Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!rsiatl!jgd
From: jgd@rsiatl.UUCP (John G. De Armond)
Newsgroups: comp.sys.laptops
Subject: Re: airport x-ray machines/laptops
Keywords: laptops, eproms, x-ray
Message-ID: <1436@rsiatl.UUCP>
Date: 6 Feb 90 07:45:58 GMT
References: <6325@rice-chex.ai.mit.edu>
Organization: Radiation Systems, Inc. (a thinktank, motorcycle, car and gun works facility)
Lines: 55

tmb@wheaties.ai.mit.edu (Thomas M. Breuel) writes:

>* what is the photon flux and the energy used in modern airport
>  X-ray machines? Do you know whether this is sufficient to erase
>  EPROMS, alter static RAM data, damage chips?
>* what are the magnetic fields inside the airport X-ray machines?
>* what about the new neutron-activation devices?

I think your controller problem was simply coincidence.  I've had the
opportunity to experiment a bit with radiation and memory.  I had the 
opportunity to get a large number of one-time-programmable EPROMS
(27xxx series eproms in plastic packs with no windows) that had been
pulled in an upgrade.  Being of nuclear persuasion, I decided that X-rays
might erase the chips.  To test this theory, I taped a chip to the exit
window of a 30kvp, 50 ma tube and connected the chip electrically to an
eprom programmer so as to be able to detect when the first bits changes.
(30 kev is near an absorption line of silicon and so should have enhanced
the process.)

After 48 hours of continous exposure amounting to several kiloRADs, the
result was ..... Not a bit changed.  The EPROM was a good as the day
it was programmed.  I tried another experiment involving heating the chip
while irradiating it (thinking that increased electron mobility might 
help.).  Same result.  

Summary:  These suckers are really tough.


Another experiment involved zapping some low-level dosimeters in an X-ray
machine in order to see what kind of exposure is involved.  I was interested
in looking at this from an occupational exposure perspective - in other words,
how did the dose relate to occupational exposure?  The result was that NO
detectable radiation was recorded.  

Summary:  When they say microdose, they mean it.
Summary2: Don't worry about it.

Magnetic fields are another matter.

I have not had an opportunity to examine the neutron activation detectors,
though I suspect that any damage will be from magnetic fields.  If they
use an isotopic neutron source, the magnetic fields should be zilch.  
An accelerator-based source, on the other hand, usually entails some 
hefty magnetics.

I carry media on my person because of all the OTHER things that happen
to luggage and not because of radiation hazards.

John

-- 
John De Armond, WD4OQC  | We can no more blame our loss of freedom on congress-
Radiation Systems, Inc. | men than we can prostitution on pimps.  Both simply
Atlanta, Ga             | provide broker services for their customers.
emory!rsiatl!jgd        |  - Dr. W Williams |                **I am the NRA**