==Thanks==
Thanks for help putting this together to: Guy Bernard, Gareth Morris, Jeff
Simpson, Jeff Walton, Charles Fry, Woody Conover.
==Purpose==
This document describes two procedures aimed at placing probe coils at the
center of the magnet.
First procedure (z1 cross) does it indirectly, while second one (using z
gradient map) - directly if the pfg coil is installed in the probe.
Note: most commercial probes can be installed to correct depth without
acquiring any data because they are designed to standardized dimensions.
A separate summary "installing new probe" describes some of those
procedures.
==Sample==
H2O (lock is not necessary)
==Procedure==
===Using z1 room temperature shims===
This procedure will allow placing probe coil at the center of room temp.
shim stack. More precisely it helps finding center of shims along Z
coordinate of the magnet.
Room temp. shim coils should be set at the field center at installation of
the magnet, so aligning probe to shim center will automatically place it at
the the maximum of magnetic field.
*put probe at certain depth D.
*set z1 shim at maximum and record 1D spectrum (spectrum 1); find frequency
position (F1) at center of mass of the water peak (at 50% peak integral) and
take a note of it
*set z1 shim at minimum and record 1D spectrum (spectrum 2); find new peak
center of mass (F2) and take a note of it
*repeat at series of depths
*plot (F1 vs D) and (F2 vs D)
*correct probe depth will be at the intersection of the two curves
Shapes of the two profiles will also give qualitative information on the
changes needed to the higher-order z shims.
===Using z gradient map===
(Suggested by Charles Fry)
Acquire z-gradient map for positive and negative gradients; the two maps
will be symmetric in frequency (same width-wide placement in a spectrum)
when the probe is in the magnet center.
If pfg coil is installed on the probe, this procedure is different in that
it helps to place probe at the center of the magnet, not center of the shim
stack.
-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 <http://www.physics.uci.edu/%7Ebiomolenmr>
nmrwiki.org
Received on Thu Oct 02 2008 - 09:36:06 MST