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From: John De Armond
Subject: Re: Digital Camera & Airport Security - Any Probs?
Date: Thu, 17 Jun 1999 18:19:27 EDT

Anthony wrote:
> Scott Cleveland <> wrote in message
> news:7k8jut$
> > I am planning to take an airline trip and started
> > wondering if there are any precautions that MUST
> > be observed with a digital camera + memory card?
> No, there is nothing you need worry about.
> > Wouldn't the 'magnetic' security gate possibly cause
> > problems with the stored pictures?
> No.  The memory card does not depend on magnetism, and it is unaffected by
> magnetic fields.  It is also immune to x-rays.  Security scanners do not
> depend on magnetism, either, but in any case they won't have any effect on
> your digital camera or memory card.
> Just one more advantage to digital photography.

Not so fast.  Digital memory IS sensitive to ionizing radiation. 
Indeed, the US guv'mt paid me a lot of money a few years ago to
investigate the feasibility of using RAM chips as radiation
detectors.  (Works quite well, thank you.)  While the low dose
portal monitors (what you put your carry-on luggage through) are
harmless, that cannot be said for the devices used to look at
checked baggage.  Much higher powered X-rays are used for some
checked baggage inspection in order to achieve speed.  And the
thermal neutron activation bomb detection equipment the FAA keeps
playing with may be even worse. Then there's the talk of using smart
CAT-scan technology for bomb detection. Those of us who were around
when 64k DRAM was considered impossible to make remember that the
main problem was alpha particle bombardment of the chip from trace
U/Ra/Th in the packaging material.  It was thought that 64k memory
cells would be so sensitive to alpha upset that they would not be
practical.  This was solved, of course, through process changes, low
background epoxy and passivation coatings.  But neutron activation
analysis will activate (make radioactive) elements in the chip
itself.  There are interesting isotopes of most of the common
dopants.  While they're all short-lived and present no radiation
hazard, they COULD corrupt the memory contents. I have
experimentally erased conventional EPROMs using high intensity X-ray
bursts (and they hold a LOT more charge on their storage gates than
flash memory) so I know it can happen.

There is another risk if CAT scanners are used and it is related to
high instantaneous X-ray dose rate.  High dose rate can cause the
junction between the active transistors and the substrate of IC
chips to conduct and latch up like an SCR.  Absent any external
current limiting, this is usually fatal to the chip.  Rad hardened
chips use isolated well technology to break up these potential SCR
junctions but consumer electronics certainly don't.  

Will it happen?  Dunno.  The Thermal Neutron scanners haven't worked
as well as FAA expected so the rollout is on slow/hold and I don't
know the current status of the CAT-scan initiative.  But rather than
take a chance on trashing my irreplaceable vacation pix or even my
equipment, my digital camera and memory would be carried on and not
allowed to go in checked baggage.

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