X-Rays from the X-Ray Machine.

These can penetrate the metal casing (which thru the Faraday Cage effect
is what excluded your magnetic degausser fields). Upon striking the
metal disk surface, the X-ray scattering ionizes electrons on the disk
magnetic media and scrambles enough bits to render the sector
unreadable. Well, it's readable - the parity and checksum tests fail and
the disk firmware returns a Read Error instead of the sector.

John Zoltak wrote:
>
> Hello List Member,
>
> All of this talk about airport scanners and harddrives got me thinking
> about a non-scientific test involving an old 120MB drive and a tape
> degausser. I had the two meet for a while. And the drive still had all
> of it's data intact. This is not a small degausser, it's one of those
> for doing 12" reels of 9-track tape. It has also done the 8mm and DAT
> tapes, so it's no slouch as far as magnetic field goes. I put the drive
> on the surface of the degausser, the field was strong enough to vibrate
> the drive and hold it there. I flipped it and rolled it in the field.
> And still when I tried the drive again, all was OK. I tried the same
> thing for longer periods to about 10 seconds of exposure and each time,
> AOK.
>
> So even with this purposely unshielded, strong magnetic field, I could
> not damage the drive. What other mechanism is there that could account
> for drive damage or data loss when going through airport scanners?
>
> John Zoltak
> North American Mfg Co