https://www.febo.com/pipermail/time-nuts/2017-March/104374.html
The patent that I posted at http://gonascent.com/papers/hp/US3323008.pdf has many interesting facts about the cesium beam tube. It says that the temperature of the cesium oven is 65° C. I researched the vapor pressure of cesium at various temperatures. With a change of 30° C in the oven temperature, the cesium pressure goes up or down by 10 to 1. If the oven temperature goes up by 5°C, cesium use rate goes up by 1.46 to 1. If it goes down by 5°C, cesium consumption decreases by 1.46 to 1. Cesium oven temperature is quite critical to beam tube life. The HP5061A has a switch to reduce cesium oven temperature to increase beam tube life at a price of slightly worse short term stability. If the oven is shut off in CS OFF mode, pressure drops to 1.41x10^-6 Torr at 25 at temperatures about 25° C. This is 2.8 times more that the 5x10^-7 Torr that is considered a good vacuum for the tube. good vaccum is considered 2 μA on the ion pump. This would be 5.6 μA for the higher pressure. Therefore, the tube will get somewhat gassy if the instrument is not used. If it is stored at temperatures about 25° C while not in operation, the situation is worse. I don't know what is causing higher currents but it must be contaminants beside cesium. http://www.powerstream.com/vapor-pressure.htm C° log mm Hg -18° -8 2° -7 22° -6 47° -5 77 -4 109° -3 155° -2 207° -1 252° -0 πθ°μΩω±√·Γλ WB0KVV _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.