Exactly filaments cold. KE5FX has great details on doing this for a Cs tube. Google his details. Regards Paul.
On Fri, Dec 4, 2020 at 3:24 AM Dana Whitlow <[email protected]> wrote: > I wonder if it might be good to power up the ion pump with the heaters > cold, then > after the ion current trails off to nil, begin operating the filaments at > very low voltage > (and all other voltages off except for the ion pump) and gradually ramp the > the filament > voltages up towards normal operating voltage, doing so slowly enough that > the ion > pump never trips off. Then, once things have settled down at normal > filament voltage, > set up and fire up the whole instrument. I think this might be easier on > both the filaments > and the ion pump. > > Comments? > > Dana > > > On Thu, Dec 3, 2020 at 8:34 PM <[email protected]> wrote: > > > Thanks very much for this info Corby. It explains the behaviour of my > spare > > 5061A perfectly. > > > > It also raises the question of what I could do with the spare tube I > have. > > I > > can connect a +3500V supply to the ion pump but that won't do anything > > about > > any gas molecules adsorbed onto the filaments as you described. Is it > worth > > powering up the filaments to get rid of them or can that be left for some > > indefinite time in the future when the tube could be reinstalled in a > > 5061A? > > > > Morris > > > > ------------------------------------------- > > Date: Wed, 2 Dec 2020 11:06:22 -0800 > > From: <[email protected]> > > To: [email protected] > > Subject: [time-nuts] HP5061 Cesium ion pump question > > > > The gettering in the tube is only for capturing any stray Cesium atoms > > that don't get caught in the main gettering patch. If the gettering fails > > or gets too loaded up then the Cesium background level will get too high > > causing poor SN. > > > > The ion pump is for any gases. > > > > When a tube is off for extended times any gas atoms lingering or leaking > > slowly into the tube than happen to impinge on either the mass > > Spectrometer filament or the Cs oven filaments get capture by the > > filaments. They function as excellent getters! (this even if the ion > > pump is on) > > > > Now this is not by design but results in the filaments being "loaded" > > with the gas atoms. > > > > Then when you turn the tube on the filaments light up and expell a burst > > of gas. > > > > This of coarse causes the ion pump current to rise and trips off the > > filaments, > > > > Once the ion pump removes the burst the cycle repeats until the filaments > > have expelled the trapped gases. > > > > Then the ion pump can handle the load and pump the tube down completely. > > > > Cheers, > > > > Corby > > > > > > ************************* > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
