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Muons Will Be Used to Protect You from
Terrorist Attacks
by SixWise.com
Nuclear terrorism is the greatest threat facing the United States today,
according to last fall's campaign debates of both President Bush and Senator
John Kerry. Yet despite the worries over this massive threat, less than
5 percent of the cargo entering the United States is examined for it --
largely because the U.S. government lacks a capable and reliable means
of carrying out such a task.
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Muons are formed when cosmic rays heading toward Earth interact
with atmospheric gases and produce electrically charged subatomic
particles. These particles (or muons) have a mass 207 times that
of an electron. They strike Earth at the rate of 10,000 per square
meter every minute, moving through most materials, scattering when
they come in contact with high-density materials.
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But a solution may now have been discovered.
Scientists at Los Alamos National Laboratory are testing technology that
uses muons to detect potential nuclear materials in vehicles or ship containers.
What are muons? Muons are tiny charged particles that occur naturally
in the atmosphere. They are able to penetrate virtually all substances;
they are deflected to varying degrees by denser materials such as lead
and aluminum. With an average energy of three billion electron volts,
most muons can penetrate about 1.8m of lead.
And while scientists had been studying the possibility of using muon
cosmic rays for screening purposes, the project did not gain full swing
until the Sept. 11 terror attacks occurred. Principal funding was received
in October 2003 -- two years following the attacks.
By utilizing these tiny charged particles, the scientists at Los Alamos
National Laboratory have developed a muon cosmic ray screening device
that can accurately detect smuggled nuclear weapons and materials in any
vehicle or container.
How Does the Muon Cosmic Ray Screening Device Work?
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The new device is large enough to scan a 50-foot trailer truck
or a 20-foot-long ship container. It would cost about $1 million
each and could be used for screening vehicles at border crossings
or ship cargo at major ports.
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The essential parts of the device consists of two sets of parallel tubular
sensor constructed so:
By placing detectors above and below a vehicle, scientists are able to
monitor muon interaction with different materials in the vehicle's cargo.
The denser a material is, the more muons will scatter when they make contact.
Using the scatter data, a computer creates an image of the different materials
in the vehicle. This way, instead of relying on the interpretation of
images on a screen, operators only need to consult the device's readings.
According to one scientist, the muon cosmic ray screening device is basically
a data analysis system that measures the exact amount of deflection caused
by the rays bouncing off different materials and identifies them according
to the degree of deflection.
Questions have been raised, however, concerning the speed of the device
and whether or not it is fast enough to allow prompt screening of large
numbers of vehicles or cargo containers. Currently, the system takes 30
to 60 seconds to complete an examination of a vehicle or object; however,
scientists foresee reducing that time to a mere 20 seconds, making it
possible for use with a large volume of motor traffic or cargo.
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The new system has proven to be accurate within a 3 percent margin
for error, and scientists believe they can improve that. Better
software techniques are being developed to allow rapid 3-dimensional
images of the volumes being screened. Scientists can consistently
detect a small cube of uranium--about 4 inches on a side--within
a large metal container full of sheep.
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Muons vs. X-Rays
Scientists agree X-rays (and gamma ray) detectors that are currently
being used at U.S. borders are inefficient for detecting nuclear materials
shielded with lead and steel.
The bottom line is that the muon cosmic ray screening device is superior
to X-ray devices -- such as those used at airports -- which require the
generation and focusing of radiation beams that can penetrate luggage
or metal packaging material but not highly dense lead and similar shielding.
Moreover, any X-ray systems large and powerful enough for motor vehicles
and ships' containers would not only generate a poor success rate, but
would also pose a significant health hazard. In fact, on scientist commented,
"If you had illegal migrants inside a container you would kill them
[with X-rays]."
Sources
Chicago
Tribune February 23, 2005
BBC February 21, 2005
Eurekalert
February 19, 2005
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