Magnetic shielding/effect on NMR magnets

T. Pratum (pratum@u.washington.edu)
Thu, 20 Feb 1997 09:41:41 -0800 (PST)

Hello everyone:
A question has recently come up in our Department about the shielding of
stray fields from NMR magents. The powers that be have decided to make the
room above our 750 magnet into a study center. Unfortunately, the stray
fields in this region exceed 15 gauss in many areas. A consultant was
called in and has recommended placing 1/4" steel plate over the floor in
this room. I have a couple of questions for anyone out there who has an
experience with this type of solution:

1. Will this really work?

2. Does the steel plate have a detrimental effect on the magnet below it
(in this case the magnet is about 12-15' below). There is some concern
that building vibrations might result in a time dependent field
inhomogeneity which would be observed on the 750.

3. Are there any other solutions which have been tried (other than moving
the magnet, which is not an option).

I would really appreciate any input, as we have never had to do any
magnetic shielding here in the past. I will post a summary of responses
after a sufficient number have been received.
Thank you.


Tom Pratum
Dept of Chemistry
Box 351700
Univ of Washington
pratum@u.washington.edu
http://weber.u.washington.edu/~pratum