so, one of the problems i have with so-called EMP generators, is that real EMP has, as one of it's characteristics, a field strength risetime of a few nanoseconds. however, most of the "EMP generators" i see projects for on the web, use many turns of wire, and use wire of relatively high resistance. the RL time constants are measured in MILLIseconds. the thought everybody seems to have, is that when the switch closes, the caps dump huge amounts of current through the inductor, but they don't realize there's an RL time constant involved, and it takes a while for the current to ramp up, and so the field strength has a much slower risetime than a real EMP pulse has. the fast risetime of a real EMP is one of the characteristics that makes it cause so much damage. in order to get the fast risetime of EMP, would require an inductor that has a very low impedance at 200Mhz or so, and a DC resistance low enough to discharge the very large capacitors within a few microseconds. in addition the switch needs to be a very fast switch with a very low on resistance.
the picture is from a paper by the US Air Force officer that designed EMP simulators, and describes in somewhat simple terms, the characteristics of an EMP