top. This neck exits the microwave cavity and the tip of it is RTVd into the cold end of the TED (thermoelectric device). Actually just a very tiny thermoelectric cooler like the ones you plug into your cars cigarette lighter. Now the normal state of affairs is that when initially built the rubidium in the cell is all in the tip of the neck. When the unit is warmed up not all the rubidium exits into the cell as the tip is held slightly cooler by around 250ma thru the cooler. When the unit is turned off the tip cools slightly faster than the cell and the rubidium is collected back into the neck. So as long as the unit is operating or not turned off for years at a time you are OK. Now say that the unit is in storage for years. Very slowly at ambient temperatures ALL the rubidium will effuse out into the cell and coat the walls of the tube with a thin coating of rubidium. When you turn the unit on and warm it up there is way too much rubidium in the cell and it absorbs almost all the light at the rubidium line frequency. This is cell flooding. In this situation the TED and or turning the unit back off will not draw enough rubidium back into the tip for proper operation. Performing the procedure in the book passes 1 amp thru the TED cooling it much more than normally. This causes the rubidium to be drawn back into the neck at a faster rate. It will usually take 6 days to fully "de-flood" the cell. If your signal does not improve after the 6days then cell flooding was not the problem. I usually find it safer to use a 5VDC supply thru a 1 ohm 10 watt resistor to supply the current rather than a constant current supply at such a small voltage. You do not want to burn out the TED! Hope this helps! Best regards, Corby Dawson _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
