We are planning to install a SEM at our facilities, but everywhere in the building there are fluctuations in the DC magnetic field (around 0.15-0.20 microT, with the manufacturer suggesting max 0.03 microT). Considering we can't do anything about the source of such fluctuations, is there any cheap way to shield the instrumentation? As far as I understood a Faraday cage may not work in this case.
See http://www.spicerconsulting.com/fieldcancelling.htm for a commercial system that cancels out ambient magnetic fields. Whether this is "cheap" or not is another question. I assume that the SEM is not cheap. There is a competing system at http://www.techmfg.com/products/magnetic/magnetx.htm
http://www.esongamerica.com/resources/MagEclipse.pdf claim that they are less costly .. and there may be more out there.
(Google "magnetic field SEM installation" )
When our FE-SEM was installed, there was requirement for special conditions regarding the external electric and magnetic field influence and fluctuations, so the room (ceiling, floor, doors and the walls) was isolated with at least 10 layers of thin transformer alloy and grounded. This might not be a cheap solution, but it does the work. It’s sort of Faraday cage, literally :-)
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