Hi gang.
For my probe and shim stack, Varian lineshape spec (50%/0.55%/.011%) is
0.65/8.0/16.0Hz non-spinning. I used to easily get 0.50/5.0/9.0 - gradient
shim the Z's, touch up the non-spins manually, gradient shim the Z's again
and voila.
Now I can't do better than 0.70/7.5/10.7 and I don't know why. I have
inspected and remounted probe and upper bore tube, I have repositioned and
remapped, I have looked around for environmental differences, etc., and I
simply can't get my old wonderful numbers.
Any suggestions? I can't call for service if I'm within specs, but
something has changed and I can't imagine what. The shim maps look fine:
not noisy, symmetrical about the origin, etc.
Bill
William C. Stevens, Ph.D. Nuclear Magnetic Resonance Facility
Director Southern Illinois University
Carbondale, IL 62901-4405
618-453-6498 voice
618-453-6408 fax wstevens_at_siu.edu
http://opie.nmr.siu.edu
Received on Mon Apr 01 2002 - 12:14:11 MST