==Thanks==
Dave Russell, Andy Soper, Tom Dickinson, Robert Peterson, Tim Burrow,
Alan Ronemus, George Sukenick, Jurgen Schulte, Sara Kunz, Phil
Dennison, Rui Feng, Joseph Asta.
==Purpose==
Install standard probe into the magnet. (same manufacturer of probe
and instrument)
==Notes==
My another email "(summary) centering new probe (z1 cross and z
gradient map procedures)" explains how to center probe with
non-standard dimensions.
Looks like it's common in Bruker and Varian systems to center probe
relative to the shim stack and it is assumed that
shim stack is installed at the maximum field spot.
Procedures described here may not work with third party probes or if
shim/spinner stacks have been somehow moved.
==Procedure==
It is best to look at at your probe installation manual. Most probes
just fit right if installed following proper directions.
===Bruker probes===
The following is copy from Andy Soper's response with minor edits.
The probe is held in the room-temperature shim
stack by two (gold colored) screws. Tightening these screws will
automatically centre the probe in the shim stack.
The shim-stack itself is held (in my
instruments (Andy Soper)) by 3 long screws from the top of
the magnet. Below the magnet is a clamp
which should not be hard up against the bottom
of the magnet. The shim stack should be free
to move just a little.
So the bottom line seems to be: just install the probe and tighten the screws.
===Varian probes===
Varian system with Oxford magnets use the RT shim coils the determine
the magnet center. Between the RT shim base plate and the bottom of
the magnet there should be a set of spacers. The setting of the
spacers is done when the magnet is installed. The physical center of
the RT shims is set at the center of the magnet field using these
spacers. Varian probes are designed with this setting in mind. If the
probe is mated to the upper barrel and the upper barrel is mated to
the RT shim coils then all is well.
Older PFG probes had a PFG connection through the upper barrel. On
newer probes the PFG connector plugs into the probe body. If you have
an older probe you will see pins in the top of the probe and there
will be a notched keyway as part of the top of the probe barrel. This
makes slight difference in the procedure for new and old style probes.
The old style probe cannot be rotated once PFG connector pins engages
with the socket in the upper barrel.
In summary, what you're going to do is to push the probe in too far,
then use the upper barrel to push it back out just the right amount.
This is based on Dave Russel's email:
1) The probe has a retaining flange to hold it in place in the magnet.
This flange is around the outside of the probe and has two thumbscrews
on the 'wings' to connect it to the bottom of the magnet. Get a
non-magnetic Allen key (should be one shipped in the box with the
probe) and loosen the flange until it can slide up and down on the
probe when you push a little bit. It should be tight enough to hold
the weight of the probe by friction, but no more.
2) The upper barrel is the aluminum tube sticking out the top of the
magnet... there will be roughly 1-3 inches showing. It is just
sitting on top of the shim stack, it's not actually connected to
anything. You might want to take a marker and draw a line on the
upper barrel just where it meets the top of the magnet. This is just
for reference.
3) Push the probe flange down toward the bottom of the probe. If you
have another probe from that same system to use as a guide, put the
new flange about 1 inch lower than the 'right' one.
4) Slide the probe into the magnet and feel for the probe to contact
the bottom edge of the upper barrel.
(Modification for old style probes: when the probe first just contacts
the upper barrell - spin it around. The PFG connector will key in and
you'll feel the probe slip in about 1/2 an inch. Once connector is
engaged, the probe won't spin any more.)
Push it up another 1-2 inches, lifting the upper barrel (this is
easiest if someone else is watching for the barrel to move up on the
top of the magnet while one pushes the probe in from the bottom).
5) If the flange hasn't come to the bottom of the magnet at this
point, scoot it up. Now the flange screw holes need to be adjusted
with matching holes at the bottom of the magnet. New style probe can
be rotated, but old style probe can't so the flange must be rotated
instead while keeping probe in place. Tighten the bottom screws -
these could be in the style of thumbscrews or regular flat screws (use
non-magnetic screwdriver for those)
6) Have a helper hold the probe at the bottom. Push the top of the
upper barrel back down into the magnet until is seats against the top
of the shim stack. This pushes the probe back out a little bit, too,
but it serves to align the top of the probe with the top of the shim
stack (where it belongs).
7) Tighten the Allen screw in the probe flange a little bit. Just
snug it up, no need to use 'Brutane' on it or anything.
Evgeny.
--
Evgeny Fadeev, Ph.D.
Director, BioMolecular Spectroscopy Facility
1212 Natural Sciences 1
University of California Irvine
Irvine, CA 92697
telephone: 949-824-5842
www.physics.uci.edu/~biomolenmr
nmrwiki.org
Received on Thu Oct 02 2008 - 13:43:10 MST