Biomedical Engineering Reference
In-Depth Information
US government paper is available on the Internet
which describes the theory and development of
non-nuclear ultrawideband EMP bomb, complete
with schematics [15].
19.2 Intentional EMI
As terrorist threats are increasing world-wide,
society's dependence on information and auto-
mated mission-critical and safety-critical electronic
systems create an attractive target for covert oper-
ations outside physical barriers. This can manifest
both as a “force multiplier” or as an isolated tech-
nique to disrupt infrastructure. “EM susceptibility
of new high-density Information Technology (IT)
systems working at higher frequencies and lower
voltages is increasing.” Intentional EMI (IEMI) is
further facilitated by the proliferation of techno-
logical advances that have produced high-energy
radiofrequency (RF) sources and more efficient
antennas [6,7,12].
The classic IEMI paradigm is the result of the
high altitude detonation of a nuclear weapon. Nine
countries, the US, UK, France, Russia, China,
Israel, Pakistan, India, Iran, and North Korea are
thought to have this technology [13]. A high-
altitude detonation of 1 megatons at 50-500 km
(high enough to prevent blast effects at the surface)
produces a burst of X-rays, neutrons, and gamma
rays which strip electrons from the air molecules
resulting in 1-3MeV-energy Compton electrons.
This transient electrical current induces a radi-
ating RF field of 1000 V/m in the 15-250MHz
band. This is enough to cripple sensitive equip-
ment in a 600-5000 km circle below the blast, as
anything with electrical wiring becomes a receiver
[14]. Enough to cover the entire United States.
The affected area can actually extend much farther.
A 90 percent of the Low Earth Orbit Satel-
lites (LEOS) would be lost within a month as
ionized debris interacts with the earth's magnetic
field. As these fields spread out, they induce low-
frequency fields which couple with long-distance
power lines to induce high voltages which trigger
widespread disruption of electric power circuits
(see Figure 19.4) [13].
“The best-known type consists of an explosive packed
copper cylinder surrounded by a helical, current
carrying coil. Upon detonation, the explosion flares
out the cylinder, short-circuiting the coil, and progres-
sively reducing the number of turns in the coil, thus
compressing the magnetic flux. Large flux compres-
sion generators have produced tens of gigawatts, and
they can be cascaded—connected end to end—so that
the output from one stage feeds the next. [16]”
Clearly any country with advanced technology
could construct a crude device. Any well-financed
terrorist with an advanced degree in electrical engi-
neering should be able to grasp its design (see
Figure 19.5).
Narrowband microwave devices can also be
constructed. They range from the high-power,
high-tech Shiva Star (1 TW) at Kirtland Air Force
Base in New Mexico, to commercial microwave
radar sets (20 kW; $20k-50k), to a simple waveg-
uide attached to a microwave oven (1500W,
$250) [16]. Indeed, a most effective medium-sized
directed energy weapon can be constructed from an
ionizing laser coupled to a high power microwave
source [17]. The cylinder of ionized air (a plasma)
around the beam will efficiently transmit radiofre-
quency energy below its plasma cutoff frequency.
This can be conveniently directed into buildings
to disrupt digital equipment at significant standoff
distances (see Figure 19.6).
19.3 Mitigation
Despite its potential for creating electronic
mayhem, EMI, whether intentional or not, can be
reduced or eliminated in all but the most severe
cases through proper design and mitigation tech-
niques [1,2,14]. A thorough vulnerability analysis
of existing equipment, especially high value items,
will result in a number of effective strategies (see
Figure 19.7).
19.2.1 E-Bombs
On a smaller scale, much work has been done to
develop small scale EMP devices which can act at
the local battle field level. In fact, a well-written
