RE: my earlier comments.
I should add that we cleaned the pump under the direction of a Micromass
At 09:01 12/11/99 -0500, you wrote:
>I have used an ion pump on our noble gas mass spectrometer for the past 5
>years. I sometimes have problemss with small field emission currents within
>the pump as a result of flaking and discharging edges within the pump grid.
>The effects of these field emission are generally seen as an increase in
>pressure which fluctautes even thought there is no leak within the pumping
>system itself. I remedy this by increasing the voltage to the pump which
>serves to burn off the edges etc. After this the pump works fine. Check your
>manual and see what they say regarding Field Emission Currents and how to
>> From: Graeme Burton[SMTP:[log in to unmask]]
>> Reply To: Stable Isotope Geochemistry
>> Sent: Friday, November 12, 1999 8:28 AM
>> To: [log in to unmask]
>> Subject: Re: Ion Pump Problems
>> We have cleaned out the ion pumps on our VG354. We removed the
>> mesh, small hands are useful! WE didn't bother removing teh magnets. I
>> think we used isopropyl alcohol or acetone. It took a lot of flushing and
>> light rubbing with lab tissues to remove all of the particles. We did
>> after discovering that light tapping on the ion pump caused dramatic drops
>> in the vacuum. Presumably loose particles were being liberated?
>> What about the IG filaments?
>> At 09:51 12/11/99 +0000, you wrote:
>> >Dear List Members -
>> >I'm looking for advice on Ion pumps.
>> >The source ion pump our VG354 thermal ionisation mass spec appears to
>> >partially stopped working, leaving the vacuum just below 10-6 mBar. I've
>> >baked out the system with no improvement. The pump controller is common
>> >a smaller ion pump on the analyser bench which appears to be working
>> >correctly so I suspect the actual pump itself. There are also worrying
>> >flickers on the meter of the power supply if we monitor the current being
>> >drawn by the pump.
>> >Does anyone know if the pump can be dismantled and cleaned ?
>> >Any advice on dealing with this type of problem would be gratefully
>> >received !
>> >Andy Midwood
>> >Dr Andy Midwood,
>> >Analytical Group,
>> >Macaulay Land Use Research Institute,
>> >AB15 8QH,
>> >Tel: +44 (0) 1224 318611
>> >Fax: +44 (0) 1224 311556
>> >Email: [log in to unmask]