Hi dstich,
i think a 'coil-gun' is a succession of coils,
arranged to energise sequentially to accelerate a
projectile (usually ferrous) to high speeds.
Rather like a linear motor in essence.
For very high current demands with high accuracy of
switching, i suppose a triggered spark gap is a
good choice, but the open air types deteriorate with
use, and may need cleaning and surface preparation
after even a single shot.
There are hydrogen types, which i know very little
about, but i think they are in low pressure hydrogen
and don't need cleaning as frequently.
If this is a one-shot deal,
there are aluminium foil types that only operate
once, like the old camera flash bulbs, again i know
little more about them, other than that they exist.
This is a curious area of study, for some reason
spark gaps and such trigger-able devices don't seem
to rate much interest.
Ive never heard of an 'Irradiation type' please tell
me what you can about it.
Best of luck with it, John