[3dem] NMR machines and magnetic fields.

[Ron Milligan]

NMR instruments rarely cause problems for microscopes.  They generate  
an extremely constant magnetic field - probably more stable than the  
earth's magnetic field -  so they only affect EMs when they are turned  
on and off (at which point realigning the beam is all that needs to be  
done). The fields fall off rapidly in the horizontal direction and  
more slowly in the vertical direction.
Over the years we have had a few problems with fields, but they were  
never due to the NMR instruments that were right next door. Usually  
the problem was due to some small lab instrument located nearby.
Ron