Here's one more response
-------------------------------------------------
I just read your post on ammrl, been really busy, haven't checked in there
for a while, so running late.
i agree with your responses that suggest using the RRI mapper for higher
order shims, I have known a few console engineers that could shim in a 28
channel shim set, but it could take days and the mapper does better, i have
heard people say they can shim a 40 channel shim set, but i would only
beleive it if a saw it happen.
Here's my rule of thumb
28 channel, takes 2 days to map with our RRI mapper if all working well,
maybe 1 very long day.
40 channel shim set needs twice the amount of data points per map, so is
very labor intensive( up to 4 days), i use our mapper to do the first 28,
which gives a good enough profile to use 3d gradient shimming on the console
to optimize the rest of the shims.
3D gradient mapping works very well and is quicker than mapping on a big
shim set, but it needs a decent profile to get started and usually requires
some mapping of the lower orders to get it started on the right track.
Make touching the SC shims on your magnet the last option, anytime you put
the lead in the magnet, nasty things can happen!!
If you have a quenched sc shim, it is easy enough to diagnose.
--
Evgeny Fadeev, Ph.D.
Director, BioMolecular Spectroscopy Facility
1212 Natural Sciences 1
University of California Irvine
Irvine, CA 92697
telephone: 949-824-5842
http://www.physics.uci.edu/~biomolenmr<http://www.physics.uci.edu/%7Ebiomolenmr>
http://nmrwiki.org - Share your magnetic science!
Received on Fri Oct 23 2009 - 14:55:43 MST