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Date: | Fri, 19 Dec 2008 11:10:05 +0000 |
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Hi John
We had this fault on our Delta V only last week and changing the
filament cured the problem.
John Hill
University College London
John Drake wrote:
> Hello all,
>
> I have a delta-V advantage with extremely variable box and trap
> currents. The trap varies from 0.6 to 1.2 mA over extremely short
> timescales (less than 0.5 seconds)- box and trap go up and down in
> synchrony. The cycle seems to be stable for days (i.e. the currents
> aren't changing in response to a new gas being added to the source).
> Sensitivity and linearity are within spec, vacuum and backgrounds look
> good, peak shapes and slow magnet scans look good, and data from a run
> of standards look good. Standard deviations (n= 5) for working
> standards are less than 0.1 per mil for d13C (Costech EA -> Conflo IV
> -> IRMS).
>
> In short, the machine seems to be performing well, even with
> hyper-variable box and trap currents. We recently had a He leak and the
> IRMS saw room air from the Conflo for a few hours, which could have
> damaged the filament. Thermo suggested to replace the filament, but I'm
> hesitant to do this when we're getting good performance.
>
> Has anyone else seen this? Thanks,
>
>
> John Drake
>
> Graduate Student
> Program of Ecology, Evolution, and Conservation
> University of Illinois
> 1500 IGB
> 1206 W. Gregory Drive
> Urbana, IL 61801
>
> Lab phone: 217-333-1632
>
>
>
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