High current plasma jet striking circuit
Take a leaf from the cinema projection trade (xenon lamps) and use a series injection transformer to eliminate the diode, they are standard spare parts from the suppliers of parts to that trade (There are a few left), see also the series injection choke based igniters often used in old school ion lasers. 

50A on the main current side is routine, and they easily strike an arc in a high pressure lamp. 

You may incidentally wish to investigate coax arcs, very funky physics at the point the arc collapses, to the point that if you try it in a deterium atmosphere you actually get a detectable number of neutrons produced.