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Mumetal Sources

Another idea to protect computers or any sensitive electronic equipment you may want to EMF protect is mumetal shielding. It is a metal compound composed of 80% nickel, 20% iron. Companies such as:

5 SpringField Rd.
P.O. Box 439
Goffstown, New Hampshire 03045
888-669-3539 (toll-free)
Ad-Vance Magnetics
625 Monroe Street
Rochester, Indiana 46975
219-223-3158 (tel)
219-223-2524 (fax)
VitaTech Engineering
15414 Beachview Dr.
Montclair, VA 22026
Office: (703)670-8981
FAX: (703)670-4974
Less EMF, Inc
809 Madison Ave
Albany NY 12208
tel: 518-432-1550

are a couple of sources for shielding products you might want to consider. They each have done work for the US government and military. They also carry standard enclosures for CRT monitors etc. Advance in particular has some pre-made enclosures for tape backup storage. Both companies can and do manufacture custom enclosures to customer specifications. For increased shielding, two or more concentric shields separated by at least the thickness of the material can be used. In such cases, medium permeability material should be used for one layer and a high permeability material for the other layer. The lower permeability material should be located closest to the field source. Thus the medium permeability shielding acts as a buffer that sufficiently diverts the magnetic field to enable the lower reluctance (high permeability) material to attain the required attenuation.

They also sell low and high permeability foils that you can cut and shape yourself. On the large side, Advance and Mushield can outfit an entire room to be shielded. Obviously, nuclear power plants are heavily radiation shielded with lead and lead compounds, but that offers little EMP protection. Radiation shielding is not the same as EMP shielding, though I wouldn't be surprised if it was taken into account in the design of the plant. Obviously, checking with the onsite engineers as to which areas offer what protection is important. There are a lot of websites that have basic info on EMP and EMF shielding. I have found most of them to be fluff. Get the manufacturers catalogs, which contain some pretty useful articles and discussions, as well as talk to their engineers.

Offered by Steve.

And from Clipper's correspondence:

Hello Clipper, thanks for your E-Mail of 21 May 97

In response to your question. We want to shield our computers from the magnetic variances that a pole shift would bring.

We have Mumetal cans 72 x 55 x45 mm which we sell at UKL 35 each. This is our largest so if you need something larger suggest you try Mushield. Generally Mumetal is good for shielding in low intensity fields. It will "suck" away any magnetic field from the air because it is 50,000 times more "permeable" to magnetic fields. It does however saturate in high ambient fields so if you have very strong fields you will be better off with an outer shield of soft (annealed) iron which is also much cheaper. Hope this helps.

Best regards

Brian Sowter
SOWTER Audio Transformers (E A Sowter Ltd)
Winchester, England
Tel: +44(0)1962 620135