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