During his tenure at the Lab as student and then Postdoc, Albert Colman
measured the temperature profile in our TC/EA ovens using a thermocouple.
We use a distance of 285 mm from the top of the ceramic tube to the bottom
of the graphite crucible. As far as I can tell that is the most critical
parameter of the TC/EA furnace.

Also, using square crucibles rather than original round ones, really
helped improve peak shapes.

Another odd thing about the TC/EA furnace is the offset between the
settings on the temperature controller and the actual temperature in the
furnace. It should be checked when a new furnace is installed, and if
there are any suspected problems. As we know, these furnaces "age".

You could do this yourself, or I could contract out Dr. Albert C. at the
going rate of $2500 per day (plus first class airfare and luxury
accomodations while on site), to be paid to a bank account in the Cayman
Islands in the name of Fogel, Marilyn.

Marilyn Fogel

> Greetings...
>
> A question of interest for those TC/EA users running solids.  The
> operating manual on the TC/EA quotes that the distance from the top
> of the ceramic tube to the top of the crucible should be 27 cm.  We
> are finding that when running more refractory materials such as
> phosphates or nitrates we must pack deeper than this, on the order of
> 29 cm, in order to eliminate peak tailing, and be able to run more
> than one tray of samples before changing the crucible.
>
> Yet when we repack and remove the glassy carbon tube we can see that
> there is a zone where heat must be the most intense, as this zone is
> wasted away more than the surrounding tube (plus all the yellow/white
> deposits that people have written to the list about before).  Yet
> this zone lies only 26 cm down from the top of the ceramic tube.
>
> What sorts of packing depths are people running with out there?  Why
> would we have to pack deeper than the hot zone in order to get good
> reactions/good peak shapes?  You would think that the crucible should
> lie in the center of the hot zone.  Does the helium flow downwards
> through the reactor somehow whisk some of the heat away, slightly
> lowering the hot zone on the inside of the glassy carbon reactor?
> Note that we are still running with the helium flow being supplied
> from the top, and have not yet changed to the base helium flow setup.
>
> Thanks in advance...
>
> 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]
>
>
>