Re: How do non-nuclear EMPs work?

Electromagnetic pulse (EMP) weapons are of interest because they can damage
electrical circuitry, hopefully raising havoc with an enemy's war-making
ability.  Other than the EMP produced by a nuclear weapon, lightning is a
good example of an EMP-generating effect.  A few years ago a lightning
strike near my office literally blew apart some of the chips in our
computer network, and caused a solenoid on a sprinkler valve to blow apart.
 It took over a week to repair all of the damage.

Carlo Kopp wrote an very good article on the generation of electromagnetic
pulses by non-nuclear methods.  You can find his article reproduced here:
http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp.html#0.
 He
outlines three methods of producing electromagnetic pulses.  The first is
based upon an explosively pumped flux compression generator (FCG).  The FCG
consists of a rod of explosive, surrounded by a metal (copper) tube,
surrounded by insulation, surrounded by a coil of heavy wire.  When
activated, a large current is passed through the heavy wire which sets up a
magnetic field.  The explosive charge is then set off on one end of the
explosive, causing the metal tube to expand and short out the winding.  The
magnetic field collapses into fewer and fewer windings, creating
progressively larger currents which generates an electromagnetic pulse. 
According to Kopp, a FCG may produce currents tens to thousands of times
higher than produced by a lightning strike.

The second method of producing an electromagnetic pulse is with a
magnetohydronamic generator.  A magnetohydronamic generator consists of
moving a conductor through a magnetic field to produce a large current; the
size of the current depending upon the strength of the magnetic field and
the speed of the current.  If the conductor is ionized gas generated by an
explosive seeded with conducting ions, then it could move quite rapidly,
generating relatively high currents.  Such a generator may be most useful
for generating the current for a FCG.

Perhaps you have noticed that both of the proceeding devices rely upon
explosives to operate.  Explosives don't really contain a lot of energy,
but because what energy they have is released very quickly, they are
effective tools for throwing switches very quickly or creating rapidly
moving conductors.

The last device that Kopp mentions is a High Power Microwave Source, for
example, the Vircator.  Frankly I don't understand how such devices work
but the microwave energy they produce can range from hundreds of kilowatts
to 40 gigawatts.  Additionally, the energy can be focused, allowing a
specific location to be preferrentially targeted.  Because of the short
wavelengths involved, it is more difficult to shield equipment from these
type of pulses than those previously mentioned.

Protecting equipment from the effects of EMP is increasingly important,
since DRAM and CMOS circuitry found in a typical computer chip may be
damaged by as little as 5 to 10 volts.  A Faraday cage, a metal screen
completely enclosing an electronic device, is an effective way of
protecting a piece of equipment from EMP.  However, power wires and network
wires are but two examples of how an EMP can penetrate the protection
provided by a Faraday cage.

Of course you can find additional resources on the web by searching for
electromagnetic pulse or similar search terms.  A couple of things to keep
in mind:
1.  The EMP produced by non-nuclear weapons can be effective over a range
of a couple hundred yards.  A nuclear EMP may be effective over hundreds of
square miles.  The only way that non-nuclear EMP weapons offer an advantage
over nuclear EMP is by taking advantage of the microwave frequencies
produced by some devices.
2.  EMP generators may be considered weapons, depending upon their power
and their use.  Sometimes a science experiment can have legal
ramifications, especially in this era of hightened tensions.  So...Be
careful and good luck.