From: coderman <coderman@gmail.com>
   >> However, for REAL damage, it would be useful to pulse the kilovolts
   into the
   >> magnetron:  Generally if you increase the voltage by 10, the power
   increases
   >> by 100.  Feed that microwave magnetron with brief (microseconds)
   pulses of
   >> 40,000 volts, rather than 4000, and it will probably generate close
   to 100
   >> kilowatts.  It would be necessary to establish that such a system
   will not
   >> arc with over-voltage, either within the waveguide or the associated
   >> high-voltage wiring.
   >high voltage solid state built into shielding around the
   >waveguide/magnetron cavity presents smallest external hazard and
   >compact too.
   >of course, another order-of-mag level up in explosively pumped EW
   weapons :)
   [1]http://science.howstuffworks.com/e-bomb3.htm

References

   1. http://science.howstuffworks.com/e-bomb3.htm