From:	CSBVAX::CSBVAX::MRGATE::"SMTP::PYRITE.RUTGERS.EDU::SECURITY" 25-JAN-1989 17:58
To:	MRGATE::"ARISIA::EVERHART"
Subj:	Re:  EMP (Electro-Magnetic-Pulse) Luggage scanning.


Sender: security@pyrite.rutgers.edu
Date: Wed, 11 Jan 89 22:01:40 EST
From: stiatl!john@gatech.edu
Subject: Re:  EMP (Electro-Magnetic-Pulse) Luggage scanning.
To: security@pyrite.rutgers.edu

The problem with this scheme, even if it would not damage electronics is
that it's very easy to defeat.  Simply wrap the explosive in a conductive
and/or magnetic material like Mu-metal and voila!  No Boom.

In a related issue.  Much press has been given to this new Thermal Neutron
explosive detector.  Being a Nuke by training, the underlying assumptions
give me some heartburn.

The principle of operation is that nitrogen-rich explosives, when 
irradiated with a thermal neutron flux will have some nitrogen atoms
transmuted to the N-16 isotope.  N-16 has a half-life of a few second
and decays with a highly energetic and characteristic gamma ray.
This gamma ray is detected, processed and used to generate the alarm.

Here's the rub.. Thermal neutrons are easily stopped by materials with
high cross-sections like cadmium.  No neutrons in the explosives = no
N-16.  No N-16 = no detection.  Since it is likely that Californium is
the source of neutrons, the flux is not likely to be high because of 
cost (several thousand dollars per microgram).  Thus the flux could probably
be stopped by a cadmium foil.  By implication, a perfect explosive would
be some plastique or C4 shaped like a candy bar and wrapped in cadmium 
"foil".  this would look normal to visual and X-ray inspection and would
defeat the neutron detector.

So the question arises "Is this TOO easy or am I missing something".  
Considering the government's involvement, it's quite likely the 
former.  I'm wondering if there is anybody on the net familiar with 
the specific design of the detector.  If so, am I missing something?

It seems to me that a much more suitable detector would be one of the
proven nitrate sniffers.  These things have been in use at Nuclear
plants for at least 7 or 8 years.  I can testify as to their sensitivity
after setting one off with power residue from a weekend target practice
session.  The functionality test the guards used at one site was to 
try to carry one of these nitroglycerin despensing angina patches thru 
the gate.  It would detect the fumes from the few milligrams of nitro
in these patches.

For even better sensitivity, the nitro sniffer could be coupled to the
altitude chamber now in use.  The vacuum chamber would enhance the mobility
of emitted explosive molecules and the exhaust of the vacuum pump would
contain a concentrate of the chamber atmosphere.  As an added benefit,
these things cost a few thousand bux, not a million or more like the 
neutron device.

Comments?

------------------------------------------------------------------------------- 
John De Armond, WD4OQC                              Sales Technologies, Inc 
...!gatech!stiatl!john                          Atlanta, GA  (404) 841-4000