My current setup:

2 30uf 5K VDC caps in series (15uF 10KV equiv.)
neon sign transformer with 120v primary and 18.7kv secondary
14 turns of 12 guage solid wire ( now 8 turns over 9 turns over 10 turns of #14)
a couple feet of copper strap
32kv diode network
spark gap using two nails (now three)
10KV realy for the trigger
and a variac to lower the output of the neon sign transformer to within specs of the caps

schematic