Re: X rays, high altitude, and floppy disks

[Dick King <king@reasoning.com>]

 >Date: Tue, 21 Dec 1999 14:45:06 -0500
 >From: "Paul R. Steinmeyer" <prstein@gyral.com>
 >To: radsafe@romulus.ehs.uiuc.edu
 >Subject: X rays, high altitude, and floppy disks
 >Message-ID: <385FD8C2.CEF59A09@gyral.com>
 >
 >Hello All;
 >
 >I recently got a question from a software distributor regarding
 >radiation effects on the software they distribute overseas (out of the
 >US).  Their observation is that approximately 1 in 5 floppy diskettes
 >are damaged while being shipped overseas; this problem does not occur in
 >domestic shipments.  They assumed that the damage is caused by x rays
 >used by customs inspection.  The damage is usually on the diskettes
 >closest to the exterior of the package, and they say that wrapping their
 >disks in aluminum foil eliminates the problem.
 >
 >Based on threads regarding radiation at high altitudes, my guess is that
 >the long flight at high altitude might be a more likely culprit.
 >
 >Can anyone confirm of correct me?
 >
 >Thanks in advance,
 >
 >Paul R. Steinmeyer
 >Radiation Safety Associates, Inc.
 >RSA Laboratories, Inc.
 >mailto:prstein@radpro.com

I have an alternate hypothesis.

Since the disks are inside the aircraft, which has an aluminum skin much
thicker than any aluminum foil you're likely to be using to wrap the disks, i
doubt that in-flight radiation is an issue.  Aluminum does not stop customs
X-rays, so that's unlikely to be an issue either.  I've seen my fencing
equipment go through customs X-rays.  The sword blades are steel, and they show
up as completely opaque.  However, the guards are aluminum, about 2mm thick.
They completely disappear in the X-ray image, which means that the X-rays go
through the guards as if they weren't there.

I hypothesize that the problem is the long cold soak at altitude, followed by
condensation.  To test this hypothesis, send a few disks through in sealed
plastic bags, or in self-adhering plastic wrap.  My hypothesis would be
falsified if the plastic-wrapped disks fail at a rate similar to the unwrapped
disks.  Do make sure the containers are sealed.

-dk

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