Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!portal!cup.portal.com!dbell
From: dbell@cup.portal.com (David J Bell)
Newsgroups: comp.misc
Subject: Re: Laptops and Airports
Message-ID: <17935@cup.portal.com>
Date: 4 May 89 19:21:59 GMT
References: <39382@bbn.COM>
Distribution: na
Organization: The Portal System (TM)
Lines: 36

>Does anyone know what impact the airport security systems can have on
>a portable computer?  A colleague had his laptop passed through the metal
>detector and one raster-line of the display stopped working...  it might
>be coincidence, but it sure lOOKED like the magnetic detector may have
>caused some havoc.
>
>In particular: CAN the metals detectors harm microcircuits?  How about the
>xray machine... can zapping a laptop hurt it?  Does the answer change if the
>laptop has, say, an internal hard disk?
>
>Thanks

>Bernie Cosell

1) The metal detectors use a very low level magnetic field to detect massive
   metallic objects passing through. The field strength required to zap a 
   disk of any sort is relatively enormous. The small write currents work
   only due to a *very* small head gap and *extremely* close proximity to
   the media.

2) Likewise for X-rays, only more so. I suppose a high enough dosage *could*
   have some effect on magnetic media, but I don't know what. Certainly the
   dosage used in the airport x-ray machines, which are (moderately) safe
   for unexposed film, would have no effect. As for effect on microcircuits,
   they can be damaged by ionizing radiation, but again, the level is just
   too low. Also, most MOS circuits are only transiently disturbed by
   radiation; the real damage occurs when the power is on, and a radiation
   burst causes a short or latch-up condition through two transistors that
   would normally never be both turned on simultaneously...

   On the other hand, what I've done is to hand the machine to an attendant,
telling him that I don't want it X-rayed. I am the asked to open the case,
and usually, to turn it on. Of course, we *all* know I couldn't hide more
than 8 or 16 ounces of C4 inside a working laptop... :{)

Dave      dbell@cup.portal.com