Stable Isotope Geochemistry


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Shuhei Ono <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Tue, 28 Jun 2005 10:29:36 -0400
text/plain (62 lines)

We have had a very similar issue with our 253 after we cleaned the
source; low sensitivity and slow signal rise.  We couldn't solve it by
changing filaments and a turbo pump. What Roger (Finnigan engineer)
found was that our filament was a bit miss-aligned by "about half a
mm".  The way to check is to take off the electron trap and look at the
filament from the other side of the source.  I presume Delta source has
the same basic structure with that of 253.  You need to align the
filament in the middle, otherwise you won't get a good flow of
electrons hitting your molecules; half a mm is very  critical here.  I
am not sure if your issue is the same but I thought it might worth
checking before doing something laborious.  I thought annealing was to
do with baking the organic molecules off the ceramics but I am not
sure.  You don't bake the metal part because it gets oxidized.

Hope this helps.


Shuhei Ono
Geophysical Laboratory
Carnegie Institution of Washington
5251 Broad Branch Rd., NW
Washington, DC 20015
tell) 202-478-8988
Fax) 202-478-8901
On Jun 27, 2005, at 12:17 PM, tcp121 wrote:

> Greetings...
> When cleaning the ceramics of the ion source for our Delta Plus XL I
> used a bead blaster to get rid of the ion burn rather than a diamond
> file.  The end result is the same.  But the next step in the procedure
> (found in the manual) is to anneal the ceramics.  Does anyone know the
> reason for annealing?  I wonder if it closes off pore spaces in the
> ceramics that are exposed when abrasively cleaned.  The reason I think
> this is that I did not follow this step, and now my CO peaks on the
> Delta are now slow to rise and slow to fall, as if some CO is getting
> trapped in the system somewhere.
> Any thoughts?  Is annealing necessary?
> Thanks...
> Tim Prokopiuk
> -----------------------------------------------
> Tim Prokopiuk
> B. Sc. Geology/Technician
> Saskatchewan Isotope Laboratory
> Room 241
> Department of Geological Sciences
> University of Saskatchewan
> 114 Science Place
> Saskatoon, Saskatchewan, Canada
> S7N 5E2
> Phone:  (306) 966-5712
> Fax:            (306) 966-8593
> Email:  [log in to unmask]