I tried to make a xenon flasher once.
The current IS crazy high. So high it's actually generally impractical to switch. Hundreds of amps is not uncommon. If nothing else, check your capacitance and look at the dv/dt when fired and calculate current from that. Note that it's not just a matter of the transistor's surge load at say 0.4v Vsat * 300A or 300A^2*rds-on. How much gate or base drive can the transistor actually take to keep operating as a switch? You can't exceed Vgs-max of course. A bipolar, you could probably surge the base current far above Ibe-max for a flash, but how much? If your gain's 40, you'd need a 7.5A surge.
The xenon multi-flashers I know of used one really big storage cap, a smaller flash cap, and a resistor between them that allowed amps to flow but still allows the flash cap to drain so fast that it's guaranteed that the tube will quench and require a retriggering. You can't control the pulse width doing this unfortunately, but you can control the period.
I've not seen an IGBT, or any transistor, controlling the main current between the flash cap and the tube on the devices I took apart, or in any schematics. Again, the current's just crazy high. The turn-ON time may not be an issue because the transistor gate can be "on" before the tube is triggered. The problem is in being able to support a drive of hundreds of amps and switch "off" in those conditions.
gary350, good lord, where did you get those caps?
Did you build a "quarter shrinker" or what? Isn't that enough to shrink quarters?