[time-nuts] HP5061 Cesium ion pump question

[Dana Whitlow]

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 <vilgotch1 at gmail.com> 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: <cdelect at juno.com>
> To: time-nuts at lists.febo.com
> 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
>
>
> *************************
>
>
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