Don’t be embarrassed Michael.  We have all done something(s) like this.  My most recent “operator assumption error” happened when I ran out of copper for the EA.  I assumed it wouldn’t be a problem to use slightly coarser copper in the upper 5 centimeters.  Resulted in what can best be described as a “dead volume” effect.  Live and learn.

Bye for now,

Jennifer McKay
Assistant Professor (Senior Research)
Stable Isotope Lab Manager
CEOAS, Oregon State University
Corvallis, Oregon 97331

On Feb 16, 2017, at 5:55 PM, Tuite, Michael L (3225) <[log in to unmask]> wrote:

And the winner is . . .

Installed first extraction lens 90 degrees off. 

Am I embarrassed? Yes. Will I ever do that again? No. 

Though my mistake was amateurish, I learned a number of very useful things from your responses. Thanks everyone for your help.


On Feb 15, 2017, at 1:58 PM, Tuite, Michael L (3225) <[log in to unmask]> wrote:

I recently cleaned the source in our Delta V Plus. I also replaced the slit which was quite eroded. On reinstalling the clean source, the sensitivity for both C and N is about a quarter of what it used to be. I’ve tried three different filaments, including the one that was running happily before the cleaning, all with the same results. I’ve tried manual tuning but I don’t get results any better than the auto-tune does. I’ve disassembled and reassembled again checking each ceramic piece and lead. The extraction plates are oriented correctly. The stability of the diminished signal is very good (standard deviation ~ 0.02).  We’ve cleaned the source previously with no problems.

Does this problem sound familiar to anyone? What might I be overlooking? All suggestions are welcome.


Michael Tuite, PhD
Astrobiogeochemistry Lab
Jet Propulsion Laboratory
California Institute of Technology
[log in to unmask]
818 354-1247 office
626 353-1958 cell