Hi Tim,

    Thanks for the info!  We are still trying to figure out how this
coating got there.  We did have to "make" new seats to hold the leads
of small heater bulbs.  The new metal was supposed to be stainless
steel but maybe it is our problem.  The bad thing is that we did not
notice if the coating happened suddenly or slowly over time.

    Our Physics shop has a sand blaster but not a "bead" blaster.  I'm
guessing this would be too rough.  It is a large device that you put
your material in rather than a handheld sprayer.  I'm not sure how we
would protect the parts of the source we did not want blasted.  What
does your bead blaster look like?  Any ideas on how much they would
cost?  The bead blasting seems to be the best idea so far.

Joe

> Hi Joe...
>
> We have seen a similar buildup at the base of our ion source on our
> Delta Plus XL, though it was due to a different reason.  One of the
> leads of our filaments had broken, and we used a little clamp to
> clamp the broken wire back together.  The screws in this little clamp
> were coated with zinc, which is apparently a bad metal to have under
> vacuum as it degases.  The result was a coating similar to yours.
>
> We solved the problem by using a bead blaster we have in our lab that
> we use to clean filaments for thermal mass specs.  It did a very nice
> job of cleaning off the grime without damaging the metal or ceramics.
>
> Do you know of anyone with a bead blaster?  I would suggest larger
> round beads (~ 100 micron diameter) at low pressures so as not to be
> aggressive.
>
> Hope this helps...
>
> Tim Prokopiuk
>
> On 27-Mar-06, at 3:40 PM, Joe Lambert wrote:
>
> Hi All,
>
>      We have a Delta Plus IRMS that is about 5 years old and recently
> have
> started having problems with arcing in the source, which is shutting
> off the
> high voltage on the machine.  We belive the problem has to do with a
> build-up on the ceramic leads at the base of the source (see attached
> picture).  This build-up may be graphite.  A glass-fiber brush seems to
> remove the material but the brush is too bulky to reach some of the
> surfaces
> in tight places.  Has anyone seen this happen to their source before
> or does
> anyone have any ideas on how to clean this?  Acetone and alcohol did not
> remove anything.  The ceramic pieces are not removable and if broken
> would
> be bad news.  Our last resort is a 5% nitric acid solution, which we are
> trying to stay away from if possible.  If the attached image does not go
> through, the picture of the dirty ceramics can also be viewed at:
>
> http://www.bama.ua.edu/~lambe012/DirtySource.jpg
>
> The strange thing is that the rest of the source is almost as clean
> as if it
> were brand new.
>
> Thanks,
>
> Joe Lambert
>
>
> W. Joe Lambert
> Research Scientist
> Alabama Stable Isotope Laboratory
> University of Alabama
> Geological Sciences
> 202 Bevill Building
> 7th Avenue
> P.O. Box 870338
> Tuscaloosa, AL 35487-0338
> Phone: (205) 348-4404
> Fax: (205) 348-0818
> email: [log in to unmask]
> Visit our web-site: http:www.geo.ua.edu/asil
>
>
> -------------------------------------------------
> 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]
>
>


W. Joe Lambert
Research Scientist
Alabama Stable Isotope Laboratory
University of Alabama
Geological Sciences
202 Bevill Building
7th Avenue
P.O. Box 870338
Tuscaloosa, AL 35487-0338
Phone: (205) 348-4404
Fax: (205) 348-0818
email: [log in to unmask]
Visit our web-site: http:www.geo.ua.edu/asil