Thanks Wolfram and Shuhei for your responses.

Just to clarify:

I have peak tailing of CO in both continuous flow and dual inlet modes,
so I have ruled out the peripheral devices (along with GC and Conflo)
as the cause of the tailing.  My turbo pumps all show green lights
indicating there is no problem there.  I have also baked out my inlet
valve to get rid of moisture that had collected there when I vented the
machine, with no success.  I always view the position of my filament
with the trap removed to ensure that it is properly aligned.  I also
run with my source heaters on all the time.

But I have seen this problem before when I cleaned the ion source, and
I tried several things back then to solve it: change filaments, change
ion exit slit, clean ion source again, but none of these had any
effect.  Over time the tailing disappeared though...very odd.

This led me to the following conclusions about what could be causing
the tailing: (1) could there be some sort of residue on the ion source
plates from my cleaning procedure that is interacting with the CO (my
final step is to sonicate the source in acetone then bake at about 80C
to dry before reinstallation...maybe the acetone wasn't pure enough at
99.5%).  I will try 100% ethanol next time; (2) the bead blasting of
the ceramics and failing to anneal them afterwards...could porosity
have been exposed that is sealed off during annealing?  I have a set of
ceramics on order to test this.

Thanks again...


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]