Tim,

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

--
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]