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Fwd: RE: arsclist Electromagnetic pulse weapons

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From: "Copeland, Peter" <Peter.Copeland@xxxxx>
To: "'John Hayward-Warburton'" <media@xxxxxxxxxxxxxxxxxxxxx>,
Subject: RE: arsclist Electromagnetic pulse weapons
Date: Thu, 28 Dec 2000 12:22:33 -0000
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Dear All,
    Sorry, John, but this idea was uppermost in my mind when I was appointed
conservation manager at the British Library National Sound Archive, before
the Cold War ended! The following thoughts occurred to me in this respect.
There was also an article on the subject in *New Scientist* two or three
weeks ago; I'm sorry I cannot give a formal reference, I generally pass the
magazines to my Conservation Planning Assistant, and she seems to have taken
them home to read over Christmas.
    The first solution is not "to put all your eggs in one basket." For
material only the NSA holds (with no copies existing elsewhere as far as we
know), we make two versions, an "archive copy" and a "playback copy." The
playback copy is in London and is used for the archive's day-to-day
business. The other is at the other end of the country, so if an
electromagnetic (or H-bomb) falls on London, there's another copy elsewhere.
    The second solution is to screen magnetic tapes properly. Speaking for
myself (not the NSA), I keep my most vital recordings at home in steel
film-cans, and my less-vital recordings in an earthed steel stationery
cupboard. This would reduce the electromagnetc pulse by a factor of at least
ten. It is ironical - literally! - that the film industry is now moving away
from steel film-cans, because of their autocatalytic effect upon cellulose
acetate film base.
    The third solution is to use a magnetic pigment with a high degree of
retentivity. In the very early days of magnetic recording, you John in
particular will remember how it was forbidden to take BBC magnetic tapes on
a London Underground train. I'm too young to remember H50 tape, but I do
remember H77 which had a retentivity in the order of 200 oersted. I once
made a trial recording on H77 and took it on the tube, putting it on the
floor above one of the power bogies. No effects were detectable - even when
spooling a blank bit against the heads. And now that retentivities of about
500 oersted are normal for analogue open-reel audio tape (typically twice or
three times this for "metal" tapes, although this is more to allow readable
data in a small space), it would be necessary to release many gigawatts of
electromagnetic energy to have a significant effect. This "scare" may have
been invented by BBC engineering managers, to ensure their staff used taxis
rather than public transport.
    Finally, store tapes underground, preferably on steel shelves. The
surrounding earth, the shelves themselves (forming a Faraday cage), and the
buildings above will also provide a reduction of twofold or threefold in the
    Although I can see why an H-bomb would have the necessary capacity on
thermodynamic grounds, neither the New Scientist nor I can see how a
less-destructive "bomb" could be made to provide the electromagnetic energy
required. Finally, there's no doubt that modern integrated circuits are much
more vulnerable to such electromagnetic radiation than any magnetic storage
media, so the New Scientist addressed that side of the problem!
    I should be interested to hear if any other arsclist members can provide
more concrete information.
Peter Copeland

-----Original Message-----
From: John Hayward-Warburton [mailto:media@xxxxxxxxxxxxxxxxxxxxx]
Sent: 27 December 2000 12:47
To: arsclist@xxxxxxxxxxxxxxxx
Subject: arsclist Electromagnetic pulse weapons

An interesting article here:


was referred to in today's Daily Telegraph (Britain) newspaper
during a feature about electromagnetic pulse weapons. The newspaper
mentioned that a terrorist group may have been considering the
deployment of such a weapon to halt trading in the City of London.

Around 1/3 of the way down the article, we see:

> An area worth further investigation in this context is the use of
> low frequency bombs to damage or destroy magnetic tape libraries.

I'm no big-time archivist, but have kept my work carefully over the
years. Yes, it's all on tape. Is it time to start making CD-Rs of it
all? Not that I'm expecting a war any time soon, you understand!

John Hayward-Warburton

Esther Gillie, Sound Recording Archivist Phone: 716-274-1330 Eastman Audio Archive Fax: 716-274-1088 Eastman School of Music, Sibley Music Library esth@xxxxxxxxxxxxxxxxxx 27 Gibbs Street, Rochester, NY 14604

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