[3dem] NMR machines and magnetic fields.

[Shi, Dan (NIH/NCI) [C]]

Only alternative or variable magnetic and/or electric field can generate
the e/m wave traveling long distance. A short wave length 'radio' wave
can be easily shielded off by metal, very low frequency 'radio' wave
could have 10s of miles long wavelength and we may only see electric or
magnetic field only locally. We had experienced beam instability caused
by construction work and heavy equipments running in the building
similar to other people observed nearby shakers or stirs, and those
affects could be timing depended. 

Dan  

-----Original Message-----
From: Ron Milligan [mailto:milligan at scripps.edu] 
Sent: Friday, June 05, 2009 11:27 AM
To: 3dem at ncmir.ucsd.edu
Subject: [3dem] NMR machines and magnetic fields.

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
_______________________________________________
3dem mailing list
3dem at ncmir.ucsd.edu
https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem